Molecular Basis of a Novel Type of Cytoplasmic Male Sterility in Sunflower

Abstract

ABSTRACTIn this mini-review recent progress is summarized in understanding molecular mechanisms involved in cytoplasmic male sterility (CMS) in sunflower. The focus is mainly on a new cytoplasmic male sterile sunflower genotype (CMS3) which is compared to the classical Petiolaris cytoplasmic male sterility. The sterile phenotype in Petiolaris CMS is associated with a mitochondrial rearrangement creating a novel open reading frame located 3′ to the atp A gene. Cotranscription of this open reading frame with the atp A gene and translation into a 15 kDa novel protein is assumed to play a major role in the CMS phenotype. The mitochondrial genome of GMS3 has unique rearrangements at five loci compared to the Petiolaris sterile and the fertile mitochondrial genomes. At the RNA level the transcript size and abundance of two out of the five rearranged loci, cox III and atp 6, are different between Petiolaris sterile, fertile and GMS3 sterile cytoplasm. In organelle protein synthesis experiments show that the 15 k...