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Sweany RR, Mack BM, Gebru ST, Mammel MK, Cary JW, Moore GG, Lebar MD, Carter-Wientjes CH, Gilbert MK. Divergent Aspergillus flavus corn population is composed of prolific conidium producers: Implications for saprophytic disease cycle. Mycologia 2024; 116:536-557. [PMID: 38727560 DOI: 10.1080/00275514.2024.2343645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 04/12/2024] [Indexed: 06/29/2024]
Abstract
The ascomycete fungus Aspergillus flavus infects and contaminates corn, peanuts, cottonseed, and tree nuts with toxic and carcinogenic aflatoxins. Subdivision between soil and host plant populations suggests that certain A. flavus strains are specialized to infect peanut, cotton, and corn despite having a broad host range. In this study, the ability of strains isolated from corn and/or soil in 11 Louisiana fields to produce conidia (field inoculum and male gamete) and sclerotia (resting bodies and female gamete) was assessed and compared with genotypic single-nucleotide polymorphism (SNP) differences between whole genomes. Corn strains produced upward of 47× more conidia than strains restricted to soil. Conversely, corn strains produced as much as 3000× fewer sclerotia than soil strains. Aspergillus flavus strains, typified by sclerotium diameter (small S-strains, <400 μm; large L-strains, >400 μm), belonged to separate clades. Several strains produced a mixture (M) of S and L sclerotia, and an intermediate number of conidia and sclerotia, compared with typical S-strains (minimal conidia, copious sclerotia) and L-strains (copious conidia, minimal sclerotia). They also belonged to a unique phylogenetic mixed (M) clade. Migration from soil to corn positively correlated with conidium production and negatively correlated with sclerotium production. Genetic differences correlated with differences in conidium and sclerotium production. Opposite skews in female (sclerotia) or male (conidia) gametic production by soil or corn strains, respectively, resulted in reduced effective breeding population sizes when comparing male:female gamete ratio with mating type distribution. Combining both soil and corn populations increased the effective breeding population, presumably due to contribution of male gametes from corn, which fertilize sclerotia on the soil surface. Incongruencies between aflatoxin clusters, strain morphotype designation, and whole genome phylogenies suggest a history of sexual reproduction within this Louisiana population, demonstrating the importance of conidium production, as infectious propagules and as fertilizers of the A. flavus soil population.
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Affiliation(s)
- Rebecca R Sweany
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Brian M Mack
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Solomon T Gebru
- Division of Virulence Assessment, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, 20708
| | - Mark K Mammel
- Division of Molecular Biology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, 20708
| | - Jeffrey W Cary
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Geromy G Moore
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Matthew D Lebar
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Carol H Carter-Wientjes
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Matthew K Gilbert
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
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Katati B, Kovacs S, Njapau H, Kachapulula PW, Zwaan BJ, van Diepeningen AD, Schoustra SE. Aflatoxigenic Aspergillus Modulates Aflatoxin-B1 Levels through an Antioxidative Mechanism. J Fungi (Basel) 2023; 9:690. [PMID: 37367626 DOI: 10.3390/jof9060690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 06/10/2023] [Accepted: 06/12/2023] [Indexed: 06/28/2023] Open
Abstract
Aflatoxins (AFs) are considered to play important functions in species of Aspergillus section Flavi including an antioxidative role, as a deterrent against fungivorous insects, and in antibiosis. Atoxigenic Flavi are known to degrade AF-B1 (B1). To better understand the purpose of AF degradation, we investigated the degradation of B1 and AF-G1 (G1) in an antioxidative role in Flavi. Atoxigenic and toxigenic Flavi were treated with artificial B1 and G1 with or without the antioxidant selenium (Se), which is expected to affect levels of AF. After incubations, AF levels were measured by HPLC. To estimate which population would likely be favoured between toxigenic and atoxigenic Flavi under Se, we investigated the fitness, by spore count, of the Flavi as a result of exposure to 0, 0.40, and 0.86 µg/g Se in 3%-sucrose cornmeal agar (3gCMA). Results showed that levels B1 in medium without Se were reduced in all isolates, while G1 did not significantly change. When the medium was treated with Se, toxigenic Flavi significantly digested less B1, while levels of G1 significantly increased. Se did not affect the digestion of B1 in atoxigenic Flavi, and also did not alter levels of G1. Furthermore, atoxigenic strains were significantly fitter than toxigenic strains at Se 0.86 µg/g 3gCMA. Findings show that while atoxigenic Flavi degraded B1, toxigenic Flavi modulated its levels through an antioxidative mechanism to levels less than they produced. Furthermore, B1 was preferred in the antioxidative role compared to G1 in the toxigenic isolates. The higher fitness of atoxigenic over toxigenic counterparts at a plant non-lethal dose of 0.86 µg/g would be a useful attribute for integration in the broader biocontrol prospects of toxigenic Flavi.
