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Comparative analysis of the cypAnorB gene region of Aspergillus pseudotamarii

Connel Ching'anda: University of Arizona

<div>Aflatoxins are fungal metabolites that often contaminate food and feed and cause immune suppression, stunting, and cancer. Members of <em>Aspergillu</em>s section <em>Flavi</em> vary in aflatoxin producing ability. Some members, such as <em>Aspergillus parasiticus</em> and <em>Aspergillus nomius,</em> produce both B and G aflatoxins while <em>Aspergillus flavus</em> and <em>Aspergillus pseudotamarii</em> produce only B aflatoxins. Aflatoxin biosynthesis involves at least 25 genes clustered within a 70 kb region. Lack of ability to produce G aflatoxins is attributed to loss of function of the cytochrome P450 monooxygenase encoded by <em>cypA</em>. Several <em>Aspergillus</em> taxa which produce B aflatoxins but not G aflatoxins have deletions (0.8 to 2.2 kb) bridging from <em>cypA</em> to <em>norB</em>. However, the basis for lack of G toxin production in <em>A. pseudotamarii</em> is not known. Primers designed to characterize partial deletions of <em>cypA</em> in the L and S morphotypes of <em>A. flavus</em> and in the Lethal Aflatoxicosis Fungus from Kenya failed to produce PCR products from <em>A. psuedotamarii</em>. Successful amplification of a 1 kb portion of <em>cypA</em> distal from <em>norB</em> resulted in sequence 90% similar to <em>A. flavus </em>(GeneBank accession number AY 510452.1). Efforts to amplify and sequence regions extending from <em>norB</em> towards the cyclopiazonic acid cluster are underway. Determination of the mechanism of loss of function of <em>cypA</em> will enhance our understanding of the evolutionary events leading to loss of G aflatoxin production in <em>Aspergillus</em> section <em>Flavi</em>.</div>