OGURA CYTOPLASMIC MALE-STERILITY (CMS)-ASSOCIATED ORF138 IS TRANSLATED INTO A MITOCHONDRIAL-MEMBRANE POLYPEPTIDE IN MALE-STERILE BRASSICA CYBRIDS

Transcription of a putative mitochondrial gene (orf138) has previously been correlated with Ogura cytoplasmic male-sterility (CMS) in rapeseed cybrids. In this paper, studies performed on a Brassica cybrid with a different organization of the orf138 locus confirm this association. We also show that mitochondria isolated from male-sterile rapeseed plants synthesize a polypeptide of 19 kDa, which is absent in fertile revertants. Antibodies against a glutathione S-transferase-ORF138 fusion protein were raised to establish that this 19 kDa polypeptide is the product of orf138. The anti-ORFl38 serum was used to demonstrate that the orf138 translation product occurs only in sterile cybrids and co-purifies with the mitochondrial membrane fraction.