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Affiliation(s)
- Bwalya Katati
- Laboratory of Genetics, Wageningen University and Research, 6708 PB Wageningen, The Netherlands
- Mycotoxicology Laboratory, National Institute for Scientific and Industrial Research, Lusaka 310158, Zambia
| | - Stan Kovacs
- Laboratory of Genetics, Wageningen University and Research, 6708 PB Wageningen, The Netherlands
| | - Henry Njapau
- Mycotoxicology Laboratory, National Institute for Scientific and Industrial Research, Lusaka 310158, Zambia
| | - Paul W Kachapulula
- School of Agricultural Sciences, University of Zambia, Lusaka 10101, Zambia
| | - Bas J Zwaan
- Laboratory of Genetics, Wageningen University and Research, 6708 PB Wageningen, The Netherlands
| | - Anne D van Diepeningen
- Biointeractions and Plant Health, Wageningen University and Research, 6708 PB Wageningen, The Netherlands
| | - Sijmen E Schoustra
- Laboratory of Genetics, Wageningen University and Research, 6708 PB Wageningen, The Netherlands
- School of Agricultural Sciences, University of Zambia, Lusaka 10101, Zambia
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Drott MT, Park SC, Wang YW, Harrow L, Keller NP, Pringle A. Pangenomics of the death cap mushroom Amanita phalloides, and of Agaricales, reveals dynamic evolution of toxin genes in an invasive range. THE ISME JOURNAL 2023:10.1038/s41396-023-01432-x. [PMID: 37221394 DOI: 10.1038/s41396-023-01432-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 05/01/2023] [Accepted: 05/04/2023] [Indexed: 05/25/2023]
Abstract
The poisonous European mushroom Amanita phalloides (the "death cap") is invading California. Whether the death caps' toxic secondary metabolites are evolving as it invades is unknown. We developed a bioinformatic pipeline to identify the MSDIN genes underpinning toxicity and probed 88 death cap genomes from an invasive Californian population and from the European range, discovering a previously unsuspected diversity of MSDINs made up of both core and accessory elements. Each death cap individual possesses a unique suite of MSDINs, and toxin genes are significantly differentiated between Californian and European samples. MSDIN genes are maintained by strong natural selection, and chemical profiling confirms MSDIN genes are expressed and result in distinct phenotypes; our chemical profiling also identified a new MSDIN peptide. Toxin genes are physically clustered within genomes. We contextualize our discoveries by probing for MSDINs in genomes from across the order Agaricales, revealing MSDIN diversity originated in independent gene family expansions among genera. We also report the discovery of an MSDIN in an Amanita outside the "lethal Amanitas" clade. Finally, the identification of an MSDIN gene and its associated processing gene (POPB) in Clavaria fumosa suggest the origin of MSDINs is older than previously suspected. The dynamic evolution of MSDINs underscores their potential to mediate ecological interactions, implicating MSDINs in the ongoing invasion. Our data change the understanding of the evolutionary history of poisonous mushrooms, emphasizing striking parallels to convergently evolved animal toxins. Our pipeline provides a roadmap for exploring secondary metabolites in other basidiomycetes and will enable drug prospecting.
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Affiliation(s)
- Milton T Drott
- Department of Medical Microbiology and Immunology, Department of Bacteriology, University of Wisconsin, Madison, WI, USA.
- USDA-ARS Cereal Disease Laboratory, St. Paul, MN, USA.
| | - Sung Chul Park
- Department of Medical Microbiology and Immunology, Department of Bacteriology, University of Wisconsin, Madison, WI, USA
| | - Yen-Wen Wang
- Departments of Botany and Bacteriology, University of Wisconsin, Madison, WI, USA
| | - Lynn Harrow
- Departments of Botany and Bacteriology, University of Wisconsin, Madison, WI, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, Department of Bacteriology, University of Wisconsin, Madison, WI, USA.
| | - Anne Pringle
- Departments of Botany and Bacteriology, University of Wisconsin, Madison, WI, USA.
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4
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Tannous J, Cosetta CM, Drott MT, Rush TA, Abraham PE, Giannone RJ, Keller NP, Wolfe BE. LaeA-Regulated Fungal Traits Mediate Bacterial Community Assembly. mBio 2023:e0076923. [PMID: 37162223 DOI: 10.1128/mbio.00769-23] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023] Open
Abstract
Potent antimicrobial metabolites are produced by filamentous fungi in pure culture, but their ecological functions in nature are often unknown. Using an antibacterial Penicillium isolate and a cheese rind microbial community, we demonstrate that a fungal specialized metabolite can regulate the diversity of bacterial communities. Inactivation of the global regulator, LaeA, resulted in the loss of antibacterial activity in the Penicillium isolate. Cheese rind bacterial communities assembled with the laeA deletion strain had significantly higher bacterial abundances than the wild-type strain. RNA-sequencing and metabolite profiling demonstrated a striking reduction in the expression and production of the natural product pseurotin in the laeA deletion strain. Inactivation of a core gene in the pseurotin biosynthetic cluster restored bacterial community composition, confirming the role of pseurotins in mediating bacterial community assembly. Our discovery demonstrates how global regulators of fungal transcription can control the assembly of bacterial communities and highlights an ecological role for a widespread class of fungal specialized metabolites. IMPORTANCE Cheese rinds are economically important microbial communities where fungi can impact food quality and aesthetics. The specific mechanisms by which fungi can regulate bacterial community assembly in cheeses, other fermented foods, and microbiomes in general are largely unknown. Our study highlights how specialized metabolites secreted by a Penicillium species can mediate cheese rind development via differential inhibition of bacterial community members. Because LaeA regulates specialized metabolites and other ecologically relevant traits in a wide range of filamentous fungi, this global regulator may have similar impacts in other fungus-dominated microbiomes.
