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Yu M, Zhou X, Chen D, Jiao Y, Han G, Tao F. HacA, a key transcription factor for the unfolded protein response, is required for fungal development, aflatoxin biosynthesis and pathogenicity of Aspergillus flavus. Int J Food Microbiol 2024; 417:110693. [PMID: 38653122 DOI: 10.1016/j.ijfoodmicro.2024.110693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Revised: 03/16/2024] [Accepted: 04/02/2024] [Indexed: 04/25/2024]
Abstract
Aspergillus flavus is a fungus notorious for contaminating food and feed with aflatoxins. As a saprophytic fungus, it secretes large amounts of enzymes to access nutrients, making endoplasmic reticulum (ER) homeostasis important for protein folding and secretion. The role of HacA, a key transcription factor in the unfolded protein response pathway, remains poorly understood in A. flavus. In this study, the hacA gene in A. flavus was knockout. Results showed that the absence of hacA led to a decreased pathogenicity of the strain, as it failed to colonize intact maize kernels. This may be due to retarded vegetable growth, especially the abnormal development of swollen tips and shorter hyphal septa. Deletion of hacA also hindered conidiogenesis and sclerotial development. Notably, the mutant strain failed to produce aflatoxin B1. Moreover, compared to the wild type, the mutant strain showed increased sensitivity to ER stress inducer such as Dithiothreitol (DTT), and heat stress. It also displayed heightened sensitivity to other environmental stresses, including cell wall, osmotic, and pH stresses. Further transcriptomic analysis revealed the involvement of the hacA in numerous biological processes, including filamentous growth, asexual reproduction, mycotoxin biosynthetic process, signal transduction, budding cell apical bud growth, invasive filamentous growth, response to stimulus, and so on. Taken together, HacA plays a vital role in fungal development, pathogenicity and aflatoxins biosynthesis. This highlights the potential of targeting hacA as a novel approach for early prevention of A. flavus contamination.
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Affiliation(s)
- Min Yu
- School of Life Sciences, Anhui Agricultural University, Hefei 230036, China
| | - Xiaoling Zhou
- School of Life Sciences, Anhui Agricultural University, Hefei 230036, China
| | - Dongyue Chen
- School of Life Sciences, Anhui Agricultural University, Hefei 230036, China
| | - Yuan Jiao
- School of Life Sciences, Anhui Agricultural University, Hefei 230036, China
| | - Guomin Han
- School of Life Sciences, Anhui Agricultural University, Hefei 230036, China; National Engineering Laboratory of Crop Stress Resistance Breeding, Anhui Agricultural University, Hefei 230036, China
| | - Fang Tao
- School of Life Sciences, Anhui Agricultural University, Hefei 230036, China.
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2
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Moore GG, Mack BM, Wendt KL, Castano-Duque L, Anderson VM, Cichewicz RH. Genomic and metabolomic diversity within a familial population of Aspergillus flavus. Mol Microbiol 2024; 121:927-939. [PMID: 38396382 DOI: 10.1111/mmi.15244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/12/2024] [Accepted: 02/11/2024] [Indexed: 02/25/2024]
Abstract
Aspergillus flavus is an agriculturally significant micro-fungus having potential to contaminate food and feed crops with toxic secondary metabolites such as aflatoxin (AF) and cyclopiazonic acid (CPA). Research has shown A. flavus strains can overcome heterokaryon incompatibility and undergo meiotic recombination as teleomorphs. Although evidence of recombination in the AF gene cluster has been reported, the impacts of recombination on genotype and metabolomic phenotype in a single generation are lacking. In previous studies, we paired an aflatoxigenic MAT1-1 A. flavus strain with a non-aflatoxigenic MAT1-2 A. flavus strain that had been tagged with green fluorescent protein and then 10 F1 progenies (a mix of fluorescent and non-fluorescent) were randomly selected from single-ascospore colonies and broadly examined for evidence of recombination. In this study, we determined four of those 10 F1 progenies were recombinants because they were not vegetatively compatible with either parent or their siblings, and they exhibited other distinctive traits that could only result from meiotic recombination. The other six progenies examined shared genomic identity with the non-aflatoxigenic, fluorescent, and MAT1-2 parent, but were metabolically distinct. This study highlights phenotypic and genomic changes that may occur in a single generation from the outcrossing of sexually compatible strains of A. flavus.
