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Qin L, Li D, Zhao J, Yang G, Wang Y, Yang K, Tumukunde E, Wang S, Yuan J. The membrane mucin Msb2 regulates aflatoxin biosynthesis and pathogenicity in fungus Aspergillus flavus. Microb Biotechnol 2020; 14:628-642. [PMID: 33159717 PMCID: PMC7936294 DOI: 10.1111/1751-7915.13701] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 10/17/2020] [Accepted: 10/20/2020] [Indexed: 12/12/2022] Open
Abstract
As a pathogenic fungus, Aspergillus flavus can produce carcinogenic aflatoxins (AFs), which poses a great threat to crops and animals. Msb2, the signalling mucin protein, is a part of mitogen‐activated protein kinase (MAPK) pathway which contributes to a range of physiological processes. In this study, the roles of membrane mucin Msb2 were explored in A. flavus by the application of gene disruption. The deletion of msb2 gene (Δmsb2) caused defects in vegetative growth, sporulation and sclerotia formation when compared to WT and complement strain (Δmsb2C) in A. flavus. Using thin‐layer chromatography (TLC) and high‐performance liquid chromatography (HPLC) analysis, it was found that deletion of msb2 down‐regulated aflatoxin B1 (AFB1) synthesis and decreased the infection capacity of A. flavus. Consistently, Msb2 responds to cell wall stress and osmotic stress by positively regulating the phosphorylation of MAP kinase. Notably, Δmsb2 mutant exhibited cell wall defect, and it was more sensitive to inhibitor caspofungin when compared to WT and Δmsb2C. Taking together, these results revealed that Msb2 plays key roles in morphological development process, stresses adaptation, secondary metabolism and pathogenicity in fungus A. flavus.
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Affiliation(s)
- Ling Qin
- 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, 350002, China
| | - Ding Li
- 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, 350002, China
| | - Jiaru Zhao
- 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, 350002, China
| | - Guang Yang
- 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, 350002, China
| | - Yinchun 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, 350002, China
| | - Kunlong Yang
- 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, 350002, China
| | - Elisabeth Tumukunde
- 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, 350002, 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, 350002, 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, 350002, China
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2
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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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Zhao Q, Qiu Y, Wang X, Gu Y, Zhao Y, Wang Y, Yue T, Yuan Y. Inhibitory Effects of Eurotium cristatum on Growth and Aflatoxin B 1 Biosynthesis in Aspergillus flavus. Front Microbiol 2020; 11:921. [PMID: 32477315 PMCID: PMC7242626 DOI: 10.3389/fmicb.2020.00921] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 04/17/2020] [Indexed: 12/20/2022] Open
Abstract
Probiotic strain Eurotium cristatum was isolated from Chinese Fuzhuan brick-tea and tested for its in vitro activity against aflatoxigenic Aspergillus flavus. Results indicated that E. cristatum can inhibit the radial growth of A. flavus. Furthermore, this inhibition might be caused by E. cristatum secondary metabolites. The ability of culture filtrate of strain E. cristatum against growth and aflatoxin B1 production by toxigenic A. flavus was evaluated in vitro. Meanwhile, the influence of filtrate on spore morphology of A. flavus was analyzed by scanning electron microscopy (SEM). Results demonstrated that both radial growth of A. flavus and aflatoxin B1 production were significantly weakened following increases in the E. cristatum culture filtrate concentration. In addition, SEM showed that the culture filtrate seriously damaged hyphae morphology. Gas chromatography mass spectrometry (GC/MS) analysis of the E. cristatum culture supernatant revealed the presence of multiple antifungal compounds. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis showed that the expression of aflatoxin biosynthesis-related genes (aflD, aflQ, and aflS) were down-regulated. Importantly, this latter occurrence resulted in a reduction of the AflS/AflR ratio. Interestingly, cell-free supernatants of E. cristatum facilitated the effective degradation of aflatoxin B1. In addition, two degradation products of aflatoxin B1 lacking the toxic and carcinogenic lactone ring were identified. A toxicity study on the HepG2 cells showed that the degradation compounds were less toxic when compared with AFB1.
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Affiliation(s)
- Qiannan Zhao
- College of Food Science and Engineering, Northwest A&F University, Yangling, China.,Laboratory of Quality & Safety Risk Assessment for Agro-products, Ministry of Agriculture, Yangling, China
| | - Yue Qiu
- College of Food Science and Engineering, Northwest A&F University, Yangling, China.,Laboratory of Quality & Safety Risk Assessment for Agro-products, Ministry of Agriculture, Yangling, China
| | - Xin Wang
- College of Food Science and Engineering, Northwest A&F University, Yangling, China.,Laboratory of Quality & Safety Risk Assessment for Agro-products, Ministry of Agriculture, Yangling, China
| | - Yuanyuan Gu
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Yuzhu Zhao
- College of Food Science and Technology, Northwest University, Xi'an, China
| | - Yidi Wang
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Tianli Yue
- College of Food Science and Engineering, Northwest A&F University, Yangling, China.,Laboratory of Quality & Safety Risk Assessment for Agro-products, Ministry of Agriculture, Yangling, China.,College of Food Science and Technology, Northwest University, Xi'an, China.,College of Enology, Northwest A&F University, Yangling, China
| | - Yahong Yuan
- College of Food Science and Engineering, Northwest A&F University, Yangling, China.,Laboratory of Quality & Safety Risk Assessment for Agro-products, Ministry of Agriculture, Yangling, China
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Rahnama M, Maclean P, Fleetwood DJ, Johnson RD. VelA and LaeA are Key Regulators of Epichloë festucae Transcriptomic Response during Symbiosis with Perennial Ryegrass. Microorganisms 2019; 8:microorganisms8010033. [PMID: 31878026 PMCID: PMC7023048 DOI: 10.3390/microorganisms8010033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 12/20/2019] [Accepted: 12/20/2019] [Indexed: 12/29/2022] Open
Abstract
VelA (or VeA) is a key global regulator in fungal secondary metabolism and development which we previously showed is required during the symbiotic interaction of Epichloë festucae with perennial ryegrass. In this study, comparative transcriptomic analyses of ∆velA mutant compared to wild-type E. festucae, under three different conditions (in culture, infected seedlings, and infected mature plants), were performed to investigate the impact of VelA on E. festucae transcriptome. These comparative transcriptomic studies showed that VelA regulates the expression of genes encoding proteins involved in membrane transport, fungal cell wall biosynthesis, host cell wall degradation, and secondary metabolism, along with a number of small secreted proteins and a large number of proteins with no predictable functions. In addition, these results were compared with previous transcriptomic experiments that studied the impact of LaeA, another key global regulator of secondary metabolism and development that we have shown is important for E. festucae–perennial ryegrass interaction. The results showed that although VelA and LaeA regulate a subset of E. festucae genes in a similar manner, they also regulated many other genes independently of each other suggesting specialised roles.
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Affiliation(s)
- Mostafa Rahnama
- AgResearch, Grasslands Research Centre, Palmerston North 4442, New Zealand; (P.M.); (D.J.F.)
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Correspondence: (M.R.); (R.D.J.)
| | - Paul Maclean
- AgResearch, Grasslands Research Centre, Palmerston North 4442, New Zealand; (P.M.); (D.J.F.)
| | - Damien J. Fleetwood
- AgResearch, Grasslands Research Centre, Palmerston North 4442, New Zealand; (P.M.); (D.J.F.)
- Biotelliga Ltd, Auckland 1052, New Zealand
| | - Richard D. Johnson
- AgResearch, Grasslands Research Centre, Palmerston North 4442, New Zealand; (P.M.); (D.J.F.)
- Correspondence: (M.R.); (R.D.J.)
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Effect of allyl isothiocyanate on transcriptional profile, aflatoxin synthesis, and Aspergillus flavus growth. Food Res Int 2019; 128:108786. [PMID: 31955757 DOI: 10.1016/j.foodres.2019.108786] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 10/18/2019] [Accepted: 10/28/2019] [Indexed: 12/19/2022]
Abstract
The goals of this study were to determine the efficacy of allyl isothiocyanate (AITC) against the growth of A. flavus and Aflatoxin B1 (AFB1) production as well as to evaluate changes in the transcriptome profile when colonizing maize. A. flavus was inoculated in potato dextrose agar (PDA), the plates were placed inside glass jars and the mycelial growth (MG) was monitored for 7 d. Likewise, maize grains were contaminated with A. flavus in glass jars of 1 L and treated with 0.125, 0.25, 0.5, 1 and 5 µL of AITC. The moisture content (MC) of grains was 15 and 21%. After 7 days of storage, the MG was significantly reduced in doses higher than 0.125 µL/L of AITC. All doses of AITC reduced significantly the fungal growth and AFB1 production in maize after 30 d, regardless of MC. The transcriptional changes caused by AITC treatment showed significant overexpression for environmental and global transcription factors. These results suggest that AITC could be used as a fumigant to avoid the growth of A. flavus and the production of AFB1, moreover, confirm transcriptional alteration of genes involved in AFB1 and other processes key for normal fungal growth and development.
