Evolutionary Origins of the Fumonisin Secondary Metabolite Gene Cluster inFusarium verticillioidesandAspergillus niger

Abstract

The secondary metabolite gene clusters of euascomycete fungi are among the largest known clusters of functionally related genes in eukaryotes. Most of these clusters are species specific or genus specific, and little is known about how they are formed during evolution. We used a comparative genomics approach to study the evolutionary origins of a secondary metabolite cluster that synthesizes a polyketide derivative, namely, the fumonisin (FUM) cluster ofFusarium verticillioides, and that ofAspergillus nigeranother fumonisin (fumonisin B) producing species. We identified homologs in other euascomycetes of theFusarium verticillioides FUMgenes and their flanking genes. We discuss four models for the origin of theFUMcluster inFusarium verticillioidesand argue that two of these are plausible: (i) assembly by relocation of initially scattered genes in a recentFusarium verticillioides; or (ii) horizontal transfer of theFUMcluster from a distantly related Sordariomycete species. We also propose that theFUMcluster was horizontally transferred intoAspergillus niger, most probably from a Sordariomycete species.