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Affiliation(s)
- Geromy G Moore
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana, USA
| | - Brian M Mack
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana, USA
| | - Karen L Wendt
- Department of Chemistry and Biochemistry, Natural Products Discovery Group, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
| | - Lina Castano-Duque
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana, USA
| | - Victoria M Anderson
- Department of Chemistry and Biochemistry, Natural Products Discovery Group, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
| | - Robert H Cichewicz
- Department of Chemistry and Biochemistry, Natural Products Discovery Group, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
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3
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Recombination-aware phylogeographic inference using the structured coalescent with ancestral recombination. PLoS Comput Biol 2022; 18:e1010422. [PMID: 35984849 PMCID: PMC9447913 DOI: 10.1371/journal.pcbi.1010422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 09/06/2022] [Accepted: 07/21/2022] [Indexed: 11/19/2022] Open
Abstract
Movement of individuals between populations or demes is often restricted, especially between geographically isolated populations. The structured coalescent provides an elegant theoretical framework for describing how movement between populations shapes the genealogical history of sampled individuals and thereby structures genetic variation within and between populations. However, in the presence of recombination an individual may inherit different regions of their genome from different parents, resulting in a mosaic of genealogical histories across the genome, which can be represented by an Ancestral Recombination Graph (ARG). In this case, different genomic regions may have different ancestral histories and so different histories of movement between populations. Recombination therefore poses an additional challenge to phylogeographic methods that aim to reconstruct the movement of individuals from genealogies, although also a potential benefit in that different loci may contain additional information about movement. Here, we introduce the Structured Coalescent with Ancestral Recombination (SCAR) model, which builds on recent approximations to the structured coalescent by incorporating recombination into the ancestry of sampled individuals. The SCAR model allows us to infer how the migration history of sampled individuals varies across the genome from ARGs, and improves estimation of key population genetic parameters such as population sizes, recombination rates and migration rates. Using the SCAR model, we explore the potential and limitations of phylogeographic inference using full ARGs. We then apply the SCAR to lineages of the recombining fungus Aspergillus flavus sampled across the United States to explore patterns of recombination and migration across the genome. Phylogeographic methods are widely used to reconstruct the historical movement of individuals between different populations. When applied to infectious pathogens, these methods are often used to reconstruct the origin or source of novel pathogen lineages. Most existing phylogeographic methods reconstruct movement based on a single phylogenetic tree, which is assumed to reflect the genetic ancestry of all sampled individuals. However in populations undergoing recombination, genetic material can be exchanged between lineages such that individuals may inherit different regions of their genome from different ancestors. In this case, phylogenetic relationships among individuals can only be captured by a reticulated network rather than any single tree. Ancestral Recombination Graphs (ARGs) provide one way of capturing these reticulate relationships and we develop new models that allow for demographic inference of historical population sizes, recombination rates and migration rates between subpopulations from ARGs. By accounting for recombination, our models not only allow for accurate demographic inference, but can take full advantage of the additional information contained in ARGs about how ancestry varies across genomes to more precisely reconstruct the movement of genetic material between populations.