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Lv C, Jin J, Wang P, Dai X, Liu Y, Zheng M, Xing F. Interaction of water activity and temperature on the growth, gene expression and aflatoxin production by Aspergillus flavus on paddy and polished rice. Food Chem 2019; 293:472-478. [PMID: 31151636 DOI: 10.1016/j.foodchem.2019.05.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 04/15/2019] [Accepted: 05/01/2019] [Indexed: 10/26/2022]
Abstract
Water activity (aw) and temperature are two pivotal environmental factors affecting Aspergillus flavus growth and aflatoxin production. Here, we found that AFB1 production on polished rice can occur over a wider range of temperature × aw levels than that on paddies. For fungal growth on polished rice, the optimum conditions were aw 0.92-0.96 and 28-37 °C. The maximum amounts of AFB1 on polished rice was observed at 33 °C and aw 0.96. Compared to 33 °C, all tested genes of A. flavus on polished rice were significantly up-regulated at 25 °C under aw 0.96. The late structural genes of pathway were significantly down-regulated at 37 °C under aw 0.96, although aflR and aflS and most of early structural genes were up-regulated. Compared to aw 0.96, most of pathway genes were significantly down-regulated at aw 0.90 and 0.99 under 33 °C, although two regulatory genes were up-regulated at aw 0.90.
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Affiliation(s)
- Cong Lv
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China
| | - Jing Jin
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China
| | - Ping Wang
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China
| | - Xiaofeng Dai
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China
| | - Yang Liu
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China.
| | - Mumin Zheng
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China
| | - Fuguo Xing
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, PR China.
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Wang DY, Tong SM, Guan Y, Ying SH, Feng MG. The velvet protein VeA functions in asexual cycle, stress tolerance and transcriptional regulation of Beauveria bassiana. Fungal Genet Biol 2019; 127:1-11. [PMID: 30807832 DOI: 10.1016/j.fgb.2019.02.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 02/14/2019] [Accepted: 02/21/2019] [Indexed: 10/27/2022]
Abstract
VeA is a key velvet protein that regulates sexual/asexual development and secondary metabolism in filamentous fungi, particularly Aspergilli, but has not been explored yet in asexual insect mycopathogens, such as Beauveria bassiana. Here, we report a localization of B. bassiana VeA in the cytoplasm of hyphal cells exposed to either light or dark cue and its migration to the nucleus only in darkness. Deletion of veA resulted in facilitated hyphal growth and decreased cell length on rich media, light growth defects on scant media, and increased sensitivities to oxidation, high osmolarity and prolonged heat shock during colony growth. Compared to wild-type, the deletion mutant was much more triggered in conidiation at optimal 25 °C in darkness than in a light/dark (L:D) cycle of 12:12, indicating the role of VeA acting as a negative regulator of conidiation in a light-dependent manner. The mutant conidia produced at L:D 12:12 showed defects in germination, thermotolerance and UVB resistance but no change in virulence, contrasting to attenuated virulence for the mutant conidia produced in darkness. Intriguingly, fungal outgrowth and conidiation were markedly suppressed on the surfaces of the mutant-mummified insect cadavers, suggesting a significant role of VeA in fungal survival, dispersal and prevalence in host habitats. Transcriptomic analysis revealed 1248 and 1183 differentially expressed genes in the deletion mutant versus wild-type grown at L:D 0:24 and 12:12 respectively, including those involved in central developmental pathway and secondary metabolism. Altogether, VeA is functionally involved in asexual cycle, stress tolerance and transcriptional regulation of B. bassiana.
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Affiliation(s)
- Ding-Yi Wang
- MOE Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Sen-Miao Tong
- MOE Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China; College of Agricultural and Food Science, Zhejiang A&F University, Lin'an, Zhejiang 311300, China.
| | - Yi Guan
- MOE Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China; Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou University, Fuzhou, Fujian 350108, China
| | - Sheng-Hua Ying
- MOE Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Ming-Guang Feng
- MOE Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China.
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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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Eshelli M, Qader MM, Jambi EJ, Hursthouse AS, Rateb ME. Current Status and Future Opportunities of Omics Tools in Mycotoxin Research. Toxins (Basel) 2018; 10:E433. [PMID: 30373184 PMCID: PMC6267353 DOI: 10.3390/toxins10110433] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 10/20/2018] [Accepted: 10/24/2018] [Indexed: 12/12/2022] Open
Abstract
Mycotoxins are toxic secondary metabolites of low molecular weight produced by filamentous fungi, such as Aspergillus, Fusarium, and Penicillium spp. Mycotoxins are natural contaminants of agricultural commodities and their prevalence may increase due to global warming. Dangerous mycotoxins cause a variety of health problems not only for humans, but also for animals. For instance, they possess carcinogenic, immunosuppressive, hepatotoxic, nephrotoxic, and neurotoxic effects. Hence, various approaches have been used to assess and control mycotoxin contamination. Significant challenges still exist because of the complex heterogeneous nature of food composition. The potential of combined omics approaches such as metabolomics, genomics, transcriptomics, and proteomics would contribute to our understanding about pathogen fungal crosstalk as well as strengthen our ability to identify, isolate, and characterise mycotoxins pre and post-harvest. Multi-omics approaches along with advanced analytical tools and chemometrics provide a complete annotation of such metabolites produced before/during the contamination of crops. We have assessed the merits of these individual and combined omics approaches and their promising applications to mitigate the issue of mycotoxin contamination. The data included in this review focus on aflatoxin, ochratoxin, and patulin and would be useful as benchmark information for future research.
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Affiliation(s)
- Manal Eshelli
- School of Computing, Engineering, & Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, UK.
- Food Science and Technology Department, Faculty of Agriculture, University of Tripoli, Tripoli 13538, Libya.
| | - M Mallique Qader
- School of Computing, Engineering, & Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, UK.
- National Institute of Fundamental Studies, Hantana Road, Kandy 20000, Sri Lanka.
| | - Ebtihaj J Jambi
- Biochemistry Department, Faculty of Science, Girls Section, King Abdulaziz University, Jeddah 21551, Saudi Arabia.
| | - Andrew S Hursthouse
- School of Computing, Engineering, & Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, UK.
| | - Mostafa E Rateb
- School of Computing, Engineering, & Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, UK.
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Characterization of the velvet regulators in Aspergillus flavus. J Microbiol 2018; 56:893-901. [PMID: 30361976 DOI: 10.1007/s12275-018-8417-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 08/22/2018] [Accepted: 08/28/2018] [Indexed: 12/14/2022]
Abstract
Fungal development and secondary metabolism are closely associated via the activities of the fungal NK-kB-type velvet regulators that are highly conserved in filamentous fungi. Here, we investigated the roles of the velvet genes in the aflatoxigenic fungus Aspergillus flavus. Distinct from other Aspergillus species, the A. flavus genome contains five velvet genes, veA, velB, velC, velD, and vosA. The deletion of velD blocks the production of aflatoxin B1, but does not affect the formation of sclerotia. Expression analyses revealed that vosA and velB mRNAs accumulated at high levels during the late phase of asexual development and in conidia. The absence of vosA or velB decreased the content of conidial trehalose and the tolerance of conidia to the thermal and UV stresses. In addition, double mutant analyses demonstrated that VosA and VelB play an inter-dependent role in trehalose biosynthesis and conidial stress tolerance. Together with the findings of previous studies, the results of the present study suggest that the velvet regulators play the conserved and vital role in sporogenesis, conidial trehalose biogenesis, stress tolerance, and aflatoxin biosynthesis in A. flavus.
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Wu Y, Xu L, Yin Z, Dai Q, Gao X, Feng H, Voegele RT, Huang L. Two members of the velvet family, VmVeA and VmVelB, affect conidiation, virulence and pectinase expression in Valsa mali. MOLECULAR PLANT PATHOLOGY 2018; 19:1639-1651. [PMID: 29127722 PMCID: PMC6638101 DOI: 10.1111/mpp.12645] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 10/28/2017] [Accepted: 11/09/2017] [Indexed: 05/26/2023]
Abstract
Velvet protein family members are important fungal-specific regulators which are involved in conidial development, secondary metabolism and virulence. To gain a broader insight into the physiological functions of the velvet protein family of Valsa mali, which causes a highly destructive canker disease on apple, we conducted a functional analysis of two velvet protein family members (VmVeA and VmVelB) via a gene replacement strategy. Deletion mutants of VmVeA and VmVelB showed increased melanin production, conidiation and sensitivity to abiotic stresses, but exhibited reduced virulence on detached apple leaves and twigs. Further studies demonstrated that the regulation of conidiation by VmVeA and VmVelB was positively correlated with the melanin synthesis transcription factor VmCmr1. More importantly, transcript levels of pectinase genes were shown to be decreased in deletion mutants compared with those of the wild-type during infection. However, the expression of other cell wall-degrading enzyme genes, including cellulase, hemi-cellulase and ligninase genes, was not affected in the deletion mutants. Furthermore, the determination of pectinase activity and immunogold labelling of pectin demonstrated that the capacity for pectin degradation was attenuated as a result of deletions of VmVeA and VmVelB. Finally, the interaction of VmVeA with VmVelB was identified through co-immunoprecipitation assays. VmVeA and VmVelB play critical roles in conidiation and virulence, probably via the regulation of the melanin synthesis transcription factor VmCmr1 and their effect on pectinase gene expression in V. mali, respectively.
