DIFFERENT ORGANIZATION AND ALTERED TRANSCRIPTION OF THE MITOCHONDRIAL ATP6 GENE IN THE MALE-STERILE CYTOPLASM OF RAPESEED (BRASSICA-NAPUS L)

The F(o)-ATPase subunit 6 gene (atp6) of rapeseed mitochondria has been isolated from both pol male-sterile and normal (fertile) cytoplasms in order to determine whether the rearrangements around the atp6 locus in pol male-sterile cytoplasm play a role in cytoplasmic male-sterility (cms). The pol cms and normal atp6 genes are identical and encode a 261-amino acid polypeptide. As a result of extensive rearrangement, a novel reading frame (pol-urf) was generated upstream of the atp6 gene only in pol cms mitochondria, which encoded 105 amino acids and might be co-transcribed with atp6. A 5'-portion of pol-urf shows sequence homology to the Oenothera ORFB gene associated with coxIII. A 5'-flanking region of the pol-urf also shows homology to that of ORF 105 in Ogura cms radish mitochondria. These DNA rearrangements which give rise to pol-urf in the vicinity of the atp6 locus may be responsible for cms in rapeseed.