Required for chloroplast protein synthesis and accumulation of subunits of the thylakoid protein complexes. Activates psaC and petA translation by binding their 5'-UTRs. Required for the correct processing of petB and petD mRNAs. Interacts with the petB and petD intergenic region and is required for the generation of petB and petD monocistronic RNAs. Interacts with PDE338. Seedling lethality under normal growth conditions. Belongs to the PPR family. P subfamily.