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Wang W, Liang X, Li Y, Wang P, Keller NP. Genetic Regulation of Mycotoxin Biosynthesis. J Fungi (Basel) 2022; 9:jof9010021. [PMID: 36675842 PMCID: PMC9861139 DOI: 10.3390/jof9010021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 12/20/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
Mycotoxin contamination in food poses health hazards to humans. Current methods of controlling mycotoxins still have limitations and more effective approaches are needed. During the past decades of years, variable environmental factors have been tested for their influence on mycotoxin production leading to elucidation of a complex regulatory network involved in mycotoxin biosynthesis. These regulators are putative targets for screening molecules that could inhibit mycotoxin synthesis. Here, we summarize the regulatory mechanisms of hierarchical regulators, including pathway-specific regulators, global regulators and epigenetic regulators, on the production of the most critical mycotoxins (aflatoxins, patulin, citrinin, trichothecenes and fumonisins). Future studies on regulation of mycotoxins will provide valuable knowledge for exploring novel methods to inhibit mycotoxin biosynthesis in a more efficient way.
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Affiliation(s)
- Wenjie Wang
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Correspondence: (W.W.); (N.P.K.)
| | - Xinle Liang
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Yudong Li
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Pinmei Wang
- Ocean College, Zhejiang University, Zhoushan 316021, China
| | - Nancy P. Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Correspondence: (W.W.); (N.P.K.)
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2
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Tini F, Beccari G, Marconi G, Porceddu A, Sulyok M, Gardiner DM, Albertini E, Covarelli L. Identification of Putative Virulence Genes by DNA Methylation Studies in the Cereal Pathogen Fusarium graminearum. Cells 2021; 10:cells10051192. [PMID: 34068122 PMCID: PMC8152758 DOI: 10.3390/cells10051192] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 05/03/2021] [Accepted: 05/10/2021] [Indexed: 01/17/2023] Open
Abstract
DNA methylation mediates organisms’ adaptations to environmental changes in a wide range of species. We investigated if a such a strategy is also adopted by Fusarium graminearum in regulating virulence toward its natural hosts. A virulent strain of this fungus was consecutively sub-cultured for 50 times (once a week) on potato dextrose agar. To assess the effect of subculturing on virulence, wheat seedlings and heads (cv. A416) were inoculated with subcultures (SC) 1, 23, and 50. SC50 was also used to re-infect (three times) wheat heads (SC50×3) to restore virulence. In vitro conidia production, colonies growth and secondary metabolites production were also determined for SC1, SC23, SC50, and SC50×3. Seedling stem base and head assays revealed a virulence decline of all subcultures, whereas virulence was restored in SC50×3. The same trend was observed in conidia production. The DNA isolated from SC50 and SC50×3 was subject to a methylation content-sensitive enzyme and double-digest, restriction-site-associated DNA technique (ddRAD-MCSeEd). DNA methylation analysis indicated 1024 genes, whose methylation levels changed in response to the inoculation on a healthy host after subculturing. Several of these genes are already known to be involved in virulence by functional analysis. These results demonstrate that the physiological shifts following sub-culturing have an impact on genomic DNA methylation levels and suggest that the ddRAD-MCSeEd approach can be an important tool for detecting genes potentially related to fungal virulence.
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Affiliation(s)
- Francesco Tini
- Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno, 74, 06121 Perugia, Italy; (F.T.); (G.B.); (E.A.); (L.C.)
| | - Giovanni Beccari
- Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno, 74, 06121 Perugia, Italy; (F.T.); (G.B.); (E.A.); (L.C.)
| | - Gianpiero Marconi
- Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno, 74, 06121 Perugia, Italy; (F.T.); (G.B.); (E.A.); (L.C.)
- Correspondence:
| | - Andrea Porceddu
- Department of Agriculture, University of Sassari, Viale Italia, 39a, 07100 Sassari, Italy;
| | - Micheal Sulyok
- Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Applied Life Sciences, Vienna (BOKU), Konrad Lorenz Strasse, 20, A-3430 Tulln, Austria;
| | - Donald M. Gardiner
- Commonwealth Scientific and Industrial Research Organisation, Agriculture and Food, 306 Carmody Road, St Lucia, QLD 4067, Australia;
| | - Emidio Albertini
- Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno, 74, 06121 Perugia, Italy; (F.T.); (G.B.); (E.A.); (L.C.)
| | - Lorenzo Covarelli
- Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno, 74, 06121 Perugia, Italy; (F.T.); (G.B.); (E.A.); (L.C.)