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Affiliation(s)
- Joanna Tannous
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Casey M Cosetta
- Department of Biology, Tufts University, Medford, Massachusetts, USA
| | - Milton T Drott
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- USDA-ARS Cereal Disease Laboratory, St. Paul, Minnesota, USA
| | - Tomás A Rush
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Paul E Abraham
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Richard J Giannone
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Benjamin E Wolfe
- Department of Biology, Tufts University, Medford, Massachusetts, USA
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5
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Tannous J, Labbé J, Keller NP. Identifying Fungal Secondary Metabolites and Their Role in Plant Pathogenesis. Methods Mol Biol 2023; 2659:193-218. [PMID: 37249895 DOI: 10.1007/978-1-0716-3159-1_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Pathogenic fungi are the main infectious agents of plants. Secondary metabolites produced by these fungi, also recognized as natural products, are key mediators of plant-fungal interactions. Knowledge on the biosynthesis of these metabolites, the accessibility to fungal genome sequences, and the development of gene disruption techniques open up opportunities to identify many more of these metabolites both in vitro and in planta. This methodology chapter gives a detailed systematic approach aiming to discover new natural products from phytopathogenic fungi and characterize their role in triggering plant cell death and plant disease. This approach takes advantage of the global regulation of fungal secondary metabolite production by regulatory proteins reported in various fungal species.
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Affiliation(s)
- Joanna Tannous
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
| | - Jesse Labbé
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Invaio Sciences, Cambridge, MA, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA.
- Department of Pathology, University of Wiconsin-Madison, Madison, WI, USA.
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6
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Sweany RR, Breunig M, Opoku J, Clay K, Spatafora JW, Drott MT, Baldwin TT, Fountain JC. Why Do Plant-Pathogenic Fungi Produce Mycotoxins? Potential Roles for Mycotoxins in the Plant Ecosystem. PHYTOPATHOLOGY 2022; 112:2044-2051. [PMID: 35502928 DOI: 10.1094/phyto-02-22-0053-sym] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
For many plant-pathogenic or endophytic fungi, production of mycotoxins, which are toxic to humans, may present a fitness gain. However, associations between mycotoxin production and plant pathogenicity or virulence is inconsistent and difficult due to the complexity of these host-pathogen interactions and the influences of environmental and insect factors. Aflatoxin receives a lot of attention due to its potent toxicity and carcinogenicity but the connection between aflatoxin production and pathogenicity is complicated by the pathogenic ability and prevalence of nonaflatoxigenic isolates in crops. Other toxins directly aid fungi in planta, trichothecenes are important virulence factors, and ergot alkaloids limit herbivory and fungal consumption due to insect toxicity. We review a panel discussion at the American Phytopathological Society's Plant Health 2021 conference, which gathered diverse experts representing different research sectors, career stages, ethnicities, and genders to discuss the diverse roles of mycotoxins in the lifestyles of filamentous fungi of the families Clavicipitaceae, Trichocomaceae (Eurotiales), and Nectriaceae (Hypocreales).