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Systematic Characterization of bZIP Transcription Factors Required for Development and Aflatoxin Generation by High-Throughput Gene Knockout in Aspergillus flavus. J Fungi (Basel) 2022; 8:jof8040356. [PMID: 35448587 PMCID: PMC9031554 DOI: 10.3390/jof8040356] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/23/2022] [Accepted: 03/23/2022] [Indexed: 12/31/2022] Open
Abstract
The basic leucine zipper (bZIP) is an important transcription factor required for fungal development, nutrient utilization, biosynthesis of secondary metabolites, and defense against various stresses. Aspergillus flavus is a major producer of aflatoxin and an opportunistic fungus on a wide range of hosts. However, little is known about the role of most bZIP genes in A. flavus. In this study, we developed a high-throughput gene knockout method based on an Agrobacterium-mediated transformation system. Gene knockout construction by yeast recombinational cloning and screening of the null mutants by double fluorescence provides an efficient way to construct gene-deleted mutants for this multinucleate fungus. We deleted 15 bZIP genes in A. flavus. Twelve of these genes were identified and characterized in this strain for the first time. The phenotypic analysis of these mutants showed that the 15 bZIP genes play a diverse role in mycelial growth (eight genes), conidiation (13 genes), aflatoxin biosynthesis (10 genes), oxidative stress response (11 genes), cell wall stress (five genes), osmotic stress (three genes), acid and alkali stress (four genes), and virulence to kernels (nine genes). Impressively, all 15 genes were involved in the development of sclerotia, and the respective deletion mutants of five of them did not produce sclerotia. Moreover, MetR was involved in this biological process. In addition, HapX and MetR play important roles in the adaptation to excessive iron and sulfur metabolism, respectively. These studies provide comprehensive insights into the role of bZIP transcription factors in this aflatoxigenic fungus of global significance.
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Zhou Y, Du C, Odiba AS, He R, Ahamefule CS, Wang B, Jin C, Fang W. Phosphoglucose Isomerase Plays a Key Role in Sugar Homeostasis, Stress Response, and Pathogenicity in Aspergillus flavus. Front Cell Infect Microbiol 2022; 11:777266. [PMID: 34976860 PMCID: PMC8715936 DOI: 10.3389/fcimb.2021.777266] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 11/17/2021] [Indexed: 01/22/2023] Open
Abstract
Aspergillus flavus is one of the important human and plant pathogens causing not only invasive aspergillosis in immunocompromised patients but also crop contamination resulting from carcinogenic aflatoxins (AFs). Investigation of the targeting factors that are involved in pathogenicity is of unmet need to dismiss the hazard. Phosphoglucose isomerase (PGI) catalyzes the reversible conversion between glucose-6-phosphate and fructose-6-phosphate, thus acting as a key node for glycolysis, pentose phosphate pathway, and cell wall biosynthesis in fungi. In this study, we constructed an A. flavus pgi deletion mutant, which exhibited specific carbon requirement for survival, reduced conidiation, and slowed germination even under optimal experimental conditions. The Δpgi mutant lost the ability to form sclerotium and displayed hypersusceptibility to osmotic, oxidative, and temperature stresses. Furthermore, significant attenuated virulence of the Δpgi mutant was documented in the Caenorhabditis elegans infection model, Galleria mellonella larval model, and crop seeds. Our results indicate that PGI in A. flavus is a key enzyme in maintaining sugar homeostasis, stress response, and pathogenicity of A. flavus. Therefore, PGI is a potential target for controlling infection and AF contamination caused by A. flavus.