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Affiliation(s)
- Yuxing Wu
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
| | - Liangsheng Xu
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
| | - Zhiyuan Yin
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
| | - Qingqing Dai
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
| | - Xiaoning Gao
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
| | - Hao Feng
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
| | - Ralf T. Voegele
- Institut für Phytomedizin, Universität Hohenheim70599 StuttgartGermany
| | - Lili Huang
- State Key Laboratory of Crop Stress Biology for Arid Areas, China–Australia Joint Research Centre for Abiotic and Biotic Stress Management, College of Plant ProtectionNorthwest A&F UniversityShaanxiYangling 712100China
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Lebar MD, Cary JW, Majumdar R, Carter-Wientjes CH, Mack BM, Wei Q, Uka V, De Saeger S, Diana Di Mavungu J. Identification and functional analysis of the aspergillic acid gene cluster in Aspergillus flavus. Fungal Genet Biol 2018; 116:14-23. [PMID: 29674152 DOI: 10.1016/j.fgb.2018.04.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 04/04/2018] [Accepted: 04/12/2018] [Indexed: 10/17/2022]
Abstract
Aspergillus flavus can colonize important food staples and produce aflatoxins, a group of toxic and carcinogenic secondary metabolites. Previous in silico analysis of the A. flavus genome revealed 56 gene clusters predicted to be involved in the biosynthesis of secondary metabolites. A. flavus secondary metabolites produced during infection of maize seed are of particular interest, especially with respect to their roles in the biology of the fungus. A predicted nonribosomal peptide synthetase-like (NRPS-like) gene, designated asaC (AFLA_023020), present in the uncharacterized A. flavus secondary metabolite gene cluster 11 was previously shown to be expressed during the earliest stages of maize kernel infection. Cluster 11 is composed of six additional genes encoding a number of putative decorating enzymes as well as a transporter and transcription factor. We generated knock-out mutants of the seven predicted cluster 11 genes. LC-MS analysis of extracts from knockout mutants of these genes showed that they were responsible for the synthesis of the previously characterized antimicrobial mycotoxin aspergillic acid. Extracts of the asaC mutant showed no production of aspergillic acid or its precursors. Knockout of the cluster 11 P450 oxidoreductase afforded a pyrazinone metabolite, the aspergillic acid precursor deoxyaspergillic acid. The formation of hydroxyaspergillic acid was abolished in a desaturase/hydroxylase mutant. The hydroxamic acid functional group in aspergillic acid allows the molecule to bind to iron resulting in the production of a red pigment in A. flavus identified previously as ferriaspergillin. A reduction of aflatoxin B1 and cyclopiazonic acid that correlated with reduced fungal growth was observed in maize kernel infection assays when aspergillic acid biosynthesis in A. flavus is halted.
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Affiliation(s)
- Matthew D Lebar
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA.
| | - Jeffrey W Cary
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | | | | | - Brian M Mack
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | - Qijian Wei
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | - Valdet Uka
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Sarah De Saeger
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - José Diana Di Mavungu
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
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Aspergillus flavus Secondary Metabolites: More than Just Aflatoxins. Food Saf (Tokyo) 2018; 6:7-32. [PMID: 32231944 DOI: 10.14252/foodsafetyfscj.2017024] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 03/09/2018] [Indexed: 11/21/2022] Open
Abstract
Aspergillus flavus is best known for producing the family of potent carcinogenic secondary metabolites known as aflatoxins. However, this opportunistic plant and animal pathogen also produces numerous other secondary metabolites, many of which have also been shown to be toxic. While about forty of these secondary metabolites have been identified from A. flavus cultures, analysis of the genome has predicted the existence of at least 56 secondary metabolite gene clusters. Many of these gene clusters are not expressed during growth of the fungus on standard laboratory media. This presents researchers with a major challenge of devising novel strategies to manipulate the fungus and its genome so as to activate secondary metabolite gene expression and allow identification of associated cluster metabolites. In this review, we discuss the genetic, biochemical and bioinformatic methods that are being used to identify previously uncharacterized secondary metabolite gene clusters and their associated metabolites. It is important to identify as many of these compounds as possible to determine their bioactivity with respect to fungal development, survival, virulence and especially with respect to any potential synergistic toxic effects with aflatoxin.
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14
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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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Majumdar R, Lebar M, Mack B, Minocha R, Minocha S, Carter-Wientjes C, Sickler C, Rajasekaran K, Cary JW. The Aspergillus flavus Spermidine Synthase ( spds) Gene, Is Required for Normal Development, Aflatoxin Production, and Pathogenesis During Infection of Maize Kernels. FRONTIERS IN PLANT SCIENCE 2018; 9:317. [PMID: 29616053 PMCID: PMC5870473 DOI: 10.3389/fpls.2018.00317] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 02/27/2018] [Indexed: 05/10/2023]
Abstract
Aspergillus flavus is a soil-borne saprophyte and an opportunistic pathogen of both humans and plants. This fungus not only causes disease in important food and feed crops such as maize, peanut, cottonseed, and tree nuts but also produces the toxic and carcinogenic secondary metabolites (SMs) known as aflatoxins. Polyamines (PAs) are ubiquitous polycations that influence normal growth, development, and stress responses in living organisms and have been shown to play a significant role in fungal pathogenesis. Biosynthesis of spermidine (Spd) is critical for cell growth as it is required for hypusination-mediated activation of eukaryotic translation initiation factor 5A (eIF5A), and other biochemical functions. The tri-amine Spd is synthesized from the diamine putrescine (Put) by the enzyme spermidine synthase (Spds). Inactivation of spds resulted in a total loss of growth and sporulation in vitro which could be partially restored by addition of exogenous Spd. Complementation of the Δspds mutant with a wild type (WT) A. flavus spds gene restored the WT phenotype. In WT A. flavus, exogenous supply of Spd (in vitro) significantly increased the production of sclerotia and SMs. Infection of maize kernels with the Δspds mutant resulted in a significant reduction in fungal growth, sporulation, and aflatoxin production compared to controls. Quantitative PCR of Δspds mutant infected seeds showed down-regulation of aflatoxin biosynthetic genes in the mutant compared to WT A. flavus infected seeds. Expression analyses of PA metabolism/transport genes during A. flavus-maize interaction showed significant increase in the expression of arginine decarboxylase (Adc) and S-adenosylmethionine decarboxylase (Samdc) genes in the maize host and PA uptake transporters in the fungus. The results presented here demonstrate that Spd biosynthesis is critical for normal development and pathogenesis of A. flavus and pre-treatment of a Δspds mutant with Spd or Spd uptake from the host plant, are insufficient to restore WT levels of pathogenesis and aflatoxin production during seed infection. The data presented here suggest that future studies targeting spermidine biosynthesis in A. flavus, using RNA interference-based host-induced gene silencing approaches, may be an effective strategy to reduce aflatoxin contamination in maize and possibly in other susceptible crops.
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Affiliation(s)
- Rajtilak Majumdar
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Matt Lebar
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Brian Mack
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Rakesh Minocha
- United States Department of Agriculture Forest Service, Northern Research Station, Durham, NH, United States
| | - Subhash Minocha
- Department of Biological Sciences, University of New Hampshire, Durham, NH, United States
| | - Carol Carter-Wientjes
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Christine Sickler
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Kanniah Rajasekaran
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Jeffrey W. Cary
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
- *Correspondence: Jeffrey W. Cary,
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Effect of water activity and temperature on the growth of Aspergillus flavus, the expression of aflatoxin biosynthetic genes and aflatoxin production in shelled peanuts. Food Control 2017. [DOI: 10.1016/j.foodcont.2017.07.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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17
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Detection of Transcriptionally Active Mycotoxin Gene Clusters: DNA Microarray. Methods Mol Biol 2016. [PMID: 27924550 DOI: 10.1007/978-1-4939-6707-0_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Various bioanalytical tools including DNA microarrays are frequently used to map global transcriptional changes in mycotoxin producer filamentous fungi. This effective hybridization-based transcriptomics technology helps researchers to identify genes of secondary metabolite gene clusters and record concomitant gene expression changes in these clusters initiated by versatile environmental conditions and/or gene deletions. Such transcriptional data are of great value when future mycotoxin control technologies are considered and elaborated. Giving the readers insights into RNA extraction and DNA microarray hybridization steps routinely used in our laboratories and also into the normalization and evaluation of primary gene expression data, we would like to contribute to the interlaboratory standardization of DNA microarray based transcriptomics studies being carried out in many laboratories worldwide in this important field of fungal biology.
