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Camargo AF, Bonatto C, Scapini T, Klanovicz N, Tadioto V, Cadamuro RD, Bazoti SF, Kubeneck S, Michelon W, Reichert Júnior FW, Mossi AJ, Alves Júnior SL, Fongaro G, Treichel H. Fungus-based bioherbicides on circular economy. Bioprocess Biosyst Eng 2023; 46:1729-1754. [PMID: 37743409 DOI: 10.1007/s00449-023-02926-w] [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: 08/01/2023] [Accepted: 09/06/2023] [Indexed: 09/26/2023]
Abstract
This review aimed to show that bioherbicides are possible in organic agriculture as natural compounds from fungi and metabolites produced by them. It is discussed that new formulations must be developed to improve field stability and enable the commercialization of microbial herbicides. Due to these bottlenecks, it is crucial to advance the bioprocesses behind the formulation and fermentation of bio-based herbicides, scaling up, strategies for field application, and the potential of bioherbicides in the global market. In this sense, it proposed insights for modern agriculture based on sustainable development and circular economy, precisely the formulation, scale-up, and field application of microbial bioherbicides.
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Affiliation(s)
- Aline Frumi Camargo
- Graduate Program in Biotechnology and Biosciences, Federal University of Santa Catarina, Florianópolis, Brazil
- Laboratory of Microbiology and Bioprocesses, Federal University of Fronteira Sul, Erechim, Brazil
| | - Charline Bonatto
- Laboratory of Microbiology and Bioprocesses, Federal University of Fronteira Sul, Erechim, Brazil
| | - Thamarys Scapini
- Department of Bioprocess Engineering and Biotechnology, Federal University of Paraná, Curitiba, Brazil
| | - Natalia Klanovicz
- Research Group in Advanced Oxidation Processes (AdOx), Department of Chemical Engineering, University of São Paulo, São Paulo, Brazil
| | - Viviani Tadioto
- Graduate Program in Biotechnology and Biosciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Rafael Dorighello Cadamuro
- Graduate Program in Biotechnology and Biosciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Suzana Fátima Bazoti
- Department of Chemical and Food Engineering, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Simone Kubeneck
- Laboratory of Microbiology and Bioprocesses, Federal University of Fronteira Sul, Erechim, Brazil
| | | | | | - Altemir José Mossi
- Laboratory of Agroecology, Federal University of Fronteira Sul, Erechim, Brazil
| | | | - Gislaine Fongaro
- Graduate Program in Biotechnology and Biosciences, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Helen Treichel
- Graduate Program in Biotechnology and Biosciences, Federal University of Santa Catarina, Florianópolis, Brazil.
- Laboratory of Microbiology and Bioprocesses, Federal University of Fronteira Sul, Erechim, Brazil.
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2
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Arreguin-Perez CA, Miranda-Miranda E, Folch-Mallol JL, Cossío-Bayúgar R. Identification of Virulence Factors in Entomopathogenic Aspergillus flavus Isolated from Naturally Infected Rhipicephalus microplus. Microorganisms 2023; 11:2107. [PMID: 37630667 PMCID: PMC10457961 DOI: 10.3390/microorganisms11082107] [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: 07/25/2023] [Revised: 08/10/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
Aspergillus flavus has been found to be an effective entomopathogenic fungus for various arthropods, including ticks. In particular, natural fungal infections in cattle ticks show promise for biocontrol of the Rhipicephalus (Boophilus) microplus tick, which is a major ectoparasite affecting cattle worldwide. Our study aimed to elucidate the specific entomopathogenic virulence factors encoded in the genome of an A. flavus strain isolated from naturally infected cattle ticks. We performed morphological and biochemical phenotyping alongside complete genome sequencing, which revealed that the isolated fungus was A. flavus related to the L morphotype, capable of producing a range of gene-coded entomopathogenic virulence factors, including ribotoxin, aflatoxin, kojic acid, chitinases, killer toxin, and satratoxin. To evaluate the efficacy of this A. flavus strain against ticks, we conducted experimental bioassays using healthy engorged female ticks. A morbidity rate of 90% was observed, starting at a concentration of 105 conidia/mL. At a concentration of 107 conidia/mL, we observed a 50% mortality rate and a 21.5% inhibition of oviposition. The highest levels of hatch inhibition (30.8%) and estimated reproduction inhibition (34.64%) were achieved at a concentration of 108 conidia/mL. Furthermore, the tick larval progeny that hatched from the infected tick egg masses showed evident symptoms of Aspergillus infection after incubation.
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Affiliation(s)
- Cesar A. Arreguin-Perez
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias INIFAP, Boulevard Cuauhnahuac 8534, Jiutepec 62574, Morelos, Mexico; (C.A.A.-P.); (E.M.-M.)
- Centro de Investigación en Biotecnología, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Cuernavaca 62209, Morelos, Mexico;
| | - Estefan Miranda-Miranda
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias INIFAP, Boulevard Cuauhnahuac 8534, Jiutepec 62574, Morelos, Mexico; (C.A.A.-P.); (E.M.-M.)
| | - Jorge Luis Folch-Mallol
- Centro de Investigación en Biotecnología, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Cuernavaca 62209, Morelos, Mexico;
| | - Raquel Cossío-Bayúgar
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias INIFAP, Boulevard Cuauhnahuac 8534, Jiutepec 62574, Morelos, Mexico; (C.A.A.-P.); (E.M.-M.)
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3
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Nji QN, Babalola OO, Mwanza M. Soil Aspergillus Species, Pathogenicity and Control Perspectives. J Fungi (Basel) 2023; 9:766. [PMID: 37504754 PMCID: PMC10381279 DOI: 10.3390/jof9070766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/05/2023] [Accepted: 07/18/2023] [Indexed: 07/29/2023] Open
Abstract
Five Aspergillus sections have members that are established agricultural pests and producers of different metabolites, threatening global food safety. Most of these pathogenic Aspergillus species have been isolated from almost all major biomes. The soil remains the primary habitat for most of these cryptic fungi. This review explored some of the ecological attributes that have contributed immensely to the success of the pathogenicity of some members of the genus Aspergillus over time. Hence, the virulence factors of the genus Aspergillus, their ecology and others were reviewed. Furthermore, some biological control techniques were recommended. Pathogenic effects of Aspergillus species are entirely accidental; therefore, the virulence evolution prediction model in such species becomes a challenge, unlike their obligate parasite counterparts. In all, differences in virulence among organisms involved both conserved and species-specific genetic factors. If the impacts of climate change continue, new cryptic Aspergillus species will emerge and mycotoxin contamination risks will increase in all ecosystems, as these species can metabolically adjust to nutritional and biophysical challenges. As most of their gene clusters are silent, fungi continue to be a source of underexplored bioactive compounds. The World Soil Charter recognizes the relevance of soil biodiversity in supporting healthy soil functions. The question of how a balance may be struck between supporting healthy soil biodiversity and the control of toxic fungi species in the field to ensure food security is therefore pertinent. Numerous advanced strategies and biocontrol methods so far remain the most environmentally sustainable solution to the control of toxigenic fungi in the field.
