Isolation and Analysis of Rice Rf1-Orthologus PPR Genes Co-segregating with Rf3 in Maize

Using an in silico cloning approach, five putative maize pentatricopeptide repeat (PPR)-containing protein genes (PPR-814a, PPR-814b, PPR-814c, PPR-816, PPR-817) with complete open reading frames were identified in the inbred line S-Mo17(Rf3Rf3). The amino acid sequence indicated that these genes encoded mitochondrially targeted proteins containing repeats of a 35-aa PPR motif. The genes were mapped into the interval umc1525-bnlg1520 on chromosome 2. In a non-restoring genotype, we identified three homologous genes that contained deletions or nucleotide substitutions in the coding region. Sequence analysis revealed that one of the three genes (PPR-814a, PPR-814b, PPR-814c) could be considered a candidate restorer gene for S male sterility cytoplasm, and linkage analysis demonstrated that the genes co-segregated with the fertility restorer gene Rf3.