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rtfA, a putative RNA-Pol II transcription elongation factor gene, is necessary for normal morphological and chemical development in Aspergillus flavus. Appl Microbiol Biotechnol 2016; 100:5029-41. [PMID: 27020290 DOI: 10.1007/s00253-016-7418-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 02/22/2016] [Accepted: 02/24/2016] [Indexed: 01/05/2023]
Abstract
The filamentous fungus Aspergillus flavus is an agriculturally important opportunistic plant pathogen that produces potent carcinogenic compounds called aflatoxins. We identified the A. flavus rtfA gene, the ortholog of rtf1 in Saccharomyces cerevisiae and rtfA in Aspergillus nidulans. Interestingly, rtfA has multiple cellular roles in this mycotoxin-producing fungus. In this study, we show that rtfA regulates conidiation. The rtfA deletion mutant presented smaller conidiophores with significantly reduced conidial production compared to the wild-type strain. The absence of rtfA also resulted in a significant decrease or lack of sclerotial production under conditions that allowed abundant production of these resistance structures in the wild type. Importantly, the deletion of rtfA notably reduced the production of aflatoxin B1, indicating that rtfA is a regulator of mycotoxin biosynthesis in A. flavus. In addition, the deletion rtfA also altered the production of several unknown secondary metabolites indicating a broader regulatory scope. Furthermore, our study revealed that rtfA controls the expression of the global regulators veA and laeA, which further influence morphogenesis and secondary metabolism in A. flavus.
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Fanelli F, Geisen R, Schmidt-Heydt M, Logrieco A, Mulè G. Light regulation of mycotoxin biosynthesis: new perspectives for food safety. WORLD MYCOTOXIN J 2016. [DOI: 10.3920/wmj2014.1860] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Mycotoxins are secondary metabolites produced by toxigenic fungi contaminating foods and feeds in pre-, post-harvest and processing, and represent a great concern worldwide, both for the economic implications and for the health of the consumers. Many environmental conditions are involved in the regulation of mycotoxin biosynthesis. Among these, light represents one of the most important signals for fungi, influencing several physiological responses such as pigmentation, sexual development and asexual conidiation, primary and secondary metabolism, including mycotoxin biosynthesis. In this review we summarise some recent findings on the effect of specific light wavelength and intensity on mycotoxin biosynthesis in the main toxigenic fungal genera. We describe the molecular mechanism underlying light perception and its involvement in the regulation of secondary metabolism, focusing on VeA, global regulator in Aspergillus nidulans, and the White-Collar proteins, key components of light response in Neurospora crassa. Light of specific wavelength and intensity exerts different effects both on growth and on toxin production depending on the fungal genus. In Penicillium spp. red (627 nm) and blue wavelengths (455-470 nm) reduce ochratoxin A (OTA) biosynthesis by modulating the level of expression of the ochratoxin polyketide synthase. Furthermore a mutual regulation between citrinin and OTA production is reported in Penicillium toxigenic species. In Aspergillus spp. the effect of light treatment is strongly dependent on the species and culture conditions. Royal blue wavelength (455 nm) of high intensity (1,700 Lux) is capable of completely inhibit fungal growth and OTA production in Aspergillus stenyii and Penicillum verrucosum. In Fusarium spp. the effect of light exposure is less effective; mycotoxin-producing species, such as Fusarium verticillioides and Fusarium proliferatum, grow better under light conditions, and fumonisin production increased. This review provides a comprehensive picture on light regulation of mycotoxin biosynthesis and discusses possible new applications of this resource in food safety.
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Affiliation(s)
- F. Fanelli
- Institute of Sciences of Food Production, CNR, via Amendola 122/0, 70126 Bari, Italy
| | - R. Geisen
- Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, Haid-und-Neu-Str. 9, 76131 Karlsruhe, Germany
| | - M. Schmidt-Heydt
- Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, Haid-und-Neu-Str. 9, 76131 Karlsruhe, Germany
| | - A.F. Logrieco
- Institute of Sciences of Food Production, CNR, via Amendola 122/0, 70126 Bari, Italy
| | - G. Mulè
- Institute of Sciences of Food Production, CNR, via Amendola 122/0, 70126 Bari, Italy
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20
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Cary JW, Uka V, Han Z, Buyst D, Harris-Coward PY, Ehrlich KC, Wei Q, Bhatnagar D, Dowd PF, Martens SL, Calvo AM, Martins JC, Vanhaecke L, Coenye T, De Saeger S, Di Mavungu JD. An Aspergillus flavus secondary metabolic gene cluster containing a hybrid PKS–NRPS is necessary for synthesis of the 2-pyridones, leporins. Fungal Genet Biol 2015; 81:88-97. [DOI: 10.1016/j.fgb.2015.05.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/22/2015] [Accepted: 05/26/2015] [Indexed: 01/04/2023]
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21
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Transcriptome Analysis of Aspergillus flavus Reveals veA-Dependent Regulation of Secondary Metabolite Gene Clusters, Including the Novel Aflavarin Cluster. EUKARYOTIC CELL 2015. [PMID: 26209694 DOI: 10.1128/ec.00092-15] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The global regulatory veA gene governs development and secondary metabolism in numerous fungal species, including Aspergillus flavus. This is especially relevant since A. flavus infects crops of agricultural importance worldwide, contaminating them with potent mycotoxins. The most well-known are aflatoxins, which are cytotoxic and carcinogenic polyketide compounds. The production of aflatoxins and the expression of genes implicated in the production of these mycotoxins are veA dependent. The genes responsible for the synthesis of aflatoxins are clustered, a signature common for genes involved in fungal secondary metabolism. Studies of the A. flavus genome revealed many gene clusters possibly connected to the synthesis of secondary metabolites. Many of these metabolites are still unknown, or the association between a known metabolite and a particular gene cluster has not yet been established. In the present transcriptome study, we show that veA is necessary for the expression of a large number of genes. Twenty-eight out of the predicted 56 secondary metabolite gene clusters include at least one gene that is differentially expressed depending on presence or absence of veA. One of the clusters under the influence of veA is cluster 39. The absence of veA results in a downregulation of the five genes found within this cluster. Interestingly, our results indicate that the cluster is expressed mainly in sclerotia. Chemical analysis of sclerotial extracts revealed that cluster 39 is responsible for the production of aflavarin.
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22
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Bok JW, Wiemann P, Garvey GS, Lim FY, Haas B, Wortman J, Keller NP. Illumina identification of RsrA, a conserved C2H2 transcription factor coordinating the NapA mediated oxidative stress signaling pathway in Aspergillus. BMC Genomics 2014; 15:1011. [PMID: 25416206 PMCID: PMC4252986 DOI: 10.1186/1471-2164-15-1011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 11/12/2014] [Indexed: 12/30/2022] Open
Abstract
Background Chemical mutagenesis screens are useful to identify mutants involved in biological processes of interest. Identifying the mutation from such screens, however, often fails when using methodologies involving transformation of the mutant to wild type phenotype with DNA libraries. Results Here we analyzed Illumina sequence of a chemically derived mutant of Aspergillus nidulans and identified a gene encoding a C2H2 transcription factor termed RsrA for regulator of stress response. RsrA is conserved in filamentous fungal genomes, and upon deleting the gene in three Aspergillus species (A. nidulans, A. flavus and A. fumigatus), we found two conserved phenotypes: enhanced resistance to oxidative stress and reduction in sporulation processes. For all species, rsrA deletion mutants were more resistant to hydrogen peroxide treatment. In depth examination of this latter characteristic in A. nidulans showed that upon exposure to hydrogen peroxide, RsrA loss resulted in global up-regulation of several components of the oxidative stress metabolome including the expression of napA and atfA, the two bZIP transcription factors mediating resistance to reactive oxygen species (ROS) as well as NapA targets in thioredoxin and glutathione systems. Coupling transcriptional data with examination of ΔrsrAΔatfA and ΔrsrAΔnapA double mutants indicate that RsrA primarily operates through NapA-mediated stress response pathways. A model of RsrA regulation of ROS response in Aspergillus is presented. Conclusion RsrA, found in a highly syntenic region in Aspergillus genomes, coordinates a NapA mediated oxidative response in Aspergillus fungi. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1011) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA.
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23
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Baidya S, Duran RM, Lohmar JM, Harris-Coward PY, Cary JW, Hong SY, Roze LV, Linz JE, Calvo AM. VeA is associated with the response to oxidative stress in the aflatoxin producer Aspergillus flavus. EUKARYOTIC CELL 2014; 13:1095-103. [PMID: 24951443 PMCID: PMC4135802 DOI: 10.1128/ec.00099-14] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/14/2014] [Indexed: 12/20/2022]
Abstract
Survival of fungal species depends on the ability of these organisms to respond to environmental stresses. Osmotic stress or high levels of reactive oxygen species (ROS) can cause stress in fungi resulting in growth inhibition. Both eukaryotic and prokaryotic cells have developed numerous mechanisms to counteract and survive the stress in the presence of ROS. In many fungi, the HOG signaling pathway is crucial for the oxidative stress response as well as for osmotic stress response. This study revealed that while the osmotic stress response is only slightly affected by the master regulator veA, this gene, also known to control morphological development and secondary metabolism in numerous fungal species, has a profound effect on the oxidative stress response in the aflatoxin-producing fungus Aspergillus flavus. We found that the expression of A. flavus homolog genes involved in the HOG signaling pathway is regulated by veA. Deletion of veA resulted in a reduction in transcription levels of oxidative stress response genes after exposure to hydrogen peroxide. Furthermore, analyses of the effect of VeA on the promoters of cat1 and trxB indicate that the presence of VeA alters DNA-protein complex formation. This is particularly notable in the cat1 promoter, where the absence of VeA results in abnormally stronger complex formation with reduced cat1 expression and more sensitivity to ROS in a veA deletion mutant, suggesting that VeA might prevent binding of negative transcription regulators to the cat1 promoter. Our study also revealed that veA positively influences the expression of the transcription factor gene atfB and that normal formation of DNA-protein complexes in the cat1 promoter is dependent on AtfB.
