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Sweany RR, Mack BM, Gebru ST, Mammel MK, Cary JW, Moore GG, Lebar MD, Carter-Wientjes CH, Gilbert MK. Divergent Aspergillus flavus corn population is composed of prolific conidium producers: Implications for saprophytic disease cycle. Mycologia 2024; 116:536-557. [PMID: 38727560 DOI: 10.1080/00275514.2024.2343645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 04/12/2024] [Indexed: 06/29/2024]
Abstract
The ascomycete fungus Aspergillus flavus infects and contaminates corn, peanuts, cottonseed, and tree nuts with toxic and carcinogenic aflatoxins. Subdivision between soil and host plant populations suggests that certain A. flavus strains are specialized to infect peanut, cotton, and corn despite having a broad host range. In this study, the ability of strains isolated from corn and/or soil in 11 Louisiana fields to produce conidia (field inoculum and male gamete) and sclerotia (resting bodies and female gamete) was assessed and compared with genotypic single-nucleotide polymorphism (SNP) differences between whole genomes. Corn strains produced upward of 47× more conidia than strains restricted to soil. Conversely, corn strains produced as much as 3000× fewer sclerotia than soil strains. Aspergillus flavus strains, typified by sclerotium diameter (small S-strains, <400 μm; large L-strains, >400 μm), belonged to separate clades. Several strains produced a mixture (M) of S and L sclerotia, and an intermediate number of conidia and sclerotia, compared with typical S-strains (minimal conidia, copious sclerotia) and L-strains (copious conidia, minimal sclerotia). They also belonged to a unique phylogenetic mixed (M) clade. Migration from soil to corn positively correlated with conidium production and negatively correlated with sclerotium production. Genetic differences correlated with differences in conidium and sclerotium production. Opposite skews in female (sclerotia) or male (conidia) gametic production by soil or corn strains, respectively, resulted in reduced effective breeding population sizes when comparing male:female gamete ratio with mating type distribution. Combining both soil and corn populations increased the effective breeding population, presumably due to contribution of male gametes from corn, which fertilize sclerotia on the soil surface. Incongruencies between aflatoxin clusters, strain morphotype designation, and whole genome phylogenies suggest a history of sexual reproduction within this Louisiana population, demonstrating the importance of conidium production, as infectious propagules and as fertilizers of the A. flavus soil population.
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Affiliation(s)
- Rebecca R Sweany
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Brian M Mack
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Solomon T Gebru
- Division of Virulence Assessment, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, 20708
| | - Mark K Mammel
- Division of Molecular Biology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, 20708
| | - Jeffrey W Cary
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Geromy G Moore
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Matthew D Lebar
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Carol H Carter-Wientjes
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Matthew K Gilbert
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
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2
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Li F, Zhang J, Zhong H, Yu K, Chen J. Comprehensive Insights into the Remarkable Function and Regulatory Mechanism of FluG during Asexual Development in Beauveria bassiana. Int J Mol Sci 2024; 25:6261. [PMID: 38892450 PMCID: PMC11173134 DOI: 10.3390/ijms25116261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Revised: 05/24/2024] [Accepted: 05/31/2024] [Indexed: 06/21/2024] Open
Abstract
Asexual development is the main propagation and transmission mode of Beauveria bassiana and the basis of its pathogenicity. The regulation mechanism of conidiation and the key gene resources for utilization are key links to improving the conidia yield and quality of Beauveria bassiana. Their clarification may promote the industrialization of fungal pesticides. Here, we compared the regulation of morphology, resistance to external stress, virulence, and nutrient utilization capacity between the upstream developmental regulatory gene fluG and the key genes brlA, abaA, and wetA in the central growth and development pathway. The results showed that the ΔbrlA and ΔabaA mutants completely lost the capacity to conidiate and that the ΔwetA mutant had seriously reduced conidiation capacity. Although the deletion of fluG did not reduce the conidiation ability as much as deletions of brlA, abaA, and wetA, it significantly reduced the fungal response to external stress, virulence, and nutrient utilization, while the deletion of the three other genes had little effect. Via transcriptome analysis and screening the yeast nuclear system library, we found that the differentially expressed genes in the ΔfluG mutants were concentrated in the signaling pathways of ABC transporters, propionate metabolism, tryptophan metabolism, DNA replication, mismatch repair, and fatty acid metabolism. FluG directly acted on 40 proteins that were involved in various signaling pathways such as metabolism, oxidative stress, and cell homeostasis. The analysis indicated that the regulatory function of fluG was mainly involved in DNA replication, cell homeostasis, fungal growth and metabolism, and the response to external stress. Our results revealed the biological function of fluG in asexual development and the responses to several environmental stresses as well as its influence on the asexual development regulatory network in B. bassiana.
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Affiliation(s)
| | - Juefeng Zhang
- Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; (F.L.); (H.Z.); (K.Y.)
| | | | | | - Jianming Chen
- Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; (F.L.); (H.Z.); (K.Y.)
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3
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Rasheed U, Cotty PJ, Ain QU, Wang Y, Liu B. Efficacy of atoxigenic Aspergillus flavus from southern China as biocontrol agents against aflatoxin contamination in corn and peanuts. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2024; 201:105887. [PMID: 38685218 DOI: 10.1016/j.pestbp.2024.105887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/23/2024] [Accepted: 03/24/2024] [Indexed: 05/02/2024]
Abstract
Aspergillus flavus is a ubiquitous facultative pathogen that routinely infects important crops leading to formation of aflatoxins during crop development and after harvest. Corn and peanuts in warm and/or drought-prone regions are highly susceptible to aflatoxin contamination. Controlling aflatoxin using atoxigenic A. flavus is a widely adopted strategy. However, no A. flavus genotypes are currently approved for use in China. The current study aimed to select atoxigenic A. flavus endemic to Guangxi Zhuang Autonomous Region with potential as active ingredients of aflatoxin biocontrol products. A total of 204 A. flavus isolates from corn, peanuts, and field soil were evaluated for ability to produce the targeted mycotoxins. Overall, 57.3% could not produce aflatoxins while 17.15% were incapable of producing both aflatoxins and CPA. Atoxigenic germplasm endemic to Guangxi was highly diverse, yielding 8 different gene deletion patterns in the aflatoxin and CPA biosynthesis gene clusters ranging from no deletion to deletion of both clusters. Inoculation of corn and peanuts with both an aflatoxin producer and selected atoxigenic genotypes showed significant reduction (74 to 99%) in aflatoxin B1 (AFB1) formation compared with inoculation with the aflatoxin producer alone. Atoxigenic genotypes also efficiently degraded AFB1 (61%). Furthermore, atoxigenic isolates were also highly efficient at reducing aflatoxin concentrations even when present at lower concentrations than aflatoxin producers. The use of multiple atoxigenics was not always as effective as the use of a single atoxigenic. Effective atoxigenic genotypes of A. flavus with known mechanisms of atoxigenicity are demonstrated to be endemic to Southern China. These A. flavus may be utilized as active ingredients of biocontrol products without concern for detrimental impacts that may result from introduction of exotic fungi. Field efficacy trials in the agroecosystems of Southern China are needed to determine the extent to which such products may allow the production of safer food and feed.
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Affiliation(s)
- Usman Rasheed
- Institute of Applied Microbiology, College of Agriculture, Guangxi University, Guangxi Key Laboratory for Agro-Environment and Agro-Product Safety, Nanning 530004, China
| | - Peter J Cotty
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, China
| | - Qurat Ul Ain
- Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning, China
| | - YiFan Wang
- Institute of Applied Microbiology, College of Agriculture, Guangxi University, Guangxi Key Laboratory for Agro-Environment and Agro-Product Safety, Nanning 530004, China
| | - Bin Liu
- Institute of Applied Microbiology, College of Agriculture, Guangxi University, Guangxi Key Laboratory for Agro-Environment and Agro-Product Safety, Nanning 530004, China.
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Karahoda B, Pfannenstiel BT, Sarikaya-Bayram Ö, Dong Z, Ho Wong K, Fleming AB, Keller NP, Bayram Ö. The KdmB-EcoA-RpdA-SntB (KERS) chromatin regulatory complex controls development, secondary metabolism and pathogenicity in Aspergillus flavus. Fungal Genet Biol 2023; 169:103836. [PMID: 37666447 PMCID: PMC10841535 DOI: 10.1016/j.fgb.2023.103836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/28/2023] [Accepted: 09/01/2023] [Indexed: 09/06/2023]
Abstract
The filamentous fungus Aspergillus flavus is a plant and human pathogen predominantly found in the soil as spores or sclerotia and is capable of producing various secondary metabolites (SM) such as the carcinogenic mycotoxin aflatoxin. Recently, we have discovered a novel nuclear chromatin binding complex (KERS) that contains the JARID1-type histone demethylase KdmB, a putative cohesion acetyl transferase EcoA, a class I type histone deacetylase RpdA and the PHD ring finger reader protein SntB in the model filamentous fungus Aspergillus nidulans. Here, we show the presence of the KERS complex in A. flavus by immunoprecipitation-coupled mass spectrometry and constructed kdmBΔ and rpdAΔ strains to study their roles in fungal development, SM production and histone post-translational modifications (HPTMs). We found that KdmB and RpdA couple the regulation of SM gene clusters with fungal light-responses and HPTMs. KdmB and RpdA have opposing roles in light-induced asexual conidiation, while both factors are positive regulators of sclerotia development through the nsdC and nsdD pathway. KdmB and RpdA are essential for the productions of aflatoxin (similar to findings for SntB) as well as cyclopiazonic acid, ditryptophenaline and leporin B through controlling the respective SM biosynthetic gene clusters. We further show that both KdmB and RpdA regulate H3K4me3 and H3K9me3 levels, while RpdA also acts on H3K14ac levels in nuclear extracts. Therefore, the chromatin modifiers KdmB and RpdA of the KERS complex are key regulators for fungal development and SM metabolism in A. flavus.
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Affiliation(s)
- Betim Karahoda
- Biology Department, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Brandon T Pfannenstiel
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, USA
| | | | - Zhiqiang Dong
- Faculty of Health Sciences, University of Macau, Macau
| | - Koon Ho Wong
- Faculty of Health Sciences, University of Macau, Macau; Institute of Translational Medicine, University of Macau, Macau; Ministry of Education Frontiers Science Center for Precision Oncology, University of Macau, Macau
| | - Alastair B Fleming
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin, Ireland
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, USA
| | - Özgür Bayram
- Biology Department, Maynooth University, Maynooth, Co. Kildare, Ireland.
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Hao L, Zhang M, Yang C, Pan X, Wu D, Lin H, Ma D, Yao Y, Fu W, Chang J, Yang Y, Zhuang Z. The epigenetic regulator Set9 harmonizes fungal development, secondary metabolism, and colonization capacity of Aspergillus flavus. Int J Food Microbiol 2023; 403:110298. [PMID: 37392609 DOI: 10.1016/j.ijfoodmicro.2023.110298] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 05/17/2023] [Accepted: 06/18/2023] [Indexed: 07/03/2023]
Abstract
As a widely distributed food-borne pathogenic fungus, Aspergillus flavus and its secondary metabolites, mainly aflatoxin B1 (AFB1), pose a great danger to humans. It is urgent to reveal the complex regulatory network of toxigenic and virulence of this fungus. The bio-function of Set9, a SET-domain-containing histone methyltransferase, is still unknown in A. flavus. By genetic engineering means, this study revealed that, through catalyzing H4K20me2 and -me3, Set9 is involved in fungal growth, reproduction, and mycotoxin production via the orthodox regulation pathway, and regulates fungal colonization on crop kernels through adjusting fungal sensitivity reactions to oxidation stress and cell wall integrity stress. Further domain deletion and point mutation inferred that the SET domain is the core element in catalyzing H4K20 methylation, and D200 site of the domain is the key amino acid in the active center of the methyltransferase. Combined with RNA-seq analysis, this study revealed that Set9 regulates the aflatoxin gene cluster by the AflR-like protein (ALP), other than traditional AflR. This study revealed the epigenetic regulation mechanism of fungal morphogenesis, secondary metabolism, and pathogenicity of A. flavus mediated by the H4K20-methyltransferase Set9, which might provide a potential new target for early prevention of contamination of A. flavus and its deadly mycotoxins.
