Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2004
Publication Date: 5/30/2004
Citation: Yu, J., Kim, H., Cleveland, T.E., Bhatnagar, D., Nierman, W.C. 2004. Aflatoxin biosynthetic gene profiling in Aspergillus flavus by EST and microarray [abstract]. American Society for Microbiology Annual Meeting, New Orleans, Louisiana.
Technical Abstract: Aflatoxins are the notorious carcinogens produced primarily by the fungi Aspergillus flavus and A. parasiticus. Molecular studies on the genetics of aflatoxin biosynthesis established a well organized aflatoxin pathway gene cluster consisting of 25 genes within 70 kb DNA region. Biochemical studies demonstrated that over 16 enzymatic reactions are directly involved in the biochemical conversion from precursors to aflatoxins. In addition, carbon and nitrogen metabolisms may also be related to aflatoxin formation. It is believed that numerous signal transduction factors may play a role in connecting primary and secondary metabolism and in turning on aflatoxin synthesis. In order to better understand the molecular mechanism and regulation of aflatoxin biosynthesis, gene profiling through A. flavus Expressed Sequenced Tag (EST) and microarray technologies have been carried out. Microarray containing all of these unique genes has been used in gene profiling under aflatoxin supportive and non-supportive medium conditions. A total of 7,214 unique EST sequences have been identified from a normalized A. flavus NRRL 3357 cDNA library. Among the genes identified, many are rare copy genes potentially involved in secondary metabolism and gene regulation. In addition to the known aflatoxin biosynthetic genes identified among the sequenced clones in the library, we have identified many of the genes that may be involved directly or indirectly in aflatoxin formation. They are: regulatory genes that have the potential to regulate aflatoxin production or signal transduction; genes that have the potential to contribute to fungal virulence or pathogeneicity; and genes involved in fungal development. Some unique genes in the EST library show sequence homology to genes encoding hydrolytic enzymes. Such hydrolytic enzymes could be highly expressed virulence factors during invasion of A. flavus into crops. These genes identified could be targeted for genetic engineering of antifungal crops for eliminating aflatoxin contamination of food and feed commodity.