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3
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Chen J, Li Z, Cheng Y, Gao C, Guo L, Wang T, Xu J. Sphinganine-Analog Mycotoxins (SAMs): Chemical Structures, Bioactivities, and Genetic Controls. J Fungi (Basel) 2020; 6:E312. [PMID: 33255427 PMCID: PMC7711896 DOI: 10.3390/jof6040312] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/20/2020] [Accepted: 11/22/2020] [Indexed: 12/20/2022] Open
Abstract
Sphinganine-analog mycotoxins (SAMs) including fumonisins and A. alternata f. sp. Lycopersici (AAL) toxins are a group of related mycotoxins produced by plant pathogenic fungi in the Fusarium genus and in Alternaria alternata f. sp. Lycopersici, respectively. SAMs have shown diverse cytotoxicity and phytotoxicity, causing adverse impacts on plants, animals, and humans, and are a destructive force to crop production worldwide. This review summarizes the structural diversity of SAMs and encapsulates the relationships between their structures and biological activities. The toxicity of SAMs on plants and animals is mainly attributed to their inhibitory activity against the ceramide biosynthesis enzyme, influencing the sphingolipid metabolism and causing programmed cell death. We also reviewed the detoxification methods against SAMs and how plants develop resistance to SAMs. Genetic and evolutionary analyses revealed that the FUM (fumonisins biosynthetic) gene cluster was responsible for fumonisin biosynthesis in Fusarium spp. Sequence comparisons among species within the genus Fusarium suggested that mutations and multiple horizontal gene transfers involving the FUM gene cluster were responsible for the interspecific difference in fumonisin synthesis. We finish by describing methods for monitoring and quantifying SAMs in food and agricultural products.
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Affiliation(s)
- Jia Chen
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
| | - Zhimin Li
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
| | - Yi Cheng
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
| | - Chunsheng Gao
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
| | - Litao Guo
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
| | - Tuhong Wang
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
| | - Jianping Xu
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; (J.C.); (Z.L.); (Y.C.); (C.G.); (L.G.); (T.W.)
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
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Kamle M, Mahato DK, Devi S, Lee KE, Kang SG, Kumar P. Fumonisins: Impact on Agriculture, Food, and Human Health and their Management Strategies. Toxins (Basel) 2019; 11:E328. [PMID: 31181628 PMCID: PMC6628439 DOI: 10.3390/toxins11060328] [Citation(s) in RCA: 123] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 06/04/2019] [Accepted: 06/04/2019] [Indexed: 11/17/2022] Open
Abstract
The fumonisins producing fungi, Fusarium spp., are ubiquitous in nature and contaminate several food matrices that pose detrimental health hazards on humans as well as on animals. This has necessitated profound research for the control and management of the toxins to guarantee better health of consumers. This review highlights the chemistry and biosynthesis process of the fumonisins, their occurrence, effect on agriculture and food, along with their associated health issues. In addition, the focus has been put on the detection and management of fumonisins to ensure safe and healthy food. The main focus of the review is to provide insights to the readers regarding their health-associated food consumption and possible outbreaks. Furthermore, the consumers' knowledge and an attempt will ensure food safety and security and the farmers' knowledge for healthy agricultural practices, processing, and management, important to reduce the mycotoxin outbreaks due to fumonisins.
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Affiliation(s)
- Madhu Kamle
- Department of Forestry, North Eastern Regional Institute of Science and Technology, Nirjuli-791109, Arunachal Pradesh, India.
| | - Dipendra K Mahato
- School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Hwy, Burwood VIC 3125, Australia.
| | - Sheetal Devi
- SAB Miller India Ltd., Sonipat, Haryana 131001, India.
| | - Kyung Eun Lee
- Molecular Genetics Laboratory, Department of Biotechnology, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 38541, Korea.
| | - Sang G Kang
- Molecular Genetics Laboratory, Department of Biotechnology, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 38541, Korea.
- Stemforce, 302 Institute of Industrial Technology, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Korea.
| | - Pradeep Kumar
- Department of Forestry, North Eastern Regional Institute of Science and Technology, Nirjuli-791109, Arunachal Pradesh, India.
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5
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New insights into fumonisin production and virulence of Fusarium proliferatum underlying different carbon sources. Food Res Int 2019; 116:397-407. [DOI: 10.1016/j.foodres.2018.08.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 08/08/2018] [Accepted: 08/18/2018] [Indexed: 01/09/2023]
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Kim M, Zhang H, Woloshuk C, Shim WB, Yoon BJ. Computational Prediction of Pathogenic Network Modules in Fusarium verticillioides. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2018; 15:506-515. [PMID: 29610099 DOI: 10.1109/tcbb.2015.2440232] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fusarium verticillioides is a fungal pathogen that triggers stalk rots and ear rots in maize. In this study, we performed a comparative analysis of wild type and loss-of-virulence mutant F. verticillioides co-expression networks to identify subnetwork modules that are associated with its pathogenicity. We constructed the F. verticillioides co-expression networks from RNA-Seq data and searched through these networks to identify subnetwork modules that are differentially activated between the wild type and mutant F. verticillioides, which considerably differ in terms of pathogenic potentials. A greedy seed-and-extend approach was utilized in our search, where we also used an efficient branch-out technique for reliable prediction of functional subnetwork modules in the fungus. Through our analysis, we identified four potential pathogenicity-associated subnetwork modules, each of which consists of interacting genes with coordinated expression patterns, but whose activation level is significantly different in the wild type and the mutant. The predicted modules were comprised of functionally coherent genes and topologically cohesive. Furthermore, they contained several orthologs of known pathogenic genes in other fungi, which may play important roles in the fungal pathogenesis.