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Affiliation(s)
- Ling Hao
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Mengjuan Zhang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Chi Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China; Institute of Edible Mushroom, Fujian Academy of Agricultural Sciences, Fuzhou 350014, China
| | - Xiaohua Pan
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China; Fujian Key Laboratory of Propagated Sensation along Meridian, Fujian Academy of Chinese Medical Sciences, Fuzhou 350003, China
| | - Dandan Wu
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Hong Lin
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Dongmei Ma
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Animal Sciences (College of Bee Science), Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yanfang Yao
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Wangzhuo Fu
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Jiarui Chang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yanling Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Zhenhong Zhuang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, Proteomic Research Center, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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6
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Li Z, Sun Y, Gu L, Wang Y, Xu M, Zhou Y, Hu Y, Ma W. Ar-turmerone suppresses Aspergillus flavus growth and aflatoxin accumulation: Finding a new antifungal agent based on stored maize. Food Res Int 2023; 168:112735. [PMID: 37120196 DOI: 10.1016/j.foodres.2023.112735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 03/15/2023] [Accepted: 03/17/2023] [Indexed: 04/03/2023]
Abstract
Aspergillus flavus (A. flavus) is a common saprophytic pathogenic fungus that produces toxic and carcinogenic aflatoxins prone to contaminate food. Here, we optimized the synthesis method of Ar-turmerone, the main active ingredient in turmeric essential oil, improved its yield and reduced the operation requirements. Moreover, 50.0 μg/mL Ar-turmerone 100.0 % inhibited the colonies growth, spore germination, mycelium biomass and aflatoxin accumulation in 7 days. 2,018 differentially expressed genes (DEGs) such as catA, ppoC, erg7, erg6 and aflO related to the A. flavus growth and aflatoxin product were significantly downregulated including 45 DEGs were 100.0 % suppressed. Besides, Ar-turmerone greatly reduced A. flavus in maize, the optimal storage conditions for maize to avoid A. flavus contamination were determined as 0.940 aw, 400.0 μg/mL Ar-turmerone, and 16.0 °C. Satisfactory odor, luster, taste, and mildew in maize observed after three weeks of storage under the optimal conditions. Thus, Ar-turmerone can be used as a potential food antifungal agent against A. flavus growth and aflatoxin accumulation during food storage.
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Affiliation(s)
- Zheyu Li
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu 610052, China.
| | - Yanan Sun
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Food and Biological Engineering, Chengdu University, Chengdu 610106, People's Republic of China
| | - Linghui Gu
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu 610052, China
| | - Yuchi Wang
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu 610052, China
| | - Mingqin Xu
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu 610052, China
| | - Yunhao Zhou
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu 610052, China
| | - Yichen Hu
- Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, College of Food and Biological Engineering, Chengdu University, Chengdu 610106, People's Republic of China.
| | - Wenbo Ma
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, Chengdu 610052, China.
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7
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Katayama T, Maruyama JI. Trace copper-mediated asexual development via a superoxide dismutase and induction of AobrlA in Aspergillus oryzae. Front Microbiol 2023; 14:1135012. [PMID: 36970664 PMCID: PMC10030727 DOI: 10.3389/fmicb.2023.1135012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 02/15/2023] [Indexed: 03/11/2023] Open
Abstract
The filamentous fungus Aspergillus oryzae, in which sexual reproduction remains to be discovered, proliferates mainly via asexual spores (conidia). Therefore, despite its industrial importance in food fermentation and recombinant protein production, breeding beneficial strains by genetic crosses is difficult. In Aspergillus flavus, which is genetically close to A. oryzae, structures known as sclerotia are formed asexually, but they are also related to sexual development. Sclerotia are observed in some A. oryzae strains, although no sclerotia formation has been reported in most strains. A better understanding of the regulatory mechanisms underlying sclerotia formation in A. oryzae may contribute to discover its sexual development. Some factors involved in sclerotia formation have been previously identified, but their regulatory mechanisms have not been well studied in A. oryzae. In this study, we found that copper strongly inhibited sclerotia formation and induced conidiation. Deletion of AobrlA encoding a core regulator of conidiation and ecdR involved in transcriptional induction of AobrlA suppressed the copper-mediated inhibition of sclerotia formation, suggesting that AobrlA induction in response to copper leads not only to conidiation but also to inhibition of sclerotia formation. In addition, deletion of the copper-dependent superoxide dismutase (SOD) gene and its copper chaperone gene partially suppressed such copper-mediated induction of conidiation and inhibition of sclerotia formation, indicating that copper regulates asexual development via the copper-dependent SOD. Taken together, our results demonstrate that copper regulates asexual development, such as sclerotia formation and conidiation, via the copper-dependent SOD and transcriptional induction of AobrlA in A. oryzae.
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Affiliation(s)
- Takuya Katayama
- Department of Biotechnology, The University of Tokyo, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
| | - Jun-ichi Maruyama
- Department of Biotechnology, The University of Tokyo, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
- *Correspondence: Jun-ichi Maruyama,
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Wang J, Liang L, Wei S, Zhang S, Hu Y, Lv Y. Histone 2-Hydroxyisobutyryltransferase Encoded by Afngg1 Is Involved in Pathogenicity and Aflatoxin Biosynthesis in Aspergillus flavus. Toxins (Basel) 2022; 15:7. [PMID: 36668827 PMCID: PMC9861817 DOI: 10.3390/toxins15010007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/07/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022] Open
Abstract
Aflatoxin, a carcinogenic secondary metabolite produced by Aspergillus flavus, is a significant threat to human health and agricultural production. Histone 2-hydroxyisobutyrylation is a novel post-translational modification that regulates various biological processes, including secondary metabolism. In this study, we identified the novel histone 2-hydroxyisobutyryltransferase Afngg1 in A. flavus, and explored its role in cell growth, development and aflatoxin biosynthesis. Afngg1 gene deletion markedly decreased lysine 2-hydroxyisobutyrylation modification of histones H4K5 and H4K8 compared with the control strain. Additionally, Afngg1 deletion inhibited mycelial growth of A. flavus, and the number of conidia and hydrophobicity were significantly decreased. Notably, aflatoxin B1 biosynthesis and sclerotia production were completely inhibited in the ΔAfngg1 strain. Furthermore, the pathogenicity of the ΔAfngg1 strain infecting peanut and corn grains was also diminished, including reduced spore production and aflatoxin biosynthesis compared with A. flavus control and Afngg1 complementation strains. Transcriptome analysis showed that, compared with control strains, differentially expressed genes in ΔAfngg1 were mainly involved in chromatin remodelling, cell development, secondary metabolism and oxidative stress. These results suggest that Afngg1 is involved in histone 2-hydroxyisobutyrylation and chromatin modification, and thus affects cell development and aflatoxin biosynthesis in A. flavus. Our results lay a foundation for in-depth research on the 2-hydroxyisobutyrylation modification in A. flavus, and may provide a novel target for aflatoxin contamination prevention.
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Affiliation(s)
- Jing Wang
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Liuke Liang
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Shan Wei
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Shuaibing Zhang
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Yuansen Hu
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Yangyong Lv
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
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9
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Lv Y, Yang H, Wang J, Wei S, Zhai H, Zhang S, Hu Y. Afper1 contributes to cell development and aflatoxin biosynthesis in Aspergillus flavus. Int J Food Microbiol 2022; 377:109828. [PMID: 35843028 DOI: 10.1016/j.ijfoodmicro.2022.109828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 06/22/2022] [Accepted: 07/02/2022] [Indexed: 11/28/2022]
Abstract
Aspergillus flavus contaminates crops and produces carcinogenic aflatoxins that pose severe threat to food safety and human health. To identify potential targets to control aflatoxin contamination, we characterized a novel Afper1 protein, which regulates cell development and secondary metabolite biosynthesis in A. flavus. Afper1 is localized in the nucleus and is required for hyphal growth, conidial and sclerotial production, and responses to osmotic stress and essential oils such as cinnamaldehyde and thymol. More importantly, aflatoxin production was impaired in the Afper1 deletion mutant. Proteomics analysis revealed that extracellular hydrolases and proteins involved in conidial development, endoplasmic reticulum (ER) homeostasis, and aflatoxin biosynthesis were differentially regulated in ΔAfper1. Unexpectedly, enzymes participated in reactive oxygen species (ROS) scavenging, including catalase (catA, catB) and superoxide dismutase (sodM) were significantly downregulated, and the ROS accumulation and sensitivity to hydrogen peroxide were confirmed experimentally. Additionally, Afper1 deletion significantly upregulated heterochromatin protein HepA and downregulated acetyltransferases involved in heterochromatin formation. Accompanying ROS accumulation and chromatin remodeling, proteins related to aflatoxins, ustiloxin B and gliotoxin were downregulated. These results implied that Afper1 deletion affected chromatin remodeling and disturbed ER homeostasis, leading to ROS accumulation, and ultimately resulting in defective growth and impaired secondary metabolite biosynthesis.
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Affiliation(s)
- Yangyong Lv
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China.
| | - Haojie Yang
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Jing Wang
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Shan Wei
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Huanchen Zhai
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Shuaibing Zhang
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Yuansen Hu
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China.
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Cho HJ, Son SH, Chen W, Son YE, Lee I, Yu JH, Park HS. Regulation of Conidiogenesis in Aspergillus flavus. Cells 2022; 11:cells11182796. [PMID: 36139369 PMCID: PMC9497164 DOI: 10.3390/cells11182796] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 08/29/2022] [Accepted: 09/06/2022] [Indexed: 11/16/2022] Open
Abstract
Aspergillus flavus is a representative fungal species in the Aspergillus section Flavi and has been used as a model system to gain insights into fungal development and toxin production. A. flavus has several adverse effects on humans, including the production of the most carcinogenic mycotoxin aflatoxins and causing aspergillosis in immune-compromised patients. In addition, A. flavus infection of crops results in economic losses due to yield loss and aflatoxin contamination. A. flavus is a saprophytic fungus that disperses in the ecosystem mainly by producing asexual spores (conidia), which also provide long-term survival in the harsh environmental conditions. Conidia are composed of the rodlet layer, cell wall, and melanin and are produced from an asexual specialized structure called the conidiophore. The production of conidiophores is tightly regulated by various regulators, including the central regulatory cascade composed of BrlA-AbaA-WetA, the fungi-specific velvet regulators, upstream regulators, and developmental repressors. In this review, we summarize the findings of a series of recent studies related to asexual development in A. flavus and provide insights for a better understanding of other fungal species in the section Flavi.
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Affiliation(s)
- He-Jin Cho
- School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea
| | - Sung-Hun Son
- School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea
| | - Wanping Chen
- Department of Molecular Microbiology and Genetics, University of Göttingen, 37077 Göttingen, Germany
| | - Ye-Eun Son
- School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea
| | - Inhyung Lee
- Department of Bio and Fermentation Convergence Technology, Kookmin University, Seoul 02707, Korea
| | - Jae-Hyuk Yu
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706, USA
- Department of Systems Biotechnology, Konkuk University, Seoul 05029, Korea
| | - Hee-Soo Park
- School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea
- Department of Integrative Biology, Kyungpook National University, Daegu 41566, Korea
- Correspondence: ; Tel.: +82-53-950-5751
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FluG and FluG-like FlrA Coregulate Manifold Gene Sets Vital for Fungal Insect-Pathogenic Lifestyle but Not Involved in Asexual Development. mSystems 2022; 7:e0031822. [PMID: 35862810 PMCID: PMC9426541 DOI: 10.1128/msystems.00318-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The central developmental pathway (CDP) activator gene brlA is activated by the upstream genes fluG and flbA–flbE in Aspergillus nidulans. Increasing evidences of fungal genome divergence make it necessary to clarify whether such genetic principles fit Pezizomycotina. Previously, fluG disruption resulted in limited conidiation defect and little effect on the expression of brlA and flbA–flbE in Beauveria bassiana possessing the other FluG-like regulator FlrA. Here, single-disruption (SD) mutants of flrA and double-disruption (DD) mutants of flrA and fluG were analyzed to clarify whether FlrA and FluG are upstream regulators of key CDP genes. Despite similar subcellular localization, no protein-protein interaction was detected between FlrA and FluG, suggesting mutual independence. Three flrA SD mutants showed phenotypes similar to those previously described for ΔfluG, including limited conidiation defect, facilitated blastospore production, impaired spore quality, blocked host infection, delayed proliferation in vivo, attenuated virulence, and increased sensitivities to multiple stresses. Three DD mutants resembled the SD mutants in all phenotypes except more compromised pathogenicity and tolerance to heat shock- or calcofluor white-induced stress. No CDP gene appeared in 1,622 and 2,234 genes dysregulated in the ΔflrA and ΔfluG mutants, respectively. The majority (up/down ratio: 540:875) of those dysregulated genes were co-upregulated or co-downregulated at similar levels in the two mutants. These findings unravel novel roles for flrA and fluG in coregulating manifold gene sets vital for fungal adaptation to insect-pathogenic lifestyle and environment but not involved in CDP activation. IMPORTANCE FluG is a core regulator upstream of central developmental pathway (CDP) in Aspergillus nidulans but multiple FluG-like regulators (FLRs) remain functionally uncharacterized in ascomycetes. Our previous study revealed no role for FluG in the CDP activation and an existence of sole FLR (FlrA) in an insect-pathogenic fungus. This study reveals a similarity of FlrA to FluG in domain architecture and subcellular localization. Experimental data from analyses of targeted single- and double-gene knockout mutants demonstrate similar roles of FrlA and FluG in stress tolerance and infection cycle but no role of either in CDP activation. Transcriptomic analyses reveal that FlrA and FluG coregulate a large number of same genes at similar levels. However, the regulated genes include no key CDP gene. These findings uncover that FlrA and FluG play similar roles in the fungal adaptation to insect-pathogenic lifestyle and environment but no role in the activation of CDP.
