Binds specific group II introns in chloroplasts and facilitates their splicing. Acts on subgroup IIB introns. The substrates of the subgroup IIB also require the CRM domain proteins CAF1 or CAF2, with a simultaneous binding of CFM3A and CAF1 or CAF2. Required for seed development. May influence the biogenesis of the mitochondrial small ribosomal subunit. Interacts with RNA. Part of large ribonucleo-protein particles that contain CAF1 and/or CAF2, and RNC1. Albino seeds that fail to germinate or yield very slow-growing seedlings and stunted plants. The seeds of the double mutant plants cfm3a-4 and cfm3b-2 fail to germinate. Sequencing errors.