MITOCHONDRIAL RNA EDITING OF CYTOCHROME-C-OXIDASE SUBUNIT-II (COXII) IN THE PRIMITIVE VASCULAR PLANT PSILOTUM-NUDUM

A 634-nucleotide tract, including primers, was amplified via the polymerase chain reaction within a mitochondrial coxII gene of the primitive vascular plant Psilotum nudum and sequenced. Alignment with homologous coxII gene sequences from diverse plant species having known RNA editing sites which restore amino acid sequence consensus was used to infer eight sites of C-to-U transitions in Psilotum. In every case, the predicted editing event would confer the selective advantage of conserving the amino acid residue at a site where amino acid sequence divergence has not been observed in other plant species. The plant mitochondrial editing machinery is shown for the first time to extend to one of the deepest branches of vascular plant phylogeny.