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Affiliation(s)
- Yao Zhou
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China.,College of Life Science and Technology, Guangxi University, Nanning, China
| | - Chao Du
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China.,College of Life Science and Technology, Guangxi University, Nanning, China
| | - Arome Solomon Odiba
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China
| | - Rui He
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China.,College of Life Science and Technology, Guangxi University, Nanning, China
| | | | - Bin Wang
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China.,National Engineering Research Center for Non-Food Biorefinery, Guangxi Academy of Sciences, Nanning, China
| | - Cheng Jin
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China.,College of Life Science and Technology, Guangxi University, Nanning, China.,State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Wenxia Fang
- State Key Laboratory of Non-Food Biomass and Enzyme Technology, Guangxi Academy of Sciences, Nanning, China.,National Engineering Research Center for Non-Food Biorefinery, Guangxi Academy of Sciences, Nanning, China
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6
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Wong SSW, Venugopalan LP, Beaussart A, Karnam A, Mohammed MRS, Jayapal JM, Bretagne S, Bayry J, Prajna L, Kuppamuthu D, Latgé JP, Aimanianda V. Species-Specific Immunological Reactivities Depend on the Cell-Wall Organization of the Two Aspergillus, Aspergillus fumigatus and A. flavus. Front Cell Infect Microbiol 2021; 11:643312. [PMID: 33718288 PMCID: PMC7950546 DOI: 10.3389/fcimb.2021.643312] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 01/15/2021] [Indexed: 12/12/2022] Open
Abstract
Although belong to the same genus, Aspergillus fumigatus is primarily involved in invasive pulmonary infection, whereas Aspergillus flavus is a common cause of superficial infection. In this study, we compared conidia (the infective propagules) of these two Aspergillus species. In immunocompetent mice, intranasal inoculation with conidia of A. flavus resulted in significantly higher inflammatory responses in the lungs compared to mice inoculated with A. fumigatus conidia. In vitro assays revealed that the dormant conidia of A. flavus, unlike A. fumigatus dormant conidia, are immunostimulatory. The conidial surface of A. fumigatus was covered by a rodlet-layer, while that of A. flavus were presented with exposed polysaccharides. A. flavus harbored significantly higher number of proteins in its conidial cell wall compared to A. fumigatus conidia. Notably, β-1,3-glucan in the A. flavus conidial cell-wall showed significantly higher percentage of branching compared to that of A. fumigatus. The polysaccharides ensemble of A. flavus conidial cell wall stimulated the secretion of proinflammatory cytokines, and conidial cell wall associated proteins specifically stimulated IL-8 secretion from the host immune cells. Furthermore, the two species exhibited different sensitivities to antifungal drugs targeting cell wall polysaccharides, proposing the efficacy of species-specific treatment strategies. Overall, the species-specific organization of the conidial cell wall could be important in establishing infection by the two Aspergillus species.
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Affiliation(s)
- Sarah Sze Wah Wong
- Institut Pasteur, Unité des Aspergillus, Paris, France.,Institut Pasteur, Molecular Mycology Unit, CNRS, UMR-2000, Paris, France
| | | | | | - Anupama Karnam
- Institut National de la Santé et de la Recherche Médicale, Centre de Recherché des Cordeliers, Sorbonne Université, Université de Paris, Paris, France
| | | | - Jeya Maheshwari Jayapal
- Department of Proteomics & Ocular Microbiology, Aravind Medical Research Foundation, Madurai, India
| | - Stéphane Bretagne
- Institut Pasteur, Molecular Mycology Unit, CNRS, UMR-2000, Paris, France
| | - Jagadeesh Bayry
- Institut National de la Santé et de la Recherche Médicale, Centre de Recherché des Cordeliers, Sorbonne Université, Université de Paris, Paris, France
| | - Lalitha Prajna
- Department of Ocular Microbiology, Aravind Eye Hospital, Madurai, India
| | - Dharmalingam Kuppamuthu
- Department of Proteomics & Ocular Microbiology, Aravind Medical Research Foundation, Madurai, India
| | | | - Vishukumar Aimanianda
- Institut Pasteur, Unité des Aspergillus, Paris, France.,Institut Pasteur, Molecular Mycology Unit, CNRS, UMR-2000, Paris, France
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8
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Wang Y, Wang S, Nie X, Yang K, Xu P, Wang X, Liu M, Yang Y, Chen Z, Wang S. Molecular and structural basis of nucleoside diphosphate kinase-mediated regulation of spore and sclerotia development in the fungus Aspergillus flavus. J Biol Chem 2019; 294:12415-12431. [PMID: 31243100 DOI: 10.1074/jbc.ra119.007505] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 06/10/2019] [Indexed: 12/14/2022] Open
Abstract
The fundamental biological function of nucleoside diphosphate kinase (NDK) is to catalyze the reversible exchange of the γ-phosphate between nucleoside triphosphate (NTP) and nucleoside diphosphate (NDP). This kinase also has functions that extend beyond its canonically defined enzymatic role as a phosphotransferase. However, the role of NDK in filamentous fungi, especially in Aspergillus flavus (A. flavus), is not yet known. Here we report that A. flavus has two NDK-encoding gene copies as assessed by qPCR. Using gene-knockout and complementation experiments, we found that AfNDK regulates spore and sclerotia development and is involved in plant virulence as assessed in corn and peanut seed-based assays. An antifungal test with the inhibitor azidothymidine suppressed AfNDK activity in vitro and prevented spore production and sclerotia formation in A. flavus, confirming AfNDK's regulatory functions. Crystallographic analysis of AfNDK, coupled with site-directed mutagenesis experiments, revealed three residues (Arg-104, His-117, and Asp-120) as key sites that contribute to spore and sclerotia development. These results not only enrich our knowledge of the regulatory role of this important protein in A. flavus, but also provide insights into the prevention of A. flavus infection in plants and seeds, as well as into the structural features relevant for future antifungal drug development.