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12
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Yuan XY, Li JY, Zhi QQ, Chi SD, Qu S, Luo YF, He ZM. SfgA Renders Aspergillus flavus More Stable to the External Environment. J Fungi (Basel) 2022; 8:jof8060638. [PMID: 35736121 PMCID: PMC9224668 DOI: 10.3390/jof8060638] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 06/07/2022] [Accepted: 06/08/2022] [Indexed: 02/04/2023] Open
Abstract
sfgA is known as a key negative transcriptional regulator gene of asexual sporulation and sterigmatocystin production in Aspergillus nidulans. However, here, we found that the homolog sfgA gene shows a broad and complex regulatory role in governing growth, conidiation, sclerotia formation, secondary metabolism, and environmental stress responses in Aspergillus flavus. When sfgA was deleted in A. flavus, the fungal growth was slowed, but the conidiation was significantly increased, and the sclerotia formation displayed different behavior at different temperatures, which increased at 30 °C but decreased at 36 °C. In addition, sfgA regulated aflatoxin biosynthesis in a complex way that was associated with the changes in cultured conditions, and the increased production of aflatoxin in the ∆sfgA mutant was associated with a decrease in sclerotia size. Furthermore, the ∆sfgA mutant exhibited sensitivity to osmotic, oxidative, and cell wall stresses but still produced dense conidia. Transcriptome data indicated that numerous development- and secondary-metabolism-related genes were expressed differently when sfgA was deleted. Additionally, we also found that sfgA functions downstream of fluG in A. flavus, which is consistent with the genetic position in FluG-mediated conidiation in A. nidulans. Collectively, sfgA plays a critical role in the development, secondary metabolism, and stress responses of A. flavus, and sfgA renders A. flavus more stable to the external environment.
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Affiliation(s)
- Xiao-Yu Yuan
- The Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China; (X.-Y.Y.); (J.-Y.L.); (Q.-Q.Z.); (S.-D.C.); (S.Q.)
| | - Jie-Ying Li
- The Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China; (X.-Y.Y.); (J.-Y.L.); (Q.-Q.Z.); (S.-D.C.); (S.Q.)
| | - Qing-Qing Zhi
- The Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China; (X.-Y.Y.); (J.-Y.L.); (Q.-Q.Z.); (S.-D.C.); (S.Q.)
- College of Agriculture and Biology, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
| | - Sheng-Da Chi
- The Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China; (X.-Y.Y.); (J.-Y.L.); (Q.-Q.Z.); (S.-D.C.); (S.Q.)
| | - Su Qu
- The Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China; (X.-Y.Y.); (J.-Y.L.); (Q.-Q.Z.); (S.-D.C.); (S.Q.)
| | - Yan-Feng Luo
- Guangdong Jinyinshan Environmental Protection Technology Co., Ltd., Guangzhou 510705, China;
| | - Zhu-Mei He
- The Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Science, Sun Yat-sen University, Guangzhou 510275, China; (X.-Y.Y.); (J.-Y.L.); (Q.-Q.Z.); (S.-D.C.); (S.Q.)
- Correspondence:
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13
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Regulator of G Protein Signaling Contributes to the Development and Aflatoxin Biosynthesis in Aspergillus flavus through the Regulation of Gα Activity. Appl Environ Microbiol 2022; 88:e0024422. [PMID: 35638847 PMCID: PMC9238415 DOI: 10.1128/aem.00244-22] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heterotrimeric G-proteins play crucial roles in growth, asexual development, and pathogenicity of fungi. The regulator of G-protein signaling (RGS) proteins function as negative regulators of the G proteins to control the activities of GTPase in Gα subunits. In this study, we functionally characterized the six RGS proteins (i.e., RgsA, RgsB, RgsC, RgsD, RgsE, and FlbA) in the pathogenic fungus Aspergillus flavus. All the aforementioned RGS proteins were also found to be functionally different in conidiation, aflatoxin (AF) biosynthesis, and pathogenicity in A. flavus. Apart from FlbA, all other RGS proteins play a negative role in regulating both the synthesis of cyclic AMP (cAMP) and the activation of protein kinase A (PKA). Additionally, we also found that although RgsA and RgsE play a negative role in regulating the FadA-cAMP/PKA pathway, they function distinctly in aflatoxin biosynthesis. Similarly, RgsC is important for aflatoxin biosynthesis by negatively regulating the GanA-cAMP/PKA pathway. PkaA, which is the cAMP-dependent protein kinase catalytic subunit, also showed crucial influences on A. flavus phenotypes. Overall, our results demonstrated that RGS proteins play multiple roles in the development, pathogenicity, and AF biosynthesis in A. flavus through the regulation of Gα subunits and cAMP-PKA signals. IMPORTANCE RGS proteins, as crucial regulators of the G protein signaling pathway, are widely distributed in fungi, while little is known about their roles in Aspergillus flavus development and aflatoxin. In this study, we identified six RGS proteins in A. flavus and revealed that these proteins have important functions in the regulation of conidia, sclerotia, and aflatoxin formation. Our findings provide evidence that the RGS proteins function upstream of cAMP-PKA signaling by interacting with the Gα subunits (GanA and FadA). This study provides valuable information for controlling the contamination of A. flavus and mycotoxins produced by this fungus in pre- and postharvest of agricultural crops.
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Lv Y, Wang J, Yang H, Li N, Farzaneh M, Wei S, Zhai H, Zhang S, Hu Y. Lysine 2-hydroxyisobutyrylation orchestrates cell development and aflatoxin biosynthesis in Aspergillus flavus. Environ Microbiol 2022; 24:4356-4368. [PMID: 35621059 DOI: 10.1111/1462-2920.16077] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 05/17/2022] [Indexed: 11/30/2022]
Abstract
Lysine 2-hydroxyisobutyrylation (Khib ) is a recently identified post-translational modifications (PTM) that regulates numerous cellular metabolic processes. In pathogenic microorganism, although glycolysis and fungal virulence are regulated by Khib , its potential roles in fungi remains to be elusive. Our preliminary results showed that levels of Khib fluctuate over time in Aspergillus flavus, which frequently contaminates crops and produces carcinogenic aflatoxins. However, the perception of Khib function in A. flavus is limited, especially in mycotoxin-producing strains. Here, we performed a comprehensive analysis of Khib in A. flavus, and 7156 Khib sites were identified in 1473 proteins. Notably, we demonstrated that Khib of AflM, a key enzyme in aflatoxin biosynthesis, affected conidia production and sclerotia formation. Furthermore, aflM deletion impaired aflatoxin biosynthesis, and more importantly, strains in which Khib was mimicked by K to T mutation at K49, K179 and K180 sites showed reduced aflatoxin production compared with wild type and ΔaflM complementation strains. These results indicate that Khib at these sites of AflM negatively regulates aflatoxin biosynthesis in A. flavus. In summary, our study revealed the potential roles of Khib in A. flavus, and particularly shed light on a new way to regulate aflatoxin production via Khib . This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Yangyong Lv
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Jing Wang
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Haojie Yang
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Na Li
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Mohsen Farzaneh
- Department of Agriculture, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, 1983969411, Tehran, Iran
| | - Shan Wei
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Huanchen Zhai
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Shuaibing Zhang
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Yuansen Hu
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
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Yang L, Li X, Ma Y, Zhang K, Yang J. The Arf-GAP Proteins AoGcs1 and AoGts1 Regulate Mycelial Development, Endocytosis, and Pathogenicity in Arthrobotrys oligospora. J Fungi (Basel) 2022; 8:463. [PMID: 35628718 PMCID: PMC9146637 DOI: 10.3390/jof8050463] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 04/28/2022] [Accepted: 04/28/2022] [Indexed: 12/10/2022] Open
Abstract
Small GTPases from the ADP-ribosylation factor (Arf) family and their activating proteins (Arf-GAPs) regulate mycelial development, endocytosis, and virulence in fungi. Here, we identified two orthologous Arf-GAP proteins, AoGcs1 and AoGts1, in a typical nematode-trapping fungus Arthrobotrys oligospora. The transcription of Aogcs1 and Aogts1 was highly expressed in the sporulation stage. The deletion of Aogcs1 and Aogts1 caused defects in DNA damage, endocytosis, scavenging of reactive oxygen species, lipid droplet storage, mitochondrial activity, autophagy, serine protease activity, and the response to endoplasmic reticulum stress. The combined effects resulted in slow growth, decreased sporulation capacity, increased susceptibility to chemical stressors and heat shock, and decreased pathogenicity of the mutants compared with the wild-type (WT) strain. Although deletion of Aogcs1 and Aogts1 produced similar phenotfypic traits, their roles varied in conidiation and proteolytic activity. The ΔAogts1 mutant showed a remarkable reduction in conidial yield compared with the WT strain but not in proteolytic activity; in contrast, the ΔAogcs1 mutant showed an increase in proteolytic activity but not in sporulation. In addition, the growth of ΔAogcs1 and ΔAogts1 mutants was promoted by rapamycin, and the ΔAogts1 mutant was sensitive to H-89. Collectively, the ΔAogts1 mutant showed a more remarkable difference compared with the WT strain than the ΔAogcs1 mutant. Our study further illustrates the importance of Arf-GAPs in the growth, development, and pathogenicity of nematode-trapping fungi.
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Affiliation(s)
| | | | | | | | - Jinkui Yang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Key Laboratory for Southwest Microbial Diversity of the Ministry of Education, School of Life Science, Yunnan University, Kunming 650032, China; (L.Y.); (X.L.); (Y.M.); (K.Z.)
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16
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Systematic Characterization of bZIP Transcription Factors Required for Development and Aflatoxin Generation by High-Throughput Gene Knockout in Aspergillus flavus. J Fungi (Basel) 2022; 8:jof8040356. [PMID: 35448587 PMCID: PMC9031554 DOI: 10.3390/jof8040356] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/23/2022] [Accepted: 03/23/2022] [Indexed: 12/31/2022] Open
Abstract
The basic leucine zipper (bZIP) is an important transcription factor required for fungal development, nutrient utilization, biosynthesis of secondary metabolites, and defense against various stresses. Aspergillus flavus is a major producer of aflatoxin and an opportunistic fungus on a wide range of hosts. However, little is known about the role of most bZIP genes in A. flavus. In this study, we developed a high-throughput gene knockout method based on an Agrobacterium-mediated transformation system. Gene knockout construction by yeast recombinational cloning and screening of the null mutants by double fluorescence provides an efficient way to construct gene-deleted mutants for this multinucleate fungus. We deleted 15 bZIP genes in A. flavus. Twelve of these genes were identified and characterized in this strain for the first time. The phenotypic analysis of these mutants showed that the 15 bZIP genes play a diverse role in mycelial growth (eight genes), conidiation (13 genes), aflatoxin biosynthesis (10 genes), oxidative stress response (11 genes), cell wall stress (five genes), osmotic stress (three genes), acid and alkali stress (four genes), and virulence to kernels (nine genes). Impressively, all 15 genes were involved in the development of sclerotia, and the respective deletion mutants of five of them did not produce sclerotia. Moreover, MetR was involved in this biological process. In addition, HapX and MetR play important roles in the adaptation to excessive iron and sulfur metabolism, respectively. These studies provide comprehensive insights into the role of bZIP transcription factors in this aflatoxigenic fungus of global significance.
