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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 11/6/2014 Publication Date: 11/25/2014 Citation: Kim, J.H., Chan, K.L. 2014. Model fungal systems for investigating food plant mycotoxins. In: Cheung, P., Mehta, B.M. editors. Handbook of Food Chemistry. Berlin, Germany: Springer-Verlag Berlin Heidelberg. p. 1-16. Interpretive Summary: Contamination of food, feed or other agro-products by aflatoxins triggers a food safety issue, imposing serious health concerns. Considering the increasingly strict regulations worldwide, there is an urgent demand to develop methods for preventing aflatoxin contamination in agricultural commodities. Controlling fungi that produce aflatoxins in crops is problematic as effective fungicides for treating aflatoxin-producing fungi are very limited. Therefore, new methods are continually needed for control of aflatoxigenic fungal pathogens. The baker’s yeast Saccharomyces cerevisiae is a useful tool for examining mechanisms of toxicities of aflatoxins, or for screening antifungal agents. S. cerevisiae has also been used as an aflatoxin decontaminating agent, where aflatoxins physically interact with the cell wall components of yeasts. S. cerevisiae is one of the few organisms for which the structure of the cell walls are well characterized, thus allowing effective decontamination of aflatoxins. In this book chapter, recent progress in the use of the yeast S. cerevisiae for effective control of aflatoxins and fungal pathogens is discussed. Technical Abstract: Aflatoxins are carcinogenic mycotoxins produced mainly by Aspergillus flavus and A. parasiticus. Aflatoxins, when metabolically activated by hepatic cytochrome P450s (CYPs), trigger genotoxicity in mammals through the formation of reactive aflatoxin-8,9-exo-epoxide. The resulting 8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin adduct causes mutations or DNA damage, thus negatively affects human or animal health. The yeast Saccharomyces cerevisiae is a useful system for investigating the mechanisms of toxicity of aflatoxins, where human or animal CYPs can be functionally expressed to metabolically activate aflatoxins. Using recombinant S. cerevisiae, the consequences of CYP polymorphisms on the differential aflatoxin toxicity, effects of CYP-inhibitory phytochemicals on aflatoxin activation, transcriptional responses of cells to aflatoxins, etc., have been investigated. Of note, the aflatoxicosis could be ameliorated by S. cerevisiae cell walls. Aflatoxins interact with S. cerevisiae cell wall components, thus adsorbing/removing aflatoxins from the contaminated sources. Lastly, S. cerevisiae strains, such as gene deletion mutants, could also serve as useful genetic tools for identifying molecular targets or mode of actions of antifungal agents. This facilitates expedited development of new, safe antifungal drugs/fungicides, resulting in the effective control of aflatoxin-producing aspergilli. |
