Isolation and some characterization of a pentatricopeptide repeat protein gene, orf687, required for fertility restoration of cytoplasmic male-sterility in Kosena radish

Abstract

Regulation of cytoplasmic male sterility (CMS) by fertility restorer (Rf) genes is one of the suitable systems for molecular-genetic analysis of the interactions between mitochondria and nuclear genome. In Kosena CMS, presence of a CMS-associated gene, orf125, in the cytoplasm and the accumulation of ORF125 protein are strongly associated with the CMS phenotype. The fertility restoration was accompanied by a decrease in the amount of the mitochondial protein. To understand the molecular mechanisms by which the Rf gene acts on the expression of orf125, the gene was cloned by a positional cloning strategy. The cloned gene, orf687, encodes a protein that comprises sixteen repeats of pentatricopeptide repeat motif and a putative mitochondrial target sequence. Analysis of the temporal and developmental expression of orf687 and its homologues are in progress. Based upon these results, we will discuss possible mechanism of orf687 gene on the expression of the CMS gene.