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Affiliation(s)
- Rebecca R Sweany
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS) Food and Feed Safety Research Unit, Southern Regional Research Center, New Orleans, LA 70124
| | - Mikaela Breunig
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 78824
| | - Joseph Opoku
- USDA-ARS Pest Management and Biological Control Research Unit, U.S. Arid-Land Agricultural Research Center, Tucson, AZ 85701
| | - Keith Clay
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA 70118
| | - Joseph W Spatafora
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97333
| | - Milton T Drott
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
| | - Thomas T Baldwin
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58108
| | - Jake C Fountain
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, MS State, MS 39762
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7
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Yuan Z, Wu Q, Xu L, Druzhinina IS, Stukenbrock EH, Nieuwenhuis BPS, Zhong Z, Liu ZJ, Wang X, Cai F, Kubicek CP, Shan X, Wang J, Shi G, Peng L, Martin FM. Genomic landscape of a relict fir-associated fungus reveals rapid convergent adaptation towards endophytism. THE ISME JOURNAL 2022; 16:1294-1305. [PMID: 34916613 PMCID: PMC9038928 DOI: 10.1038/s41396-021-01176-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 12/02/2021] [Accepted: 12/08/2021] [Indexed: 12/24/2022]
Abstract
Comparative and pan-genomic analyses of the endophytic fungus Pezicula neosporulosa (Helotiales, Ascomycota) from needles of the relict fir, Abies beshanzuensis, showed expansions of carbohydrate metabolism and secondary metabolite biosynthetic genes characteristic for unrelated plant-beneficial helotialean, such as dark septate endophytes and ericoid mycorrhizal fungi. The current species within the relatively young Pliocene genus Pezicula are predominantly saprotrophic, while P. neosporulosa lacks such features. To understand the genomic background of this putatively convergent evolution, we performed population analyses of 77 P. neosporulosa isolates. This revealed a mosaic structure of a dozen non-recombining and highly genetically polymorphic subpopulations with a unique mating system structure. We found that one idiomorph of a probably duplicated mat1-2 gene was found in putatively heterothallic isolates, while the other co-occurred with mat1-1 locus suggesting homothallic reproduction for these strains. Moreover, 24 and 81 genes implicated in plant cell-wall degradation and secondary metabolite biosynthesis, respectively, showed signatures of the balancing selection. These findings highlight the evolutionary pattern of the two gene families for allowing the fungus a rapid adaptation towards endophytism and facilitating diverse symbiotic interactions.
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Affiliation(s)
- Zhilin Yuan
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, 100091, Beijing, China. .,Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China.
| | - Qi Wu
- grid.458488.d0000 0004 0627 1442State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, China
| | - Liangxiong Xu
- grid.411411.00000 0004 0644 5457School of Life Sciences, Huizhou University, Huizhou, 516007 China
| | - Irina S. Druzhinina
- grid.27871.3b0000 0000 9750 7019Key Laboratory of Plant Immunity, Fungal Genomics Laboratory (FungiG), College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China ,grid.5329.d0000 0001 2348 4034Institute of Chemical, Environmental & Bioscience Engineering (ICEBE), TU Wien, Vienna, A1060 Austria
| | - Eva H. Stukenbrock
- grid.9764.c0000 0001 2153 9986Botanical Institute, Christian-Albrechts Universität zu Kiel, 24118 Kiel, Germany ,grid.419520.b0000 0001 2222 4708Environmental Genomics Research Group, Max-Planck Institute for Evolutionary Biology, 24306 Plön, Germany
| | - Bart P. S. Nieuwenhuis
- grid.5252.00000 0004 1936 973XDivision of Evolutionary Biology, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Zhenhui Zhong
- grid.256111.00000 0004 1760 2876State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002 China ,grid.19006.3e0000 0000 9632 6718Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA 90095 USA
| | - Zhong-Jian Liu
- grid.256111.00000 0004 1760 2876Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization at College of Landscape Architecture, Fujian Agriculture and Forestry University, Fuzhou, 350002 China
| | - Xinyu Wang
- grid.509676.bResearch Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400 China
| | - Feng Cai
- grid.27871.3b0000 0000 9750 7019Key Laboratory of Plant Immunity, Fungal Genomics Laboratory (FungiG), College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China
| | - Christian P. Kubicek
- grid.5329.d0000 0001 2348 4034Institute of Chemical, Environmental & Bioscience Engineering (ICEBE), TU Wien, Vienna, A1060 Austria
| | - Xiaoliang Shan
- grid.216566.00000 0001 2104 9346State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, 100091 Beijing, China ,grid.509676.bResearch Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400 China
| | - Jieyu Wang
- grid.458495.10000 0001 1014 7864Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650 China
| | - Guohui Shi
- grid.458488.d0000 0004 0627 1442State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, China
| | - Long Peng
- grid.216566.00000 0001 2104 9346State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, 100091 Beijing, China ,grid.509676.bResearch Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400 China
| | - Francis M. Martin
- grid.29172.3f0000 0001 2194 6418Université de Lorraine, INRAe, UMR 1136 Interactions Arbres/Microorganismes, INRAe-Grand Est-Nancy, 54280 Champenoux, France
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8
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Microevolution in the pansecondary metabolome of Aspergillus flavus and its potential macroevolutionary implications for filamentous fungi. Proc Natl Acad Sci U S A 2021; 118:2021683118. [PMID: 34016748 DOI: 10.1073/pnas.2021683118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Fungi produce a wealth of pharmacologically bioactive secondary metabolites (SMs) from biosynthetic gene clusters (BGCs). It is common practice for drug discovery efforts to treat species' secondary metabolomes as being well represented by a single or a small number of representative genomes. However, this approach misses the possibility that intraspecific population dynamics, such as adaptation to environmental conditions or local microbiomes, may harbor novel BGCs that contribute to the overall niche breadth of species. Using 94 isolates of Aspergillus flavus, a cosmopolitan model fungus, sampled from seven states in the United States, we dereplicate 7,821 BGCs into 92 unique BGCs. We find that more than 25% of pangenomic BGCs show population-specific patterns of presence/absence or protein divergence. Population-specific BGCs make up most of the accessory-genome BGCs, suggesting that different ecological forces that maintain accessory genomes may be partially mediated by population-specific differences in secondary metabolism. We use ultra-high-performance high-resolution mass spectrometry to confirm that these genetic differences in BGCs also result in chemotypic differences in SM production in different populations, which could mediate ecological interactions and be acted on by selection. Thus, our results suggest a paradigm shift that previously unrealized population-level reservoirs of SM diversity may be of significant evolutionary, ecological, and pharmacological importance. Last, we find that several population-specific BGCs from A. flavus are present in Aspergillus parasiticus and Aspergillus minisclerotigenes and discuss how the microevolutionary patterns we uncover inform macroevolutionary inferences and help to align fungal secondary metabolism with existing evolutionary theory.
