The involvement of a PPR protein of the P subfamily in partial RNA editing of an Arabidopsis mitochondrial transcript.

C-to-U RNA editing (i.e., alteration of a C in the genomic sequence to U in the transcript) has been confirmed widely in angiosperm organellar genomes. During the C-to-U RNA editing event, incomplete edited transcripts have been observed at many sites in the steady-state mRNA population (partial editing). Here, by using coexpression analysis and the surveillance of whole editing status on the mitochondrial genome, we have revealed that a pentatricopeptide repeat (PPR) protein classified into the P subfamily (PPR596) has site-specific influence on the efficiency of C-to-U RNA editing events at partial editing sites on the Arabidopsis thaliana mitochondrial genome. Previous works have revealed that PPR proteins classified into the PLS subfamily containing the E or E and DYW motif are involved in RNA editing as trans-factors; they are believed to recruit deaminase at editing sites. In contrast with the mutant analyses of PLS-subfamily PPR proteins, the editing efficiency at rps3eU1344SS was revealed to be significantly increased in ppr596 mutants. Our study implies P-subfamily PPR protein is involved in the control of the degree of partial editing.