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17
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Differential Roles of Five Fluffy Genes (flbA–flbE) in the Lifecycle In Vitro and In Vivo of the Insect–Pathogenic Fungus Beauveria bassiana. J Fungi (Basel) 2022; 8:jof8040334. [PMID: 35448565 PMCID: PMC9031332 DOI: 10.3390/jof8040334] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/18/2022] [Accepted: 03/21/2022] [Indexed: 01/06/2023] Open
Abstract
The fluffy genes flbA–flbE are well-known players in the upstream developmental activation pathway that activates the key gene brlA of central developmental pathway (CDP) to initiate conidiation in Aspergillus nidulans. Here, we report insignificant roles of their orthologs in radial growth of Beauveria bassiana under normal culture conditions and different stresses although flbA and flbD were involved in respective responses to heat shock and H2O2. Aerial conidiation level was lowered in the deletion mutants of flbB and flbE (~15%) less than of flbA and flbC (~30%), in which the key CDP genes brlA and abaA were repressed consistently during normal incubation. The CDP-controlled blastospore production in submerged cultures mimicking insect hemolymph was abolished in the flbA mutant with brlA and abaA being sharply repressed, and decreased by 55% in the flbC mutant with only abaA being downregulated. The fungal virulence against a model insect was attenuated in the absence of flbA more than of flbC irrespective of normal cuticle infection or cuticle-bypassing infection (intrahemocoel injection). These findings unravel more important role of flbA than of flbC, but null roles of flbB/D/E, in B. bassiana’s insect–pathogenic lifecycle and a scenario distinctive from that in A.nidulans.
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Arunachalam D, Ramanathan SM, Menon A, Madhav L, Ramaswamy G, Namperumalsamy VP, Prajna L, Kuppamuthu D. Expression of immune response genes in human corneal epithelial cells interacting with Aspergillus flavus conidia. BMC Genomics 2022; 23:5. [PMID: 34983375 PMCID: PMC8728928 DOI: 10.1186/s12864-021-08218-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 11/18/2021] [Indexed: 12/19/2022] Open
Abstract
Background Aspergillus flavus, one of the causative agents of human fungal keratitis, can be phagocytosed by human corneal epithelial (HCE) cells and the conidia containing phagosomes mature into phagolysosomes. But the immunological responses of human corneal epithelial cells interacting with A. flavus are not clear. In this study, we report the expression of immune response related genes of HCE cells exposed to A. flavus spores using targeted transcriptomics. Methods Human corneal epithelial cell line and primary cultures were grown in a six-well plate and used for coculture experiments. Internalization of the conidia was confirmed by immunofluorescence microscopy of the colocalized endosomal markers CD71 and LAMP1. Total RNA was isolated, and the quantity and quality of the isolated RNA were assessed using Qubit and Bioanalyzer. NanoString nCounter platform was used for the analysis of mRNA abundance using the Human Immunology panel. R-package and nSolver software were used for data analysis. KEGG and FunRich 3.1.3 tools were used to analyze the differentially expressed genes. Results Different morphotypes of conidia were observed after 6 h of coculture with human corneal epithelial cells and found to be internalized by epithelial cells. NanoString profiling showed more than 20 differentially expressed genes in immortalized human corneal epithelial cell line and more than ten differentially expressed genes in primary corneal epithelial cells. Distinct set of genes were altered in their expression in cell line and primary corneal epithelial cells. KEGG pathway analysis revealed that genes associated with TNF signaling, NF-KB signaling, and Th17 signaling were up-regulated, and genes associated with chemokine signaling and B cell receptor signaling were down regulated. FunRich pathway analysis showed that pathways such as CDC42 signaling, PI3K signaling, and Arf6 trafficking events were activated by the clinical isolates CI1123 and CI1698 in both type of cells. Conclusions Combining the transcript analysis data from cell lines and primary cultures, we showed the up regulation of immune defense genes in A. flavus infected cells. At the same time, chemokine signaling and B cell signaling pathways are downregulated. The variability in the expression levels in the immortalized cell line and the primary cultures is likely due to the variable epigenetic reprogramming in the immortalized cells and primary cultures in the absence of any changes in the genome. It highlights the importance of using both cell types in host-pathogen interaction studies. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-021-08218-5.
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Affiliation(s)
- Divya Arunachalam
- Proteomics Department, Aravind Medical Research Foundation, Dr. G. Venkataswamy Eye Research Institute, Aravind Eye Care System, Madurai, Tamil Nadu, India.,Department of Biotechnology, Alagappa University, Karaikudi, Tamil Nadu, India
| | - Shruthi Mahalakshmi Ramanathan
- Proteomics Department, Aravind Medical Research Foundation, Dr. G. Venkataswamy Eye Research Institute, Aravind Eye Care System, Madurai, Tamil Nadu, India
| | - Athul Menon
- Theracues Innovations Private Limited, Bangalore, India, Karnataka
| | - Lekshmi Madhav
- Theracues Innovations Private Limited, Bangalore, India, Karnataka
| | | | | | - Lalitha Prajna
- Department of Ocular Microbiology, Aravind Eye Hospital, Aravind Eye Care System, Madurai, Tamil Nadu, India
| | - Dharmalingam Kuppamuthu
- Proteomics Department, Aravind Medical Research Foundation, Dr. G. Venkataswamy Eye Research Institute, Aravind Eye Care System, Madurai, Tamil Nadu, India. .,Department of Biotechnology, Alagappa University, Karaikudi, Tamil Nadu, India. .,Aravind Medical Research Foundation, Dr. G.Venkataswamy Eye Research Institute, Aravind Eye Care System, No.1 Anna Nagar, Madurai, Tamil Nadu, India.
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19
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Chang P, Tai B, Zheng M, Yang Q, Xing F. Inhibition of Aspergillus flavus growth and aflatoxin B1 production by natamycin. WORLD MYCOTOXIN J 2021. [DOI: 10.3920/wmj2020.2620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Aspergillus flavus causes huge crop losses, reduces crop quality and has adverse effects on human and animal health. A large amount of food contaminated with aflatoxin can greatly increase the risk of liver cancer. Therefore, prevention and control of aflatoxin production have aroused attention of research in various countries. Natamycin extracted from Streptomyces spp. has been widely used in production practice due to its good specificity and safety. Here, we found that natamycin could significantly inhibit fungal growth, conidia germination, ergosterol and AFB1 production by A. flavus in a dose-dependent manner. Scanning electron microscope analysis indicated that the number of conidia was decreased, the outer wall of conidia was destroyed, and the mycelia were shrivelled and tangled by natamycin. RNA-Seq data indicated that natamycin inhibited fungal growth and conidia development of A. flavus by significantly down-regulating some genes involved in ergosterol biosynthesis, such as Erg13, HMG1 and HMG2. It inhibited conidia germination by significantly down-regulating some genes related to conidia development, such as FluG and VosA. After natamycin exposure, the decreased ratio of aflS/aflR caused by the down-regulation of all the structural genes, which subsequently resulted in the suppression of AFB1 production. In conclusion, this study served to reveal the inhibitory mechanisms of natamycin on fungal growth and AFB1 biosynthesis in A. flavus and to provide solid evidence for its application in controlling AFB1 contamination.
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Affiliation(s)
- P. Chang
- College of Food Science and Engineering, Qingdao Agricultural University, 700 Changcheng Road, Qingdao, 266109, China P.R
| | - B. Tai
- Key Laboratory of Agro-products Quality and Safety Control in Storage and Transport Process/Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Ministry of Agriculture and Rural Affairs, Beijing 100193, China P.R
| | - M. Zheng
- College of Food Science and Engineering, Qingdao Agricultural University, 700 Changcheng Road, Qingdao, 266109, China P.R
| | - Q. Yang
- College of Food Science and Engineering, Qingdao Agricultural University, 700 Changcheng Road, Qingdao, 266109, China P.R
| | - F. Xing
- College of Food Science and Engineering, Qingdao Agricultural University, 700 Changcheng Road, Qingdao, 266109, China P.R
- Key Laboratory of Agro-products Quality and Safety Control in Storage and Transport Process/Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Ministry of Agriculture and Rural Affairs, Beijing 100193, China P.R
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Xu J, Wang P, Zhou Z, Cotty PJ, Kong Q. Selection of Atoxigenic Aspergillus flavus for Potential Use in Aflatoxin Prevention in Shandong Province, China. J Fungi (Basel) 2021; 7:jof7090773. [PMID: 34575811 PMCID: PMC8472152 DOI: 10.3390/jof7090773] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 08/13/2021] [Accepted: 09/13/2021] [Indexed: 11/17/2022] Open
Abstract
Aspergillus flavus is a common filamentous fungus widely present in the soil, air, and in crops. This facultative pathogen of both animals and plants produces aflatoxins, a group of mycotoxins with strong teratogenic and carcinogenic properties. Peanuts are highly susceptible to aflatoxin contamination and consumption of contaminated peanuts poses serious threats to the health of humans and domestic animals. Currently, the competitive displacement of aflatoxin-producers from agricultural environments by atoxigenic A. flavus is the most effective method of preventing crop aflatoxin contamination. In the current study, 47 isolates of A. flavus collected from peanut samples originating in Shandong Province were characterized with molecular methods and for aflatoxin-producing ability in laboratory studies. Isolates PA04 and PA10 were found to be atoxigenic members of the L strains morphotype. When co-inoculated with A. flavus NRRL3357 at ratios of 1:10, 1:1, and 10:1 (PA04/PA10: NRRL3357), both atoxigenic strains were able to reduce aflatoxin B1 (AFB1) levels, on both culture media and peanut kernels, by up to 90%. The extent to which atoxigenic strains reduced contamination was correlated with the inoculation ratio. Abilities to compete of PA04 and PA10 were also independently verified against local aflatoxin-producer PA37. The results suggest that the two identified atoxigenic strains are good candidates for active ingredients of biocontrol products for the prevention of aflatoxin contamination of peanuts in Shandong Province.
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Affiliation(s)
- Jia Xu
- School of Food Science and Engineering, Ocean University of China, Qingdao 266003, China; (J.X.); (P.W.); (P.J.C.)
| | - Peng Wang
- School of Food Science and Engineering, Ocean University of China, Qingdao 266003, China; (J.X.); (P.W.); (P.J.C.)
| | - Zehua Zhou
- Food Technology Department, Wageningen University & Research, 6700 AK Wageningen, The Netherlands;
| | - Peter John Cotty
- School of Food Science and Engineering, Ocean University of China, Qingdao 266003, China; (J.X.); (P.W.); (P.J.C.)
| | - Qing Kong
- School of Food Science and Engineering, Ocean University of China, Qingdao 266003, China; (J.X.); (P.W.); (P.J.C.)
- Correspondence: ; Tel.: +86-532-8203-2290; Fax: +86-532-8203-238
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21
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Guo H, Xu G, Wu R, Li Z, Yan M, Jia Z, Li Z, Chen M, Bao X, Qu Y. A Homeodomain-Containing Transcriptional Factor PoHtf1 Regulated the Development and Cellulase Expression in Penicillium oxalicum. Front Microbiol 2021; 12:671089. [PMID: 34177850 PMCID: PMC8222722 DOI: 10.3389/fmicb.2021.671089] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 05/14/2021] [Indexed: 11/13/2022] Open
Abstract
Homeodomain-containing transcription factors (Htfs) play important roles in animals, fungi, and plants during some developmental processes. Here, a homeodomain-containing transcription factor PoHtf1 was functionally characterized in the cellulase-producing fungi Penicillium oxalicum 114-2. PoHtf1 was shown to participate in colony growth and conidiation through regulating the expression of its downstream transcription factor BrlA, the key regulator of conidiation in P. oxalicum 114-2. Additionally, PoHtf1 inhibited the expression of the major cellulase genes by coordinated regulation of cellulolytic regulators CreA, AmyR, ClrB, and XlnR. Furthermore, transcriptome analysis showed that PoHtf1 participated in the secondary metabolism including the pathway synthesizing conidial yellow pigment. These data show that PoHtf1 mediates the complex transcriptional-regulatory network cascade between developmental processes and cellulolytic gene expression in P. oxalicum 114-2. Our results should assist the development of strategies for the metabolic engineering of mutants for applications in the enzymatic hydrolysis for biochemical production.
