MUSTANG is a novel family of domesticated transposase genes found in diverse angiosperms

While transposons have traditionally been viewed as genomic parasites or "junk DNA," the discovery of transposon-derived host genes has fueled an ongoing debate over the evolutionary role of transposons. In particular, while mobility-related open reading frames have been known to acquire host functions, the contribution of these types of events to the evolution of genes is not well understood. Here we report that genome-wide searches for Mutator transposase-derived host genes in Arabidopsis thaliana (Columbia-0) and Oryza sativa ssp. japonica (cv. Nipponbare) (domesticated rice) identified 121 sequences, including the taxonomically conserved MUSTANG1. Syntenic MUSTANG1 orthologs in such varied plant species as rice, poplar, Arabidopsis, and Medicago truncatula appear to be under purifying selection. However, despite the evidence of this pathway of gene evolution, MUSTANG1 belongs to one of only two Mutator-like gene families with members in both monocotyledonous and dicotyledonous plants, suggesting that Mutator-like elements seldom evolve into taxonomically widespread host genes.