Fitness Cost of Aflatoxin Production in Aspergillus flavus When Competing with Soil Microbes Could Maintain Balancing Selection
| Autor: | Michael G. Milgroom, Daniel H. Buckley, Tracy Debenport, Steven A. Higgins, Milton T. Drott |
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| Rok vydání: | 2019 |
| Předmět: |
Aflatoxin
fitness cost Aspergillus flavus Ecological and Evolutionary Science Fungus Real-Time Polymerase Chain Reaction Balancing selection Microbiology Poisons Toxicology 03 medical and health sciences Aflatoxins Virology Antibiosis Selective advantage heterocyclic compounds DNA Fungal Secondary metabolism Soil Microbiology 030304 developmental biology secondary metabolism 0303 health sciences Bacteria biology 030306 microbiology technology industry and agriculture Temperature aflatoxin food and beverages biology.organism_classification QR1-502 biological factors Genetics Population Genetic Fitness Energy Metabolism Microcosm Research Article Fitness cost |
| Zdroj: | mBio mBio, Vol 10, Iss 1, p e02782-18 (2019) mBio, Vol 10, Iss 1 (2019) |
| ISSN: | 2150-7511 2161-2129 |
| DOI: | 10.1128/mbio.02782-18 |
| Popis: | 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. 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. |
| Databáze: | OpenAIRE |
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