Filamentous fungi produce a diverse array of secondary metabolites that play ecological roles in defense, virulence, and inter- and intra-species communication. The biosynthetic genes required for the production of individual secondary metabolites are arranged in contiguous genomic clusters. These pathways are narrowly taxonomically distributed and highly diverse between species, and are among the most fast-evolving protein-coding elements in filamentous fungal genomes. To gain insight into the diversity of secondary metabolic gene clusters in fungal populations and its drivers, we examined the conservation and divergence of secondary metabolic gene clusters across the genomes of 40 representative isolates of the cosmopolitan opportunistic pathogen Aspergillus fumigatus. We found that a core set of secondary metabolic gene clusters were present in all isolates, but that other gene clusters were only present in subsets of isolates. We additionally identified multiple different types of gene cluster polymorphisms, including fusion of different gene clusters, alternative genomic locations for gene clusters, and clusters with multiple alternative idiomorphs (i.e., non-homologous alleles). In particular, two gene clusters flanked by transposable elements were consistently found in different genomic locations; one of these clusters showed a phylogenetic pattern consistent with horizontal gene transfer between fungi. Our results suggest that multiple genetic factors, including recombination, gene loss, and horizontal gene transfer, drive the diversification of secondary metabolism pathways.
Full conference title:
- Asperfest 14 (2017)