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7
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Niu C, Payne GA, Woloshuk CP. Involvement of FST1 from Fusarium verticillioides in virulence and transport of inositol. MOLECULAR PLANT PATHOLOGY 2017; 18:695-707. [PMID: 27195938 PMCID: PMC6638204 DOI: 10.1111/mpp.12430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 05/11/2016] [Accepted: 05/13/2016] [Indexed: 06/05/2023]
Abstract
Fumonisin B1 (FB1), a polyketide mycotoxin produced by Fusarium verticillioides during the colonization of maize kernels, is detrimental to human and animal health. FST1 encodes a putative protein with 12 transmembrane domains; however, its function remains unknown. The FST1 gene is highly expressed by the fungus in the endosperm of maize kernels compared with the levels of expression in germ tissues. Previous research has shown that FST1 affects FB1 production, virulence, hydrogen peroxide resistance, hydrophobicity and macroconidia production. Here, we examine the phylogeny of FST1, its expression in a Saccharomyces cerevisiae strain lacking a functional myo-inositol transporter (ITR1) and the effect of amino acid changes in the central loop and C-terminus regions of FST1 on functionality. The results indicate that expression of FST1 in an ITR1 mutant strain restores growth on myo-inositol medium to wild-type levels and restores the inhibitory effects of FB1, suggesting that FST1 can transport both myo-inositol and FB1 into yeast cells. Our results with engineered FST1 also indicate that amino acids in the central loop and C-terminus regions are important for FST1 functionality in both S. cerevisiae and F. verticillioides. Overall, this research has established the first characterized inositol transporter in filamentous fungi and has advanced our knowledge about the global regulatory functions of FST1.
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Affiliation(s)
- Chenxing Niu
- Department of Botany and Plant PathologyPurdue UniversityWest LafayetteIN47907‐2054USA
| | - Gary A. Payne
- Department of Plant PathologyNorth Carolina State UniversityRaleighNC27695‐7567USA
| | - Charles P. Woloshuk
- Department of Botany and Plant PathologyPurdue UniversityWest LafayetteIN47907‐2054USA
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Ridenour JB, Bluhm BH. The novel fungal-specific gene FUG1 has a role in pathogenicity and fumonisin biosynthesis in Fusarium verticillioides. MOLECULAR PLANT PATHOLOGY 2017; 18:513-528. [PMID: 27071505 PMCID: PMC6638258 DOI: 10.1111/mpp.12414] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Revised: 04/06/2016] [Accepted: 04/07/2016] [Indexed: 05/05/2023]
Abstract
Fusarium verticillioides is a globally important pathogen of maize, capable of causing severe yield reductions and economic losses. In addition, F. verticillioides produces toxic secondary metabolites during kernel colonization that pose significant threats to human and animal health. Fusarium verticillioides and other plant-pathogenic fungi possess a large number of genes with no known or predicted function, some of which could encode novel virulence factors or antifungal targets. In this study, we identified and characterized the novel gene FUG1 (Fungal Unknown Gene 1) in F. verticillioides through functional genetics. Deletion of FUG1 impaired maize kernel colonization and fumonisin biosynthesis. In addition, deletion of FUG1 increased sensitivity to the antimicrobial compound 2-benzoxazolinone and to hydrogen peroxide, which indicates that FUG1 may play a role in mitigating stresses associated with host defence. Transcriptional profiling via RNA-sequencing (RNA-seq) identified numerous fungal genes that were differentially expressed in the kernel environment following the deletion of FUG1, including genes involved in secondary metabolism and mycelial development. Sequence analysis of the Fug1 protein provided evidence for nuclear localization, DNA binding and a domain of unknown function associated with previously characterized transcriptional regulators. This information, combined with the observed transcriptional reprogramming in the deletion mutant, suggests that FUG1 represents a novel class of fungal transcription factors or genes otherwise involved in signal transduction.