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Affiliation(s)
- Yu Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Sen Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Xinyi Nie
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Kunlong Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Peng Xu
- State Key Laboratory of Structural Chemistry and CAS Key Laboratory, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
| | - Xiuna Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Mengxin Liu
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yongshuai Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China; State Key Laboratory of Structural Chemistry and CAS Key Laboratory, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
| | - Zhuo Chen
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China; State Key Laboratory of Structural Chemistry and CAS Key Laboratory, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 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, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Frisvad J, Hubka V, Ezekiel C, Hong SB, Nováková A, Chen A, Arzanlou M, Larsen T, Sklenář F, Mahakarnchanakul W, Samson R, Houbraken J. Taxonomy of Aspergillus section Flavi and their production of aflatoxins, ochratoxins and other mycotoxins. Stud Mycol 2019; 93:1-63. [PMID: 30108412 PMCID: PMC6080641 DOI: 10.1016/j.simyco.2018.06.001] [Citation(s) in RCA: 258] [Impact Index Per Article: 51.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aflatoxins and ochratoxins are among the most important mycotoxins of all and producers of both types of mycotoxins are present in Aspergillus section Flavi, albeit never in the same species. Some of the most efficient producers of aflatoxins and ochratoxins have not been described yet. Using a polyphasic approach combining phenotype, physiology, sequence and extrolite data, we describe here eight new species in section Flavi. Phylogenetically, section Flavi is split in eight clades and the section currently contains 33 species. Two species only produce aflatoxin B1 and B2 (A. pseudotamarii and A. togoensis), and 14 species are able to produce aflatoxin B1, B2, G1 and G2: three newly described species A. aflatoxiformans, A. austwickii and A. cerealis in addition to A. arachidicola, A. minisclerotigenes, A. mottae, A. luteovirescens (formerly A. bombycis), A. nomius, A. novoparasiticus, A. parasiticus, A. pseudocaelatus, A. pseudonomius, A. sergii and A. transmontanensis. It is generally accepted that A. flavus is unable to produce type G aflatoxins, but here we report on Korean strains that also produce aflatoxin G1 and G2. One strain of A. bertholletius can produce the immediate aflatoxin precursor 3-O-methylsterigmatocystin, and one strain of Aspergillus sojae and two strains of Aspergillus alliaceus produced versicolorins. Strains of the domesticated forms of A. flavus and A. parasiticus, A. oryzae and A. sojae, respectively, lost their ability to produce aflatoxins, and from the remaining phylogenetically closely related species (belonging to the A. flavus-, A. tamarii-, A. bertholletius- and A. nomius-clades), only A. caelatus, A. subflavus and A. tamarii are unable to produce aflatoxins. With exception of A. togoensis in the A. coremiiformis-clade, all species in the phylogenetically more distant clades (A. alliaceus-, A. coremiiformis-, A. leporis- and A. avenaceus-clade) are unable to produce aflatoxins. Three out of the four species in the A. alliaceus-clade can produce the mycotoxin ochratoxin A: A. alliaceus s. str. and two new species described here as A. neoalliaceus and A. vandermerwei. Eight species produced the mycotoxin tenuazonic acid: A. bertholletius, A. caelatus, A. luteovirescens, A. nomius, A. pseudocaelatus, A. pseudonomius, A. pseudotamarii and A. tamarii while the related mycotoxin cyclopiazonic acid was produced by 13 species: A. aflatoxiformans, A. austwickii, A. bertholletius, A. cerealis, A. flavus, A. minisclerotigenes, A. mottae, A. oryzae, A. pipericola, A. pseudocaelatus, A. pseudotamarii, A. sergii and A. tamarii. Furthermore, A. hancockii produced speradine A, a compound related to cyclopiazonic acid. Selected A. aflatoxiformans, A. austwickii, A. cerealis, A. flavus, A. minisclerotigenes, A. pipericola and A. sergii strains produced small sclerotia containing the mycotoxin aflatrem. Kojic acid has been found in all species in section Flavi, except A. avenaceus and A. coremiiformis. Only six species in the section did not produce any known mycotoxins: A. aspearensis, A. coremiiformis, A. lanosus, A. leporis, A. sojae and A. subflavus. An overview of other small molecule extrolites produced in Aspergillus section Flavi is given.