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Affiliation(s)
- Sachin Baidya
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Rocio M Duran
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Jessica M Lohmar
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Pamela Y Harris-Coward
- Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA
| | - Jeffrey W Cary
- Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA
| | - Sung-Yong Hong
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ludmila V Roze
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - John E Linz
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ana M Calvo
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
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Chang PK, Scharfenstein LL, Mack B, Yu J, Ehrlich KC. Transcriptomic profiles of Aspergillus flavus CA42, a strain that produces small sclerotia, by decanal treatment and after recovery. Fungal Genet Biol 2014; 68:39-47. [DOI: 10.1016/j.fgb.2014.04.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 04/08/2014] [Accepted: 04/15/2014] [Indexed: 01/12/2023]
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25
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Wu X, Zhou B, Yin C, Guo Y, Lin Y, Pan L, Wang B. Characterization of natural antisense transcript, sclerotia development and secondary metabolism by strand-specific RNA sequencing of Aspergillus flavus. PLoS One 2014; 9:e97814. [PMID: 24849659 PMCID: PMC4029826 DOI: 10.1371/journal.pone.0097814] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 04/23/2014] [Indexed: 12/23/2022] Open
Abstract
Aspergillus flavus has received much attention owing to its severe impact on agriculture and fermented products induced by aflatoxin. Sclerotia morphogenesis is an important process related to A. flavus reproduction and aflatoxin biosynthesis. In order to obtain an extensive transcriptome profile of A. flavus and provide a comprehensive understanding of these physiological processes, the isolated mRNA of A. flavus CA43 cultures was subjected to high-throughput strand-specific RNA sequencing (ssRNA-seq). Our ssRNA-seq data profiled widespread transcription across the A. flavus genome, quantified vast transcripts (73% of total genes) and annotated precise transcript structures, including untranslated regions, upstream open reading frames (ORFs), alternative splicing variants and novel transcripts. We propose natural antisense transcripts in A. flavus might regulate gene expression mainly on the post-transcriptional level. This regulation might be relevant to tune biological processes such as aflatoxin biosynthesis and sclerotia development. Gene Ontology annotation of differentially expressed genes between the mycelia and sclerotia cultures indicated sclerotia development was related closely to A. flavus reproduction. Additionally, we have established the transcriptional profile of aflatoxin biosynthesis and its regulation model. We identified potential genes linking sclerotia development and aflatoxin biosynthesis. These genes could be used as targets for controlled regulation of aflatoxigenic strains of A. flavus.
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Affiliation(s)
- Xinliang Wu
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
| | - Bin Zhou
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
| | - Chao Yin
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
| | - Yong Guo
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
| | - Ying Lin
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
| | - Li Pan
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
| | - Bin Wang
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, Guangdong, China
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26
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Molecular mechanisms of Aspergillus flavus secondary metabolism and development. Fungal Genet Biol 2014; 66:11-8. [DOI: 10.1016/j.fgb.2014.02.008] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 02/21/2014] [Accepted: 02/25/2014] [Indexed: 12/16/2022]
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27
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Duran RM, Gregersen S, Smith TD, Bhetariya PJ, Cary JW, Harris-Coward PY, Mattison CP, Grimm C, Calvo AM. The role of Aspergillus flavus veA in the production of extracellular proteins during growth on starch substrates. Appl Microbiol Biotechnol 2014; 98:5081-94. [DOI: 10.1007/s00253-014-5598-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Revised: 02/03/2014] [Accepted: 02/04/2014] [Indexed: 01/21/2023]
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Cary JW, Harris-Coward PY, Ehrlich KC, Di Mavungu JD, Malysheva SV, De Saeger S, Dowd PF, Shantappa S, Martens SL, Calvo AM. Functional characterization of a veA-dependent polyketide synthase gene in Aspergillus flavus necessary for the synthesis of asparasone, a sclerotium-specific pigment. Fungal Genet Biol 2014; 64:25-35. [DOI: 10.1016/j.fgb.2014.01.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 12/03/2013] [Accepted: 01/02/2014] [Indexed: 11/28/2022]
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VelC positively controls sexual development in Aspergillus nidulans. PLoS One 2014; 9:e89883. [PMID: 24587098 PMCID: PMC3938535 DOI: 10.1371/journal.pone.0089883] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 01/29/2014] [Indexed: 12/18/2022] Open
Abstract
Fungal development and secondary metabolism is intimately associated via activities of the fungi-specific velvet family proteins including VeA, VosA, VelB and VelC. Among these, VelC has not been characterized in Aspergillus nidulans. In this study, we characterize the role of VelC in asexual and sexual development in A. nidulans. The velC mRNA specifically accumulates during the early phase of sexual development. The deletion of velC leads to increased number of conidia and reduced production of sexual fruiting bodies (cleistothecia). In the velC deletion mutant, mRNA levels of the brlA, abaA, wetA and vosA genes that control sequential activation of asexual sporulation increase. Overexpression of velC causes increased formation of cleistothecia. These results suggest that VelC functions as a positive regulator of sexual development. VelC is one of the five proteins that physically interact with VosA in yeast two-hybrid and GST pull down analyses. The ΔvelC ΔvosA double mutant produced fewer cleistothecia and behaved similar to the ΔvosA mutant, suggesting that VosA is epistatic to VelC in sexual development, and that VelC might mediate control of sex through interacting with VosA at specific life stages for sexual fruiting.
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López-Berges MS, Schäfer K, Hera C, Di Pietro A. Combinatorial function of velvet and AreA in transcriptional regulation of nitrate utilization and secondary metabolism. Fungal Genet Biol 2013; 62:78-84. [PMID: 24240057 DOI: 10.1016/j.fgb.2013.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/29/2013] [Accepted: 11/03/2013] [Indexed: 12/11/2022]
Abstract
Velvet is a conserved protein complex that functions as a regulator of fungal development and secondary metabolism. In the soil-inhabiting pathogen Fusarium oxysporum, velvet governs mycotoxin production and virulence on plant and mammalian hosts. Here we report a previously unrecognized role of the velvet complex in regulation of nitrate metabolism. F. oxysporum mutants lacking VeA or LaeA, two key components of the complex, were impaired in growth on the non-preferred nitrogen sources nitrate and nitrite. Both velvet and the general nitrogen response GATA factor AreA were required for transcriptional activation of nitrate (nit1) and nitrite (nii1) reductase genes under de-repressing conditions, as well as for the nitrate-triggered increase in chromatin accessibility at the nit1 locus. AreA also contributed to chromatin accessibility and expression of two velvet-regulated gene clusters, encoding biosynthesis of the mycotoxin beauvericin and of the siderophore ferricrocin. Thus, velvet and AreA coordinately orchestrate primary and secondary metabolism as well as virulence functions in F. oxysporum.
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Affiliation(s)
- Manuel S López-Berges
- Departamento de Genética, Facultad de Ciencias, Universidad de Córdoba, 14071 Córdoba, Spain; Campus de Excelencia Internacional Agroalimentario ceiA3, 14071 Córdoba, Spain
| | - Katja Schäfer
- Departamento de Genética, Facultad de Ciencias, Universidad de Córdoba, 14071 Córdoba, Spain; Campus de Excelencia Internacional Agroalimentario ceiA3, 14071 Córdoba, Spain
| | - Concepción Hera
- Departamento de Genética, Facultad de Ciencias, Universidad de Córdoba, 14071 Córdoba, Spain; Campus de Excelencia Internacional Agroalimentario ceiA3, 14071 Córdoba, Spain
| | - Antonio Di Pietro
- Departamento de Genética, Facultad de Ciencias, Universidad de Córdoba, 14071 Córdoba, Spain; Campus de Excelencia Internacional Agroalimentario ceiA3, 14071 Córdoba, Spain.
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Dhingra S, Lind AL, Lin HC, Tang Y, Rokas A, Calvo AM. The fumagillin gene cluster, an example of hundreds of genes under veA control in Aspergillus fumigatus. PLoS One 2013; 8:e77147. [PMID: 24116213 PMCID: PMC3792039 DOI: 10.1371/journal.pone.0077147] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 08/25/2013] [Indexed: 01/24/2023] Open
Abstract
Aspergillus fumigatus is the causative agent of invasive aspergillosis, leading to infection-related mortality in immunocompromised patients. We previously showed that the conserved and unique-to-fungi veA gene affects different cell processes such as morphological development, gliotoxin biosynthesis and protease activity, suggesting a global regulatory effect on the genome of this medically relevant fungus. In this study, RNA sequencing analysis revealed that veA controls the expression of hundreds of genes in A. fumigatus, including those comprising more than a dozen known secondary metabolite gene clusters. Chemical analysis confirmed that veA controls the synthesis of other secondary metabolites in this organism in addition to gliotoxin. Among the secondary metabolite gene clusters regulated by veA is the elusive but recently identified gene cluster responsible for the biosynthesis of fumagillin, a meroterpenoid known for its anti-angiogenic activity by binding to human methionine aminopeptidase 2. The fumagillin gene cluster contains a veA-dependent regulatory gene, fumR (Afu8g00420), encoding a putative C6 type transcription factor. Deletion of fumR results in silencing of the gene cluster and elimination of fumagillin biosynthesis. We found expression of fumR to also be dependent on laeA, a gene encoding another component of the fungal velvet complex. The results in this study argue that veA is a global regulator of secondary metabolism in A. fumigatus, and that veA may be a conduit via which chemical development is coupled to morphological development and other cellular processes.
