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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL CONTROL OF INSECTS AND MICROORGANISMS TO PREVENT MYCOTOXIN CONTAMINATION

Location: Foodborne Toxin Detection and Prevention

Title: Influence of Gene Expression on Variable Aflatoxin Production by Different Strains of Aspergillus flavus

Authors
item Hua, Sui Sheng
item Shih, Henry
item Sarreal, Siov
item Chang, Perng Kuang
item Cheng, Luisa Wai Wai

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2009
Publication Date: N/A

Technical Abstract: Aspergillus flavus is a globally distributed fungus. It causes disease in human and crop plants due to the production of numerous conidia dispersed by air movement and possibly by insects. The fungus is an economically important food contaminant because it produces the most potent natural carcinogenic compounds known as “aflatoxins” in agricultural crops and food products such as corn, peanuts, cotton and tree nuts. The genes directly involved in aflatoxin (AF) production have been identified in an 82kb cluster. Genetic studies of AF biosynthesis led to the cloning of 29 genes responsible for enzymatic reactions. Aflatoxin concentrations produced by different strains of A. flavus in the same nutrient medium vary greatly. Concentrations of aflatoxin in high producers can be 100 fold over the low producers. The factors underlying different levels of aflatoxin production among these strains are not well understood. We resorted to real time RT-PCR assays of genes involved in aflatoxin biosynthesis. The expression of several well defined genes, aflJ, aflR, omtB, pksA in these isolates was analyzed. The transcriptional levels of aflJ and pksA were higher in all the isolates of high aflatoxin production compared to strain CA18, a low produce of aflatoxin. Levels of omtB gene expression showed a wide variation among isolates. The AF cluster genes, aflJ, aflR, pksA, omtB were expressed at higher levels in afltoxingenic isolates in comparison to strains which do not produce aflatoxin (strain CA88 which has the genes present). It appears that expression of pksA and aflJ positively influenced the quantity of aflatoxin production in various isolates found in food products.

Last Modified: 9/21/2014
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