Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2006
Publication Date: 3/1/2007
Citation: Wilkinson, J.R., Yu, J., Bland, J.M., Nierman, W.C., Bhatnagar, D., Cleveland, T.E. 2007. Amino acid supplementation reveals differential regulation of aflatoxin biosynthesis in Aspergillus flavus NRRL 3357 and Aspergillus parasiticus SRRC 143. Applied Microbiology and Biotechnology. 74:1308-1319. Interpretive Summary: Aflatoxins are toxic and carcinogenic compounds produced by fungal molds. When they contaminate agricultural food and feed commodities, health risk to human and animal are high, and economic losses due to aflatoxin contamination are significant. In order to better understand the molecular mechanisms that regulate aflatoxin production, the amino acid effects on aflatoxin biosynthesis in A. flavus and A. parasiticus were examined. We found that the amino acid tryptophan exhibits inhibitive effect to aflatoxin formation. Using DNA microarray technologies we identified seventy seven genes that are related to aflatoxin production. This information could help in solving aflatoxin contamination in food and feed.
Technical Abstract: Aflatoxins are toxic and carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and A. parasiticus. In order to better understand the molecular mechanisms that regulate aflatoxin production, the biosynthesis of the toxin in A. flavus and A. parasiticus grown in yeast extract sucrose media supplemented with 50 mM tryptophan (Trp) were examined. A. flavus grown in the presence of 50 mM tryptophan was found to have significantly reduced aflatoxin B1 and B2 biosynthesis, while A. parasiticus cultures had significantly increased B1 and G1 biosynthesis. Microarray analysis of RNA extracted from fungi grown under these conditions revealed seventy seven genes to be significant, including the aflatoxin biosynthetic genes aflD (nor-1), aflE (norA) and aflO (omtB). It is clear that the regulatory mechanisms of aflatoxin biosynthesis in response to Trp in A. flavus and A. parasiticus are different. Further investigation of these candidate genes may help to identify a regulatory factor of aflatoxin biosynthesis at either the transcriptional or translational level.