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Affiliation(s)
- J.C. Frisvad
- Department of Biotechnology and Biomedicine, DTU-Bioengineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - V. Hubka
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, 128 01 Prague 2, Czech Republic
- Institute of Microbiology of the CAS, v.v.i., Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - C.N. Ezekiel
- Department of Microbiology, Babcock University, Ilishan Rémo, Nigeria
| | - S.-B. Hong
- Korean Agricultural Culture Collection, National Academy of Agricultural Science, RDA, Suwon, South Korea
| | - A. Nováková
- Institute of Microbiology of the CAS, v.v.i., Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - A.J. Chen
- Institute of Medical Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, PR China
- Westerdijk Fungal Biodiversity Institute, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - M. Arzanlou
- Department of Plant Protection, University of Tabriz, Tabriz, Iran
| | - T.O. Larsen
- Department of Biotechnology and Biomedicine, DTU-Bioengineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - F. Sklenář
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, 128 01 Prague 2, Czech Republic
- Institute of Microbiology of the CAS, v.v.i., Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - W. Mahakarnchanakul
- Department of Food Science and Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand
| | - R.A. Samson
- Westerdijk Fungal Biodiversity Institute, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - J. Houbraken
- Westerdijk Fungal Biodiversity Institute, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
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11
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Islam MS, Callicott KA, Mutegi C, Bandyopadhyay R, Cotty PJ. Aspergillus flavus resident in Kenya: High genetic diversity in an ancient population primarily shaped by clonal reproduction and mutation-driven evolution. FUNGAL ECOL 2018; 35:20-33. [PMID: 30283498 PMCID: PMC6131765 DOI: 10.1016/j.funeco.2018.05.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 12/30/2022]
Abstract
Aspergillus flavus has long been considered to be an asexual species. Although a sexual stage was recently reported for this species from in vitro studies, the amount of recombination ongoing in natural populations and the genetic distance across which meiosis occurs is largely unknown. In the current study, genetic diversity, reproduction and evolution of natural A. flavus populations endemic to Kenya were examined. A total of 2744 isolates recovered from 629 maize-field soils across southern Kenya in two consecutive seasons were characterized at 17 SSR loci, revealing high genetic diversity (9-72 alleles/locus and 2140 haplotypes). Clonal reproduction and persistence of clonal lineages predominated, with many identical haplotypes occurring in multiple soil samples and both seasons. Genetic analyses predicted three distinct lineages with linkage disequilibrium and evolutionary relationships among haplotypes within each lineage suggesting mutation-driven evolution followed by clonal reproduction. Low genetic differentiation among adjacent communities reflected frequent short distance dispersal.
