THE POTATO MITOCHONDRIAL ATP SYNTHASE SUBUNIT-9 - GENE STRUCTURE, RNA EDITING AND PARTIAL PROTEIN-SEQUENCE

The mitochondrial genome of Solanum tuberosum contains one functional gene for the proteolipid subunit of the ATP synthase complex (atp9). This gene appears to be organized as an independent transcriptional unit, since only one major transcript of 350 nucleotides was detected. Editing of atp9 transcripts has been studied by cDNA sequence analysis. Ten C residues are edited into U in the mRNA, resulting in seven amino acid changes and a new stop codon which eliminated 3 carboxy-terminal residues, compared to the polypeptide deduced from the genomic sequence. N-terminal protein sequence analysis confirmed the first editing event. Most changes increase the homology between potato polypeptide and the corresponding protein of non plant organisms. Interestingly, an apparently non transcribed, truncated atp9 gene is also present in the potato mitochondrial genome. This pseudogene lacks 5' coding sequences and probably arises from recombination events.