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Affiliation(s)
- John B. Ridenour
- Department of Plant PathologyUniversity of Arkansas Division of AgricultureFayettevilleAR 72701USA
| | - Burton H. Bluhm
- Department of Plant PathologyUniversity of Arkansas Division of AgricultureFayettevilleAR 72701USA
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9
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Ridenour JB, Smith JE, Bluhm BH. The HAP Complex Governs Fumonisin Biosynthesis and Maize Kernel Pathogenesis in Fusarium verticillioides. J Food Prot 2016; 79:1498-1507. [PMID: 28221941 DOI: 10.4315/0362-028x.jfp-15-596] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Contamination of maize ( Zea mays ) with fumonisins produced by the fungus Fusarium verticillioides is a global concern for food safety. Fumonisins are a group of polyketide-derived secondary metabolites linked to esophageal cancer and neural tube birth defects in humans and numerous toxicoses in livestock. Despite the importance of fumonisins in global maize production, the regulation of fumonisin biosynthesis during kernel pathogenesis is poorly understood. The HAP complex is a conserved, heterotrimeric transcriptional regulator that binds the consensus sequence CCAAT to modulate gene expression. Recently, functional characterization of the Hap3 subunit linked the HAP complex to the regulation of secondary metabolism and stalk rot pathogenesis in F. verticillioides . Here, we determine the involvement of HAP3 in fumonisin biosynthesis and kernel pathogenesis. Deletion of HAP3 suppressed fumonisin biosynthesis on both nonviable and live maize kernels and impaired pathogenesis in living kernels. Transcriptional profiling via RNA sequencing indicated that the HAP complex regulates at least 1,223 genes in F. verticillioides , representing nearly 10% of all predicted genes. Disruption of the HAP complex caused the misregulation of biosynthetic gene clusters underlying the production of secondary metabolites, including fusarins. Taken together, these results reveal that the HAP complex is a central regulator of fumonisin biosynthesis and kernel pathogenesis and works as both a positive and negative regulator of secondary metabolism in F. verticillioides .
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Affiliation(s)
- John B Ridenour
- Department of Plant Pathology, Division of Agriculture, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Jonathon E Smith
- Department of Plant Pathology, Division of Agriculture, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Burton H Bluhm
- Department of Plant Pathology, Division of Agriculture, University of Arkansas, Fayetteville, Arkansas 72701, USA
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Oh M, Son H, Choi GJ, Lee C, Kim JC, Kim H, Lee YW. Transcription factor ART1 mediates starch hydrolysis and mycotoxin production in Fusarium graminearum and F. verticillioides. MOLECULAR PLANT PATHOLOGY 2016; 17:755-68. [PMID: 26456718 PMCID: PMC6638531 DOI: 10.1111/mpp.12328] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Molecular mechanisms underlying the responses to environmental factors, such as nitrogen, carbon and pH, involve components that regulate the production of secondary metabolites, including mycotoxins. In this study, we identified and characterized a gene in the FGSG_02083 locus, designated as FgArt1, which was predicted to encode a Zn(II)2 Cys6 zinc finger transcription factor. An FgArt1 deletion mutant of Fusarium graminearum exhibited impaired starch hydrolysis as a result of significantly reduced α-amylase gene expression. The deletion strain was unable to produce trichothecenes and exhibited low Tri5 and Tri6 expression levels, whereas the complemented strain showed a similar ability to produce trichothecenes as the wild-type strain. In addition, FgArt1 deletion resulted in impairment of germination in starch liquid medium and reduced pathogenicity on flowering wheat heads. To investigate the roles of the FgArt1 homologue in F. verticillioides, we deleted the FVEG_02083 gene, and the resulting strain showed defects in starch hydrolysis, similar to the FgArt1 deletion strain, and produced no detectable level of fumonisin B1 . Fum1 and Fum12 expression levels were undetectable in the deletion strain. However, when the FvArt1-deleted F. verticillioides strain was complemented with FgArt1, the resulting strain was unable to recover the production of fumonisin B1 , although FgArt1 expression and starch hydrolysis were induced. Thus, our results suggest that there are different regulatory pathways governed by each ART1 transcription factor in trichothecene and fumonisin biosynthesis. Taken together, we suggest that ART1 plays an important role in both trichothecene and fumonisin biosynthesis by the regulation of genes involved in starch hydrolysis.
