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Title: Cryptic Sexuality in Aspergillus parasiticus and A. flavus

item Ramirez-prado, Jorge
item Moore, Geromy
item Horn, Bruce
item Carbone, Ignazio

Submitted to: International Workshop on Penicillium and Aspergillus
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2007
Publication Date: 6/7/2007
Citation: Ramirez-Prado, J.H., Moore, G.G., Horn, B.W., Carbone, I. 2007. Cryptic Sexuality in Aspergillus parasiticus and A. flavus. International Workshop on Penicillium and Aspergillus.

Interpretive Summary: None required.

Technical Abstract: Ascomycetous fungi of the genus Aspergillus comprise a wide variety of species of biotechnological importance (e.g. A. sojae, A. oryzae, A. niger) as well as pathogens and toxin producers (e.g. A. flavus, A. parasiticus, A. fumigatus, A. nidulans). With the exception of A. nidulans, which is a homothallic fungus, these species were previously thought to be strictly asexual. Recent studies report A. fumigatus to be heterothallic and possibly undergoing sexual reproduction. Our population genetic analysis of the aflatoxin gene cluster in a Georgia population of A. parasiticus showed evidence of five distinct recombination blocks each showing a pattern of significant linkage disequilibrium and shared evolutionary history, thus providing indirect evidence of the possibility of sexual recombination in nature. We therefore investigated whether compatible mating type “MAT” genes (MAT1-1 alpha box gene and MAT1-2 HMG gene) were present. We found that each distinct A. parasiticus chemotype lineage (OMST and G1 dominant) was heterothallic and possessed a single MAT locus, containing either a MAT1-1 (G1 dominant) or a MAT1-2 (OMST) idiomorph. We observed a similar heterothallic organization of the MAT locus in A. flavus sampled from the same Georgia field but there was no association of mating type idiomorph with a specific chemotype lineage. The existence of both mating type idiomorphs in equal proportions in A. parasiticus and A. flavus populations indicates the potential for a cryptic sexual state in these agriculturally important species.