Title: Evolution of a Secondary Metabolite Biosynthetic Gene Cluster in Fusarium by Gene Relocation Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 2008
Publication Date: March 22, 2009
Citation: Proctor, R., Mccormick, S.P., Alexander, N.J., Desjardins, A.E. 2009. Evolution of a Secondary Metabolite Biosynthetic Gene Cluster in Fusarium by Gene Relocation [abstract]. Proceedings of the 25th Fungal Genetics Conference. p. 218. Technical Abstract: Trichothecenes are secondary metabolites produced by multiple genera of fungi, including some plant pathogenic species of Fusarium. Trichothecenes contribute to virulence of Fusarium on some plants and are considered to be mycotoxins because of their human and animal toxicity. Previous analyses of Fusarium graminearum and F. sporotrichioides demonstrated that three loci encode trichothecene biosynthetic enzymes: 1) the 12-gene, core TRI cluster, 2) the two-gene TRI1/TRI16 locus, and 3) the single-gene TRI101 locus. Here, sequence analysis revealed that in F. equiseti TRI1 and TRI101 are located in the core cluster but TRI16 is not. Analysis of trichothecene-nonproducing Fusaria distantly related to producing species revealed the presence of TRI101 remnants in the same genetic environment as the intact TRI101 in F. graminearum and F. sporotrichioides. Thus, TRI101 likely occurred at this location prior to divergence of trichothecene-producing and nonproducing species. Phylogenetic analysis of 16 trichothecene-producing Fusarium species revealed a lack of correlation between TRI1-based phylogenies and phylogenies based on primary metabolic genes or genes in the core cluster. In contrast, TRI1 and TRI16-based phylogenies are highly correlated whether or not the genes are at the same locus. These results suggest that TRI1 and TRI16 occurred together at a locus distinct from the core TRI cluster in the ancestral Fusarium and that TRI1 moved into the cluster during the evolutionary history of F. equiseti. Thus, our results provide evidence that filamentous fungal gene clusters can expand by relocation of genes into the clusters from elsewhere in the same genome.