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Affiliation(s)
- Sourabh Dhingra
- Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, United States of America
| | - Abigail L. Lind
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Hsiao-Ching Lin
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California, United States of America
| | - Yi Tang
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Antonis Rokas
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Ana M. Calvo
- Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, United States of America
- * E-mail:
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Yang Q, Chen Y, Ma Z. Involvement of BcVeA and BcVelB in regulating conidiation, pigmentation and virulence in Botrytis cinerea. Fungal Genet Biol 2013; 50:63-71. [DOI: 10.1016/j.fgb.2012.10.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Revised: 10/16/2012] [Accepted: 10/16/2012] [Indexed: 10/27/2022]
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Ramamoorthy V, Shantappa S, Dhingra S, Calvo AM. veA-dependent RNA-pol II transcription elongation factor-like protein, RtfA, is associated with secondary metabolism and morphological development in Aspergillus nidulans. Mol Microbiol 2012; 85:795-814. [PMID: 22783880 PMCID: PMC3418472 DOI: 10.1111/j.1365-2958.2012.08142.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In Aspergillus nidulans the global regulatory gene veA is necessary for the biosynthesis of several secondary metabolites, including the mycotoxin sterigmatocystin (ST). In order to identify additional veA-dependent genetic elements involved in regulating ST production, we performed a mutagenesis on a deletion veA (ΔveA) strain to obtain revertant mutants (RM) that regained the capability to produce toxin. Genetic analysis and molecular characterization of one of the revertant mutants, RM3, revealed that a point mutation occurred at the coding region of the rtfA gene, encoding a RNA-pol II transcription elongation factor-like protein, similar to Saccharomyces cerevisiae Rtf1. The A. nidulans rtfA gene product accumulates in nuclei. Deletion of rtfA gene in a ΔveA background restored mycotoxin production in a medium-dependent manner. rtfA also affects the production of other metabolites including penicillin. Biosynthesis of this antibiotic decreased in the absence of rtfA. Furthermore, rtfA is necessary for normal morphological development. Deletion of the rtfA gene in wild-type strains (veA+) resulted in a slight decrease in growth rate, drastic reduction in conidiation, and complete loss of sexual development. This is the first study of an Rtf1 like gene in filamentous fungi. We found rtfA putative orthologues extensively conserved in numerous fungal species.
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Affiliation(s)
| | | | | | - Ana M. Calvo
- Author to whom correspondence should be addressed [telephone: (815) 753-0451; fax (815) 753-0461;
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NsdC and NsdD affect Aspergillus flavus morphogenesis and aflatoxin production. EUKARYOTIC CELL 2012; 11:1104-11. [PMID: 22798394 DOI: 10.1128/ec.00069-12] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The transcription factors NsdC and NsdD are required for sexual development in Aspergillus nidulans. We now show these proteins also play a role in asexual development in the agriculturally important aflatoxin (AF)-producing fungus Aspergillus flavus. We found that both NsdC and NsdD are required for production of asexual sclerotia, normal aflatoxin biosynthesis, and conidiophore development. Conidiophores in nsdC and nsdD deletion mutants had shortened stipes and altered conidial heads compared to those of wild-type A. flavus. Our results suggest that NsdC and NsdD regulate transcription of genes required for early processes in conidiophore development preceding conidium formation. As the cultures aged, the ΔnsdC and ΔnsdD mutants produced a dark pigment that was not observed in the wild type. Gene expression data showed that although AflR is expressed at normal levels, a number of aflatoxin biosynthesis genes are expressed at reduced levels in both nsd mutants. Expression of aflD, aflM, and aflP was greatly reduced in nsdC mutants, and neither aflatoxin nor the proteins for these genes could be detected. Our results support previous studies showing that there is a strong association between conidiophore and sclerotium development and aflatoxin production in A. flavus.
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Merhej J, Urban M, Dufresne M, Hammond-Kosack KE, Richard-Forget F, Barreau C. The velvet gene, FgVe1, affects fungal development and positively regulates trichothecene biosynthesis and pathogenicity in Fusarium graminearum. MOLECULAR PLANT PATHOLOGY 2012; 13:363-74. [PMID: 22013911 PMCID: PMC6638759 DOI: 10.1111/j.1364-3703.2011.00755.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Trichothecenes are a group of toxic secondary metabolites produced mainly by Fusarium graminearum (teleomorph: Gibberella zeae) during the infection of crop plants, including wheat, maize, barley, oats, rye and rice. Some fungal genes involved in trichothecene biosynthesis have been shown to encode regulatory proteins. However, the global regulation of toxin biosynthesis is still enigmatic. In addition to the production of secondary metabolites belonging to the trichothecene family, F. graminearum produces the red pigment aurofusarin. The gene regulation underlying the production of aurofusarin is not well understood. The velvet gene (veA) is conserved in various genera of filamentous fungi. Recently, the veA gene from Aspergillus nidulans has been shown to be the key component of the velvet complex regulating development and secondary metabolism. Using blast analyses, we identified the velvet gene from F. graminearum, FgVe1. Disruption of FgVe1 causes several phenotypic effects. However, the complementation of this mutant with the FgVe1 gene restores the wild-type phenotypes. The in vitro phenotypes include hyperbranching of the mycelium, suppression of aerial hyphae formation, reduced hydrophobicity of the mycelium and highly reduced sporulation. Our data also show that FgVe1 modulates the production of the aurofusarin pigment and is essential for the expression of Tri genes and the production of trichothecenes. Pathogenicity studies performed on flowering wheat plants indicate that FgVe1 is a positive regulator of virulence in F. graminearum.
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Affiliation(s)
- Jawad Merhej
- INRA, UR1264 MycSA, 71, Avenue Edouard Bourleaux, BP81, F-33883 Villenave d'Ornon, France
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Chettri P, Calvo AM, Cary JW, Dhingra S, Guo Y, McDougal RL, Bradshaw RE. The veA gene of the pine needle pathogen Dothistroma septosporum regulates sporulation and secondary metabolism. Fungal Genet Biol 2011; 49:141-51. [PMID: 22227160 DOI: 10.1016/j.fgb.2011.11.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 11/18/2011] [Accepted: 11/21/2011] [Indexed: 02/06/2023]
Abstract
Fungi possess genetic systems to regulate the expression of genes involved in complex processes such as development and secondary metabolite biosynthesis. The product of the velvet gene veA, first identified and characterized in Aspergillus nidulans, is a key player in the regulation of both of these processes. Since its discovery and characterization in many Aspergillus species, VeA has been found to have similar functions in other fungi, including the Dothideomycete Mycosphaerella graminicola. Another Dothideomycete, Dothistroma septosporum, is a pine needle pathogen that produces dothistromin, a polyketide toxin very closely related to aflatoxin (AF) and sterigmatocystin (ST) synthesized by Aspergillus spp. Dothistromin is unusual in that, unlike most other secondary metabolites, it is produced mainly during the early exponential growth phase in culture. It was therefore of interest to determine whether the regulation of dothistromin production in D. septosporum differs from the regulation of AF/ST in Aspergillus spp. To begin to address this question, a veA ortholog was identified and its function analyzed in D. septosporum. Inactivation of the veA gene resulted in reduced dothistromin production and a corresponding decrease in expression of dothistromin biosynthetic genes. Expression of other putative secondary metabolite genes in D. septosporum such as polyketide synthases and non-ribosomal peptide synthases showed a range of different responses to loss of Ds-veA. Asexual sporulation was also significantly reduced in the mutants, accompanied by a reduction in the expression of a putative stuA regulatory gene. The mutants were, however, able to infect Pinus radiata seedlings and complete their life cycle under laboratory conditions. Overall this work suggests that D. septosporum has a veA ortholog that is involved in the control of both developmental and secondary metabolite biosynthetic pathways.
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Affiliation(s)
- Pranav Chettri
- Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand
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Identification and characterization of Penicillium citrinum VeA and LaeA as global regulators for ML-236B production. Curr Genet 2011; 58:1-11. [PMID: 22198576 DOI: 10.1007/s00294-011-0359-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 12/06/2011] [Accepted: 12/11/2011] [Indexed: 10/14/2022]
Abstract
In filamentous fungi, production of multiple secondary metabolites is controlled by so-called global regulators. In this study, two genes encoding homologs of VeA and LaeA, representative fungal global regulators, were identified in ML-236B-producing Penicillium citrinum. Disruption of VeA and/or LaeA and complementation clearly demonstrated that both of them played critical roles in ML-236B production by controlling the expression of mlcR, the pathway-specific activator gene for ML-236B biosynthesis. Moreover, sequence analysis revealed that laeA in a mutant strain producing high levels of ML-236B (strain S-1567) possessed a single nucleotide alteration, which resulted in 15 surplus amino acids at the carboxyl terminus of LaeA compared to the LaeA in the wild-type strain (strain SANK18767). Introduction of the mutated laeA into SANK18767 proved that the extended carboxyl region plays a crucial role in the higher production of ML-236B. These results indicated that VeA and LaeA dominantly control the biosynthesis of ML-236B, and the enhanced production in the strain S-1567 is attributable to the mutation in laeA.