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Affiliation(s)
- Md-Sajedul Islam
- Agricultural Research Service, United States Department of Agriculture, School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Kenneth A. Callicott
- Agricultural Research Service, United States Department of Agriculture, School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Charity Mutegi
- International Institute of Tropical Agriculture, Nairobi, Kenya
| | | | - Peter J. Cotty
- Agricultural Research Service, United States Department of Agriculture, School of Plant Sciences, University of Arizona, Tucson, AZ, USA
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Han G, Shao Q, Li C, Zhao K, Jiang L, Fan J, Jiang H, Tao F. An efficient Agrobacterium-mediated transformation method for aflatoxin generation fungus Aspergillus flavus. J Microbiol 2018; 56:356-364. [DOI: 10.1007/s12275-018-7349-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 02/13/2018] [Accepted: 02/19/2018] [Indexed: 10/17/2022]
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13
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Impact of Morphological Sectors on Antifungal Susceptibility Testing and Virulence Studies. Antimicrob Agents Chemother 2017; 61:AAC.00755-17. [PMID: 28993330 DOI: 10.1128/aac.00755-17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 09/30/2017] [Indexed: 12/11/2022] Open
Abstract
Morphological heterogeneity of Aspergillus terreus cultures was observed during continued cultivation of amphotericin B (AMB)-resistant isolates on drug-free medium. Outgrowth leads to the emergence of multiple sectors that might result from increased growth rates at drug-free conditions. We evaluated the differences in AMB susceptibility and virulence between sector subcultures (ATSec), AMB-resistant (ATR) strains, and AMB-susceptible (ATS) strains. By comparing A. terreus AMB-resistant (ATR) strains and A. terreus sector (ATSec) cultures we observed a highly significant reduction of AMB MICs in ATSec (ATR MIC, 2 to 32 μg/ml; ATSec MIC, 0.12 to 5 μg/ml). Furthermore, Galleria mellonella survival studies revealed an enhanced virulence of ATSec, which was comparable with that of AMB-sensitive Aspergillus terreus strains (median survival rates for ATS isolates, 72 h; for ATSec isolate ATSecG1, 84 h; for ATR isolates, 144 h). Our findings clearly demonstrate that spontaneous culture degeneration occurs in A. terreus and, most importantly, crucially impacts drug efficacy and virulence.
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14
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Zhao X, Spraker JE, Bok JW, Velk T, He ZM, Keller NP. A Cellular Fusion Cascade Regulated by LaeA Is Required for Sclerotial Development in Aspergillus flavus. Front Microbiol 2017; 8:1925. [PMID: 29051754 PMCID: PMC5633613 DOI: 10.3389/fmicb.2017.01925] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/21/2017] [Indexed: 11/13/2022] Open
Abstract
Aspergillus flavus is a saprophytic soil fungus that poses a serious threat worldwide as it contaminates many food and feed crops with the carcinogenic mycotoxin called aflatoxin. This pathogen persists as sclerotia in the soil which enables fungal survival in harsh environmental conditions. Sclerotia formation by A. flavus depends on successful cell communication and hyphal fusion events. Loss of LaeA, a conserved developmental regulator in fungi, abolishes sclerotia formation in this species whereas overexpression (OE) of laeA results in enhanced sclerotia production. Here we demonstrate that sclerotia loss and inability to form heterokaryons in A. flavusΔlaeA is mediated by homologs of the Neurospora crassa ham (hyphal anastomosis) genes termed hamE-I in A. flavus. LaeA positively regulates ham gene expression and deletion of hamF, G, H, or I phenocopies ΔlaeA as demonstrated by heterokaryon and sclerotia loss and reduced aflatoxin synthesis and virulence of these mutants. Deletion of hamE showed a less severe phenotype. hamE-I homologs are positively regulated by the clock controlled transcription factor ADV-1 in N. crassa. Similarly, the ADV-1 homolog NosA regulates hamE-I expression in A. flavus, is required for sclerotial development and is itself positively regulated by LaeA. We speculate that a putative LaeA>NosA>fusion cascade underlies the previously described circadian clock regulation of sclerotia production in A. flavus.