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Affiliation(s)
- Mira Oh
- Center for Eco-Friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, 305-600, South Korea
- Department of Green Chemistry and Environmental Biotechnology, Korea University of Science and Technology, Daejeon, 305-350, South Korea
| | - Hokyoung Son
- Department of Agricultural Biotechnology and Center for Fungal Pathogenesis, Seoul National University, Seoul, 151-921, South Korea
| | - Gyung Ja Choi
- Center for Eco-Friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, 305-600, South Korea
| | - Chanhui Lee
- Department of Plant and Environmental New Resources, Kyung Hee University, Yongin, 446-701, South Korea
| | - Jin-Cheol Kim
- Division of Applied Bioscience and Biotechnology, Chonnam National University, Gwangju, 500-757, South Korea
| | - Hun Kim
- Center for Eco-Friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, 305-600, South Korea
- Department of Green Chemistry and Environmental Biotechnology, Korea University of Science and Technology, Daejeon, 305-350, South Korea
| | - Yin-Won Lee
- Department of Agricultural Biotechnology and Center for Fungal Pathogenesis, Seoul National University, Seoul, 151-921, South Korea
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Song XS, Xing S, Li HP, Zhang JB, Qu B, Jiang JH, Fan C, Yang P, Liu JL, Hu ZQ, Xue S, Liao YC. An antibody that confers plant disease resistance targets a membrane-bound glyoxal oxidase in Fusarium. THE NEW PHYTOLOGIST 2016; 210:997-1010. [PMID: 26720747 DOI: 10.1111/nph.13806] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Accepted: 11/12/2015] [Indexed: 06/05/2023]
Abstract
Plant germplasm resources with natural resistance against globally important toxigenic Fusarium are inadequate. CWP2, a Fusarium genus-specific antibody, confers durable resistance to different Fusarium pathogens that infect cereals and other crops, producing mycotoxins. However, the nature of the CWP2 target is not known. Thus, investigation of the gene coding for the CWP2 antibody target will likely provide critical insights into the mechanism underlying the resistance mediated by this disease-resistance antibody. Immunoblots and mass spectrometry analysis of two-dimensional electrophoresis gels containing cell wall proteins from Fusarium graminearum (Fg) revealed that a glyoxal oxidase (GLX) is the CWP2 antigen. Cellular localization studies showed that GLX is localized to the plasma membrane. This GLX efficiently catalyzes hydrogen peroxide production; this enzymatic activity was specifically inhibited by the CWP2 antibody. GLX-deletion strains of Fg, F. verticillioides (Fv) and F. oxysporum had significantly reduced virulence on plants. The GLX-deletion Fg and Fv strains had markedly reduced mycotoxin accumulation, and the expression of key genes in mycotoxin metabolism was downregulated. This study reveals a single gene-encoded and highly conserved cellular surface antigen that is specifically recognized by the disease-resistance antibody CWP2 and regulates both virulence and mycotoxin biosynthesis in Fusarium species.
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Affiliation(s)
- Xiu-Shi Song
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Shu Xing
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - He-Ping Li
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Jing-Bo Zhang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Bo Qu
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Jin-He Jiang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Chao Fan
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Peng Yang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Jin-Long Liu
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Zu-Quan Hu
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Sheng Xue
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Yu-Cai Liao
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan, 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
- National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China
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12
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Kim M, Zhang H, Woloshuk C, Shim WB, Yoon BJ. Computational identification of genetic subnetwork modules associated with maize defense response to Fusarium verticillioides. BMC Bioinformatics 2015; 16 Suppl 13:S12. [PMID: 26423221 PMCID: PMC4597171 DOI: 10.1186/1471-2105-16-s13-s12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Background Maize, a crop of global significance, is vulnerable to a variety of biotic stresses resulting in economic losses. Fusarium verticillioides (teleomorph Gibberella moniliformis) is one of the key fungal pathogens of maize, causing ear rots and stalk rots. To better understand the genetic mechanisms involved in maize defense as well as F. verticillioides virulence, a systematic investigation of the host-pathogen interaction is needed. The aim of this study was to computationally identify potential maize subnetwork modules associated with its defense response against F. verticillioides. Results We obtained time-course RNA-seq data from B73 maize inoculated with wild type F. verticillioides and a loss-of-virulence mutant, and subsequently established a computational pipeline for network-based comparative analysis. Specifically, we first analyzed the RNA-seq data by a cointegration-correlation-expression approach, where maize genes were jointly analyzed with known F. verticillioides virulence genes to find candidate maize genes likely associated with the defense mechanism. We predicted maize co-expression networks around the selected maize candidate genes based on partial correlation, and subsequently searched for subnetwork modules that were differentially activated when inoculated with two different fungal strains. Based on our analysis pipeline, we identified four potential maize defense subnetwork modules. Two were directly associated with maize defense response and were associated with significant GO terms such as GO:0009817 (defense response to fungus) and GO:0009620 (response to fungus). The other two predicted modules were indirectly involved in the defense response, where the most significant GO terms associated with these modules were GO:0046914 (transition metal ion binding) and GO:0046686 (response to cadmium ion). Conclusion Through our RNA-seq data analysis, we have shown that a network-based approach can enhance our understanding of the complicated host-pathogen interactions between maize and F. verticillioides by interpreting the transcriptome data in a system-oriented manner. We expect that the proposed analytic pipeline can also be adapted for investigating potential functional modules associated with host defense response in diverse plant-pathogen interactions.