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Affiliation(s)
- Hao Guo
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Gen Xu
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Ruimei Wu
- Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhigang Li
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Mengdi Yan
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Zhilei Jia
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Zhonghai Li
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Mei Chen
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Xiaoming Bao
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China.,Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, China
| | - Yinbo Qu
- State Key Laboratory of Microbial Technology, School of Life Sciences, National Glycoengineering Research Center, Shandong University, Qingdao, China
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22
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The PHD transcription factor Cti6 is involved in the fungal colonization and aflatoxin B1 biological synthesis of Aspergillus flavus. IMA Fungus 2021; 12:12. [PMID: 34006318 PMCID: PMC8130384 DOI: 10.1186/s43008-021-00062-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 04/08/2021] [Indexed: 11/26/2022] Open
Abstract
Aspergillus flavus and its main secondary metabolite AFB1 pose a serious threat to several important crops worldwide. Recently, it has been reported that some PHD family transcription factors are involved in the morphogenesis and AFB1 biological synthesis in A. flavus, but the role of Cti6, a PHD domain containing protein in A. flavus, is totally unknown. The study was designed to reveal the biological function of Cti6 in the fungus by deletion of cti6, and its two domains (PHD and Atrophin-1) through homologous recombination, respectively. The results showed that Cti6 might up-regulate the mycelium growth, conidiation, sclerotia formation and AFB1 biological synthesis of A. flavus by its PHD domain, while Atrophin-1 also improved the conidiation of the fungus. The qRT-PCR analysis showed that Cti6 increased the conidiation of the fungus through AbaA and BrlA mediated conidiation pathway, triggered the formation of sclerotia by orthodox sclerotia formation pathway, and improved the production of AFB1 by orthodox AFB1 synthesis pathway. Crops models analysis showed that A. flavus Cti6 plays vital role in colonization and the production of AFB1 on the host grains mainly via PHD domain. Bioinformatics analysis showed Cti6 is conservative in Aspergillus spp., and mCherry mediated subcellular localization showed that most Cti6 accumulated in the nuclei, which reflected that Cti6 performed its important biological function in the nuclei in Aspergillus spp.. The results of the current study elucidate the roles of PHD domain containing proteins in the mechanism of the infection of crops by A. flavus, and provided a novel target for effectively controlling the contamination of Aspergillus spp. to crops.
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23
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Hu Z, Yuan K, Zhou Q, Lu C, Du L, Liu F. Mechanism of antifungal activity of Perilla frutescens essential oil against Aspergillus flavus by transcriptomic analysis. Food Control 2021. [DOI: 10.1016/j.foodcont.2020.107703] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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24
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Guo CT, Peng H, Tong SM, Ying SH, Feng MG. Distinctive role of fluG in the adaptation of Beauveria bassiana to insect-pathogenic lifecycle and environmental stresses. Environ Microbiol 2021; 23:5184-5199. [PMID: 33817932 DOI: 10.1111/1462-2920.15500] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/31/2021] [Accepted: 04/02/2021] [Indexed: 12/11/2022]
Abstract
The upstream developmental activation (UDA) pathway comprises three fluG-cored cascades (fluG-flbA, fluG-flbE/B/D and fluG-flbC) that activate the key gene brlA of central developmental pathway (CDP) to initiate conidiation in aspergilli. However, the core role of fluG remains poorly understood in other fungi. Here, we report distinctive role of fluG in the insect-pathogenic lifecycle of Beauveria bassiana. Disruption of fluG resulted in limited conidiation defect, which was mitigated with incubation time and associated with time-course up-regulation/down-regulation of all flb and CDP genes and another fluG-like gene (BBA_06309). In ΔfluG, increased sensitivities to various stresses correlated with repression of corresponding stress-responsive genes. Its virulence through normal cuticle infection was attenuated greatly due to blocked secretion of cuticle-degrading enzymes and delayed formation of hyphal bodies (blastospores) to accelerate proliferation in vivo and host death. In submerged ΔfluG cultures mimicking insect haemolymph, largely increased blastospore production concurred with drastic up-regulation of the CDP genes brlA and abaA, which was associated with earlier up-regulation of most flb genes in the cultures. Our results unveil an essentiality of fluG for fungal adaptation to insect-pathogenic lifecycle and suggest the other fluG-like gene to act as an alternative player in the UDA pathway of B. bassiana.
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Affiliation(s)
- Chong-Tao Guo
- MOE Laboratory of Biosystems Homeostasis & Protection, Institute of Microbiology, College of Life Sciences, Zhejiang University, Zhejiang, Hangzhou, 310058, China
| | - Han Peng
- MOE Laboratory of Biosystems Homeostasis & Protection, Institute of Microbiology, College of Life Sciences, Zhejiang University, Zhejiang, Hangzhou, 310058, China
| | - Sen-Miao Tong
- College of Agricultural and Food Science, Zhejiang A & F University, Lin'an, Zhejiang, 311300, China
| | - Sheng-Hua Ying
- MOE Laboratory of Biosystems Homeostasis & Protection, Institute of Microbiology, College of Life Sciences, Zhejiang University, Zhejiang, Hangzhou, 310058, China
| | - Ming-Guang Feng
- MOE Laboratory of Biosystems Homeostasis & Protection, Institute of Microbiology, College of Life Sciences, Zhejiang University, Zhejiang, Hangzhou, 310058, China
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25
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Li J, Zhi QQ, Zhang J, Yuan XY, Jia LH, Wan YL, Liu QY, Shi JR, He ZM. Synthetic antimicrobial agents inhibit aflatoxin production. Braz J Microbiol 2021; 52:821-835. [PMID: 33447936 DOI: 10.1007/s42770-021-00423-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 01/05/2021] [Indexed: 11/25/2022] Open
Abstract
Antimicrobial peptides (AMPs) are biologically active molecules that can eradicate bacteria by destroying the bacterial membrane structure, causing the bacteria to rupture. However, little is known about the extent and effect of AMPs on filamentous fungi. In this study, we synthesized small molecular polypeptides by an inexpensive heat conjugation approach and examined their effects on the growth of Aspergillus flavus and its secondary metabolism. The antimicrobial agents significantly inhibited aflatoxin production, conidiation, and sclerotia formation in A. flavus. Furthermore, we found that the expression of aflatoxin structural genes was significantly inhibited, and the intracellular reactive oxygen species (ROS) level was reduced. Additionally, the antimicrobial agents can change membrane permeability. Overall, our results demonstrated that antimicrobial agents, safe to mammalian cells, have an obvious impact on aflatoxin production, which indicated that antimicrobial agents may be adopted as a new generation of potential agents for controlling aflatoxin contamination.
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Affiliation(s)
- Jing Li
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Qing-Qing Zhi
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Jie Zhang
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Xiao-Yu Yuan
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Li-Hong Jia
- The Guangdong Provincial Key Laboratory for Biotechnology Drug Candidates, School of Bioscience and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou, 510006, China
| | - Yu-Lin Wan
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Qiu-Yun Liu
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China.
| | - Jian-Rong Shi
- Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Nanjing, 210000, China.
| | - Zhu-Mei He
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China.
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26
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Jun SC, Kim JH, Han KH. The Conserved MAP Kinase MpkB Regulates Development and Sporulation without Affecting Aflatoxin Biosynthesis in Aspergillus flavus. J Fungi (Basel) 2020; 6:jof6040289. [PMID: 33207581 PMCID: PMC7711526 DOI: 10.3390/jof6040289] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/12/2020] [Accepted: 11/13/2020] [Indexed: 12/20/2022] Open
Abstract
In eukaryotes, the MAP kinase signaling pathway plays pivotal roles in regulating the expression of genes required for growth, development, and stress response. Here, we deleted the mpkB gene (AFLA_034170), an ortholog of the Saccharomyces cerevisiae FUS3 gene, to characterize its function in Aspergillus flavus, a cosmopolitan, pathogenic, and aflatoxin-producing fungus. Previous studies revealed that MpkB positively regulates sexual and asexual differentiation in Aspergillus nidulans. In A. flavus, mpkB deletion resulted in an approximately 60% reduction in conidia production compared to the wild type without mycelial growth defects. Moreover, the mutant produced immature and abnormal conidiophores exhibiting vesicular dome-immaturity in the conidiophore head, decreased phialide numbers, and very short stalks. Interestingly, the ΔmpkB mutant could not produce sclerotia but produced aflatoxin B1 normally. Taken together, these results suggest that the A. flavus MpkB MAP kinase positively regulates conidiation and sclerotia formation but is not involved in the production of secondary metabolites such as aflatoxin B1.
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Affiliation(s)
| | - Jong-Hwa Kim
- Correspondence: (J.-H.K.); (K.-H.H.); Tel.: +82-63-290-1439 (J.-H.K.); +82-63-290-1427 (K.-H.H.)
| | - Kap-Hoon Han
- Correspondence: (J.-H.K.); (K.-H.H.); Tel.: +82-63-290-1439 (J.-H.K.); +82-63-290-1427 (K.-H.H.)
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27
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Ssu72 Regulates Fungal Development, Aflatoxin Biosynthesis and Pathogenicity in Aspergillus flavus. Toxins (Basel) 2020; 12:toxins12110717. [PMID: 33202955 PMCID: PMC7696088 DOI: 10.3390/toxins12110717] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 11/02/2020] [Accepted: 11/03/2020] [Indexed: 12/18/2022] Open
Abstract
The RNA polymerase II (Pol II) transcription process is coordinated by the reversible phosphorylation of its largest subunit-carboxy terminal domain (CTD). Ssu72 is identified as a CTD phosphatase with specificity for phosphorylation of Ser5 and Ser7 and plays critical roles in regulation of transcription cycle in eukaryotes. However, the biofunction of Ssu72 is still unknown in Aspergillus flavus, which is a plant pathogenic fungus and produces one of the most toxic mycotoxins-aflatoxin. Here, we identified a putative phosphatase Ssu72 and investigated the function of Ssu72 in A. flavus. Deletion of ssu72 resulted in severe defects in vegetative growth, conidiation and sclerotia formation. Additionally, we found that phosphatase Ssu72 positively regulates aflatoxin production through regulating expression of aflatoxin biosynthesis cluster genes. Notably, seeds infection assays indicated that phosphatase Ssu72 is crucial for pathogenicity of A. flavus. Furthermore, the Δssu72 mutant exhibited more sensitivity to osmotic and oxidative stresses. Taken together, our study suggests that the putative phosphatase Ssu72 is involved in fungal development, aflatoxin production and pathogenicity in A. flavus, and may provide a novel strategy to prevent the contamination of this pathogenic fungus.
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28
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Jørgensen TR, Burggraaf AM, Arentshorst M, Schutze T, Lamers G, Niu J, Kwon MJ, Park J, Frisvad JC, Nielsen KF, Meyer V, van den Hondel CA, Dyer PS, Ram AF. Identification of SclB, a Zn(II)2Cys6 transcription factor involved in sclerotium formation in Aspergillus niger. Fungal Genet Biol 2020; 139:103377. [DOI: 10.1016/j.fgb.2020.103377] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Revised: 02/07/2020] [Accepted: 02/14/2020] [Indexed: 10/24/2022]
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29
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The MAP kinase AflSlt2 modulates aflatoxin biosynthesis and peanut infection in the fungus Aspergillus flavus. Int J Food Microbiol 2020; 322:108576. [PMID: 32240921 DOI: 10.1016/j.ijfoodmicro.2020.108576] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/21/2020] [Accepted: 02/29/2020] [Indexed: 12/20/2022]
Abstract
Aflatoxin contamination in food and feed products has been brought into sharp focus over the last few decades in the world. However, there is no effective strategy for solving the problem thus far. Therefore, basic research on the aflatoxin-producer Aspergillus flavus is an urgent need. The vital role of mitogen-activated protein kinases (MAPKs) in signal transduction has been documented in various pathogenic fungi, but their functions in A. flavus have rarely been investigated. Herein, we characterized the detailed function of one of these MAPKs, AflSlt2. Targeted deletion of AflSlt2 gene indicates that this kinase is required for vegetative growth, conidia generation, and sclerotium formation. The analysis of AflSlt2 deletion mutant revealed hypersensitivity to cell wall-damaging chemicals and resistance against hydrogen peroxide. Interestingly, the ability of the ΔAflSlt2 mutant to generate aflatoxins in medium was significantly increased compared to wild type. However, a pathogenicity assay indicated that the ΔAflSlt2 mutant was deficient in peanut infection. Site-directed mutation study uncovered that the function of AflSlt2 was dependent on the phosphorylated residues (Thr-186 and Tyr-188) within the activation loop and the phosphotransfer residue (Lys-52) within the subdomain II. Interestingly, an autophosphorylation mutant of AflSlt2 (AflSlt2R66S) displayed wild type-like phenotypes. Bringing these observations together, we propose that Slt2-MAPK pathway is involved in development, stress response, aflatoxin biosynthesis, and pathogenicity in A. flavus. This study may be useful to unveil the regulation mechanism of aflatoxin biosynthesis and provide strategy to control A. flavus contamination.
