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Aflatoxins are toxic and carcinogenic compounds produced in food by the fungus Aspergillus flavus. Contamination often occurs before harvest and no effective control procedures are available. The goal of this research is to understand the factors that regulate aflatoxin biosynthesis such that plant gene products or synthesized compounds can be employed to inhibit aflatoxin formation.
One approach to study regulation of aflatoxin in biosynthesis is to determine those genes expressed during aflatoxin biosynthesis that are not expressed under conditions unfavorable for aflatoxin formation. Several different physiological conditions known to be favorable or unfavorable for aflatoxin biosynthesis will be compared. DNA from A. flavus cDNA library will be spotted on filters and probed with DNA made from mRNA expressed during conditions either coundusive or nonconducive for aflatoxin biosynthesis. Genes that are expressed during aflatoxin biosynthesis but not expressed under conditions unfavorable for aflatoxin biosynthesis will be isolated, sequenced, and their function determined.
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A second approach to identify aflatoxin regulatory genes will involve generating mutants unable to induce transcription of the pathway specific regulatory gene aflR. Presumably, these mutants will have a mutation in genes that regulate aflR. To identify the functional copy of the mutated genes, the mutant will be transformed with DNA clones from a genomic library of A. flavus representing all of the genes of the fungus. The gene that restores function will be sequenced and characterized. Once regulatory genes are identified by the procedures above their profile of expression and order in the regulatory circuit will be determined.