Essential protein required during embryogenesis (PubMed:15266054, PubMed:22495966). Mediates group II organellar RNA introns splicing (e.g. ycf3-2 and trnA) (PubMed:22495966). Binds weakly to specific RNA (PubMed:22495966, PubMed:24047899). Promotes the biogenesis of chloroplast thylakoid membranes (PubMed:22495966). Pigment defective embryo arrested at cotyledon stage in homozygous plants, partially rescued when grown on sucrose-containing medium (PubMed:15266054, PubMed:22495966). Retarded growth and greening. Reduced abundance of both the excised intron and the spliced product from ycf3-2 and trnA (PubMed:22495966). Belongs to the PPR family. P subfamily.