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Affiliation(s)
- Queenta Ngum Nji
- Food Security and Safety Focus Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
| | - Olubukola Oluranti Babalola
- Food Security and Safety Focus Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
| | - Mulunda Mwanza
- Food Security and Safety Focus Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
- Department of Animal Health, Faculty of Natural and Agricultural Sciences, North-West University, Private Bag X2046, Mmabatho 2735, South Africa
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4
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Deng L, Zhong M, Li Y, Hu G, Zhang C, Peng Q, Zhang Z, Fang J, Yu X. High hydrostatic pressure harnesses the biosynthesis of secondary metabolites via the regulation of polyketide synthesis genes of hadal sediment-derived fungi. Front Microbiol 2023; 14:1207252. [PMID: 37383634 PMCID: PMC10293889 DOI: 10.3389/fmicb.2023.1207252] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 05/24/2023] [Indexed: 06/30/2023] Open
Abstract
Deep-sea fungi have evolved extreme environmental adaptation and possess huge biosynthetic potential of bioactive compounds. However, not much is known about the biosynthesis and regulation of secondary metabolites of deep-sea fungi under extreme environments. Here, we presented the isolation of 15 individual fungal strains from the sediments of the Mariana Trench, which were identified by internal transcribed spacer (ITS) sequence analysis as belonging to 8 different fungal species. High hydrostatic pressure (HHP) assays were performed to identify the piezo-tolerance of the hadal fungi. Among these fungi, Aspergillus sydowii SYX6 was selected as the representative due to the excellent tolerance of HHP and biosynthetic potential of antimicrobial compounds. Vegetative growth and sporulation of A. sydowii SYX6 were affected by HHP. Natural product analysis with different pressure conditions was also performed. Based on bioactivity-guided fractionation, diorcinol was purified and characterized as the bioactive compound, showing significant antimicrobial and antitumor activity. The core functional gene associated with the biosynthetic gene cluster (BGC) of diorcinol was identified in A. sydowii SYX6, named as AspksD. The expression of AspksD was apparently regulated by the HHP treatment, correlated with the regulation of diorcinol production. Based on the effect of the HHP tested here, high pressure affected the fungal development and metabolite production, as well as the expression level of biosynthetic genes which revealed the adaptive relationship between the metabolic pathway and the high-pressure environment at the molecular level.
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Affiliation(s)
- Ludan Deng
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Maosheng Zhong
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Yongqi Li
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Guangzhao Hu
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Changhao Zhang
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Qingqing Peng
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Zhizhen Zhang
- Ocean College, Zhoushan Campus, Zhejiang University, Zhoushan, China
| | - Jiasong Fang
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
| | - Xi Yu
- Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, China
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5
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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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6
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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: 4] [Impact Index Per Article: 4.0] [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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7
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Remesh AV, Raveendran A, Bincy K, Wagh VS, Dastager SG, Babu CV. Insights on biorational potential of Ocimum gratissimum essential oil and its binary combination with monoterpene phenol for control of rice weevil (Sitophilus oryzae) and aflatoxigenic fungi. FOOD BIOSCI 2022. [DOI: 10.1016/j.fbio.2022.102019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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8
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Molo MS, White JB, Cornish V, Gell RM, Baars O, Singh R, Carbone MA, Isakeit T, Wise KA, Woloshuk CP, Bluhm BH, Horn BW, Heiniger RW, Carbone I. Asymmetrical lineage introgression and recombination in populations of Aspergillus flavus: Implications for biological control. PLoS One 2022; 17:e0276556. [PMID: 36301851 PMCID: PMC9620740 DOI: 10.1371/journal.pone.0276556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 10/08/2022] [Indexed: 11/23/2022] Open
Abstract
Aspergillus flavus is an agriculturally important fungus that causes ear rot of maize and produces aflatoxins, of which B1 is the most carcinogenic naturally-produced compound. In the US, the management of aflatoxins includes the deployment of biological control agents that comprise two nonaflatoxigenic A. flavus strains, either Afla-Guard (member of lineage IB) or AF36 (lineage IC). We used genotyping-by-sequencing to examine the influence of both biocontrol agents on native populations of A. flavus in cornfields in Texas, North Carolina, Arkansas, and Indiana. This study examined up to 27,529 single-nucleotide polymorphisms (SNPs) in a total of 815 A. flavus isolates, and 353 genome-wide haplotypes sampled before biocontrol application, three months after biocontrol application, and up to three years after initial application. Here, we report that the two distinct A. flavus evolutionary lineages IB and IC differ significantly in their frequency distributions across states. We provide evidence of increased unidirectional gene flow from lineage IB into IC, inferred to be due to the applied Afla-Guard biocontrol strain. Genetic exchange and recombination of biocontrol strains with native strains was detected in as little as three months after biocontrol application and up to one and three years later. There was limited inter-lineage migration in the untreated fields. These findings suggest that biocontrol products that include strains from lineage IB offer the greatest potential for sustained reductions in aflatoxin levels over several years. This knowledge has important implications for developing new biocontrol strategies.
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Affiliation(s)
- Megan S. Molo
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
| | - James B. White
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
| | - Vicki Cornish
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
| | - Richard M. Gell
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
- Program of Genetics, North Carolina State University, Raleigh, North
Carolina, United States of America
| | - Oliver Baars
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
| | - Rakhi Singh
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
| | - Mary Anna Carbone
- Center for Integrated Fungal Research and Department of Plant and
Microbial Biology, North Carolina State University, Raleigh, NC, United States
of America
| | - Thomas Isakeit
- Department of Plant Pathology and Microbiology, Texas AgriLife Extension
Service, Texas A&M University, College Station, TX, United States of
America
| | - Kiersten A. Wise
- Department of Plant Pathology, University of Kentucky, Princeton, KY,
United States of America
| | - Charles P. Woloshuk
- Department of Plant Pathology and Botany, Purdue University, West
Lafayette, IN, United States of America
| | - Burton H. Bluhm
- University of Arkansas Division of Agriculture, Department of Entomology
and Plant Pathology, Fayetteville, AR, United States of
America
| | - Bruce W. Horn
- United States Department of Agriculture, Agriculture Research Service,
Dawson, GA, United States of America
| | - Ron W. Heiniger
- Department of Crop and Soil Sciences, North Carolina State University,
Raleigh, NC, United States of America
| | - Ignazio Carbone
- Department of Entomology and Plant Pathology, Center for Integrated
Fungal Research, North Carolina State University, Raleigh, NC, United States of
America
- Program of Genetics, North Carolina State University, Raleigh, North
Carolina, United States of America
- * E-mail:
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9
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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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10
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Abstract
The fungus Rhizopus microsporus harbors a bacterial endosymbiont (Mycetohabitans rhizoxinica) for the production of the antimitotic toxin rhizoxin. Although rhizoxin is the causative agent of rice seedling blight, the toxinogenic bacterial-fungal alliance is, not restricted to the plant disease. It has been detected in numerous environmental isolates from geographically distinct sites covering all five continents, thus raising questions regarding the ecological role of rhizoxin beyond rice seedling blight. Here, we show that rhizoxin serves the fungal host in fending off protozoan and metazoan predators. Fluorescence microscopy and coculture experiments with the fungivorous amoeba Protostelium aurantium revealed that ingestion of R. microsporus spores is toxic to P. aurantium. This amoebicidal effect is caused by the dominant bacterial rhizoxin congener rhizoxin S2, which is also lethal toward the model nematode Caenorhabditis elegans. By combining stereomicroscopy, automated image analysis, and quantification of nematode movement, we show that the fungivorous nematode Aphelenchus avenae actively feeds on R. microsporus that is lacking endosymbionts, whereas worms coincubated with symbiotic R. microsporus are significantly less lively. This study uncovers an unexpected ecological role of rhizoxin as shield against micropredators. This finding suggests that predators may function as an evolutionary driving force to maintain toxin-producing endosymbionts in nonpathogenic fungi.
