EVOLUTIONARY TRANSFER OF THE CHLOROPLAST TUFA GENE TO THE NUCLEUS

Evolutionary gene transfer is a basic corollary of the now widely accepted endosymbiotic theory, which proposes that mitochondria and chloroplasts originated from once free-living eubacteria1. The small organellar chromosomes are remnants of larger bacterial genomes, with most endosymbiont genes having been either transferred to the nucleus2 soon after endosymbiosis3,4 or lost entirely, with some being functionally replaced by preexisting nuclear genes5,6. Several lines of evidence indicate that relocation of some organelle genes could have been more recent. These include the abundance of non-functional organelle sequences of recent origin in nuclear DNA7,8, successful artificial transfer of functional organelle genes to the nucleus9, and several examples of recently lost organelle genes4,10, although none of these is known to have been replaced by a nuclear homologue that is clearly of organellar ancestry. We present gene sequence and molecular phylogenetic evidence for the transfer of the chloroplast tuf A gene to the nucleus in the green algal ancestor of land plants. © 1990 Nature Publishing Group.