Binds specific group II introns in chloroplasts and facilitates their splicing (PubMed:18799595, PubMed:32143506). Exhibits non-specific action during plastid rRNA biogenesis; RFC3 prevents unaccurate splicing to improve the accuracy of plastid rRNA processing (PubMed:32143506). Acts on subgroup IIB introns (PubMed:18799595). The substrates of the subgroup IIB also require the CRM domain proteins CAF1 or CAF2, with a simultaneous binding of CFM3B and CAF1 or CAF2 (PubMed:18799595). Required for seed development (PubMed:18799595). Interacts with RNA (By similarity). Part of large ribonucleo-protein particles that contain CAF1 and/or CAF2, and RNC1 (By similarity). Interacts with RFC3 in plastids (PubMed:32143506). Localized to root plastids. Expressed at low levels in roots and shoots. No visible phenotype under normal growth conditions, but the seeds of the double mutant plants cfm3a-4 and cfm3b-2 fail to germinate (PubMed:18799595). The double mutant rfc3-2 sprt2-1 is rescued for primary and lateral root development, intracellular distributions of plastids in roots, as well as for plastid rRNA level compared to the single mutant rfc3-2 (PubMed:32143506).