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11
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Ajmal M, Alshannaq AF, Moon H, Choi D, Akram A, Nayyar BG, Gibbons JG, Yu JH. Characterization of 260 Isolates of Aspergillus Section Flavi Obtained from Sesame Seeds in Punjab, Pakistan. Toxins (Basel) 2022; 14:toxins14020117. [PMID: 35202144 PMCID: PMC8876583 DOI: 10.3390/toxins14020117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 11/16/2022] Open
Abstract
Sesame Sesamum indicum L. is a major oil-based seed crop that has been widely cultivated and consumed in Pakistan. Unfortunately, sesame is highly prone to Aspergillus fungal growth in the field, and under inappropriate storage conditions can become contaminated with aflatoxins, the most potent carcinogen found in nature. Here, we have isolated a high number of Aspergillus isolates from sesame seeds in fresh and stored conditions obtained from rainfed and irrigated zones of Punjab, Pakistan, and characterized them for aflatoxigenic potentials. Using morphological identification techniques, 260 isolates were grouped as potential Aspergillus section Flavi, with 126 and 134 originating from the rainfed and irrigated zones, respectively. Out of 260 in total, 188 isolates were confirmed to produce aflatoxins. There were no significant differences in potential aflatoxigenic isolates with respect to the rainfed and irrigated zones. However, the number of potential aflatoxigenic isolates was significantly higher (p < 0.05) in stored samples than that of those from fresh sesame seeds in the rainfed and irrigated zone. Whole genome sequencing and comparative analyses of 12 select isolates have revealed that one of the A. flavus isolates, which produced very low aflatoxins (AFP10), has an elevated missense variant rate, numerous high impact mutations, and a 600 base pair deletion in the norB gene. In summary, our study provides insights into aflatoxigenic potential and the associated genetic diversity of indigenous Aspergillus section Flavi isolates and potential management strategies for reducing aflatoxin contamination levels in a major crop consumed in Punjab, Pakistan.
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Affiliation(s)
- Maryam Ajmal
- Department of Botany, Faculty of Sciences, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi 46300, Pakistan; (M.A.); (A.A.)
| | - Ahmad F. Alshannaq
- Department of Bacteriology, Food Research Institute, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA; (A.F.A.); (H.M.); (D.C.)
| | - Heungyun Moon
- Department of Bacteriology, Food Research Institute, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA; (A.F.A.); (H.M.); (D.C.)
| | - Dasol Choi
- Department of Bacteriology, Food Research Institute, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA; (A.F.A.); (H.M.); (D.C.)
| | - Abida Akram
- Department of Botany, Faculty of Sciences, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi 46300, Pakistan; (M.A.); (A.A.)
| | - Brian Gagosh Nayyar
- Department of Botany, Faculty of Sciences, University of Sialkot, Sialkot 51310, Pakistan;
| | - John G. Gibbons
- Department of Food Science, College of Natural Sciences, University of Massachusetts, Amherst, MA 01003, USA;
| | - Jae-Hyuk Yu
- Department of Bacteriology, Food Research Institute, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA; (A.F.A.); (H.M.); (D.C.)
- Department of Systems Biotechnology, Konkuk Institute of Science and Technology, Konkuk University, Seoul 05029, Korea
- Correspondence:
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12
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Abstract
The fungus Aspergillus nidulans produces secondary metabolites during sexual development to protect itself from predators.
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Affiliation(s)
- Milton T Drott
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Wisconsin-Madison, United States
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13
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Duarte S, Magro A, Tomás J, Hilário C, Alvito P, Ferreira RB, Carvalho MO. The Interaction between Tribolium castaneum and Mycotoxigenic Aspergillus flavus in Maize Flour. INSECTS 2021; 12:insects12080730. [PMID: 34442296 PMCID: PMC8396807 DOI: 10.3390/insects12080730] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/09/2021] [Accepted: 08/13/2021] [Indexed: 11/16/2022]
Abstract
Simple Summary It is important to hold cereals in storage conditions that exclude insect pests such as the red flour beetle and fungi, especially mycotoxin-producing ones (as a few strains of Aspergillus flavus). This work aims to investigate the interaction between these two organisms when thriving in maize flour. It was observed that when both organisms were together, the mycotoxins detected in maize flour were far higher than when the fungi were on their own, suggesting that the presence of insects may contribute positively to fungi development and mycotoxin production. The insects in contact with the fungi were almost all dead at the end of the trials, suggesting a negative effect of the fungi growth on the insects. Both organisms interacted when in contact. This is the first study on this issue, although further investigation would benefit from clarification on the mechanisms leading to the nature of the detected interactions. Abstract Tribolium castaneum is one of the most common insect pests of stored products. Its presence makes cereals more susceptible to the spread of the fungi Aspergillus flavus, which may produce mycotoxins. The aim of this work was to evaluate the influence of T. castaneum adults on the development of a mycotoxigenic A. flavus strain in maize flour as well as the influence of this fungus on the insects. Maize flour was exposed to T. castaneum, spores of A. flavus or to both. The results revealed an interaction between T. castaneum and A. flavus as the flour exposed to both organisms was totally colonized by the fungus whereas almost all the insects were killed. Aflatoxin B1 (AFB1) revealed a significantly higher concentration in the flour inoculated with both organisms (18.8 µg/kg), being lower when exposed only to A. flavus, suggesting that the presence of insects may trigger fungal development and enhance mycotoxin production. The ability of these organisms to thrive under the same conditions and the chemical compounds they release makes the interaction between them a subject of great importance to maintain the safety of stored maize. This is the first work evaluating the interaction between T. castaneum and A. flavus mycotoxin production.
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Affiliation(s)
- Sónia Duarte
- Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal; (S.D.); (J.T.); (C.H.); (R.B.F.); (M.O.C.)