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Dyer PS, O'Gorman CM. Sexual development and cryptic sexuality in fungi: insights from Aspergillus species. FEMS Microbiol Rev 2011; 36:165-92. [PMID: 22091779 DOI: 10.1111/j.1574-6976.2011.00308.x] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 09/04/2011] [Indexed: 11/30/2022] Open
Abstract
Major insights into sexual development and cryptic sexuality within filamentous fungi have been gained from investigations using Aspergillus species. Here, an overview is first given into sexual morphogenesis in the aspergilli, describing the different types of sexual structures formed and how their production is influenced by a variety of environmental and nutritional factors. It is argued that the formation of cleistothecia and accessory tissues, such as Hülle cells and sclerotia, should be viewed as two independent but co-ordinated developmental pathways. Next, a comprehensive survey of over 75 genes associated with sexual reproduction in the aspergilli is presented, including genes relating to mating and the development of cleistothecia, sclerotia and ascospores. Most of these genes have been identified from studies involving the homothallic Aspergillus nidulans, but an increasing number of studies have now in addition characterized 'sex-related' genes from the heterothallic species Aspergillus fumigatus and Aspergillus flavus. A schematic developmental genetic network is proposed showing the inter-relatedness between these genes. Finally, the discovery of sexual reproduction in certain Aspergillus species that were formerly considered to be strictly asexual is reviewed, and the importance of these findings for cryptic sexuality in the aspergilli as a whole is discussed.
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Affiliation(s)
- Paul S Dyer
- School of Biology, University of Nottingham, Nottingham, UK.
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Kamerewerd J, Zadra I, Kürnsteiner H, Kück U. PcchiB1, encoding a class V chitinase, is affected by PcVelA and PcLaeA, and is responsible for cell wall integrity in Penicillium chrysogenum. MICROBIOLOGY-SGM 2011; 157:3036-3048. [PMID: 21816879 DOI: 10.1099/mic.0.051896-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Penicillin production in Penicillium chrysogenum is controlled by PcVelA and PcLaeA, two components of the regulatory velvet-like complex. Comparative microarray analysis with mutants lacking PcVelA or PcLaeA revealed a set of 62 common genes affected by the loss of both components. A downregulated gene in both knockout strains is PcchiB1, potentially encoding a class V chitinase. Under nutrient-depleted conditions, transcript levels of PcchiB1 are strongly upregulated, and the gene product contributes to more than 50 % of extracellular chitinase activity. Functional characterization by generating PcchiB1-disruption strains revealed that PcChiB1 is responsible for cell wall integrity and pellet formation in P. chrysogenum. Further, fluorescence microscopy with a DsRed-labelled chitinase suggests a cell wall association of the protein. An unexpected phenotype occurred when knockout strains were grown on media containing N-acetylglucosamine as the sole C and N source, where, in contrast to the recipient, a penicillin producer strain, the mutants and an ancestral strain show distinct mycelial growth. We discuss the relevance of this class V chitinase for morphology in an industrially important fungus.
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Affiliation(s)
- Jens Kamerewerd
- Christian Doppler Laboratory for 'Fungal Biotechnology', Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
| | - Ivo Zadra
- Anti Infectives Microbiology, Sandoz GmbH, Biochemiestraße 10, 6250 Kundl, Austria
| | - Hubert Kürnsteiner
- Anti Infectives Microbiology, Sandoz GmbH, Biochemiestraße 10, 6250 Kundl, Austria
| | - Ulrich Kück
- Christian Doppler Laboratory for 'Fungal Biotechnology', Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
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Bayram O, Braus GH. Coordination of secondary metabolism and development in fungi: the velvet family of regulatory proteins. FEMS Microbiol Rev 2011; 36:1-24. [PMID: 21658084 DOI: 10.1111/j.1574-6976.2011.00285.x] [Citation(s) in RCA: 376] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Filamentous fungi produce a number of small bioactive molecules as part of their secondary metabolism ranging from benign antibiotics such as penicillin to threatening mycotoxins such as aflatoxin. Secondary metabolism can be linked to fungal developmental programs in response to various abiotic or biotic external triggers. The velvet family of regulatory proteins plays a key role in coordinating secondary metabolism and differentiation processes such as asexual or sexual sporulation and sclerotia or fruiting body formation. The velvet family shares a protein domain that is present in most parts of the fungal kingdom from chytrids to basidiomycetes. Most of the current knowledge derives from the model Aspergillus nidulans where VeA, the founding member of the protein family, was discovered almost half a century ago. Different members of the velvet protein family interact with each other and the nonvelvet protein LaeA, primarily in the nucleus. LaeA is a methyltransferase-domain protein that functions as a regulator of secondary metabolism and development. A comprehensive picture of the molecular interplay between the velvet domain protein family, LaeA and other nuclear regulatory proteins in response to various signal transduction pathway starts to emerge from a jigsaw puzzle of several recent studies.
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Affiliation(s)
- Ozgür Bayram
- Institut für Mikrobiologie und Genetik, Abteilung Molekulare Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Göttingen, Germany
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Loss of msnA, a putative stress regulatory gene, in Aspergillus parasiticus and Aspergillus flavus increased production of conidia, aflatoxins and kojic acid. Toxins (Basel) 2011; 3:82-104. [PMID: 22069691 PMCID: PMC3210457 DOI: 10.3390/toxins3010082] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 12/30/2010] [Accepted: 01/06/2011] [Indexed: 12/28/2022] Open
Abstract
Production of the harmful carcinogenic aflatoxins by Aspergillus parasiticus and Aspergillus flavus has been postulated to be a mechanism to relieve oxidative stress. The msnA gene of A. parasiticus and A. flavus is the ortholog of Saccharomyces cerevisiae MSN2 that is associated with multi-stress response. Compared to wild type strains, the msnA deletion (∆msnA) strains of A. parasiticus and A. flavus exhibited retarded colony growth with increased conidiation. The ∆msnA strains also produced slightly higher amounts of aflatoxins and elevated amounts of kojic acid on mixed cereal medium. Microarray assays showed that expression of genes encoding oxidative stress defense enzymes, i.e., superoxide dismutase, catalase, and cytochrome c peroxidase in A. parasiticus ∆msnA, and the catalase A gene in A. flavus ∆msnA, was up-regulated. Both A. parasiticus and A. flavus ∆msnA strains produced higher levels of reactive oxygen species (ROS), and ROS production of A. flavus msnA addback strains was decreased to levels comparable to that of the wild type A. flavus. The msnA gene appears to be required for the maintenance of the normal oxidative state. The impairment of msnA resulted in the aforementioned changes, which might be used to combat the increased oxidative stress in the cells.
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Abstract
Aspergillus flavus is saprophytic soil fungus that infects and contaminates preharvest and postharvest seed crops with the carcinogenic secondary metabolite aflatoxin. The fungus is also an opportunistic animal and human pathogen causing aspergillosis diseases with incidence increasing in the immunocompromised population. Whole genome sequences of A. flavus have been released and reveal 55 secondary metabolite clusters that are regulated by different environmental regimes and the global secondary metabolite regulators LaeA and VeA. Characteristics of A. flavus associated with pathogenicity and niche specialization include secondary metabolite production, enzyme elaboration, and a sophisticated oxylipin host crosstalk associated with a quorum-like development program. One of the more promising strategies in field control involves the use of atoxic strains of A. flavus in competitive exclusion studies. In this review, we discuss A. flavus as an agricultural and medical threat and summarize recent research advances in genomics, elucidation of parameters of pathogenicity, and control measures.
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Affiliation(s)
- Saori Amaike
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53706, USA
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MVE1, encoding the velvet gene product homolog in Mycosphaerella graminicola, is associated with aerial mycelium formation, melanin biosynthesis, hyphal swelling, and light signaling. Appl Environ Microbiol 2010; 77:942-53. [PMID: 21115702 DOI: 10.1128/aem.01830-10] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The ascomycete fungus Mycosphaerella graminicola is an important pathogen of wheat that causes Septoria tritici blotch. Despite the serious impact of M. graminicola on wheat production worldwide, knowledge about its molecular biology is limited. The velvet gene, veA, is one of the key regulators of diverse cellular processes, including development and secondary metabolism in many fungi. However, the species analyzed to date are not related to the Dothideomycetes, the largest class of plant-pathogenic fungi, and the function of veA in this group is not known. To test the hypothesis that the velvet gene has similar functions in the Dothideomycetes, a veA-homologous gene, MVE1, was identified and gene deletion mutations (Δmve1) were generated in M. graminicola. All of the MVE1 mutants exhibited consistent pleiotropic phenotypes, indicating the involvement of MVE1 in multiple signaling pathways. Δmve1 strains displayed albino phenotypes with significant reductions in melanin biosynthesis and less production of aerial mycelia on agar plates. In liquid culture, Δmve1 strains showed abnormal hyphal swelling, which was suppressed completely by osmotic stress or lower temperature. In addition, MVE1 gene deletion led to hypersensitivity to shaking, reduced hydrophobicity, and blindness to light-dependent stimulation of aerial mycelium production. However, pathogenicity was not altered in Δmve1 strains. Therefore, the light-signaling pathway associated with MVE1 does not appear to be important for Septoria tritici blotch disease. Our data suggest that the MVE1 gene plays crucial roles in multiple key signaling pathways and is associated with light signaling in M. graminicola.