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30
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Aflatoxin Biosynthesis and Genetic Regulation: A Review. Toxins (Basel) 2020; 12:toxins12030150. [PMID: 32121226 PMCID: PMC7150809 DOI: 10.3390/toxins12030150] [Citation(s) in RCA: 134] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 01/27/2020] [Accepted: 02/25/2020] [Indexed: 12/15/2022] Open
Abstract
The study of fungal species evolved radically with the development of molecular techniques and produced new evidence to understand specific fungal mechanisms such as the production of toxic secondary metabolites. Taking advantage of these technologies to improve food safety, the molecular study of toxinogenic species can help elucidate the mechanisms underlying toxin production and enable the development of new effective strategies to control fungal toxicity. Numerous studies have been made on genes involved in aflatoxin B1 (AFB1) production, one of the most hazardous carcinogenic toxins for humans and animals. The current review presents the roles of these different genes and their possible impact on AFB1 production. We focus on the toxinogenic strains Aspergillus flavus and A. parasiticus, primary contaminants and major producers of AFB1 in crops. However, genetic reports on A. nidulans are also included because of the capacity of this fungus to produce sterigmatocystin, the penultimate stable metabolite during AFB1 production. The aim of this review is to provide a general overview of the AFB1 enzymatic biosynthesis pathway and its link with the genes belonging to the AFB1 cluster. It also aims to illustrate the role of global environmental factors on aflatoxin production and the recent data that demonstrate an interconnection between genes regulated by these environmental signals and aflatoxin biosynthetic pathway.
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31
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Wang P, Chang PK, Kong Q, Shan S, Wei Q. Comparison of aflatoxin production of Aspergillus flavus at different temperatures and media: Proteome analysis based on TMT. Int J Food Microbiol 2019; 310:108313. [DOI: 10.1016/j.ijfoodmicro.2019.108313] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 08/13/2019] [Accepted: 08/23/2019] [Indexed: 01/10/2023]
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32
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Yang K, Liu Y, Wang S, Wu L, Xie R, Lan H, Fasoyin OE, Wang Y, Wang S. Cyclase-Associated Protein Cap with Multiple Domains Contributes to Mycotoxin Biosynthesis and Fungal Virulence in Aspergillus flavus. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:4200-4213. [PMID: 30916945 DOI: 10.1021/acs.jafc.8b07115] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In Aspergillus, the cyclic adenosine monophosphate (cAMP) signaling modulates asexual development and mycotoxin biosynthesis. Here, we characterize the cyclase-associated protein Cap in the pathogenic fungus Aspergillus flauvs. The cap disruption mutant exhibited dramatic reduction in hyphal growth, conidiation, and spore germination, while an enhanced production of the sclerotia was observed in this mutant. Importantly, the cap gene was found to be important for mycotoxin biosynthesis and virulence. The domain deletion study demonstrated that each domain played an important role for the Cap protein in regulating cAMP/protein kinase A (PKA) signaling, while only P1 and CARP domains were essential for the full function of Cap. The phosphorylation of Cap at S35 was identified in A. flavus, which was found to play a negligible role for the function of Cap. Overall, our results indicated that Cap with multiple domains engages in mycotoxin production and fungal pathogenicity, which could be designed as potential control targets for preventing this fungal pathogen.
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Affiliation(s)
- Kunlong Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
- School of Life Science , Jiangsu Normal University , Xuzhou , Jiangsu 221116 , People's Republic of China
| | - Yinghang Liu
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
- State Key Laboratory of Microbial Technology , Shandong University , Jinan , Shandong 250100 , People's Republic of China
| | - Sen Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
| | - Lianghuan Wu
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
| | - Rui Xie
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
| | - Huahui Lan
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
| | - Opemipo Esther Fasoyin
- Biotechnology Research Institute , Chinese Academy of Agricultural Sciences , 12 Zhongguancun South Street , Beijing 100081 , People's Republic of China
| | - Yu Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China
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33
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Iradi-Serrano M, Tola-García L, Cortese MS, Ugalde U. The Early Asexual Development Regulator fluG Codes for a Putative Bifunctional Enzyme. Front Microbiol 2019; 10:778. [PMID: 31057506 PMCID: PMC6478659 DOI: 10.3389/fmicb.2019.00778] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 03/27/2019] [Indexed: 11/13/2022] Open
Abstract
FluG is a long recognized early regulator of asexual development in Aspergillus nidulans. fluG null mutants show profuse aerial growth and no conidial production. Initial studies reported sequence homology of FluG with a prokaryotic type I glutamine synthetase, but catalytic activity has not been demonstrated. In this study, we conducted an in-depth analysis of the FluG sequence, which revealed a single polypeptide containing a putative N-terminal amidohydrolase region linked to a putative C-terminal γ-glutamyl ligase region. Each region corresponded, separately and completely, to respective single function bacterial enzymes. Separate expression of these regions confirmed that the C-terminal region was essential for asexual development. The N-terminal region alone did not support conidial development, but contributed to increased conidial production under high nutrient availability. Point mutations directed at respective key catalytic residues in each region demonstrated that they were essential for biological function. Moreover, the substitution of the N- and C-terminal regions with homologs from Lactobacillus paracasei and Pseudomonas aeruginosa, respectively, maintained functionality, albeit with altered characteristics. Taken together, the results lead us to conclude that FluG is a bifunctional enzyme that participates in an as yet unidentified metabolic or signaling pathway involving a γ-glutamylated intermediate that contributes to developmental fate.
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Affiliation(s)
| | | | | | - Unai Ugalde
- Microbial Biochemistry Laboratory, Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country, San Sebastian, Spain
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The Aspergillus flavus rtfA Gene Regulates Plant and Animal Pathogenesis and Secondary Metabolism. Appl Environ Microbiol 2019; 85:AEM.02446-18. [PMID: 30635379 DOI: 10.1128/aem.02446-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 12/31/2018] [Indexed: 02/04/2023] Open
Abstract
Aspergillus flavus is an opportunistic fungal plant and human pathogen and a producer of mycotoxins, including aflatoxin B1 (AFB1). As part of our ongoing studies to elucidate the biological functions of the A. flavus rtfA gene, we examined its role in the pathogenicity of both plant and animal model systems. rtfA encodes a putative RNA polymerase II (Pol II) transcription elongation factor previously characterized in Saccharomyces cerevisiae, Aspergillus nidulans, and Aspergillus fumigatus, where it was shown to regulate several important cellular processes, including morphogenesis and secondary metabolism. In addition, an initial study in A. flavus indicated that rtfA also influences development and production of AFB1; however, its effect on virulence is unknown. The current study reveals that the rtfA gene is indispensable for normal pathogenicity in plants when using peanut seed as an infection model, as well as in animals, as shown in the Galleria mellonella infection model. Interestingly, rtfA positively regulates several processes known to be necessary for successful fungal invasion and colonization of host tissue, such as adhesion to surfaces, protease and lipase activity, cell wall composition and integrity, and tolerance to oxidative stress. In addition, metabolomic analysis revealed that A. flavus rtfA affects the production of several secondary metabolites, including AFB1, aflatrem, leporins, aspirochlorine, ditryptophenaline, and aflavinines, supporting a role of rtfA as a global regulator of secondary metabolism. Heterologous complementation of an A. flavus rtfA deletion strain with rtfA homologs from A. nidulans or S. cerevisiae fully rescued the wild-type phenotype, indicating that these rtfA homologs are functionally conserved among these three species.IMPORTANCE In this study, the epigenetic global regulator rtfA, which encodes a putative RNA-Pol II transcription elongation factor-like protein, was characterized in the mycotoxigenic and opportunistic pathogen A. flavus Specifically, its involvement in A. flavus pathogenesis in plant and animal models was studied. Here, we show that rtfA positively regulates A. flavus virulence in both models. Furthermore, rtfA-dependent effects on factors necessary for successful invasion and colonization of host tissue by A. flavus were also assessed. Our study indicates that rtfA plays a role in A. flavus adherence to surfaces, hydrolytic activity, normal cell wall formation, and response to oxidative stress. This study also revealed a profound effect of rtfA on the metabolome of A. flavus, including the production of potent mycotoxins.
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Hua SST, Sarreal SBL, Chang PK, Yu J. Transcriptional Regulation of Aflatoxin Biosynthesis and Conidiation in Aspergillus flavus by Wickerhamomyces anomalus WRL-076 for Reduction of Aflatoxin Contamination. Toxins (Basel) 2019; 11:toxins11020081. [PMID: 30717146 PMCID: PMC6410245 DOI: 10.3390/toxins11020081] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 12/12/2018] [Accepted: 01/08/2019] [Indexed: 12/22/2022] Open
Abstract
Aspergillus flavus is a ubiquitous saprophytic fungus found in soils across the world. The fungus is the major producer of aflatoxin (AF) B₁, which is toxic and a potent carcinogen to humans. Aflatoxin B₁ (AFB₁) is often detected in agricultural crops such as corn, peanut, almond, and pistachio. It is a serious and recurrent problem and causes substantial economic losses. Wickerhamomyces anomalus WRL-076 was identified as an effective biocontrol yeast against A. flavus. In this study, the associated molecular mechanisms of biocontrol were investigated. We found that the expression levels of eight genes, aflR, aflJ, norA, omtA, omtB, pksA, vbs, and ver-1 in the aflatoxin biosynthetic pathway cluster were suppressed. The decreases ranged from several to 10,000 fold in fungal samples co-cultured with W. anomalus. Expression levels of conidiation regulatory genes brlA, abaA, and wetA as well as sclerotial regulatory gene (sclR) were all down regulated. Consistent with the decreased gene expression levels, aflatoxin concentrations in cultural medium were reduced to barely detectable. Furthermore, fungal biomass and conidial number were significantly reduced by 60% and more than 95%, respectively. The results validate the biocontrol efficacy of W. anomalus WRL-076 observed in the field experiments.
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Affiliation(s)
- Sui Sheng T Hua
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710, USA.
| | - Siov Bouy L Sarreal
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710, USA.
| | - Perng-Kuang Chang
- U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, 1100 Robert E. Boulevard, New Orleans, LA 70124, USA.
| | - Jiujiang Yu
- U.S. Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Center, Beltsville, MD 70124, USA.
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Tumukunde E, Li D, Qin L, Li Y, Shen J, Wang S, Yuan J. Osmotic-Adaptation Response of sakA/hogA Gene to Aflatoxin Biosynthesis, Morphology Development and Pathogenicity in Aspergillus flavus. Toxins (Basel) 2019; 11:toxins11010041. [PMID: 30646608 PMCID: PMC6356625 DOI: 10.3390/toxins11010041] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 12/19/2018] [Accepted: 01/11/2019] [Indexed: 02/06/2023] Open
Abstract
Aspergillus flavus is one of the fungi from the big family of Aspergillus genus and it is capable of colonizing a large number of seed/crops and living organisms such as animals and human beings. SakA (also called hogA/hog1) is an integral part of the mitogen activated protein kinase signal of the high osmolarity glycerol pathway. In this study, the AfsakA gene was deleted (∆AfsakA) then complemented (∆AfsakA::AfsakA) using homologous recombination and the osmotic stress was induced by 1.2 mol/L D-sorbital and 1.2 mol/L sodium chloride. The result showed that ∆AfsakA mutant caused a significant influence on conidial formation compared to wild-type and ∆AfsakA::AfsakA strains. It was also found that AfsakA responds to both the osmotic stress and the cell wall stress. In the absence of osmotic stress, ∆AfsakA mutant produced more sclerotia in contrast to other strains, whereas all strains failed to generate sclerotia under osmotic stress. Furthermore, the deletion of AfsakA resulted in the increase of Aflatoxin B1 production compared to other strains. The virulence assay on both maize kernel and peanut seeds showed that ∆AfsakA strain drastically produced more conidia and Aflatoxin B1 than wild-type and complementary strains. AfSakA-mCherry was located to the cytoplasm in the absence of osmotic stress, while it translocated to the nucleus upon exposure to the osmotic stimuli. This study provides new insights on the development and evaluation of aflatoxin biosynthesis and also provides better understanding on how to prevent Aspergillus infections which would be considered the first step towards the prevention of the seeds damages caused by A. flavus.
