Table 1. Functionally characterized PPR-protein-encoding restorer of fertility genes (Rf-PPR) and highly related RFL genes that do not support restoration activity. Rf genes mapping within clusters of RFL genes and that are therefore strongly suspected to encode a PPR protein are also indicated. NA, not applicable.

Species		CMS	Rf or Rf-like gene	Type of PPR	# of aa	# of repeats	Mitochondrial target	Associated molecular mechanims	Refs.
Cloned Rf-PPR genes
Petunia hybrida sp.			Rf-PPR592	P	592	14	urfS	RNA processing or translation inhibition?	Bentolila 2002
Raphanus sativus		Ogura	Rfo (=Rfk1 or PPR-B)	P	687	17	orf138	translation inhibition	Brown et al, 2003; Desloire et al 2003
Raphanus sativus		Kosena	Rfk1 (=Rfo or PPR-B)	P	687	17	orf125	translation inhibition	Koizuka et al, 2003
Oryza sativa		BoroII	Rf1a	P	791	18	orf79	RNA processing	Kazama et al, 2003; Komori et al, 2003; Akagi et al, 2004; Wang et al, 2006
Oryza sativa		BoroII	Rf1b	P	506	11	orf79	RNA degradation	Wang et al, 2006
Oryza sativa		Honglian	Rf5=Rf1a	P	791	18	orfH79	RNA processing	Hu et al, 2012
Sorghum bicolor		A1	Rf1	PLS	628	14	?	RNA editing?	Klein et al, 2005
Rf genes suspected to encode a PPR protein
Mimulus guttatus	IM62		Rf1	P?	?	?	orf141?	RNA processing?	Barr et al, 2010
Mimulus guttatus	IM62		Rf2	P?	?	?	orf141?	RNA processing?	Barr et al, 2010
Sorghum bicolor	A1		Rf2	P?	?	?	?	?	Jordan et al, 2010
Sorghum bicolor	A2		Rf5	P?	?	?	?	?	Jordan et al, 2011
Functionally characterized RFL genes
Arabidopsis thaliana	NA		RPF1	P	602	14	nad4	RNA processing	Hölzle et al., 2011
Arabidopsis thaliana	NA		RPF2	P	630	16	nad9, cox3	RNA processing	Jonietz et al., 2010
Arabidopsis thaliana	NA		RPF3	P	629	15	ccmC	RNA processing	Jonietz et al., 2011
Arabidopsis thaliana	NA		NG1	P	485	12	?	?	Yang et al., 2011