Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/21/2006
Publication Date: 5/21/2006
Citation: Wilkinson, J.R., Yu, J., Abbas, H.K., Scheffler, B.E., Kim, H.S., Nierman, W.C., Bhatnagar, D., Cleveland, T.E. 2006. Media shift of Aspergillus parasiticus cultures for studying the molecular regulation of aflatoxin. In: Proceedings of the American Society for Microbiology Annual Meeting, May 21-26, 2006, Orlando, FL. Abstract #O-064, p. 433.
Technical Abstract: Aflatoxins are secondary metabolites produced by the fungi Aspergillus flavus and A. parasiticus. These compounds are toxic and carcinogenic. Many nutritional and environmental factors are known to affect aflatoxin formation. In order to better understand the molecular mechanisms that control or regulate aflatoxin production, microarrays containing 5,002 unique A. flavus gene amplicons were used for a time course study of A. parasiticus. Mycelia were isolated from A. parasiticus grown 48 hours in Yeast Extract (YE), an incomplete media, and then shifted to Yeast Extract Sucrose (YES), a complete media. Tissue was isolated from the 48 YE sample and at 3, 6, 12, 18, 24 and 48 hours after shifting to the YES. The isolated tissues were used for RNA and aflatoxin extractions. After the shift from YE to YES, aflatoxin levels were found to initially decrease before increasing and surpassing initial production. Aflatoxin levels were reduced by 3 hours post-shift, the biosynthesis remained depressed until 18 hours post-shift when levels increase to half of YE levels. By 24 hours post-shift toxin biosynthesis had exceeded that in YE by 10 fold. Microarray analysis was done to compare 48 hr YE to post-shift YES samples. The analyses revealed that the transcript levels of several aflatoxin biosynthetic pathway genes within the aflatoxin gene cluster were temporarily reduced at 6 hours post-shift, but returned to levels similar to YE by 12 hours post-shift. ANOVA of the results revealed that the expression of 173 genes were significantly altered (increased or decreased) across all experiments, including norB and verB (ie. genes within the biosynthetic cluster). Using these genes expression profiles as templates, candidate genes will be identified that function to regulate aflatoxin biosynthesis at either the gene or protein level.