Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/7/2007
Publication Date: 6/11/2007
Citation: Carbone, I., Jakobek, J., Ramirez-Prado, J.H., Horn, B.W. 2007. Evolution of Aflatoxigenicity in Aspergillus . Meeting Proceedings. Interpretive Summary: None required.
Technical Abstract: Our goal in the proposed research is to understand the evolution of the aflatoxin biosynthetic gene cluster. We are using a combination of macro- and micro-evolutionary approaches to identify the forces driving and maintaining genes in clusters. Previously, we examined nucleotide sequence variation in 21 intergenic regions across the entire aflatoxin gene cluster of A. parasiticus and found evidence of recombination blocks – groups of two or more genes in the cluster with different evolutionary histories. The same blocks appear to be conserved for putative orthologs of these genes in A. nidulans, A. flavus, and A. fumigatus. This is first-time evidence in support of recombination among cluster genes. Our hypothesis is that a low level of recombination and possibly gene flow are significantly contributing to the persistence and further evolution of aflatoxigenic strains and the evolution of new species. The objectives of this proposal will test this hypothesis by focusing on A. flavus and A. parasiticus, the two most abundant species found in soil. Our specific objectives are: 1. To examine population structure and recombination block patterns in the aflatoxin gene cluster of A. flavus sampled from the same peanut field in Georgia as our previously analyzed A. parasiticus sample. Preliminary population-level variation in intergenic regions of A. flavus in Georgia is revealing a complex history of mutation, recombination, and selection in the AF gene cluster. We plan to expand our sample to include geographically and ecologically isolated populations of A. flavus and A. parasiticus from major peanut-growing regions in Texas, Virginia, Australia, West Africa and Argentina. This is important to further understand the roles of vegetative incompatibility, speciation and isolation on cluster evolution. 2. To use our inferences of recombination blocks to estimate the magnitude, timing and frequency of recombination and gene flow in the aflatoxin gene cluster of A. flavus and A. parasiticus. These estimates are important in predicting the direction of evolution of different genes in the aflatoxin cluster and in assessing the long-term impact of an introduced biocontrol strain on population structure and speciation.