Involved in C-to-U editing of chloroplastic RNA. Functions as major chloroplastic editing factor. Controls 62 percent of the chloroplastic editing sites. Binds RNA close to ORRM1-dependent editing sites in vitro. Binds the editing recognition trans-factors PCMP-H51/CRR28 and PCMP-H12/OTP82. Interacts with PCMP-H51/CRR28 and PCMP-H12/OTP82 (PubMed:23487777). Interacts with MORF8/RIP1, MORF2/RIP2 and VAR3/OZ1 (PubMed:25768119). No visible phenotype under normal growth conditions, but mutant plants exhibit severe editing defects in chloroplastic transcripts.