- LEAF—Linking Landscape, Environment, Agriculture and Food, Tapada da Ajuda, 1349-017 Lisboa, Portugal
| | - Ana Magro
- Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal; (S.D.); (J.T.); (C.H.); (R.B.F.); (M.O.C.)
- Correspondence:
| | - Joanna Tomás
- Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal; (S.D.); (J.T.); (C.H.); (R.B.F.); (M.O.C.)
| | - Carolina Hilário
- Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal; (S.D.); (J.T.); (C.H.); (R.B.F.); (M.O.C.)
| | - Paula Alvito
- National Health Institute Dr. Ricardo Jorge (INSA), 1600-609 Lisboa, Portugal;
- Centre for Environmental and Marine Studies (CESAM), University of Aveiro, 3810-193 Aveiro, Portugal
| | - Ricardo Boavida Ferreira
- Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal; (S.D.); (J.T.); (C.H.); (R.B.F.); (M.O.C.)
- LEAF—Linking Landscape, Environment, Agriculture and Food, Tapada da Ajuda, 1349-017 Lisboa, Portugal
| | - Maria Otília Carvalho
- Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal; (S.D.); (J.T.); (C.H.); (R.B.F.); (M.O.C.)
- LEAF—Linking Landscape, Environment, Agriculture and Food, Tapada da Ajuda, 1349-017 Lisboa, Portugal
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14
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Ortega-Beltran A, Agbetiameh D, Atehnkeng J, Falade TDO, Bandyopadhyay R. Does Use of Atoxigenic Biocontrol Products to Mitigate Aflatoxin in Maize Increase Fumonisin Content in Grains? PLANT DISEASE 2021; 105:2196-2201. [PMID: 33210967 DOI: 10.1094/pdis-07-20-1447-re] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the tropics and subtropics, maize (Zea mays) and other crops are frequently contaminated with aflatoxins by Aspergillus flavus. Treatment of crops with atoxigenic isolates of A. flavus formulated into biocontrol products can significantly reduce aflatoxin contamination. Treated crops contain up to 100% fewer aflatoxins compared with untreated crops. However, there is the notion that protecting crops from aflatoxin contamination may result in increased accumulation of other toxins, particularly fumonisins produced by a few Fusarium species. The objective of this study was to determine if treatment of maize with aflatoxin biocontrol products increased fumonisin concentration and fumonisin-producing fungi in grains. Over 200 maize samples from fields treated with atoxigenic biocontrol products in Nigeria and Ghana were examined for fumonisin content and contrasted with maize from untreated fields. Apart from low aflatoxin levels, most treated maize also harbored fumonisin levels considered safe by the European Union (<1 part per million; ppm). Most untreated maize also harbored equally low fumonisin levels but contained higher aflatoxin levels. In addition, during one year, we detected considerably lower Fusarium spp. densities in treated maize than in untreated maize. Our results do not support the hypothesis that treating crops with atoxigenic isolates of A. flavus used in biocontrol formulations results in higher grain fumonisin levels.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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Affiliation(s)
| | - Daniel Agbetiameh
- International Institute of Tropical Agriculture, Ibadan 200001, Nigeria
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
- Department of Agro Enterprise Development, Faculty of Applied Science and Technology, Ho Technical University, Ho, Ghana
| | - Joseph Atehnkeng
- International Institute of Tropical Agriculture, Bukavu, D. R. Congo
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15
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Abstract
The fungal kingdom has provided advances in our ability to identify biosynthetic gene clusters (BGCs) and to examine how gene composition of BGCs evolves across species and genera. However, little is known about the evolution of specific BGC regulators that mediate how BGCs produce secondary metabolites (SMs). A bioinformatics search for conservation of the Aspergillus fumigatus xanthocillin BGC revealed an evolutionary trail of xan-like BGCs across Eurotiales species. Although the critical regulatory and enzymatic genes were conserved in Penicillium expansum, overexpression (OE) of the conserved xan BGC transcription factor (TF) gene, PexanC, failed to activate the putative xan BGC transcription or xanthocillin production in P. expansum, in contrast to the role of AfXanC in A. fumigatus. Surprisingly, OE::PexanC was instead found to promote citrinin synthesis in P. expansum via trans induction of the cit pathway-specific TF, ctnA, as determined by cit BGC expression and chemical profiling of ctnA deletion and OE::PexanC single and double mutants. OE::AfxanC results in significant increases of xan gene expression and metabolite synthesis in A. fumigatus but had no effect on either xanthocillin or citrinin production in P. expansum. Bioinformatics and promoter mutation analysis led to the identification of an AfXanC binding site, 5'-AGTCAGCA-3', in promoter regions of the A. fumigatus xan BGC genes. This motif was not in the ctnA promoter, suggesting a different binding site of PeXanC. A compilation of a bioinformatics examination of XanC orthologs and the presence/absence of the 5'-AGTCAGCA-3' binding motif in xan BGCs in multiple Aspergillus and Penicillium spp. supports an evolutionary divergence of XanC regulatory targets that we speculate reflects an exaptation event in the Eurotiales. IMPORTANCE Fungal secondary metabolites (SMs) are an important source of pharmaceuticals on one hand and toxins on the other. Efforts to identify the biosynthetic gene clusters (BGCs) that synthesize SMs have yielded significant insights into how variation in the genes that compose BGCs may impact subsequent metabolite production within and between species. However, the role of regulatory genes in BGC activation is less well understood. Our finding that the bZIP transcription factor XanC, located in the xanthocillin BGC of both Aspergillus fumigatus and Penicillium expansum, has functionally diverged to regulate different BGCs in these two species emphasizes that the diversification of BGC regulatory elements may sometimes occur through exaptation, which is the co-option of a gene that evolved for one function to a novel function. Furthermore, this work suggests that the loss/gain of transcription factor binding site targets may be an important mediator in the evolution of secondary-metabolism regulatory elements.
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16
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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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17
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Soni P, Ghufran MS, Olakkaran S, Puttaswamygowda GH, Duddukuri GR, Kanade SR. Epigenetic alterations induced by aflatoxin B 1: An in vitro and in vivo approach with emphasis on enhancer of zeste homologue-2/p21 axis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 762:143175. [PMID: 33131875 DOI: 10.1016/j.scitotenv.2020.143175] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/21/2020] [Accepted: 10/14/2020] [Indexed: 06/11/2023]
Abstract
The potent environmental toxicant aflatoxin B1 (AFB1), is a group I carcinogen reported to induce the expression of many cancer associated proteins. Epigenetic alterations such as DNA methylation and histone modifications play vital role in AFB1-mediated carcinogenesis. These epigenetic modifications may result in the recruitment of specific proteins and transcription factors to the promoter region and regulate gene expression. Here we show that AFB1, at lower concentrations (100 and 1000 nM) induced proliferation in L-132 and HaCaT cells with activation of the Akt pathway, which ultimately steered abnormal proliferation and transmission of survival signals. We demonstrated a significant reduction in the expression of p21 with a remarkable increase in the expression of cyclin D1 that correlated with increased methylation of CpG dinucleotides in p21 proximal promoter, while cyclin D1 promoter remained unmethylated. The chromatin immunoprecipitation results revealed the enrichment of DNMT3a and H3K27me3 repressive marks on the p21 proximal promoter where EZH2 mediated H3K27me3 mark enhanced the binding of DNMT3a at the promoter and further contributed to the transcriptional inactivation. The overall study provided the novel information on the impact of AFB1 on p21 inactivation via EZH2 and promoter methylation which is known to be a vital process in proliferation. Furthermore, AFB1 induced the expression of EZH2 analogue protein E(z), cyclin D1 analogue cyclin D and decreased the expression of p21 analogue Dacapo in Drosophila melanogaster. Interestingly, the aggressiveness in their expression upon re-exposure in successive generations suggested first hand perspectives on multigenerational epigenetic memory.
