Études fonctionnelles des protéines PPR dans les organites d'Arabidopsis thaliana =Functional studies of PPR proteins in Arabidopsis organelles

In plant organelles, nuclear encoded proteins targeted to the organelles control posttranscriptional mechanisms. The PentatricoPeptide Repeat proteins (PPR) whose family has greatly expanded in land plants, are good candidates to play such regulatory roles. We used a reverse genetic screen in Arabidopsis thaliana to assign new functions to PPR genes. RNA editing in higher plant organelles results in the conversion of specific cytidine residues to uridine residues in RNA. The recognition of a specific target C site by the editing machinery involves trans-acting factors that bind to the RNA upstream of the C to be edited. We identified six new PPR chloroplast editing factors in Arabidopsis thaliana (OTP80, OTP81, OTP82, OTP84, OTP85, and OTP86). These six factors account for nine editing sites not previously assigned to an editing factor and, together with the nine PPR editing proteins previously described, explain more than half of the 34 editing events in Arabidopsis chloroplasts.