Abstract
Cytoplasmic male sterility (CMS), a trait of failure to produce functional pollen caused by the aberrant mitochondrial genes, has been focused to study plant mitochondrial-nuclear communication. The sterility is repressed by nuclear genes designated as restorer of fertility (Rf) genes, which mostly encode pentatricopeptide repeat (PPR) proteins. Actual molecular mechanisms of Rfs are largely unknown, although it has been speculated the Rf protein directly suppresses the expression of CMS gene at RNA level.
The aberrant mitochondrial orf125 is associated with Kosena CMS radish, and the fertility is restored by a PPR protein, Raphanus sativus Rf (rsRf). To elucidate the molecular mechanism of reduction of ORF125 by rsRf, the RNA binding properties of recombinant rsRf with orf125 mRNA was analyzed. The rsRf was shown to interact with the downstream of start codon of orf125 mRNA.
It has been identified rsRf-like genes from various radish species with several amino acid polymorphisms, which could influence the restoration of fertility. We would also present our current studies involving the RNA binding activity of the polymorphic rsRf genes to discuss their functions as the restorers.