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Niu C, Payne GA, Woloshuk CP. Transcriptome changes in Fusarium verticillioides caused by mutation in the transporter-like gene FST1. BMC Microbiol 2015; 15:90. [PMID: 25906821 PMCID: PMC4422464 DOI: 10.1186/s12866-015-0427-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 02/19/2015] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Fusarium verticillioides causes an important seed disease on maize and produces the fumonisin group of mycotoxins, which are toxic to humans and livestock. A previous study discovered that a gene (FST1) in the pathogen affects fumonisin production and virulence. Although the predicted amino acid sequence of FST1 is similar to hexose transporters, previous experimental evidence failed to prove function. RESULTS Three new phenotypes were identified that are associated with the FST1 mutant of F. verticillioides (Δfst1), namely reduction in macroconidia production, increased sensitivity to hydrogen peroxide, and reduced mycelial hydrophobicity. A transcriptome comparison of the wild type and strain Δfst1 grown on autoclaved maize kernels for six days identified 2677 genes that were differentially expressed. Through gene ontology analysis, 961 genes were assigned to one of 12 molecular function categories. Sets of down-regulated genes in strain Δfst1 were identified that could account for each of the mutant phenotypes. CONCLUSION The study provides evidence that disruption of FST1 causes several metabolic and developmental defects in F. verticillioides. FST1 appears to connect the expression of several gene networks, including those involved in secondary metabolism, cell wall structure, conidiogenesis, virulence, and resistance to reactive oxygen species. The results support our hypothesis that FST1 functions within the framework of environmental sensing.
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Affiliation(s)
- Chenxing Niu
- Department of Botany and Plant Pathology, Purdue University, 915 W. State Street, West Lafayette, IN, 47907-2054, USA.
| | - Gary A Payne
- Department of Plant Pathology, North Carolina State University, 851 Main Campus Drive, Raleigh, NC, 27695-7567, USA.
| | - Charles P Woloshuk
- Department of Botany and Plant Pathology, Purdue University, 915 W. State Street, West Lafayette, IN, 47907-2054, USA.
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Zhang L, Hua C, Stassen JHM, Chatterjee S, Cornelissen M, van Kan JAL. Genome-wide analysis of pectate-induced gene expression in Botrytis cinerea: identification and functional analysis of putative d-galacturonate transporters. Fungal Genet Biol 2014; 72:182-191. [PMID: 24140151 DOI: 10.1016/j.fgb.2013.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 10/03/2013] [Indexed: 11/22/2022]
Abstract
The fungal plant pathogen Botrytis cinerea produces a spectrum of cell wall degrading enzymes for the decomposition of host cell wall polysaccharides and the consumption of the monosaccharides that are released. Especially pectin is an abundant cell wall component, and the decomposition of pectin by B. cinerea has been extensively studied. An effective concerted action of the appropriate pectin depolymerising enzymes, monosaccharide transporters and catabolic enzymes is important for complete d-galacturonic acid utilization by B. cinerea. In this study, we performed RNA sequencing to compare genome-wide transcriptional profiles between B. cinerea cultures grown in media containing pectate or glucose as sole carbon source. Transcript levels of 32 genes that are induced by pectate were further examined in cultures grown on six different monosaccharides, by means of quantitative RT-PCR, leading to the identification of 8 genes that are exclusively induced by d-galacturonic acid. Among these, the hexose transporter encoding genes Bchxt15 and Bchxt19 were functionally characterised. The subcellular location was studied of BcHXT15-GFP and BcHXT19-GFP fusion proteins expressed under control of their native promoter, in a B. cinerea wild-type strain. Both genes are expressed during growth on d-galacturonic acid and the fusion proteins are localized in plasma membranes and intracellular vesicles. Target gene knockout analysis revealed that BcHXT15 contributes to d-galacturonic acid uptake at pH 5∼5.6. The virulence of all B. cinerea hexose transporter mutants tested was unaltered on tomato and Nicotiana benthamiana leaves.
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Affiliation(s)
- Lisha Zhang
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany.
| | - Chenlei Hua
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Joost H M Stassen
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; Department of Animal and Plant Sciences, University of Sheffield, United Kingdom
| | - Sayantani Chatterjee
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Maxim Cornelissen
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Jan A L van Kan
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
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Ridenour JB, Smith JE, Hirsch RL, Horevaj P, Kim H, Sharma S, Bluhm BH. UBL1 of Fusarium verticillioides links the N-end rule pathway to extracellular sensing and plant pathogenesis. Environ Microbiol 2013; 16:2004-22. [PMID: 24237664 DOI: 10.1111/1462-2920.12333] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 11/07/2013] [Indexed: 01/06/2023]
Abstract
Fusarium verticillioides produces fumonisin mycotoxins during colonization of maize. Currently, molecular mechanisms underlying responsiveness of F.verticillioides to extracellular cues during pathogenesis are poorly understood. In this study, insertional mutants were created and screened to identify genes involved in responses to extracellular starch. In one mutant, the restriction enzyme-mediated integration cassette disrupted a gene (UBL1) encoding a UBR-Box/RING domain E3 ubiquitin ligase involved in the N-end rule pathway. Disruption of UBL1 in F.verticillioides (Δubl1) influenced conidiation, hyphal morphology, pigmentation and amylolysis. Disruption of UBL1 also impaired kernel colonization, but the ratio of fumonisin B1 per unit growth was not significantly reduced. The inability of a Δubl1 mutant to recognize an N-end rule degron confirmed involvement of UBL1 in the N-end rule pathway. Additionally, Ubl1 physically interacted with two G protein α subunits of F.verticillioides, thus implicating UBL1 in G protein-mediated sensing of the external environment. Furthermore, deletion of the UBL1 orthologue in F.graminearum reduced virulence on wheat and maize, thus indicating that UBL1 has a broader role in virulence among Fusarium species. This study provides the first linkage between the N-end rule pathway and fungal pathogenesis, and illustrates a new mechanism through which fungi respond to the external environment.