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Affiliation(s)
- Priyanka Soni
- Department of Biochemistry and Molecular Biology, School of Biological Sciences, Central University of Kerala, Tejaswini Hills, Periye, Kasargod 671316, Kerala, India
| | - Md Sajid Ghufran
- Department of Biochemistry and Molecular Biology, School of Biological Sciences, Central University of Kerala, Tejaswini Hills, Periye, Kasargod 671316, Kerala, India
| | - Shilpa Olakkaran
- Department of Zoology, School of Biological Sciences, Central University of Kerala, Tejaswini Hills, Periye, Kasargod 671316, Kerala, India
| | | | - Govinda Rao Duddukuri
- Department of Biochemistry and Molecular Biology, School of Biological Sciences, Central University of Kerala, Tejaswini Hills, Periye, Kasargod 671316, Kerala, India
| | - Santosh R Kanade
- Department of Plant Science, School of Life Science, University of Hyderabad, Prof. C. R. Rao Road Gachibowli, Hyderabad 500046, India.
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18
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Ramos-Martínez E, Hernández-González L, Ramos-Martínez I, Pérez-Campos Mayoral L, López-Cortés GI, Pérez-Campos E, Mayoral Andrade G, Hernández-Huerta MT, José MV. Multiple Origins of Extracellular DNA Traps. Front Immunol 2021; 12:621311. [PMID: 33717121 PMCID: PMC7943724 DOI: 10.3389/fimmu.2021.621311] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 01/06/2021] [Indexed: 01/21/2023] Open
Abstract
Extracellular DNA traps (ETs) are evolutionarily conserved antimicrobial mechanisms present in protozoa, plants, and animals. In this review, we compare their similarities in species of different taxa, and put forward the hypothesis that ETs have multiple origins. Our results are consistent with a process of evolutionary convergence in multicellular organisms through the application of a congruency test. Furthermore, we discuss why multicellularity is related to the presence of a mechanism initiating the formation of ETs.
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Affiliation(s)
- Edgar Ramos-Martínez
- School of Sciences, Benito Juárez Autonomous University of Oaxaca, Oaxaca, Mexico
| | | | - Iván Ramos-Martínez
- Glycobiology, Cell Growth and Tissue Repair Research Unit (Gly-CRRET), Université Paris Est Créteil (UPEC), Créteil, France
| | - Laura Pérez-Campos Mayoral
- Research Centre Medicine UNAM-UABJO, Faculty of Medicine, Benito Juárez Autonomous University of Oaxaca, Oaxaca, Mexico
| | | | - Eduardo Pérez-Campos
- Biochemistry and Immunology Unit, National Technological of Mexico/ITOaxaca, Oaxaca, Mexico
- Research Centre Medicine UNAM-UABJO, Faculty of Medicine, Benito Juárez Autonomous University of Oaxaca, Oaxaca, Mexico
| | - Gabriel Mayoral Andrade
- Research Centre Medicine UNAM-UABJO, Faculty of Medicine, Benito Juárez Autonomous University of Oaxaca, Oaxaca, Mexico
| | | | - Marco V. José
- Theoretical Biology Group, National Autonomous University of Mexico, Mexico City, Mexico
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19
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Moore GG. Practical considerations will ensure the continued success of pre-harvest biocontrol using non-aflatoxigenic Aspergillus flavus strains. Crit Rev Food Sci Nutr 2021; 62:4208-4225. [PMID: 33506687 DOI: 10.1080/10408398.2021.1873731] [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: 12/27/2022]
Abstract
There is an important reason for the accelerated use of non-aflatoxigenic Aspergillus flavus to mitigate pre-harvest aflatoxin contamination… it effectively addresses the imperative need for safer food and feed. Now that we have decades of proof of the effectiveness of A. flavus as biocontrol, it is time to improve several aspects of this strategy. If we are to continue relying heavily on this form of aflatoxin mitigation, there are considerations we must acknowledge, and actions we must take, to ensure that we are best wielding this strategy to our advantage. These include its: (1) potential to produce other mycotoxins, (2) persistence in the field in light of several ecological factors, (3) its reproductive and genetic stability, (4) the mechanism(s) employed that allow it to elicit control over aflatoxigenic strains and species of agricultural importance and (5) supplemental alternatives that increase its effectiveness. There is a need to be consistent, practical and thoughtful when it comes to implementing this method of mycotoxin mitigation since these fungi are living organisms that have been adapting, evolving and surviving on this planet for tens-of-millions of years. This document will serve as a critical review of the literature regarding pre-harvest A. flavus biocontrol and will discuss opportunities for improvements.
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Affiliation(s)
- Geromy G Moore
- United States Department of Agriculture, Agricultural Research Service, New Orleans, USA
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20
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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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21
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Gharsallah H, Ksentini I, Naayma S, Hadj Taieb K, Abdelhedi N, Schuster C, Triki MA, Ksantini M, Leclerque A. Identification of fungi in Tunisian olive orchards: characterization and biological control potential. BMC Microbiol 2020; 20:307. [PMID: 33046014 PMCID: PMC7552492 DOI: 10.1186/s12866-020-01997-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 10/05/2020] [Indexed: 01/08/2023] Open
Abstract
Background Olive production is the main agricultural activity in Tunisia. The diversity of fungi was explored in two different olive groves located in two distant geographical zones in Sfax (Tunisia) with different management practices. Results Fungal isolation was made from soil and the major olive tree pests, namely the Olive fly, Bactrocera oleae Gmelin (Diptera: Tephritidae), and the Olive psyllid, Euphyllura olivina Costa (Homoptera: Psyllidae). A total of 34 fungal isolates were identified according to their phenotypic, genotypic, biochemical and biological activities. Twenty fungal species were identified belonging to six different genera (Alternaria, Aspergillus, Cladosporium, Fusarium, Lecanicillium and Penicillium) by the analysis of their ITS1–5.8S–ITS2 ribosomal DNA region. Different bioassays performed in this work revealed that 25/34 (73.5%) of the identified fungal isolates showed an entomopathogenic and/or antagonistic activity, 9/34 (26.5%) of them displayed phytopathogenic features. Conclusions Fungal species that showed entomopathogenic and/or antagonistic potentialities and that are non-phytopathogenic, (17/34; 50%) of our fungal isolates, could be explored for olive protection against fungal diseases and pests, and might have a future application as biocontrol agents.
