Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 6/6/2007
Publication Date: 7/10/2007
Citation: Ramirez-Prado, J.H., Moore, G.G., Horn, B.W., Carbone, I. 2007. Cryptic Sexuality Influences Aflatoxigenicity in Aspergillus parasiticus and A. flavus. American Phytopathological Society Annual Meeting. Interpretive Summary: None required.
Technical Abstract: Ascomycetous fungi of the genus Aspergillus comprise a wide variety of species of biotechnological importance as well as pathogens and toxin producers. Recent studies report A. fumigatus to be heterothallic and possibly undergoing sexual reproduction. We therefore investigated whether compatible mating type MAT genes (MAT1-1 alpha box and MAT1-2 HMG) were present in A. parasiticus and A. flavus, the major aflatoxin-producing species. 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 two evolutionary distinct lineages of A. flavus sampled from the same Georgia field but there was no association of mating type idiomorph with a specific lineage. Ongoing recombination between A. parasiticus OMST and G1 dominant strains has resulted in lower G1/B1 ratios but may have also served as a mechanism for maintaining OMST and G1 dominant chemotypes, by removing deleterious mutations. In A. flavus, one lineage is under the influence of balancing selection that is acting to stabilize the nonaflatoxigenic phenotype. A second lineage is undergoing extensive recombination and maintaining aflatoxin concentrations at equilibrium.