ARS | Publication request: CHARACTERIZATION OF DELETIONS IN THE AFLATOXIN BIOSYNTHETIC GENE CLUSTER OF NONAFLATOXIGENIC ASPERGILLUS FLAVUS ISOLATES

Submitted to: ASM Conference
Publication Type: Abstract Only
Publication Acceptance Date: December 30, 2004
Publication Date: May 25, 2005
Citation: Chang, P., Horn, B.W., Dorner, J.W. 2005. Characterization of deletions in the aflatoxin biosynthetic gene cluster of nonaflatoxigenic Aspergillus flavus isolates [abstract]. 105th General Meeting of the American Society for Microbiology, June 5-9, 2005, Atlanta, Georgia. p. 152.

Technical Abstract: Aflatoxin (AF) and cyclopiazonic acid (CPA) commonly occur together in agricultural commodities, such as corn, cottonseed, and peanuts. The contamination is largely attributable to Aspergillus flavus. However, A. flavus isolates that produce either, neither, or both toxins have been reported. A gene cluster of 66 kilobases is responsible for the synthesis of AF by A. flavus and A. parasiticus. Using PCR amplification with AF-gene specific primers, we examined the intactness of the AF gene cluster of 16 AF-negative/CPA-positive and 24 AF-negative/CPA-negative A. flavus isolates obtained from agricultural soils of the southern United States. Results show that three of the 16 AF-negative/CPA-positive isolates have a deletion in the region between the cypA gene and the avnA gene. In contrast, five of the AF-negative/CPA-negative A. flavus isolates have larger deletions that extend 10 kb beyond one end (the norB gene) of the AF gene cluster. Moreover, 18 of the AF-negative/CPA-negative isolates have completely lost the AF gene cluster. Thus, deletion of the AF gene cluster in the genome of the AF-negative/CPA-negative isolates appears to be more extensive than that of the AF-negative/CPA-positive A. flavus isolates.