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Affiliation(s)
- Houda Gharsallah
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia.
| | - Ines Ksentini
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia
| | - Sourour Naayma
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia
| | - Karama Hadj Taieb
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia.,University of Sousse, Higher Institute of Agronomic Sciences of Chott Meriem, 4042, Sousse, Tunisia
| | - Nour Abdelhedi
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia
| | - Christina Schuster
- Institute for Microbiology and Biochemistry, Geisenheim University, Geisenheim, Germany.,Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - Mohamed Ali Triki
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia
| | - Mohieddine Ksantini
- Laboratory of Improvement and Protection of Genetic Resources of Olive Tree, Tunisian Olive Institute, University of Sfax, Airport Road, P.B. 1087, 3000, Sfax, Tunisia
| | - Andreas Leclerque
- Institute for Microbiology and Biochemistry, Geisenheim University, Geisenheim, Germany.,Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
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22
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Chalivendra S, Huang F, Busman M, Williams WP, Ham JH. Low Aflatoxin Levels in Aspergillus flavus-Resistant Maize Are Correlated With Increased Corn Earworm Damage and Enhanced Seed Fumonisin. FRONTIERS IN PLANT SCIENCE 2020; 11:565323. [PMID: 33101334 PMCID: PMC7546873 DOI: 10.3389/fpls.2020.565323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 08/19/2020] [Indexed: 06/11/2023]
Abstract
Preharvest mycotoxin contamination of field-grown crops is influenced not only by the host genotype, but also by inoculum load, insect pressure and their confounding interactions with seasonal weather. In two different field trials, we observed a preference in the natural infestation of corn earworm (CEW; Helicoverpa zea Boddie) to specific maize (Zea mays L.) genotypes and investigated this observation. The field trials involved four maize lines with contrasting levels of resistance to Aspergillus flavus. The resistant lines had 7 to 14-fold greater infested ears than the susceptible lines. Seed aflatoxin B1 (AF) levels, in mock- and A. flavus-inoculated ears were consistent with genotype resistance to A. flavus, in that the resistant lines showed low levels of AF (<30 ppb), whereas the susceptible lines had up to 500 ppb. On the other hand, CEW infestation showed a positive correlation with seed fumonisins (FUM) contamination by native Fusarium verticillioides strains. We inferred that the inverse trend in the correlation of AF and FUM with H. zea infestation may be due to a differential sensitivity of CEW to the two mycotoxins. This hypothesis was tested by toxin-feeding studies. H. zea larvae showed decreasing mass with increasing AF in the diet and incurred >30% lethality at 250 ppb. In contrast, CEW was tolerant to fumonisin with no significant loss in larval mass even at 100 ppm, implicating the low seed aflatoxin content as a predominant factor for the prevalence of CEW infestation and the associated fumonisin contamination in A. flavus resistant maize lines. Further, delayed flowering of the two resistant maize lines might have contributed to the pervasive H. zea damage of these lines by providing young silk for egg-laying. These results highlight the need for integrated strategies targeting mycotoxigenic fungi as well as their insect vectors for enhanced food safety.
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Affiliation(s)
- Subbaiah Chalivendra
- Department of Plant Pathology and Crop Physiology, Louisiana State University AgCenter, Baton Rouge, LA, United States
| | - Fangneng Huang
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, LA, United States
| | - Mark Busman
- Bacterial Foodborne Pathogens and Mycology Research Unit, USDA-ARS-NCAUR, Peoria, IL, United States
| | - W. Paul Williams
- Corn Host Plant Resistance Research Unit, USDA-ARS, Mississippi State, MS, United States
| | - Jong Hyun Ham
- Department of Plant Pathology and Crop Physiology, Louisiana State University AgCenter, Baton Rouge, LA, United States
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23
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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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Molecular crosstalk between the endophyte Paraconiothyrium variabile and the phytopathogen Fusarium oxysporum – Modulation of lipoxygenase activity and beauvericin production during the interaction. Fungal Genet Biol 2020; 139:103383. [DOI: 10.1016/j.fgb.2020.103383] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 03/16/2020] [Accepted: 03/31/2020] [Indexed: 11/17/2022]
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Trienens M, Rohlfs M. A Potential Collective Defense of Drosophila Larvae Against the Invasion of a Harmful Fungus. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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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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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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Sweany RR, Damann KE. Influence of Neighboring Clonal-Colonies on Aflatoxin Production by Aspergillus flavus. Front Microbiol 2020; 10:3038. [PMID: 32010096 PMCID: PMC6974465 DOI: 10.3389/fmicb.2019.03038] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Accepted: 12/17/2019] [Indexed: 11/13/2022] Open
Abstract
Aspergillus flavus is an ascomycete fungus that infects and contaminates corn, peanuts, cottonseed, and treenuts with acutely toxic and carcinogenic aflatoxins. The ecological function of aflatoxin production is not well understood; though not phytotoxic, aflatoxin may be involved in resisting oxidative stress responses from infection or drought stress in plants. Observation of aflatoxin stimulation in 48-well plates in response to increasing inoculated wells sparked an investigation to determine if A. flavus volatiles influence aflatoxin production in neighboring colonies. Experiments controlling several culture conditions demonstrated a stimulation of aflatoxin production with increased well occupancy independent of pH buffer, moisture, or isolate. However, even with all wells inoculated, aflatoxin production was less in interior wells. Only one isolate stimulated aflatoxin production in a large Petri-dish format containing eight small Petri dishes with shared headspace. Other isolates consistently inhibited aflatoxin production when all eight Petri dishes were inoculated with A. flavus. No contact between cultures and only shared headspace implied the fungus produced inhibitory and stimulatory gases. Adding activated charcoal between wells and dishes prevented inhibition but not stimulation indicating stimulatory and inhibitory gases are different and/or gas is inhibitory at high concentration and stimulatory at lower concentrations. Characterizing stimulatory and inhibitory effects of gases in A. flavus headspace as well as the apparently opposing results in the two systems deserves further investigation. Determining how gases contribute to quorum sensing and communication could facilitate managing or using the gases in modified atmospheres during grain storage to minimize aflatoxin contamination.