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Suppressor mutagenesis identifies a velvet complex remediator of Aspergillus nidulans secondary metabolism. EUKARYOTIC CELL 2010; 9:1816-24. [PMID: 20935144 DOI: 10.1128/ec.00189-10] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Fungal secondary metabolites (SM) are bioactive compounds that are important in fungal ecology and, moreover, both harmful and useful in human endeavors (e.g., as toxins and pharmaceuticals). Recently a nuclear heterocomplex termed the Velvet complex, characterized in the model ascomycete Aspergillus nidulans, was found to be critical for SM production. Deletion of two members of the Velvet complex, laeA and veA, results in near loss of SM and defective sexual spore production in A. nidulans and other species. Using a multicopy-suppressor genetics approach, we have isolated an Aspergillus nidulans gene named rsmA (remediation of secondary metabolism) based upon its ability to remediate secondary metabolism in ΔlaeA and ΔveA backgrounds. Overexpression of rsmA (OE::rsmA) restores production of sterigmatocystin (ST) (a carcinogenic SM) via transcriptional activation of ST biosynthetic genes. However, defects in sexual reproduction in either ΔlaeA or ΔveA strains cannot be overcome by OE::rsmA. An intact Velvet complex coupled with an OE::rsmA allele increases SM many fold over the wild-type level, but loss of rsmA does not decrease SM. RsmA encodes a putative bZIP basic leucine zipper-type transcription factor.
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Roze LV, Chanda A, Laivenieks M, Beaudry RM, Artymovich KA, Koptina AV, Awad DW, Valeeva D, Jones AD, Linz JE. Volatile profiling reveals intracellular metabolic changes in Aspergillus parasiticus: veA regulates branched chain amino acid and ethanol metabolism. BMC BIOCHEMISTRY 2010; 11:33. [PMID: 20735852 PMCID: PMC2939540 DOI: 10.1186/1471-2091-11-33] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/24/2010] [Indexed: 01/17/2023]
Abstract
Background Filamentous fungi in the genus Aspergillus produce a variety of natural products, including aflatoxin, the most potent naturally occurring carcinogen known. Aflatoxin biosynthesis, one of the most highly characterized secondary metabolic pathways, offers a model system to study secondary metabolism in eukaryotes. To control or customize biosynthesis of natural products we must understand how secondary metabolism integrates into the overall cellular metabolic network. By applying a metabolomics approach we analyzed volatile compounds synthesized by Aspergillus parasiticus in an attempt to define the association of secondary metabolism with other metabolic and cellular processes. Results Volatile compounds were examined using solid phase microextraction - gas chromatography/mass spectrometry. In the wild type strain Aspergillus parasiticus SU-1, the largest group of volatiles included compounds derived from catabolism of branched chain amino acids (leucine, isoleucine, and valine); we also identified alcohols, esters, aldehydes, and lipid-derived volatiles. The number and quantity of the volatiles produced depended on media composition, time of incubation, and light-dark status. A block in aflatoxin biosynthesis or disruption of the global regulator veA affected the volatile profile. In addition to its multiple functions in secondary metabolism and development, VeA negatively regulated catabolism of branched chain amino acids and synthesis of ethanol at the transcriptional level thus playing a role in controlling carbon flow within the cell. Finally, we demonstrated that volatiles generated by a veA disruption mutant are part of the complex regulatory machinery that mediates the effects of VeA on asexual conidiation and sclerotia formation. Conclusions 1) Volatile profiling provides a rapid, effective, and powerful approach to identify changes in intracellular metabolic networks in filamentous fungi. 2) VeA coordinates the biosynthesis of secondary metabolites with catabolism of branched chain amino acids, alcohol biosynthesis, and β-oxidation of fatty acids. 3) Intracellular chemical development in A. parasiticus is linked to morphological development. 4) Understanding carbon flow through secondary metabolic pathways and catabolism of branched chain amino acids is essential for controlling and customizing production of natural products.
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Affiliation(s)
- Ludmila V Roze
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI, USA.
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Two components of a velvet-like complex control hyphal morphogenesis, conidiophore development, and penicillin biosynthesis in Penicillium chrysogenum. EUKARYOTIC CELL 2010; 9:1236-50. [PMID: 20543063 DOI: 10.1128/ec.00077-10] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Penicillium chrysogenum is the industrial producer of the antibiotic penicillin, whose biosynthetic regulation is barely understood. Here, we provide a functional analysis of two major homologues of the velvet complex in P. chrysogenum, which we have named P. chrysogenum velA (PcvelA) and PclaeA. Data from array analysis using a DeltaPcvelA deletion strain indicate a significant role of PcVelA on the expression of biosynthesis and developmental genes, including PclaeA. Northern hybridization and high-performance liquid chromatography quantifications of penicillin titers clearly show that both PcVelA and PcLaeA play a major role in penicillin biosynthesis in a producer strain that underwent several rounds of UV mutagenesis during a strain improvement program. Both regulators are further involved in different developmental processes. While PcvelA deletion leads to light-independent conidial formation, dichotomous branching of hyphae, and pellet formation in shaking cultures, a DeltaPclaeA strain shows a severe impairment in conidiophore formation under both light and dark conditions. Bimolecular fluorescence complementation assays provide evidence for a velvet-like complex in P. chrysogenum, with structurally conserved components that have distinct developmental roles, illustrating the functional plasticity of these regulators in genera other than Aspergillus.
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Development and refinement of a high-efficiency gene-targeting system for Aspergillus flavus. J Microbiol Methods 2010; 81:240-6. [DOI: 10.1016/j.mimet.2010.03.010] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 02/19/2010] [Accepted: 03/04/2010] [Indexed: 10/19/2022]
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Han KH. Molecular Genetics of Emericella nidulans Sexual Development. MYCOBIOLOGY 2009; 37:171-82. [PMID: 23983529 PMCID: PMC3749384 DOI: 10.4489/myco.2009.37.3.171] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 09/14/2009] [Indexed: 05/16/2023]
Abstract
Many aspergilli that belongs to ascomycetes have sexuality. In a homothallic or self-fertile fungus, a number of fruiting bodies or cleistothecia are formed in a thallus grown from a single haploid conidia or ascospores. Genome-sequencing project revealed that two mating genes (MAT) encoding the regulatory proteins that are necessary for controlling partner recognition in heterothallic fungi were conserved in most aspergilli. The MAT gene products in some self-fertile species were not required for recognition of mating partner at pheromone-signaling stage but required at later stages of sexual development. Various environmental factors such as nutritional status, culture conditions and several stresses, influence the decision or progression of sexual reproduction. A large number of genes are expected to be involved in sexual development of Emericella nidulans (anamorph: Aspergillus nidulans), a genetic and biological model organism in aspergilli. The sexual development process can be grouped into several development stages, including the decision of sexual reproductive cycle, mating process, growth of fruiting body, karyogamy followed by meiosis, and sporulation process. Complicated regulatory networks, such as signal transduction pathways and gene expression controls, may work in each stage and stage-to-stage linkages. In this review, the components joining in the regulatory pathways of sexual development, although they constitute only a small part of the whole regulatory networks, are briefly mentioned. Some of them control sexual development positively and some do negatively. Regarding the difficulties for studying sexual differentiation compare to asexual one, recent progresses in molecular genetics of E. nidulans enlarge the boundaries of understanding sexual development in the non-fertile species as well as in fertile fungi.
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Affiliation(s)
- Kap-Hoon Han
- Department of Pharmaceutical Engineering, Woosuk University, Wanju 565-701, Korea
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The RNA interference-virus interplay: tools of nature for gene modulation, morphogenesis, evolution and a possible mean for aflatoxin control. Appl Microbiol Biotechnol 2009; 83:611-5. [PMID: 19466405 DOI: 10.1007/s00253-009-2007-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Revised: 04/08/2009] [Accepted: 04/08/2009] [Indexed: 11/27/2022]
Abstract
This article points out, that viruses, in an interplay with RNA interference and as vehicles for intergenic and interspecies gene transfer, may work as agents for intracellular gene modulation, for steering of individual morphogenesis and as a driving force of evolution in the toolbox of nature. This is illustrated in particular in the light of a fungal double-stranded RNA virus that may be employed as a suitable agent for a biological control of aflatoxins, the most carcinogenic natural substances occurring in food and feedstuff.
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