Genetic evidence that two types of retroelements evolved through different pathways in ectomycorrhizal homobasidiomycetes Tricholoma spp.

We designed a polymerase chain reaction that allows us to clone two types of putative reverse transcriptase genes from 11 species of ectomycorrhizal basidiomycetes that belong to the genus Tricholoma. One corresponds to the putative gene of marY1, a long terminal repeat (LTR) retroelement from Tricholoma matsutake, and the other, marY2N, a LINE-like non-LTR (L1-like) retroelement from this fungus. Putative protein products predicted from nucleotide sequencing of cloned fragments were phylogenetically analyzed. marY1-like elements had a parallel phylogenetic relationship with no apparent correlation to a current taxonomic profile, while marY2N-like elements showed a vertical one in relation to host-plant species. Data suggest that marY1-like elements and marY2N-like elements have evolved independently, and the evolution of marY1-like elements could have occurred later than the evolution of marY2N-like elements in the species of Tricholoma.