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Affiliation(s)
- Rebecca R. Sweany
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA, United States
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Lewis MH, Carbone I, Luis JM, Payne GA, Bowen KL, Hagan AK, Kemerait R, Heiniger R, Ojiambo PS. Biocontrol Strains Differentially Shift the Genetic Structure of Indigenous Soil Populations of Aspergillus flavus. Front Microbiol 2019; 10:1738. [PMID: 31417528 PMCID: PMC6685141 DOI: 10.3389/fmicb.2019.01738] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 07/15/2019] [Indexed: 01/22/2023] Open
Abstract
Biocontrol using non-aflatoxigenic strains of Aspergillus flavus has the greatest potential to mitigate aflatoxin contamination in agricultural produce. However, factors that influence the efficacy of biocontrol agents in reducing aflatoxin accumulation under field conditions are not well-understood. Shifts in the genetic structure of indigenous soil populations of A. flavus following application of biocontrol products Afla-Guard and AF36 were investigated to determine how these changes can influence the efficacy of biocontrol strains in reducing aflatoxin contamination. Soil samples were collected from maize fields in Alabama, Georgia, and North Carolina in 2012 and 2013 to determine changes in the population genetic structure of A. flavus in the soil following application of the biocontrol strains. A. flavus L was the most dominant species of Aspergillus section Flavi with a frequency ranging from 61 to 100%, followed by Aspergillus parasiticus that had a frequency of <35%. The frequency of A. flavus L increased, while that of A. parasiticus decreased after application of biocontrol strains. A total of 112 multilocus haplotypes (MLHs) were inferred from 1,282 isolates of A. flavus L using multilocus sequence typing of the trpC, mfs, and AF17 loci. A. flavus individuals belonging to the Afla-Guard MLH in the IB lineage were the most dominant before and after application of biocontrol strains, while individuals of the AF36 MLH in the IC lineage were either recovered in very low frequencies or not recovered at harvest. There were no significant (P > 0.05) differences in the frequency of individuals with MAT1-1 and MAT1-2 for clone-corrected MLH data, an indication of a recombining population resulting from sexual reproduction. Population mean mutation rates were not different across temporal and spatial scales indicating that mutation alone is not a driving force in observed multilocus sequence diversity. Clustering based on principal component analysis identified two distinct evolutionary lineages (IB and IC) across all three states. Additionally, patristic distance analysis revealed phylogenetic incongruency among single locus phylogenies which suggests ongoing genetic exchange and recombination. Levels of aflatoxin accumulation were very low except in North Carolina in 2012, where aflatoxin levels were significantly (P < 0.05) lower in grain from treated compared to untreated plots. Phylogenetic analysis showed that Afla-Guard was more effective than AF36 in shifting the indigenous soil populations of A. flavus toward the non-toxigenic or low aflatoxin producing IB lineage. These results suggest that Afla-Guard, which matches the genetic and ecological structure of indigenous soil populations of A. flavus in Alabama, Georgia, and North Carolina, is likely to be more effective in reducing aflatoxin accumulation and will also persist longer in the soil than AF36 in the southeastern United States.
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Affiliation(s)
- Mary H Lewis
- Department of Entomology and Plant Pathology, Center for Integrated Fungal Research, North Carolina State University, Raleigh, NC, United States
| | - Ignazio Carbone
- Department of Entomology and Plant Pathology, Center for Integrated Fungal Research, North Carolina State University, Raleigh, NC, United States
| | - Jane M Luis
- Department of Entomology and Plant Pathology, Center for Integrated Fungal Research, North Carolina State University, Raleigh, NC, United States
| | - Gary A Payne
- Department of Entomology and Plant Pathology, Center for Integrated Fungal Research, North Carolina State University, Raleigh, NC, United States
| | - Kira L Bowen
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States
| | - Austin K Hagan
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States
| | - Robert Kemerait
- Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, GA, United States
| | - Ron Heiniger
- Department of Crop Science, North Carolina State University, Raleigh, NC, United States
| | - Peter S Ojiambo
- Department of Entomology and Plant Pathology, Center for Integrated Fungal Research, North Carolina State University, Raleigh, NC, United States
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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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Holighaus G, Rohlfs M. Volatile and non-volatile fungal oxylipins in fungus-invertebrate interactions. FUNGAL ECOL 2019. [DOI: 10.1016/j.funeco.2018.09.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Abstract
One of the exciting movements in microbial sciences has been a refocusing and revitalization of efforts to mine the fungal secondary metabolome. The magnitude of biosynthetic gene clusters (BGCs) in a single filamentous fungal genome combined with the historic number of sequenced genomes suggests that the secondary metabolite wealth of filamentous fungi is largely untapped. Mining algorithms and scalable expression platforms have greatly expanded access to the chemical repertoire of fungal-derived secondary metabolites. In this Review, I discuss new insights into the transcriptional and epigenetic regulation of BGCs and the ecological roles of fungal secondary metabolites in warfare, defence and development. I also explore avenues for the identification of new fungal metabolites and the challenges in harvesting fungal-derived secondary metabolites.
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Drott MT, Debenport T, Higgins SA, Buckley DH, Milgroom MG. Fitness Cost of Aflatoxin Production in Aspergillus flavus When Competing with Soil Microbes Could Maintain Balancing Selection. mBio 2019; 10:e02782-18. [PMID: 30782658 PMCID: PMC6381279 DOI: 10.1128/mbio.02782-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 01/08/2019] [Indexed: 02/08/2023] Open
Abstract
Selective forces that maintain the polymorphism for aflatoxigenic and nonaflatoxigenic individuals of Aspergillus flavus are largely unknown. As soils are widely considered the natural habitat of A. flavus, we hypothesized that aflatoxin production would confer a fitness advantage in the soil environment. To test this hypothesis, we used A. flavus DNA quantified by quantitative PCR (qPCR) as a proxy for fitness of aflatoxigenic and nonaflatoxigenic field isolates grown in soil microcosms. Contrary to predictions, aflatoxigenic isolates had significantly lower fitness than did nonaflatoxigenic isolates in natural soils across three temperatures (25, 37, and 42°C). The addition of aflatoxin to soils (500 ng/g) had no effect on the growth of A. flavus Amplicon sequencing showed that neither the aflatoxin-producing ability of the fungus nor the addition of aflatoxin had a significant effect on the composition of fungal or bacterial communities in soil. We argue that the fitness disadvantage of aflatoxigenic isolates is most likely explained by the metabolic cost of producing aflatoxin. Coupled with a previous report of a selective advantage of aflatoxin production in the presence of some insects, our findings give an ecological explanation for balancing selection resulting in persistent polymorphisms in aflatoxin production.IMPORTANCE Aflatoxin, produced by the fungus Aspergillus flavus, is an extremely potent hepatotoxin that causes acute toxicosis and cancer, and it incurs hundreds of millions of dollars annually in agricultural losses. Despite the importance of this toxin to humans, it has remained unclear what the fungus gains by producing aflatoxin. In fact, not all strains of A. flavus produce aflatoxin. Previous work has shown an advantage to producing aflatoxin in the presence of some insects. Our current work demonstrates the first evidence of a disadvantage to A. flavus in producing aflatoxin when competing with soil microbes. Together, these opposing evolutionary forces could explain the persistence of both aflatoxigenic and nonaflatoxigenic strains through evolutionary time.