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Affiliation(s)
- John B Ridenour
- Department of Plant Pathology, Division of Agriculture, University of Arkansas, Fayetteville, AR, 72701, USA
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Coelho MA, Gonçalves C, Sampaio JP, Gonçalves P. Extensive intra-kingdom horizontal gene transfer converging on a fungal fructose transporter gene. PLoS Genet 2013; 9:e1003587. [PMID: 23818872 PMCID: PMC3688497 DOI: 10.1371/journal.pgen.1003587] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 05/08/2013] [Indexed: 11/19/2022] Open
Abstract
Comparative genomics revealed in the last decade a scenario of rampant horizontal gene transfer (HGT) among prokaryotes, but for fungi a clearly dominant pattern of vertical inheritance still stands, punctuated however by an increasing number of exceptions. In the present work, we studied the phylogenetic distribution and pattern of inheritance of a fungal gene encoding a fructose transporter (FSY1) with unique substrate selectivity. 109 FSY1 homologues were identified in two sub-phyla of the Ascomycota, in a survey that included 241 available fungal genomes. At least 10 independent inter-species instances of horizontal gene transfer (HGT) involving FSY1 were identified, supported by strong phylogenetic evidence and synteny analyses. The acquisition of FSY1 through HGT was sometimes suggestive of xenolog gene displacement, but several cases of pseudoparalogy were also uncovered. Moreover, evidence was found for successive HGT events, possibly including those responsible for transmission of the gene among yeast lineages. These occurrences do not seem to be driven by functional diversification of the Fsy1 proteins because Fsy1 homologues from widely distant lineages, including at least one acquired by HGT, appear to have similar biochemical properties. In summary, retracing the evolutionary path of the FSY1 gene brought to light an unparalleled number of independent HGT events involving a single fungal gene. We propose that the turbulent evolutionary history of the gene may be linked to the unique biochemical properties of the encoded transporter, whose predictable effect on fitness may be highly variable. In general, our results support the most recent views suggesting that inter-species HGT may have contributed much more substantially to shape fungal genomes than heretofore assumed.
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Affiliation(s)
- Marco A. Coelho
- Centro de Recursos Microbiológicos, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Carla Gonçalves
- Centro de Recursos Microbiológicos, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - José Paulo Sampaio
- Centro de Recursos Microbiológicos, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Paula Gonçalves
- Centro de Recursos Microbiológicos, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
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Woloshuk CP, Shim WB. Aflatoxins, fumonisins, and trichothecenes: a convergence of knowledge. FEMS Microbiol Rev 2012; 37:94-109. [PMID: 23078349 DOI: 10.1111/1574-6976.12009] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 09/27/2012] [Accepted: 10/15/2012] [Indexed: 01/03/2023] Open
Abstract
Plant pathogenic fungi Aspergillus flavus, Fusarium verticillioides, and Fusarium graminearum infect seeds of the most important food and feed crops, including maize, wheat, and barley. More importantly, these fungi produce aflatoxins, fumonisins, and trichothecenes, respectively, which threaten health and food security worldwide. In this review, we examine the molecular mechanisms and environmental factors that regulate mycotoxin biosynthesis in each fungus, and discuss the similarities and differences in the collective body of knowledge. Whole-genome sequences are available for these fungi, providing reference databases for genomic, transcriptomic, and proteomic analyses. It is well recognized that genes responsible for mycotoxin biosynthesis are organized in clusters. However, recent research has documented the intricate transcriptional and epigenetic regulation that affects these gene clusters. Significantly, molecular networks that respond to environmental factors, namely nitrogen, carbon, and pH, are connected to components regulating mycotoxin production. Furthermore, the developmental status of seeds and specific tissue types exert conditional influences during fungal colonization. A comparison of the three distinct mycotoxin groups provides insight into new areas for research collaborations that will lead to innovative strategies to control mycotoxin contamination of grain.
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Affiliation(s)
- Charles P Woloshuk
- Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.
