UNIVERSALITY OF MITOCHONDRIAL RNA EDITING IN CYTOCHROME-C-OXIDASE SUBUNIT-I (COXI) AMONG THE LAND PLANTS

Plant mitochondrial pre-mRNAs often undergo C-to-U conversions, a phen omenon termed RNA editing. The molecular source of specificity and phy logenetic depth of the editing machinery remain to be determined. We a mplified cox1 gene fragments via the polymerase chain reaction from a diversity of taxa within the land plants, and sequenced each. Alignmen t and comparison of 25 homologous cox1 gene sequences with those from plant species having known RNA editing sites which restore amino acid sequence consensus was used to infer sites of C-to-U conversions. Our results, derived using the comparative approach, imply that the plant mitochondrial editing machinery extends throughout vascular plant phyl ogeny, and also that this phenomenon is present in every major branch of the (non-vascular) Bryophyta: liverworts (Hepaticae), hornworts (An thocerotae), and mosses (Musci). These results have important conseque nces for our thoughts on the evolutionary history of the plant RNA edi ting process, as they imply that editing is older than was previously believed.