Evolution of RNA interference proteins dicer and argonaute in Basidiomycota

RNA interference (RNAi) refers to a mechanism in which cells control gene expression, protect the genome against mobile repetitive DNA sequences, retro elements and transposons, and defend themselves against viruses. Two core components, dicer and argonaute, are central in the RNAi machinery. In this study the evolution of argonaute and dicer genes were analyzed with 43 fungal genomes, with the focus on Basidiomycota. Argonaute and dicer genes are widely represented in Basidiomycota as well as in other fungal groups, but the number of copies of them vary. However, in certain lineages, argonaute or dicer is missing. Our results suggest an ancient duplication of dicer and argonaute genes concurrently with early diversification of the Basidiomycota followed by additional species-specific duplications and losses of more recent origin. Several distinct RNAi pathways exist in fungi, based on structural similarity and phylogenetic relationship, our results indicate that quelling possibly exists in most Basidiomycota, while we could not find any evidence for the MSUD (meiotic-silencing) pathway in Basidiomycota. RNAi has been developed to be an important tool for reverse genetics studies. Because both argonaute and dicer are present in almost all Basidiomycota our results indicate that it should be possible to develop RNAi as a tool for functional studies of genes in most Basidiomycota species.