Sequence breakpoints in the aflatoxin biosynthesis gene cluster and flanking regions in nonaflatoxigenic Aspergillus flavus isolates

被引:207
作者
Chang, PK
Horn, BW
Dorner, JW
机构
[1] USDA ARS, So Reg Res Ctr, New Orleans, LA 70124 USA
[2] USDA ARS, Natl Peanut Res Lab, Dawson, GA 39842 USA
关键词
breakpoint; deletion; gene cluster; Aspergillus flavus; aflatoxin; cyclopiazonic acid; sclerotia; inverse PCR; telomere;
D O I
10.1016/j.fgb.2005.07.004
中图分类号
Q3 [遗传学];
学科分类号
071007 ; 090102 ;
摘要
Aspergillus flavus populations are genetically diverse. Isolates that produce either, neither, or both aflatoxins and cyclopiazonic acid (CPA) are present in the field. We investigated defects in the aflatoxin gene cluster in 38 nonaflatoxigenic A. flavus isolates collected from southern United States. PCR assays using aflatoxin-gene-specific primers grouped these isolates into eight (A-H) deletion patterns. Patterns Q E, G, and H, which contain >= 40 kb deletions, were examined for their sequence breakpoints. Pattern C has one breakpoint in the cypA 3' untranslated region (UTR) and another in the verA coding region. Pattern E has a breakpoint in the amd/A coding region and another in the ver1 5'UTR. Pattern G contains a deletion identical to the one found in pattern C and has another deletion that extends from the cypA coding region to one end of the chromosome as suggested by the presence of telomeric sequence repeats, CCCTAATGTTGA. Pattern H has a deletion of the entire aflatoxin gene cluster from the hexA coding region in the sugar utilization gene cluster to the telomeric region. Thus, deletions in the aflatoxin gene cluster among A. flavus isolates are not rare, and the patterns appear to be diverse. Genetic drift may be a driving force that is responsible for the loss of the entire aflatoxin gene cluster in nonaflatoxigenic A. flavus isolates when aflatoxins have lost their adaptive value in nature. Published by Elsevier Inc.
引用
收藏
页码:914 / 923
页数:10
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