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9
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Majumdar R, Kandel SL, Cary JW, Rajasekaran K. Changes in Bacterial Endophyte Community Following Aspergillus flavus Infection in Resistant and Susceptible Maize Kernels. Int J Mol Sci 2021; 22:ijms22073747. [PMID: 33916873 PMCID: PMC8038446 DOI: 10.3390/ijms22073747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 03/31/2021] [Accepted: 04/01/2021] [Indexed: 01/10/2023] Open
Abstract
Aspergillus flavus (A. flavus)-mediated aflatoxin contamination in maize is a major global economic and health concern. As A. flavus is an opportunistic seed pathogen, the identification of factors contributing to kernel resistance will be of great importance in the development of novel mitigation strategies. Using V3–V4 bacterial rRNA sequencing and seeds of A. flavus-resistant maize breeding lines TZAR102 and MI82 and a susceptible line, SC212, we investigated kernel-specific changes in bacterial endophytes during infection. A total of 81 bacterial genera belonging to 10 phyla were detected. Bacteria belonging to the phylum Tenericutes comprised 86–99% of the detected phyla, followed by Proteobacteria (14%) and others (<5%) that changed with treatments and/or genotypes. Higher basal levels (without infection) of Streptomyces and Microbacterium in TZAR102 and increases in the abundance of Stenotrophomonas and Sphingomonas in MI82 following infection may suggest their role in resistance. Functional profiling of bacteria using 16S rRNA sequencing data revealed the presence of bacteria associated with the production of putative type II polyketides and sesquiterpenoids in the resistant vs. susceptible lines. Future characterization of endophytes predicted to possess antifungal/ anti-aflatoxigenic properties will aid in their development as effective biocontrol agents or microbiome markers for maize aflatoxin resistance.
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10
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Uka V, Cary JW, Lebar MD, Puel O, De Saeger S, Diana Di Mavungu J. Chemical repertoire and biosynthetic machinery of the Aspergillus flavus secondary metabolome: A review. Compr Rev Food Sci Food Saf 2020; 19:2797-2842. [PMID: 33337039 DOI: 10.1111/1541-4337.12638] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 08/23/2020] [Accepted: 08/24/2020] [Indexed: 12/18/2022]
Abstract
Filamentous fungi represent a rich source of extrolites, including secondary metabolites (SMs) comprising a great variety of astonishing structures and interesting bioactivities. State-of-the-art techniques in genome mining, genetic manipulation, and secondary metabolomics have enabled the scientific community to better elucidate and more deeply appreciate the genetic and biosynthetic chemical arsenal of these microorganisms. Aspergillus flavus is best known as a contaminant of food and feed commodities and a producer of the carcinogenic family of SMs, aflatoxins. This fungus produces many SMs including polyketides, ribosomal and nonribosomal peptides, terpenoids, and other hybrid molecules. This review will discuss the chemical diversity, biosynthetic pathways, and biological/ecological role of A. flavus SMs, as well as their significance concerning food safety and security.
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Affiliation(s)
- Valdet Uka
- Center of Excellence in Mycotoxicology and Public Health, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.,Division of Pharmacy, Faculty of Medicine, University of Pristina, Pristina, Kosovo
| | - Jeffrey W Cary
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana
| | - Matthew D Lebar
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana
| | - Olivier Puel
- Toxalim (Research Centre in Food Toxicology), INRAE, ENVT, INP-Purpan, UPS, Université de Toulouse, Toulouse, France
| | - Sarah De Saeger
- Center of Excellence in Mycotoxicology and Public Health, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium
| | - José Diana Di Mavungu
- Center of Excellence in Mycotoxicology and Public Health, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium
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11
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Diaz PI, Dongari-Bagtzoglou A. Critically Appraising the Significance of the Oral Mycobiome. J Dent Res 2020; 100:133-140. [PMID: 32924741 DOI: 10.1177/0022034520956975] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Recent efforts to understand the oral microbiome have focused on its fungal component. Since fungi occupy a low proportion of the oral microbiome biomass, mycobiome studies rely on sequencing of internal transcribed spacer (ITS) amplicons. ITS-based studies usually detect hundreds of fungi in oral samples. Here, we review the oral mycobiome, critically appraising the significance of such large fungal diversity. When harsh lysis methods are used to extract DNA, 2 oral mycobiome community types (mycotypes) are evident, each dominated by only 1 genus, either Candida or Malassezia. The rest of the diversity in ITS surveys represents low-abundance fungi possibly acquired from the environment and ingested food. So far, Candida is the only genus demonstrated to reach a significant biomass in the oral cavity and clearly shown to be associated with a distinct oral ecology. Candida thrives in the presence of lower oral pH and is enriched in caries, with mechanistic studies in animal models suggesting it participates in the disease process by synergistically interacting with acidogenic bacteria. Candida serves as the main etiological agent of oral mucosal candidiasis, in which a Candida-bacteriome partnership plays a key role. The function of other potential oral colonizers, such as lipid-dependent Malassezia, is still unclear, with further studies needed to establish whether Malassezia are metabolically active oral commensals. Low-abundance oral mycobiome members acquired from the environment may be viable in the oral cavity, and although they may not play a significant role in microbiome communities, they could serve as opportunistic pathogens in immunocompromised hosts. We suggest that further work is needed to ascertain the significance of oral mycobiome members beyond Candida. ITS-based surveys should be complemented with other methods to determine the in situ biomass and metabolic state of fungi thought to play a role in the oral environment.
