Repeated, recent and diverse transfers of a mitochondrial gene to the nucleus in flowering plants

A central component of the endosymbiotic theory for the bacterial origin of the mitochondrion is that many of its genes were transferred to the nucleu s. Most of this transfer occurred early in mitochondrial evolution(1); func tional transfer of mitochondrial genes has ceased in animals(2). Although m itochondrial gene transfer continues to occur in plants(3), no comprehensiv e study of the frequency and timing of transfers during plant evolution has been conducted. Here we report frequent loss (26 times) and transfer to th e nucleus of the mitochondrial gene rps10 among 277 diverse angiosperms. Ch aracterization of nuclear rps10 genes from 16 out of 26 loss lineages impli es that many independent, RNA-mediated rps10 transfers occurred during rece nt angiosperm evolution; each of the genes may represent a separate functio nal gene transfer. Thus, rps10 has been transferred to the nucleus at a sur prisingly high rate during angiosperm evolution. The structures of several nuclear rps10 genes reveal diverse mechanisms by which transferred genes be come activated, including parasitism of pre-existing nuclear genes for mito chondrial or cytoplasmic proteins, and activation without gain of a mitocho ndrial targeting sequence.