One C-to-U RNA Editing Site and Two Independently Evolved Editing Factors: Testing Reciprocal Complementation with DYW-Type PPR Proteins from the Moss () and the Flowering Plants and Arabidopsis.

Cytidine-to-uridine RNA editing is a posttranscriptional process in plant organelles, mediated by specific pentatricopeptide repeat (PPR) proteins. In angiosperms, hundreds of sites undergo RNA editing. By contrast, only 13 sites are edited in the moss () Some are conserved between the two species, like the mitochondrial editing site nad5eU598RC. The PPR proteins assigned to this editing site are known in both species: the DYW-type PPR protein PPR79 in and the E+-type PPR protein CWM1 in Arabidopsis (). CWM1 also edits sites ccmCeU463RC, ccmBeU428SL, and nad5eU609VV. Here, we reciprocally expressed the and Arabidopsis editing factors in the respective other genetic environment. Surprisingly, the editing factor edited all target sites when expressed in the Arabidopsis mutant background, even when carboxy-terminally truncated. Conversely, neither Arabidopsis CWM1 nor CWM1-PPR79 chimeras restored editing in plants. A CWM1-like PPR protein from the early diverging angiosperm macadamia () features a complete DYW domain and fully rescued editing of nad5eU598RC when expressed in We conclude that (1) the independently evolved editing factor PPR79 faithfully operates in the more complex Arabidopsis editing system, (2) truncated PPR79 recruits catalytic DYW domains in trans when expressed in Arabidopsis, and (3) the macadamia CWM1-like protein retains the capacity to work in the less complex editing environment.