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Affiliation(s)
- P I Diaz
- Department of Oral Biology, School of Dental Medicine, University at Buffalo, State University of New York, Buffalo, NY, USA.,UB Microbiome Center, University at Buffalo, State University of New York, Buffalo, NY, USA
| | - A Dongari-Bagtzoglou
- Division of Periodontology, Department of Oral Health and Diagnostic Sciences, School of Dental Medicine, UConn Health, Farmington, CT, USA
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12
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Accinelli C, Abbas HK, Bruno V, Nissen L, Vicari A, Bellaloui N, Little NS, Thomas Shier W. Persistence in soil of microplastic films from ultra-thin compostable plastic bags and implications on soil Aspergillus flavus population. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 113:312-318. [PMID: 32570156 DOI: 10.1016/j.wasman.2020.06.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/11/2020] [Accepted: 06/12/2020] [Indexed: 06/11/2023]
Abstract
An increasing number of states and municipalities are choosing to reduce plastic litter by replacing plastic items, particularly single-use ones, with same-use products manufactured from compostable plastics. This study investigated the formation and persistence of compostable film microplastic particles (CFMPs) from ultra-thin compostable carrier bags in soil under laboratory conditions, and the potential impact of CFMPs on Aspergillus flavus populations in the soil. During a 12-month incubation period, compostable film samples in soils with small, medium or large populations of indigenous A. flavus, underwent 5.9, 9.8, and 17.1% reduction in total surface area, respectively. Despite the low levels of deterioration, the number of CFMPs released increased steadily over the incubation period, particularly fragments with size < 0.05 mm. Up to 88.4% of the released fragments had associated A. flavus and up to 68% of isolates from CFMPs produced aflatoxins. A. flavus levels associated with CFMPs increased rapidly during the initial part of the 12-month incubation period, whereas the percent aflatoxigenicity continued to increase even after A. flavus density leveled off later. During 12 months incubation, A. flavus DNA amounts recovered from CFMPs increased in soils with all levels of indigenous A. flavus, with the largest increases (119.1%) occurring in soil containing the lowest indigenous A. flavus. These results suggest that burying compostable film in soil, or application of compost containing CFMPs, may reduce soil quality and increase risk of adverse impacts from elevated aflatoxigenic A. flavus populations in soil.
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Affiliation(s)
- Cesare Accinelli
- Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, Bologna 40127, Italy.
