Submitted to: Aflatoxin Workshop
Publication Type: Abstract only
Publication Acceptance Date: 11/25/2006
Publication Date: 3/6/2006
Citation: Carbone, I., Jakobek, J.L., Moussa, E.H., Cox, J.E., Horn, B.W. 2006. Evolutionary processes in the aflatoxin gene cluster in aspergillus. Aflatoxin Workshop. Interpretive Summary: None required.
Technical Abstract: Aflatoxins are potent natural carcinogenic secondary metabolites produced by several species in the genus Aspergillus. Recently nonaflatoxigenic A. flavus strains were approved as biocontrol agents for use on cotton and peanuts. Although these biocontrol strains have proven to be effective, we have no knowledge of the long-term effects that introduced strains have on the evolution of aflatoxigenicity. Our hypothesis is that a low level of recombination and gene flow among Aspergillus species is significantly contributing to the persistence and further evolution of aflatoxigenic strains. We are currently testing this hypothesis by focusing on A. flavus and A. parasiticus, the two most abundant aflatoxigenic species. Our examination of nucleotide sequence variation in 21 intergenic regions across the entire aflatoxin gene cluster of A. parasiticus indicates the presence of recombination blocks and there is evidence that balancing selection has influenced genetic variation in these blocks. The same blocks appear to be conserved for putative orthologs of these genes in A. nidulans, A. flavus, and A. fumigatus, indicating the potential for an introduced biocontrol strain to acquire toxigenicity genes from indigenous strains via recombination or from sympatric species via horizontal transfer. We are currently examining the timing and frequency of these events in nature.