The radish <i>Rfo</i> restorer gene of Ogura cytoplasmic male sterility encodes a protein with multiple pentatricopeptide repeats

TLDR

The Rfo locus is flanked by two similar, non‑restorer genes, and its syntenic region in Arabidopsis lacks a PPR gene at the equivalent site, though a related PPR gene lies ~40 kb away. The study examines how these observations inform the evolution of restorer genes and other PPR‑encoding genes. Using a map‑based cloning strategy that exploits synteny between radish and Arabidopsis, the authors isolated the Rfo gene. Rfo encodes a 687‑amino‑acid, mitochondria‑targeted pentatricopeptide repeat protein with 16 domains that restores Ogura cytoplasmic male sterility in Brassica napus, resembling the Petunia Rf gene.

Abstract

Summary A single radish nuclear gene, Rfo , restores Ogura ( ogu ) cytoplasmic male sterility (CMS) in Brassica napus . A map‐based cloning approach relying on synteny between radish and Arabidopsis was used to clone Rfo . A radish gene encoding a 687‐amino‐acid protein with a predicted mitochondrial targeting pre‐sequence was found to confer male fertility upon transformation into ogu CMS B. napus . This gene, like the recently described Petunia Rf gene, codes for a pentatricopeptide repeat (PPR)‐containing protein with multiple, in this case 16, PPR domains. Two similar genes that do not appear to function as Rfo flank this gene. Comparison of the Rfo region with the syntenic Arabidopsis region indicates that a PPR gene is not present at the Rfo ‐equivalent site in Arabidopsis, although a smaller and related PPR gene is found about 40 kb from this site. The implications of these findings for the evolution of restorer genes and other PPR encoding genes are discussed.