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Affiliation(s)
- Elisabeth Tumukunde
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Ding Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Ling Qin
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Yu Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Jiaojiao Shen
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Jun Yuan
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of the Ministry of Education and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Cary JW, Entwistle S, Satterlee T, Mack BM, Gilbert MK, Chang PK, Scharfenstein L, Yin Y, Calvo AM. The Transcriptional Regulator Hbx1 Affects the Expression of Thousands of Genes in the Aflatoxin-Producing Fungus Aspergillus flavus. G3 (BETHESDA, MD.) 2019; 9:167-178. [PMID: 30425054 PMCID: PMC6325891 DOI: 10.1534/g3.118.200870] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 11/09/2018] [Indexed: 12/21/2022]
Abstract
In filamentous fungi, homeobox proteins are conserved transcriptional regulators described to control conidiogenesis and fruiting body formation. Eight homeobox (hbx) genes are found in the genome of the aflatoxin-producing ascomycete, Aspergillus flavus While loss-of-function of seven of the eight genes had little to no effect on fungal growth and development, disruption of hbx1, resulted in aconidial colonies and lack of sclerotial production. Furthermore, the hbx1 mutant was unable to produce aflatoxins B1 and B2, cyclopiazonic acid and aflatrem. In the present study, hbx1 transcriptome analysis revealed that hbx1 has a broad effect on A. flavus gene expression, and the effect of hbx1 increases overtime, impacting more than five thousand protein-coding genes. Among the affected genes, those in the category of secondary metabolism (SM), followed by that of cellular transport, were the most affected. Specifically, regarding the effect of hbx1 on SM, we found that genes in 44 SM gene clusters where upregulated while 49 were downregulated in the absence of hbx1, including genes in the SM clusters responsible for the synthesis of asparasone, piperazine and aflavarin, all known to be associated with sclerotia. In addition, our study revealed that hbx1 affects the expression of other transcription factor genes involved in development, including the conidiation central regulatory pathway and flb genes.
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Affiliation(s)
- Jeffrey W Cary
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana
| | - Sarah Entwistle
- Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois
| | - Timothy Satterlee
- Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois
| | - Brian M Mack
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana
| | - Matthew K Gilbert
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana
| | - Perng K Chang
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana
| | - Leslie Scharfenstein
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana
| | - Yanbin Yin
- Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois
| | - Ana M Calvo
- Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois
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Kovač T, Šarkanj B, Crevar B, Kovač M, Lončarić A, Strelec I, Ezekiel CN, Sulyok M, Krska R. Aspergillus flavus NRRL 3251 Growth, Oxidative Status, and Aflatoxins Production Ability In Vitro under Different Illumination Regimes. Toxins (Basel) 2018; 10:E528. [PMID: 30544693 PMCID: PMC6316533 DOI: 10.3390/toxins10120528] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 12/05/2018] [Accepted: 12/06/2018] [Indexed: 12/29/2022] Open
Abstract
Aspergillus flavus is the most important mycotoxin-producing fungus involved in the global episodes of aflatoxin B₁ contamination of crops at both the pre-harvest and post-harvest stages. However, in order to effectively control aflatoxin contamination in crops using antiaflatoxigenic and/or antifungal compounds, some of which are photosensitive, a proper understanding of the photo-sensitive physiology of potential experimental strains need to be documented. The purpose of the study is therefore to evaluate the effect of visible (VIS) light illumination on growth and conidiation, aflatoxin production ability and modulation of A. flavus oxidative status during in vitro experiment. Aflatoxigenic A. flavus strain was inoculated in aflatoxin-inducing YES media and incubated under three different VIS illumination regimes during a 168 h growth period at 29 °C. VIS illumination reduced A. flavus mycelia biomass yield, both during growth on plates and in liquid media, promoted conidiation and increased the aflatoxin production. Furthermore, aflatoxin production increased with increased reactive oxidative species (ROS) levels at 96 h of growth, confirming illumination-driven oxidative stress modulation activity on A. flavus cells.
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Affiliation(s)
- Tihomir Kovač
- Department of Applied Chemistry and Ecology, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Franje Kuhača 20, Osijek 31000, Croatia.
- Center for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Life Sciences Vienna (BOKU), Konrad Lorenzstr. 20, Tulln 3430, Austria.
| | - Bojan Šarkanj
- Department of Applied Chemistry and Ecology, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Franje Kuhača 20, Osijek 31000, Croatia.
- Center for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Life Sciences Vienna (BOKU), Konrad Lorenzstr. 20, Tulln 3430, Austria.
- Department of Food technology, University North, Trg dr. Žarka Dolinara 1, Koprivnica 48000, Croatia.
| | - Biljana Crevar
- Department of Applied Chemistry and Ecology, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Franje Kuhača 20, Osijek 31000, Croatia.
| | - Marija Kovač
- Inspecto Ltd., Industrijska zona Nemetin, Vukovarska cesta 239b, Osijek 31000, Croatia.
| | - Ante Lončarić
- Department of Applied Chemistry and Ecology, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Franje Kuhača 20, Osijek 31000, Croatia.
| | - Ivica Strelec
- Department of Applied Chemistry and Ecology, Faculty of Food Technology, Josip Juraj Strossmayer University of Osijek, Franje Kuhača 20, Osijek 31000, Croatia.
| | - Chibundu N Ezekiel
- Center for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Life Sciences Vienna (BOKU), Konrad Lorenzstr. 20, Tulln 3430, Austria.
- Department of Microbiology, Babcock University, Ilishan Remo 121103, Ogun State, Nigeria.
| | - Michael Sulyok
- Center for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Life Sciences Vienna (BOKU), Konrad Lorenzstr. 20, Tulln 3430, Austria.
| | - Rudolf Krska
- Center for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Life Sciences Vienna (BOKU), Konrad Lorenzstr. 20, Tulln 3430, Austria.
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland, UK.
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Yao G, Yue Y, Fu Y, Fang Z, Xu Z, Ma G, Wang S. Exploration of the Regulatory Mechanism of Secondary Metabolism by Comparative Transcriptomics in Aspergillus flavus. Front Microbiol 2018; 9:1568. [PMID: 30131770 PMCID: PMC6090018 DOI: 10.3389/fmicb.2018.01568] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 06/25/2018] [Indexed: 12/31/2022] Open
Abstract
Mycotoxins cause a huge threaten to agriculture, food safety, and human and animal life. Among them, aflatoxins (AFs) have always been considered the most potent carcinogens, and filamentous fungi from Aspergillus genus are their major producers, especially A. flavus. Although the biosynthesis path of these chemicals had been well-identified, the regulatory mechanisms controlling expression of AF gene cluster were poorly understood. In this report, genome-wide transcriptome profiles of A. flavus from AF conducing [yeast sucrose media (YES)] and non-conducing [yeast peptone media (YEP)] conditions were compared by using deep RNA sequencing (RNA-seq), and the results revealed that AF biosynthesis pathway and biosynthesis of amino acids were significantly upregulated in YES vs. YEP. Further, a novel LaeA-like methyltransferase AFLA_121330 (Lael1) was identified for the first time, to play a specific role in the regulation of AF biosynthesis. Contrary to LaeA, which gene deletion reduced the level, lael1 deletion resulted in a significant increase in AF production. Further, co-expression network analysis revealed that mitochondrial pyruvate transport and signal peptide processing were potentially involved in AF synthesis for the first time, as well as biological processes of ribosome, branched-chain amino acid biosynthetic process and translation were co-regulated by AfRafA and AfStuA. To sum up, our analyses could provide novel insights into the molecular mechanism for controlling the AF and other secondary metabolite synthesis, adding novel targets for plant breeding and making fungicides.
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Affiliation(s)
- Guangshan Yao
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yuewei Yue
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yishi Fu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhou Fang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhangling Xu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Genli Ma
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
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Zhang F, Geng L, Huang L, Deng J, Fasoyin OE, Yao G, Wang S. Contribution of peroxisomal protein importer AflPex5 to development and pathogenesis in the fungus Aspergillus flavus. Curr Genet 2018; 64:1335-1348. [PMID: 29869688 DOI: 10.1007/s00294-018-0851-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 05/31/2018] [Accepted: 06/01/2018] [Indexed: 10/14/2022]
Abstract
Peroxisomes are important organelles that have diverse metabolic functions and participate in the pathogenicity of fungal pathogens. Previous studies indicate that most functions of peroxisomes are dependent on peroxisomal matrix proteins, which are delivered from the cytoplasm into peroxisomes by peroxisomal protein importers. In this study, the roles of peroxisomal protein importer AflPex5 were investigated in Aspergillus flavus with the application of gene disruption. AflPex5 deletion mutants failed to localize the fluorescently fused peroxisomal targeting signal 1 (PTS1) proteins to peroxisomes. Deletion of AflPex5 caused defects in sporulation, sclerotial formation, aflatoxin biosynthesis, stress response, and plant infection. Moreover, AflPex5 null mutants exhibited a significant defect in carbon metabolism and oxidants' clearance. These results indicate that the PTS1 pathway mediated by AflPex5 serves as an important role in the development, metabolism, and pathogenesis of A. flavus.
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Affiliation(s)
- Feng Zhang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Longpo Geng
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Luhua Huang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jili Deng
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Opemipo Esther Fasoyin
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guangshan Yao
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.
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Chang PK, Zhang Q, Scharfenstein L, Mack B, Yoshimi A, Miyazawa K, Abe K. Aspergillus flavus GPI-anchored protein-encoding ecm33 has a role in growth, development, aflatoxin biosynthesis, and maize infection. Appl Microbiol Biotechnol 2018; 102:5209-5220. [DOI: 10.1007/s00253-018-9012-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 12/21/2022]
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Liu Y, Yang K, Qin Q, Lin G, Hu T, Xu Z, Wang S. G Protein α Subunit GpaB is Required for Asexual Development, Aflatoxin Biosynthesis and Pathogenicity by Regulating cAMP Signaling in Aspergillus flavus. Toxins (Basel) 2018. [PMID: 29534423 PMCID: PMC5869405 DOI: 10.3390/toxins10030117] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The heterotrimeric G proteins are critical for signal transduction and function in numerous biological processes including vegetative growth, asexual development and fungal virulence in fungi. Here, we identified four G protein alpha subunits (GanA, GpaB, FadA and GaoC) in the notorious Aflatoxin-producing fungus Aspergillus flavus. GanA, GpaB and FadA have homologues in other fungal species, while GaoC is a novel one. Here, we showed that the loss function of gpaB displayed a defect in conidiophore formation and considerably reduced expression levels of conidia-specific genes brlA and abaA. A decreased viability of cell wall integrity stress and oxidative stress were also found in the ∆gpaB mutant. More importantly, aflatoxin (AF) biosynthesis and infection on crop seeds were severely impaired in the gpaB-deficient mutant. Further analyses demonstrated that the intracellular cAMP levels significantly reduced in the gpaB-deficient mutant compared to wildtype strains. Additionally, an alteration of PKA activities in the ∆gpaB mutant was also found. Overall, our results indicated that GpaB played diverse roles in asexual sporulation, AF biosynthesis and virulence by regulating cAMP signaling in Aspergillus flavus.
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Affiliation(s)
- Yinghang Liu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Kunlong Yang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Qiuping Qin
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
- Xiamen Anjie Medical Data Technology Co. Ltd., Xiamen 361115, China.
| | - Guinan Lin
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Tianran Hu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Zhangling Xu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Shihua Wang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Bhatnagar D, Rajasekaran K, Gilbert M, Cary J, Magan N. Advances in molecular and genomic research to safeguard food and feed supply from aflatoxin contamination. WORLD MYCOTOXIN J 2018. [DOI: 10.3920/wmj2017.2283] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Worldwide recognition that aflatoxin contamination of agricultural commodities by the fungus Aspergillus flavus is a global problem has significantly benefitted from global collaboration for understanding the contaminating fungus, as well as for developing and implementing solutions against the contamination. The effort to address this serious food and feed safety issue has led to a detailed understanding of the taxonomy, ecology, physiology, genomics and evolution of A. flavus, as well as strategies to reduce or control pre-harvest aflatoxin contamination, including (1) biological control, using atoxigenic aspergilli, (2) proteomic and genomic analyses for identifying resistance factors in maize as potential breeding markers to enable development of resistant maize lines, and (3) enhancing host-resistance by bioengineering of susceptible crops, such as cotton, maize, peanut and tree nuts. A post-harvest measure to prevent the occurrence of aflatoxin contamination in storage is also an important component for reducing exposure of populations worldwide to aflatoxins in food and feed supplies. The effect of environmental changes on aflatoxin contamination levels has recently become an important aspect for study to anticipate future contamination levels. The ability of A. flavus to produce dozens of secondary metabolites, in addition to aflatoxins, has created a new avenue of research for understanding the role these metabolites play in the survival and biodiversity of this fungus. The understanding of A. flavus, the aflatoxin contamination problem, and control measures to prevent the contamination has become a unique example for an integrated approach to safeguard global food and feed safety.
