Fine Mapping of Region for a Sorghum Fertility Restorer Gene and Microsynteny Analysis Across Grass Species

Cytoplasmic male sterility (CMS) is widely used to control pollination in the production of commercial F hybrid seed in sorghum. So far, 6 major fertility restorer genes, to , have been reported in sorghum. Here, we fine-mapped the locus on sorghum chromosome 5 using descendant populations of a 'Nakei MS-3A' × 'JN43' cross. The locus was narrowed to a 140-kb region in BTx623 genome (161-kb in JN43) with 16 predicted genes, including 6 homologous to the rice fertility restorer (PPR.1 to PPR.6). These 6 homologs have tandem pentatricopeptide repeat (PPR) motifs. Many genes encode PPR proteins, which bind RNA transcripts and modulate gene expression at the RNA level. No PPR genes were detected at the locus on the corresponding homologous chromosome of rice, foxtail millet, or maize, so this gene cluster may have originated by chromosome translocation and duplication after the divergence of sorghum from these species. Comparison of the sequences of these genes between fertile and CMS lines identified PPR.4 as the most plausible candidate gene for .