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Affiliation(s)
- Milton T Drott
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, USA
| | - Tracy Debenport
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, USA
| | - Steven A Higgins
- School of Integrative Plant Science, Soil and Crop Sciences Section, Cornell University, Ithaca, New York, USA
| | - Daniel H Buckley
- School of Integrative Plant Science, Soil and Crop Sciences Section, Cornell University, Ithaca, New York, 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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Olarte RA, Menke J, Zhang Y, Sullivan S, Slot JC, Huang Y, Badalamenti JP, Quandt AC, Spatafora JW, Bushley KE. Chromosome rearrangements shape the diversification of secondary metabolism in the cyclosporin producing fungus Tolypocladium inflatum. BMC Genomics 2019; 20:120. [PMID: 30732559 PMCID: PMC6367777 DOI: 10.1186/s12864-018-5399-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 12/19/2018] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Genes involved in production of secondary metabolites (SMs) in fungi are exceptionally diverse. Even strains of the same species may exhibit differences in metabolite production, a finding that has important implications for drug discovery. Unlike in other eukaryotes, genes producing SMs are often clustered and co-expressed in fungal genomes, but the genetic mechanisms involved in the creation and maintenance of these secondary metabolite biosynthetic gene clusters (SMBGCs) remains poorly understood. RESULTS In order to address the role of genome architecture and chromosome scale structural variation in generating diversity of SMBGCs, we generated chromosome scale assemblies of six geographically diverse isolates of the insect pathogenic fungus Tolypocladium inflatum, producer of the multi-billion dollar lifesaving immunosuppressant drug cyclosporin, and utilized a Hi-C chromosome conformation capture approach to address the role of genome architecture and structural variation in generating intraspecific diversity in SMBGCs. Our results demonstrate that the exchange of DNA between heterologous chromosomes plays an important role in generating novelty in SMBGCs in fungi. In particular, we demonstrate movement of a polyketide synthase (PKS) and several adjacent genes by translocation to a new chromosome and genomic context, potentially generating a novel PKS cluster. We also provide evidence for inter-chromosomal recombination between nonribosomal peptide synthetases located within subtelomeres and uncover a polymorphic cluster present in only two strains that is closely related to the cluster responsible for biosynthesis of the mycotoxin aflatoxin (AF), a highly carcinogenic compound that is a major public health concern worldwide. In contrast, the cyclosporin cluster, located internally on chromosomes, was conserved across strains, suggesting selective maintenance of this important virulence factor for infection of insects. CONCLUSIONS This research places the evolution of SMBGCs within the context of whole genome evolution and suggests a role for recombination between chromosomes in generating novel SMBGCs in the medicinal fungus Tolypocladium inflatum.
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Affiliation(s)
- Rodrigo A. Olarte
- 0000000419368657grid.17635.36Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA
| | - Jon Menke
- 0000 0001 0703 5300grid.450240.7Cargill Inc., Wayzata, MN USA
| | - Ying Zhang
- 0000000419368657grid.17635.36Minnesota Supercomputing Institute, Minneapolis, MN USA
| | | | - Jason C. Slot
- 0000 0001 2285 7943grid.261331.4Department of Plant Pathology, Ohio State University, Columbus, OH USA
| | - Yinyin Huang
- 0000000419368657grid.17635.36Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA
| | - Jonathan P. Badalamenti
- 0000000419368657grid.17635.36University of Minnesota Genomics Center, University of Minnesota, Minneapolis, MN USA
| | - Alisha C. Quandt
- 0000000096214564grid.266190.aDepartment of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO USA
| | - Joseph W. Spatafora
- 0000 0001 2112 1969grid.4391.fDepartment of Botany and Plant Pathology, Oregon State University, Corvallis, OR USA
| | - Kathryn E. Bushley
- 0000000419368657grid.17635.36Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA
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Pfannenstiel BT, Greco C, Sukowaty AT, Keller NP. The epigenetic reader SntB regulates secondary metabolism, development and global histone modifications in Aspergillus flavus. Fungal Genet Biol 2018; 120:9-18. [PMID: 30130575 PMCID: PMC6215504 DOI: 10.1016/j.fgb.2018.08.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/13/2018] [Accepted: 08/17/2018] [Indexed: 12/22/2022]
Abstract
Due to the role, both beneficial and harmful, that fungal secondary metabolites play in society, the study of their regulation is of great importance. Genes for any one secondary metabolite are contiguously arranged in a biosynthetic gene cluster (BGC) and subject to regulation through the remodeling of chromatin. Histone modifying enzymes can place or remove post translational modifications (PTM) on histone tails which influences how tight or relaxed the chromatin is, impacting transcription of BGCs. In a recent forward genetic screen, the epigenetic reader SntB was identified as a transcriptional regulator of the sterigmatocystin BGC in A. nidulans, and regulated the related metabolite aflatoxin in A. flavus. In this study we investigate the role of SntB in the plant pathogen A. flavus by analyzing both ΔsntB and overexpression sntB genetic mutants. Deletion of sntB increased global levels of H3K9K14 acetylation and impaired several developmental processes including sclerotia formation, heterokaryon compatibility, secondary metabolite synthesis, and ability to colonize host seeds; in contrast the overexpression strain displayed fewer phenotypes. ΔsntB developmental phenotypes were linked with SntB regulation of NosA, a transcription factor regulating the A. flavus cell fusion cascade.
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Affiliation(s)
| | - Claudio Greco
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Andrew T Sukowaty
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
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Drott MT, Lazzaro BP, Brown DL, Carbone I, Milgroom MG. Balancing selection for aflatoxin in Aspergillus flavus is maintained through interference competition with, and fungivory by insects. Proc Biol Sci 2018; 284:rspb.2017.2408. [PMID: 29263278 DOI: 10.1098/rspb.2017.2408] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 11/17/2017] [Indexed: 11/12/2022] Open
Abstract
The role of microbial secondary metabolites in the ecology of the organisms that produce them remains poorly understood. Variation in aflatoxin production by Aspergillus flavus is maintained by balancing selection, but the ecological function and impact on fungal fitness of this compound are unknown. We hypothesize that balancing selection for aflatoxin production in A. flavus is driven by interaction with insects. To test this, we competed naturally occurring aflatoxigenic and non-aflatoxigenic fungal isolates against Drosophila larvae on medium containing 0-1750 ppb aflatoxin, using quantitative PCR to quantify A. flavus DNA as a proxy for fungal fitness. The addition of aflatoxin across this range resulted in a 26-fold increase in fungal fitness. With no added toxin, aflatoxigenic isolates caused higher mortality of Drosophila larvae and had slightly higher fitness than non-aflatoxigenic isolates. Additionally, aflatoxin production increased an average of 1.5-fold in the presence of a single larva and nearly threefold when the fungus was mechanically damaged. We argue that the role of aflatoxin in protection from fungivory is inextricably linked to its role in interference competition. Our results, to our knowledge, provide the first clear evidence of a fitness advantage conferred to A. flavus by aflatoxin when interacting with insects.
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Affiliation(s)
- Milton T Drott
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, NY 14853, USA
| | - Brian P Lazzaro
- Department of Entomology, Cornell University, Ithaca, NY 14853, USA
| | - Dan L Brown
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
| | - Ignazio Carbone
- Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA
| | - Michael G Milgroom
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, NY 14853, USA
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