A Pentatricopeptide Repeat Protein Restores Fertility in Tadukan-Type Cytoplasmic Male Sterile Rice via the Cleavage of the Mitochondrial orf312 RNA.

Abstract

Cytoplasmic male sterility (CMS) is associated with the inhibition of pollen and/or anther development regulated by a CMS-causing gene in the mitochondrial genome; it is a useful trait for preventing self-pollination and producing F₁ hybrids, which can boost crop yields. Pollen and/or anther development can be recovered by the action of the RESTORER OF FERTILITY (Rf) gene, a nuclear-encoded gene. Most reported Rf genes encode pentatricopeptide repeat (PPR) proteins, which bind to RNA and promote RNA processing of the respective CMS-causing gene. In this study, we report the map-based cloning of the Rf gene (Rfta) for Tadukan-type CMS (TA-CMS) in rice (Oryza sativa L.), with anther dehiscence and seed setting inhibited by the mitochondrial gene orf312. The Rfta locus was delimited to a region comprising 10 PPR genes forming a cluster on chromosome 10. The complementation test revealed that the introduction of a PPR gene, PPR796, into the TA-CMS line resulted in the recovery of the anther dehiscence and seed setting. RNA-gel blot analysis and the determination of 3' ends of the orf312 RNA confirmed the PPR796-mediated cleavage of the orf312 RNA in the transgenic TA-CMS line. Furthermore, RNA gel electrophoretic mobility shift assays revealed that the recombinant PPR796 protein bound to the 3' side of the orf312 RNA in vitro. We concluded that RFta/PPR796 binds to orf312 RNA and promotes RNA cleavage to restore fertility in TA-CMS.