Abstract
Cytoplasmic male sterility (CMS) is a maternally inherited trait that results in the inability to produce fertile pollen and is often associated with an unusual open reading frame (orf) found in mitochondrial genomes. The fertility of CMS plant was restored under the nuclear encoded fertility restorer gene (Rf). LD-type CMS rice possesses a cytoplasm of Lead Rice and its pollen fertility gametophytically restored by the nuclear Rfk. We carried out map-based cloning of a Rfk and proved Rfk encodes a mitochondrial glycine-rich protein consisting of 152 amino acids. The expression of Rfk were detected in anthers at the bicellular and tricellular stage. The Rfk-GFP fusion was shown to be targeted to mitochondria. The fertility restoring allele encodes isoleucine, whereas non-restoring allele encodes threonine at the 78th amino acid residues. It was thought that a single polymorphism in amino acid in rfk was a cause of the function deficiency.
