Molecular Biology of Aflatoxin Biosynthesis in Aspergillus flavus (1998-02814)

Aflatoxins, Produced by the fungus Aspergillus jlavus, are toxic and carcinogenic compounds contaminating a variety of food products.In addition to the significant health risks associated with aflatoxins, there is also an economic burden. Millions of dollars arespent each year to test potentially affected food, including corn, peanuts, figs, tree nuts and milk. Aflatoxins are products of fungal secondary metabolism. The genes involved in the biosynthesis of aflatoxin are grouped together in a single cluster. The cluster containsat least l8 genes that code for the pathway enzymes and for regulation of aflatoxin biosynthesis. This research project will investigate an unusual mutation in A. jlavus. Strain 649 has a DNA deletion at the afl-l locus that includes the entire cluster of aflatoxin biosynthesis genes. Diploids formed by crosses between strain 649 and aflatoxin-producing strains do not produce aflatoxin.The goalof the research is to determine the mechanism responsible for this suppression of aflatoxin biosynthesis. The specific objectives are to isolate and characterize the DNA at the deletion break-junction region in strain 649, and to determine the involvement of the regulatory gene ajlR in repression of aflatoxin biosynthesis. This research will impact agriculture by furthering our understanding about the regulation of aflatoxin biosynthesis and contribute information leading to development of new strategies for eliminating aflatoxin contamination.