title: A fertility restorer gene, Rf4, widely used for hybrid rice breeding encodes a pentatricopeptide repeat protein.
abstract: BACKGROUND
  Uncontrolled expression of a certain mitochondrial gene often causes cytoplasmic male sterility (CMS) in plants. This phenotype is prevented by the presence of a fertility restorer (Rf) gene in the nuclear genome. Such CMS/Rf systems have been successfully used for breedings of F1 hybrid cultivars. In rice, approximately 99% of F1 hybrid cultivars have been developed using a wild abortive type of CMS (WA-CMS) and its Rf genes. Recently, a newly identified mitochondrial gene, orf352, was reported as a WA-CMS-causing gene.
  
  
  RESULTS
  We cloned and functionally characterized Rf4, a major Rf gene for WA-CMS. We revealed that Rf4 encoded a pentatricopeptide repeat-containing protein and reduced the orf352-containing transcripts, thereby restoring pollen fertility.
  
  
  CONCLUSIONS
  Through a map-based cloning, we have independently identified an allele of a recently reported Rf4 gene and demonstrated that the fertility restoration is controlled sporophytically.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981-8555, Japan, tomo-kazama@bios.tohoku.ac.jp.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kazama
authors.forename: Kinya
authors.initials: K
authors.lastname: Toriyama