| | - Hamed K Abbas
- USDA-ARS, Biological Control of Pests Research Unit, Stoneville, MS 38776, USA
| | - Veronica Bruno
- Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, Bologna 40127, Italy
| | - Lorenzo Nissen
- Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, Bologna 40127, Italy
| | - Alberto Vicari
- Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, Bologna 40127, Italy
| | - Nacer Bellaloui
- Crop Genetic Systems Research Unit, US Department of Agriculture, Agricultural Research Service, Stoneville, MS 38776, USA
| | - Nathan S Little
- USDA-ARS, Southern Insect Management Research Unit, Stoneville, MS 38776, USA
| | - W Thomas Shier
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, MN 55455, USA
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13
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Drott MT, Satterlee TR, Skerker JM, Pfannenstiel BT, Glass NL, Keller NP, Milgroom MG. The Frequency of Sex: Population Genomics Reveals Differences in Recombination and Population Structure of the Aflatoxin-Producing Fungus Aspergillus flavus. mBio 2020; 11:e00963-20. [PMID: 32665272 PMCID: PMC7360929 DOI: 10.1128/mbio.00963-20] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 06/18/2020] [Indexed: 11/20/2022] Open
Abstract
The apparent rarity of sex in many fungal species has raised questions about how much sex is needed to purge deleterious mutations and how differences in frequency of sex impact fungal evolution. We sought to determine how differences in the extent of recombination between populations of Aspergillus flavus impact the evolution of genes associated with the synthesis of aflatoxin, a notoriously potent carcinogen. We sequenced the genomes of, and quantified aflatoxin production in, 94 isolates of A. flavus sampled from seven states in eastern and central latitudinal transects of the United States. The overall population is subdivided into three genetically differentiated populations (A, B, and C) that differ greatly in their extent of recombination, diversity, and aflatoxin-producing ability. Estimates of the number of recombination events and linkage disequilibrium decay suggest relatively frequent sex only in population A. Population B is sympatric with population A but produces significantly less aflatoxin and is the only population where the inability of nonaflatoxigenic isolates to produce aflatoxin was explained by multiple gene deletions. Population expansion evident in population B suggests a recent introduction or range expansion. Population C is largely nonaflatoxigenic and restricted mainly to northern sampling locations through restricted migration and/or selection. Despite differences in the number and type of mutations in the aflatoxin gene cluster, codon optimization and site frequency differences in synonymous and nonsynonymous mutations suggest that low levels of recombination in some A. flavus populations are sufficient to purge deleterious mutations.IMPORTANCE Differences in the relative frequencies of sexual and asexual reproduction have profound implications for the accumulation of deleterious mutations (Muller's ratchet), but little is known about how these differences impact the evolution of ecologically important phenotypes. Aspergillus flavus is the main producer of aflatoxin, a notoriously potent carcinogen that often contaminates food. We investigated if differences in the levels of production of aflatoxin by A. flavus could be explained by the accumulation of deleterious mutations due to a lack of recombination. Despite differences in the extent of recombination, variation in aflatoxin production is better explained by the demography and history of specific populations and may suggest important differences in the ecological roles of aflatoxin among populations. Furthermore, the association of aflatoxin production and populations provides a means of predicting the risk of aflatoxin contamination by determining the frequencies of isolates from low- and high-production populations.
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Affiliation(s)
- Milton T Drott
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Tatum R Satterlee
- Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jeffrey M Skerker
- Innovative Genomics Institute, The University of California, Berkeley, California, USA
| | | | - N Louise Glass
- Innovative Genomics Institute, The University of California, Berkeley, California, USA
- Department of Plant and Microbial Biology, The University of California, Berkeley, California, USA
- Environmental Genomics and Systems Biology, The Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Michael G Milgroom
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, USA
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Rokas A, Mead ME, Steenwyk JL, Raja HA, Oberlies NH. Biosynthetic gene clusters and the evolution of fungal chemodiversity. Nat Prod Rep 2020; 37:868-878. [PMID: 31898704 PMCID: PMC7332410 DOI: 10.1039/c9np00045c] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Covering: up to 2019Fungi produce a remarkable diversity of secondary metabolites: small, bioactive molecules not required for growth but which are essential to their ecological interactions with other organisms. Genes that participate in the same secondary metabolic pathway typically reside next to each other in fungal genomes and form biosynthetic gene clusters (BGCs). By synthesizing state-of-the-art knowledge on the evolution of BGCs in fungi, we propose that fungal chemodiversity stems from three molecular evolutionary processes involving BGCs: functional divergence, horizontal transfer, and de novo assembly. We provide examples of how these processes have contributed to the generation of fungal chemodiversity, discuss their relative importance, and outline major, outstanding questions in the field.
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Affiliation(s)
- Antonis Rokas
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
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15
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Drott MT, Bastos RW, Rokas A, Ries LNA, Gabaldón T, Goldman GH, Keller NP, Greco C. Diversity of Secondary Metabolism in Aspergillus nidulans Clinical Isolates. mSphere 2020; 5:e00156-20. [PMID: 32269157 PMCID: PMC7142299 DOI: 10.1128/msphere.00156-20] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 03/11/2020] [Indexed: 01/30/2023] Open
Abstract
The filamentous fungus Aspergillus nidulans has been a primary workhorse used to understand fungal genetics. Much of this work has focused on elucidating the genetics of biosynthetic gene clusters (BGCs) and the secondary metabolites (SMs) they produce. SMs are both niche defining in fungi and of great economic importance to humans. Despite the focus on A. nidulans, very little is known about the natural diversity in secondary metabolism within this species. We determined the BGC content and looked for evolutionary patterns in BGCs from whole-genome sequences of two clinical isolates and the A4 reference genome of A. nidulans Differences in BGC content were used to explain SM profiles determined using liquid chromatography-high-resolution mass spectrometry. We found that in addition to genetic variation of BGCs contained by all isolates, nine BGCs varied by presence/absence. We discovered the viridicatumtoxin BGC in A. nidulans and suggest that this BGC has undergone a horizontal gene transfer from the Aspergillus section Nigri lineage into Penicillium sometime after the sections Nigri and Nidulantes diverged. We identified the production of viridicatumtoxin and several other compounds previously not known to be produced by A. nidulans One isolate showed a lack of sterigmatocystin production even though it contained an apparently intact sterigmatocystin BGC, raising questions about other genes and processes known to regulate this BGC. Altogether, our work uncovers a large degree of intraspecies diversity in BGC and SM production in this genetic model species and offers new avenues to understand the evolution and regulation of secondary metabolism.IMPORTANCE Much of what we know about the genetics underlying secondary metabolite (SM) production and the function of SMs in the model fungus Aspergillus nidulans comes from a single reference genome. A growing body of research indicates the importance of biosynthetic gene cluster (BGC) and SM diversity within a species. However, there is no information about the natural diversity of secondary metabolism in A. nidulans We discovered six novel clusters that contribute to the considerable variation in both BGC content and SM production within A. nidulans We characterize a diverse set of mutations and emphasize how findings of single nucleotide polymorphisms (SNPs), deletions, and differences in evolutionary history encompass much of the variation observed in nonmodel systems. Our results emphasize that A. nidulans may also be a strong model to use within-species diversity to elucidate regulatory cross talk, fungal ecology, and drug discovery systems.