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Horevaj P, Bluhm BH. BDM1, a phosducin-like gene of Fusarium graminearum, is involved in virulence during infection of wheat and maize. MOLECULAR PLANT PATHOLOGY 2012; 13:431-444. [PMID: 22044756 PMCID: PMC6638705 DOI: 10.1111/j.1364-3703.2011.00758.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Fusarium graminearum is a common pathogen of wheat and maize throughout the world. Despite recent advances in the elucidation of the genetic basis of virulence, significant gaps in the regulatory network underlying pathogenesis remain to be filled. In particular, little is known at the molecular level about the overlap among mechanisms of pathogenicity on maize and wheat. G-protein signalling has been implicated in pathogenesis in F. graminearum, although the underlying mechanisms are not fully understood. In this study, we investigated the involvement of a putative phosducin-like gene (BDM1) in growth, development and pathogenesis in F. graminearum. Targeted deletion of BDM1 revealed roles in sexual and asexual sporulation, germ tube development, hyphal branching and mycelial morphology. During pathogenesis, BDM1 is required for wild-type levels of colonization of maize silk tissue and stalks, but is dispensable for the colonization of kernels. The deletion of BDM1 also reduced the virulence of F. graminearum during the infection of wheat seedlings and heads, resulting in a significant reduction in fungal biomass and a delayed spread of visual symptom expression (i.e. bleaching in heads). Furthermore, BDM1 is required for wild-type levels of deoxynivalenol biosynthesis during the infection of wheat heads and maize silks. In summation, BDM1 is one of the few genes characterized to date in F. graminearum involved in virulence during infection of both maize and wheat. Thus, the functional characterization of BDM1 has established a new regulatory link between pathogenesis in maize and wheat, and provides a genetic resource through which the regulatory networks underlying virulence in F. graminearum can be further elucidated.
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Affiliation(s)
- Peter Horevaj
- Department of Plant Pathology, University of Arkansas Division of Agriculture, Fayetteville, AR 72701, USA
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Metabolome and transcriptome of the interaction between Ustilago maydis and Fusarium verticillioides in vitro. Appl Environ Microbiol 2012; 78:3656-67. [PMID: 22407693 DOI: 10.1128/aem.07841-11] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The metabolome and transcriptome of the maize-infecting fungi Ustilago maydis and Fusarium verticillioides were analyzed as the two fungi interact. Both fungi were grown for 7 days in liquid medium alone or together in order to study how this interaction changes their metabolomic and transcriptomic profiles. When grown together, decreased biomass accumulation occurs for both fungi after an initial acceleration of growth compared to the biomass changes that occur when grown alone. The biomass of U. maydis declined most severely over time and may be attributed to the action of F. verticillioides, which secretes toxic secondary metabolites and expresses genes encoding adhesive and cell wall-degrading proteins at higher levels than when grown alone. U. maydis responds to cocultivation by expressing siderophore biosynthetic genes and more highly expresses genes potentially involved in toxin biosynthesis. Also, higher expression was noted for clustered genes encoding secreted proteins that are unique to U. maydis and that may play a role during colonization of maize. Conversely, decreased gene expression was seen for U. maydis genes encoding the synthesis of ustilagic acid, mannosylerythritol D, and another uncharacterized metabolite. Ultimately, U. maydis is unable to react efficiently to the toxic response of F. verticillioides and proportionally loses more biomass. This in vitro study clarifies potential mechanisms of antagonism between these two fungi that also may occur in the soil or in maize, niches for both fungi where they likely interact in nature.
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Kim H, Smith JE, Ridenour JB, Woloshuk CP, Bluhm BH. HXK1 regulates carbon catabolism, sporulation, fumonisin B₁ production and pathogenesis in Fusarium verticillioides. MICROBIOLOGY-SGM 2011; 157:2658-2669. [PMID: 21719539 DOI: 10.1099/mic.0.052506-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In Fusarium verticillioides, a ubiquitous pathogen of maize, virulence and mycotoxigenesis are regulated in response to the types and amounts of carbohydrates present in maize kernels. In this study, we investigated the role of a putative hexokinase-encoding gene (HXK1) in growth, development and pathogenesis. A deletion mutant (Δhxk1) of HXK1 was not able to grow when supplied with fructose as the sole carbon source, and growth was impaired when glucose, sucrose or maltotriose was provided. Additionally, the Δhxk1 mutant produced unusual swollen hyphae when provided with fructose, but not glucose, as the sole carbon source. Moreover, the Δhxk1 mutant was impaired in fructose uptake, although glucose uptake was unaffected. On maize kernels, the Δhxk1 mutant was substantially less virulent than the wild-type, but virulence on maize stalks was not impaired, possibly indicating a metabolic response to tissue-specific differences in plant carbohydrate content. Finally, disruption of HXK1 had a pronounced effect on fungal metabolites produced during colonization of maize kernels; the Δhxk1 mutant produced approximately 50 % less trehalose and 80 % less fumonisin B₁ (FB₁) than the wild-type. The reduction in trehalose biosynthesis likely explains observations of increased sensitivity to osmotic stress in the Δhxk1 mutant. In summary, this study links early events in carbohydrate sensing and glycolysis to virulence and secondary metabolism in F. verticillioides, and thus provides a new foothold from which the genetic regulatory networks that underlie pathogenesis and mycotoxigenesis can be unravelled and defined.
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Affiliation(s)
- Hun Kim
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.,Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA
| | - Jonathon E Smith
- Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA
| | - John B Ridenour
- Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA
| | - Charles P Woloshuk
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
| | - Burton H Bluhm
- Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA
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