Transfer of rps10 from the mitochondrion to the nucleus in Arabidopsis thaliana: evidence for RNA-mediated transfer and exon shuffling at the integration site.

Rps10, a gene coding for ribosomal protein S10 of Arabidopsis mitochondria has been transferred to the nuclear compartment, while in pea and potato the active rps10 is mitochondrially located. The nuclear rps10 gene contains an intron at the junction of the target signal sequence and the mitochondrial-derived sequence, indicating that exon shuffling may have been involved in the addition of the transit peptide signal. Sequence comparison of Arabidopsis rps10 to the plant mitochondrial counterparts shows that the edited version is present in the nucleus of Arabidopsis. This finding corroborates RNA as an intermediate of a functional gene transfer between mitochondria and the nucleus. In vitro-translated RPS10 protein is efficiently imported into potato mitochondria and a presequence of about 7 kDa is removed resulting in a mature protein that is larger compared to organellar and bacterial RPS10 proteins.