Horizontal transfer and recombination fuel Ty4 retrotransposon evolution inSaccharomyces

Abstract

AbstractHorizontal transposon transfer (HTT) plays an important role in the evolution of eukaryotic genomes, however the detailed evolutionary history and impact of most HTT events remain to be elucidated. To better understand the process of HTT in closely-related microbial eukaryotes, we studied Ty4 retrotransposon subfamily content and sequence evolution across the genusSaccharomycesusing short- and long-read whole genome sequence data, including new PacBio genome assemblies for twoS. mikataestrains. We find evidence for multiple independent HTT events introducing the Tsu4 subfamily into specific lineages ofS. paradoxus,S. cerevisiae,S. eubayanus,S. kudriavzeviiand the ancestor of theS. mikatae/S. jureispecies pair. In bothS. mikataeandS. kudriavzevii, we identified novel Ty4 clades that were independently generated through recombination between resident and horizontally-transferred subfamilies. Our results reveal that recurrent HTT and lineage-specific extinction events lead to a complex pattern of Ty4 subfamily content across the genusSaccharomyces. Moreover, our results demonstrate how HTT can lead to coexistence of related retrotransposon subfamilies in the same genome that can fuel evolution of new retrotransposon cladesviarecombination.