Browsing by Author "JORDANA, X"

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    RNA EDITING OF APOCYTOCHROME-B (COB) TRANSCRIPTS IN MITOCHONDRIA FROM 2 GENERA OF PLANTS
    (1993) ZANLUNGO, S; BEGU, D; QUINONES, V; ARAYA, A; JORDANA, X
    Editing of the complete coding region of cob transcripts from two genera of plants has been studied by cDNA sequence analysis. Eighteen and nine C residues are edited into U in the mitochondrial transcripts from wheat and potato respectively. Both systems share eight common editing sites; ten codons edited in wheat are ''pre-edited'' at the genomic level in potato, and one codon edited in potato is ''pre-edited'' in wheat. Most amino-acid modifications lead to hydrophobic residues and increase the homology between the COB polypeptides and the corresponding protein of other species. In two out of the nine potato cDNA clones, an additional C-to-T modification, which also leads to a change in the encoded amino acid, was identified. Heterogeneity observed at the carboxy-terminus of the COB open reading frame in Triticum aestivum and Triticum timopheevi is not corrected by editing.
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    THE POTATO MITOCHONDRIAL ATP SYNTHASE SUBUNIT-9 - GENE STRUCTURE, RNA EDITING AND PARTIAL PROTEIN-SEQUENCE
    (1993) DELLORTO, P; MOENNE, A; GRAVES, PV; JORDANA, X
    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.
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    TRANSCRIPTION INITIATION SITES FOR THE POTATO MITOCHONDRIAL GENE CODING FOR SUBUNIT-9 OF ATP SYNTHASE (ATP9)
    (1994) LIZAMA, L; HOLUIGUE, L; JORDANA, X
    The potato mitochondrial atp9 gene has a simple expression pattern. To determine where transcription initiates, primary mitochondrial RNAs were labeled by in vitro capping and hybridized to the 5' flanking sequences of the atp9 gene. A single transcription initiation region was identified. Primer extension and nuclease S1 protection analyses were used to precisely map the transcript 5' termini in this region. These results indicate that transcription initiates at 121-128 bp upstream of the atp9 open reading frame, in a sequence which does not present any homology with proposed consensus sequences for plant mitochondrial promoters. Nuclease S1 protection were also used to map 3' termini 67-71 nucleotides downstream of a putative single-stem loop structure.