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Affiliation(s)
- Xixi Zhao
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China.,Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Joseph E Spraker
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States
| | - Jin Woo Bok
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Thomas Velk
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Zhu-Mei He
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, United States
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15
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Baranyi N, Kocsubé S, Jakšić Despot D, Šegvić Klarić M, Szekeres A, Bencsik O, Kecskeméti A, Manikandan P, Tóth B, Kredics L, Khaled JM, Alharbi NS, Vágvölgyi C, Varga J. Combined genotyping strategy reveals structural differences between Aspergillus flavus lineages from different habitats impacting human health. J Basic Microbiol 2017; 57:899-909. [PMID: 28902962 DOI: 10.1002/jobm.201700243] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/24/2017] [Accepted: 08/17/2017] [Indexed: 11/07/2022]
Abstract
Aspergillus flavus is a filamentous fungus which is widespread on agricultural products and also able to cause various human diseases. This species is frequently isolated from indoor air as well, furthermore, it is known as a common causal agent of keratomycosis, particularly in subtropical and tropical areas. It is also able to produce aflatoxins, one of the most carcinogenic mycotoxins which are harmful to animals and humans. In this study, 59 A. flavus isolates from four different habitats and 1 A. minisclerotigenes isolate were investigated. The isolates were identified and confirmed at the species level by the sequence analysis of a part of their calmodulin gene. Applying a combined analysis of UP-PCR, microsatellite, and calmodulin sequence data, the four group of isolates formed separate clusters on the phylogenetic tree. Examining the distribution of mating type genes MAT1-1 and MAT1-2, a ratio of approximately 3:1 was determined, and no correlation was found between the carried mating type gene and the aflatoxin production capability. HPLC analysis revealed that none of the examined isolates collected from indoor air or maize in Central Europe were able to produce aflatoxins, while about half of the isolates from India produced these mycotoxins under the test conditions.
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Affiliation(s)
- Nikolett Baranyi
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Sándor Kocsubé
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Daniela Jakšić Despot
- Faculty of Pharmacy and Biochemistry, Department of Microbiology, University of Zagreb, Zagreb, Croatia
| | - Maja Šegvić Klarić
- Faculty of Pharmacy and Biochemistry, Department of Microbiology, University of Zagreb, Zagreb, Croatia
| | - András Szekeres
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Ottó Bencsik
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Anita Kecskeméti
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Palanisamy Manikandan
- Greenlink Analytical and Research Laboratory India Private Ltd, Coimbatore, Tamilnadu, India
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Al-Majmaah, Saudi Arabia
| | - Beáta Tóth
- National Agricultural Research and Innovation Center, NÖKO, Szeged, Hungary
| | - László Kredics
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
| | - Jamal M Khaled
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - Naiyf S Alharbi
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - Csaba Vágvölgyi
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - János Varga
- Faculty of Science and Informatics, Department of Microbiology, University of Szeged, Szeged, Hungary
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Careful with That Axe, Gene, Genome Perturbation after a PEG-Mediated Protoplast Transformation in Fusarium verticillioides. Toxins (Basel) 2017; 9:toxins9060183. [PMID: 28561789 PMCID: PMC5488033 DOI: 10.3390/toxins9060183] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/22/2017] [Accepted: 05/26/2017] [Indexed: 11/17/2022] Open
Abstract
Fusarium verticillioides causes ear rot disease in maize and its contamination with fumonisins, mycotoxins harmful for humans and livestock. Lipids, and their oxidized forms, may drive the fate of this disease. In a previous study, we have explored the role of oxylipins in this interaction by deleting by standard transformation procedures a linoleate diol synthase-coding gene, lds1, in F. verticillioides. A profound phenotypic diversity in the mutants generated has prompted us to investigate more deeply the whole genome of two lds1-deleted strains. Bioinformatics analyses pinpoint significant differences in the genome sequences emerged between the wild type and the lds1-mutants further than those trivially attributable to the deletion of the lds1 locus, such as single nucleotide polymorphisms, small deletion/insertion polymorphisms and structural variations. Results suggest that the effect of a (theoretically) punctual transformation event might have enhanced the natural mechanisms of genomic variability and that transformation practices, commonly used in the reverse genetics of fungi, may potentially be responsible for unexpected, stochastic and henceforth off-target rearrangements throughout the genome.
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