Mycotoxin Research

, Volume 22, Issue 1, pp 3–8

Gene targets for fungal and mycotoxin control

  • J. H. Kim
  • B. C. Campbell
  • R. Molyneux
  • N. Mahoney
  • K. L. Chan
  • J. Yu
  • J. Wilkinson
  • J. Cary
  • D. Bhatnagar
  • T. E. Cleveland
Article

DOI: 10.1007/BF02954550

Cite this article as:
Kim, J.H., Campbell, B.C., Molyneux, R. et al. Mycotox Res (2006) 22: 3. doi:10.1007/BF02954550

Abstract

It was initially shown that gallic acid, from hydrolysable tannins in the pelliele of walnut kernels, dramatically inhibits biosynthesis of aflatoxin byAspergillus flavus. The mechanism of this inhibition was found to take place upstream from the gene cluster, including the regulatory gene,aflR, involved in aflatoxin biosynthesis. Additional research using other antioxidant phenolics showed similar antiaflatoxigenic activity to gallic acid. Treatment ofA. flavus withtert-butyl hydroperoxide resulted in an almost doubling of aflatoxin biosynthesis compared to untreated samples. Thus, antioxidative response systems are potentially useful molecular targets for control ofA. flavus. A high throughput screening system was developed using yeast,Saccharomyces cerevisiae, as a model fungus. This screening provided an avenue to quickly identify fungal genes that were vulnerable to treatment by phenolic compounds. The assay also provided a means to quickly assess effects of combinations of phenolics and certain fungicides affecting mitochondrial respiration. For example, theS. cerevisiae sod2† mutant was highly sensitive to treatment by certain phenolics and strobilurins/antimycin A, fungicides which inhibit complex III of the mitochondrial respiratory chain. Verification of stress to this system in the target fungus,A. flavus, was shown through complementation analysis, wherein the mitochondrial superoxide dismutase (Mn-SOD) gene (sodA) ofA. flavus in the ortholog mutant,sod2†, ofS. cerevisiae, relieved phenolic-induced stress. Mitochondrial antioxidative stress systems play an important role in fungal response to antifungals. Combined treatment of fungi with phenolics and inhibitors of mitochondrial respiration can effectively suppress growth ofA. flavus in a synergistic fashion.

Keywords

aflatoxinSaccharomyces cerevisiaeoxidative stressantioxidantsmitochondrial respiration

Copyright information

© Society of Mycotoxin Research and Springer 2006

Authors and Affiliations

  • J. H. Kim
    • 1
  • B. C. Campbell
    • 1
  • R. Molyneux
    • 1
  • N. Mahoney
    • 1
  • K. L. Chan
    • 1
  • J. Yu
    • 2
  • J. Wilkinson
    • 2
  • J. Cary
    • 2
  • D. Bhatnagar
    • 2
  • T. E. Cleveland
    • 2
  1. 1.Plant Mycotoxin ResearchUSDA-ARS Western Regional Research CenterAlbanyUSA
  2. 2.Food and Feed Safety ResearchUSDA-ARS Southern Regional Research CenterNew OrleansUSA