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Affiliation(s)
- M T Drott
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - R W Bastos
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - A Rokas
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - L N A Ries
- Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - T Gabaldón
- Life Sciences Program, Barcelona Supercomputing Centre, Barcelona, Spain
- Mechanisms of Disease Program, Institute for Research in Biomedicine, Barcelona, Spain
- ICREA, Barcelona, Spain
| | - G H Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - N P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - C Greco
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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16
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Pfliegler WP, Pócsi I, Győri Z, Pusztahelyi T. The Aspergilli and Their Mycotoxins: Metabolic Interactions With Plants and the Soil Biota. Front Microbiol 2020; 10:2921. [PMID: 32117074 PMCID: PMC7029702 DOI: 10.3389/fmicb.2019.02921] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 12/04/2019] [Indexed: 01/06/2023] Open
Abstract
Species of the highly diverse fungal genus Aspergillus are well-known agricultural pests, and, most importantly, producers of various mycotoxins threatening food safety worldwide. Mycotoxins are studied predominantly from the perspectives of human and livestock health. Meanwhile, their roles are far less known in nature. However, to understand the factors behind mycotoxin production, the roles of the toxins of Aspergilli must be understood from a complex ecological perspective, taking mold-plant, mold-microbe, and mold-animal interactions into account. The Aspergilli may switch between saprophytic and pathogenic lifestyles, and the production of secondary metabolites, such as mycotoxins, may vary according to these fungal ways of life. Recent studies highlighted the complex ecological network of soil microbiotas determining the niches that Aspergilli can fill in. Interactions with the soil microbiota and soil macro-organisms determine the role of secondary metabolite production to a great extent. While, upon infection of plants, metabolic communication including fungal secondary metabolites like aflatoxins, gliotoxin, patulin, cyclopiazonic acid, and ochratoxin, influences the fate of both the invader and the host. In this review, the role of mycotoxin producing Aspergillus species and their interactions in the ecosystem are discussed. We intend to highlight the complexity of the roles of the main toxic secondary metabolites as well as their fate in natural environments and agriculture, a field that still has important knowledge gaps.
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Affiliation(s)
- Walter P. Pfliegler
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | - István Pócsi
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | - Zoltán Győri
- Institute of Nutrition, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Debrecen, Hungary
| | - Tünde Pusztahelyi
- Central Laboratory of Agricultural and Food Products, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Debrecen, Hungary
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Drott MT, Fessler LM, Milgroom MG. Population Subdivision and the Frequency of Aflatoxigenic Isolates in Aspergillus flavus in the United States. PHYTOPATHOLOGY 2019; 109:878-886. [PMID: 30480472 DOI: 10.1094/phyto-07-18-0263-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Consumption of food contaminated with aflatoxin, from crops infected by Aspergillus flavus, is associated with acute toxicosis, cancer, and stunted growth. Although such contamination is more common in the lower latitudes of the United States, it is unclear whether this pattern is associated with differences in the relative frequencies of aflatoxigenic individuals of A. flavus. To determine whether the frequency of the aflatoxin-producing ability of A. flavus increases as latitude decreases, we sampled 281 isolates from field soils in two north-south transects in the United States and tested them for aflatoxin production. We also genotyped 161 isolates using 10 microsatellite markers to assess population structure. Although the population density of A. flavus was highest at lower latitudes, there was no difference in the frequency of aflatoxigenic A. flavus isolates in relation to latitude. We found that the U.S. population of A. flavus is subdivided into two genetically differentiated subpopulations that are not associated with the chemotype or geographic origin of the isolates. The two populations differ markedly in allelic and genotypic diversity. The less diverse population is more abundant and may represent a clonal lineage derived from the more diverse population. Overall, increased aflatoxin contamination in lower latitudes may be explained partially by differences in the population density of A. flavus, not genetic population structure.
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Affiliation(s)
- Milton T Drott
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853
| | - Lauren M Fessler
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853
| | - Michael G Milgroom
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853
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