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Affiliation(s)
- D. Bhatnagar
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - K. Rajasekaran
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - M. Gilbert
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - J.W. Cary
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - N. Magan
- Applied Mycology Group, Cranfield University, MK45 4DT, Cranfield, United Kingdom
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Ren S, Yang M, Yue Y, Ge F, Li Y, Guo X, Zhang J, Zhang F, Nie X, Wang S. Lysine Succinylation Contributes to Aflatoxin Production and Pathogenicity in Aspergillus flavus. Mol Cell Proteomics 2018; 17:457-471. [PMID: 29298838 PMCID: PMC5836371 DOI: 10.1074/mcp.ra117.000393] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/11/2017] [Indexed: 12/27/2022] Open
Abstract
Aspergillus flavus (A. flavus) is a ubiquitous saprophytic and pathogenic fungus that produces the aflatoxin carcinogen, and A. flavus can have tremendous economic and health impacts worldwide. Increasing evidence demonstrates that lysine succinylation plays an important regulatory role in metabolic processes in both bacterial and human cells. However, little is known about the extent and function of lysine succinylation in A. flavus. Here, we performed a global succinylome analysis of A. flavus using high accuracy nano-LC-MS/MS in combination with the enrichment of succinylated peptides from digested cell lysates and subsequent peptide identification. In total, 985 succinylation sites on 349 succinylated proteins were identified in this pathogen. Bioinformatics analysis revealed that the succinylated proteins were involved in various biological processes and were particularly enriched in the aflatoxin biosynthesis process. Site-specific mutagenesis and biochemical studies showed that lysine succinylation on the norsolorinic acid reductase NorA (AflE), a key enzyme in aflatoxins biosynthesis, can affect the production of sclerotia and aflatoxins biosynthesis in A. flavus. Together, our findings reveal widespread roles for lysine succinylation in regulating metabolism and aflatoxins biosynthesis in A. flavus. Our data provide a rich resource for functional analyses of lysine succinylation and facilitate the dissection of metabolic networks in this pathogen.
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Affiliation(s)
- Silin Ren
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Mingkun Yang
- §Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Yuewei Yue
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Feng Ge
- §Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Yu Li
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Xiaodong Guo
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Jia Zhang
- §Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Feng Zhang
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Xinyi Nie
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Shihua Wang
- From the ‡Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China;
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Yao G, Zhang F, Nie X, Wang X, Yuan J, Zhuang Z, Wang S. Essential APSES Transcription Factors for Mycotoxin Synthesis, Fungal Development, and Pathogenicity in Aspergillus flavus. Front Microbiol 2017; 8:2277. [PMID: 29209291 PMCID: PMC5702001 DOI: 10.3389/fmicb.2017.02277] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 11/06/2017] [Indexed: 02/04/2023] Open
Abstract
Aflatoxins are a potent carcinogenic mycotoxin and has become a research model of fungal secondary metabolism (SM). Via systematically investigating the APSES transcription factors (TFs), two APSES proteins were identified: AfRafA and AfStuA. These play central roles in the synthesis of mycotoxins including aflatoxin and cyclopiazonic acid, and fungal development and are consequently central to the pathogenicity of the aflatoxigenic A. flavus. Loss of AfRafA not only dramatically suppressed aflatoxin cluster expression, subsequently reducing toxin synthesis both in vitro and in vivo, but also impaired conidia and sclerotia development. More importantly, aflatoxin biosynthesis as well as conidia and sclerotia development were fully blocked in ΔAfStuA. In addition, our results supported that AfStuA regulated the aflatoxin synthesis in an AflR-dependent manner. Intriguingly, it was revealed that AfRafA and AfStuA exert an antagonistic role in the regulation of biosynthesis of cyclopiazonic acid. In summary, two global transcriptional regulators for fungal development, mycotoxin production, and seed pathogenicity of the A. flavus system have been established. The two novel regulators of mycotoxins are promising targets for future plant breeding and for the development of fungicides.
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Affiliation(s)
- Guangshan Yao
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Feng Zhang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xinyi Nie
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiuna Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jun Yuan
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhenhong Zhuang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
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The Aspergillus flavus Homeobox Gene, hbx1, is Required for Development and Aflatoxin Production. Toxins (Basel) 2017; 9:toxins9100315. [PMID: 29023405 PMCID: PMC5666362 DOI: 10.3390/toxins9100315] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 10/06/2017] [Accepted: 10/09/2017] [Indexed: 11/17/2022] Open
Abstract
Homeobox proteins, a class of well conserved transcription factors, regulate the expression of targeted genes, especially those involved in development. In filamentous fungi, homeobox genes are required for normal conidiogenesis and fruiting body formation. In the present study, we identified eight homeobox (hbx) genes in the aflatoxin-producing ascomycete, Aspergillus flavus, and determined their respective role in growth, conidiation and sclerotial production. Disruption of seven of the eight genes had little to no effect on fungal growth and development. However, disruption of the homeobox gene AFLA_069100, designated as hbx1, in two morphologically different A. flavus strains, CA14 and AF70, resulted in complete loss of production of conidia and sclerotia as well as aflatoxins B1 and B2, cyclopiazonic acid and aflatrem. Microscopic examination showed that the Δhbx1 mutants did not produce conidiophores. The inability of Δhbx1 mutants to produce conidia was related to downregulation of brlA (bristle) and abaA (abacus), regulatory genes for conidiophore development. These mutants also had significant downregulation of the aflatoxin pathway biosynthetic genes aflC, aflD, aflM and the cluster-specific regulatory gene, aflR. Our results demonstrate that hbx1 not only plays a significant role in controlling A. flavus development but is also critical for the production of secondary metabolites, such as aflatoxins.
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Pfannenstiel BT, Zhao X, Wortman J, Wiemann P, Throckmorton K, Spraker JE, Soukup AA, Luo X, Lindner DL, Lim FY, Knox BP, Haas B, Fischer GJ, Choera T, Butchko RAE, Bok JW, Affeldt KJ, Keller NP, Palmer JM. Revitalization of a Forward Genetic Screen Identifies Three New Regulators of Fungal Secondary Metabolism in the Genus Aspergillus. mBio 2017; 8:e01246-17. [PMID: 28874473 PMCID: PMC5587912 DOI: 10.1128/mbio.01246-17] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/08/2017] [Indexed: 11/24/2022] Open
Abstract
The study of aflatoxin in Aspergillus spp. has garnered the attention of many researchers due to aflatoxin's carcinogenic properties and frequency as a food and feed contaminant. Significant progress has been made by utilizing the model organism Aspergillus nidulans to characterize the regulation of sterigmatocystin (ST), the penultimate precursor of aflatoxin. A previous forward genetic screen identified 23 A. nidulans mutants involved in regulating ST production. Six mutants were characterized from this screen using classical mapping (five mutations in mcsA) and complementation with a cosmid library (one mutation in laeA). The remaining mutants were backcrossed and sequenced using Illumina and Ion Torrent sequencing platforms. All but one mutant contained one or more sequence variants in predicted open reading frames. Deletion of these genes resulted in identification of mutant alleles responsible for the loss of ST production in 12 of the 17 remaining mutants. Eight of these mutations were in genes already known to affect ST synthesis (laeA, mcsA, fluG, and stcA), while the remaining four mutations (in laeB, sntB, and hamI) were in previously uncharacterized genes not known to be involved in ST production. Deletion of laeB, sntB, and hamI in A. flavus results in loss of aflatoxin production, confirming that these regulators are conserved in the aflatoxigenic aspergilli. This report highlights the multifaceted regulatory mechanisms governing secondary metabolism in Aspergillus Additionally, these data contribute to the increasing number of studies showing that forward genetic screens of fungi coupled with whole-genome resequencing is a robust and cost-effective technique.IMPORTANCE In a postgenomic world, reverse genetic approaches have displaced their forward genetic counterparts. The techniques used in forward genetics to identify loci of interest were typically very cumbersome and time-consuming, relying on Mendelian traits in model organisms. The current work was pursued not only to identify alleles involved in regulation of secondary metabolism but also to demonstrate a return to forward genetics to track phenotypes and to discover genetic pathways that could not be predicted through a reverse genetics approach. While identification of mutant alleles from whole-genome sequencing has been done before, here we illustrate the possibility of coupling this strategy with a genetic screen to identify multiple alleles of interest. Sequencing of classically derived mutants revealed several uncharacterized genes, which represent novel pathways to regulate and control the biosynthesis of sterigmatocystin and of aflatoxin, a societally and medically important mycotoxin.
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Affiliation(s)
| | - Xixi Zhao
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Jennifer Wortman
- Genome Sequencing and Analysis Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Philipp Wiemann
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kurt Throckmorton
- Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Joseph E Spraker
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Alexandra A Soukup
- Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Xingyu Luo
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Daniel L Lindner
- Center for Forest Mycology Research, Northern Research Station, U.S. Forest Service, Madison, Wisconsin, USA
| | - Fang Yun Lim
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Benjamin P Knox
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Brian Haas
- Genome Sequencing and Analysis Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Gregory J Fischer
- Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Tsokyi Choera
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Robert A E Butchko
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, USA
| | - Jin-Woo Bok
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Katharyn J Affeldt
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jonathan M Palmer
- Center for Forest Mycology Research, Northern Research Station, U.S. Forest Service, Madison, Wisconsin, USA
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Liang L, Liu Y, Yang K, Lin G, Xu Z, Lan H, Wang X, Wang S. The Putative Histone Methyltransferase DOT1 Regulates Aflatoxin and Pathogenicity Attributes in Aspergillus flavus. Toxins (Basel) 2017; 9:toxins9070232. [PMID: 28737735 PMCID: PMC5535179 DOI: 10.3390/toxins9070232] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 07/20/2017] [Accepted: 07/20/2017] [Indexed: 12/14/2022] Open
Abstract
Lysine methyltransferases transfer methyl groups in specific lysine sites, which regulates a variety of important biological processes in eukaryotes. In this study, we characterized a novel homolog of the yeast methyltransferase DOT1 in A. flavus, and observed the roles of dot1 in A. flavus. Deletion of dot1 showed a significant decrease in conidiation, but an increase in sclerotia formation. A change in viability to multiple stresses was also found in the Δdot1 mutant. Additionally, aflatoxin (AF) production was found severely impaired in the Δdot1 mutant. Further analysis by qRT-PCR revealed that the transcription of AF structural genes and their regulator gene aflS were prominently suppressed in the Δdot1 mutant. Furthermore, our data revealed that Dot1 is important for colonizing maize seeds in A. flavus. Our research indicates that Dot1 is involved in fungal development, aflatoxin biosynthesis and fungal virulence in A. flavus, which might provide a potential target for controlling A. flavus with new strategies.
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Affiliation(s)
- Linlin Liang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Yinghang Liu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Kunlong Yang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Guinan Lin
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Zhangling Xu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Huahui Lan
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Xiuna Wang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Shihua Wang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Ren S, Yue Y, Li Y, Guo X, Wang S. Functional analyses of the versicolorin B synthase gene in Aspergillus flavus. Microbiologyopen 2017; 6. [PMID: 28612469 PMCID: PMC5552937 DOI: 10.1002/mbo3.471] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 01/26/2017] [Accepted: 02/08/2017] [Indexed: 02/06/2023] Open
Abstract
Aflatoxin is a toxic, carcinogenic mycotoxin primarily produced by Aspergillus parasiticus and Aspergillus flavus. Previous studies have predicted the existence of more than 20 genes in the gene cluster involved in aflatoxin biosynthesis. Among these genes, aflK encodes versicolorin B synthase, which converts versiconal to versicolorin B. Past research has investigated aflK in A. parasiticus, but few studies have characterized aflK in the animal, plant, and human pathogen A. flavus. To understand the potential role of aflK in A. flavus, its function was investigated here for the first time using gene replacement and gene complementation strategies. The aflK deletion-mutant ΔaflK exhibited a significant decrease in sclerotial production and aflatoxin biosynthesis compared with wild-type and the complementation strain ΔaflK::aflK. ΔaflK did not affect the ability of A. flavus to infect seeds, but downregulated aflatoxin production after seed infection. This is the first report of a relationship between aflK and sclerotial production in A. flavus, and our findings indicate that aflK regulates aflatoxin formation.
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Affiliation(s)
- Silin Ren
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yuewei Yue
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yu Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaodong Guo
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
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50
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Zhi QQ, Li JY, Liu QY, He ZM. A cytosine methyltransferase ortholog dmtA is involved in the sensitivity of Aspergillus flavus to environmental stresses. Fungal Biol 2017; 121:501-514. [DOI: 10.1016/j.funbio.2017.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 01/21/2017] [Accepted: 02/01/2017] [Indexed: 01/05/2023]
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