The mat-r open reading frame is transcribed from a non-canonical promoter and contains an internal promoter to co-transcribe exons nad1e and nad5III in wheat mitochondria.
The expression of the mat-r locus (mat-r-nad1e-nad5III) was studied in wheat mitochondria. Transcription initiation sites were mapped by S1 protection, primer extension and capping experiments. Two different transcription initiation sites were found. One, non-canonical promoter of low expression level generates a transcript containing the complete mat-r open reading frame (orf), suggesting that this form is the maturase-reverse transcriptase mRNA. A second transcription initiation site, found within the coding region of the mat-r orf, directs the transcription of an abundant co-transcript containing the carboxy-terminal region of the mat-r orf, exon e of the nad1 gene, exon III of the nad5 gene and their respective trains-introns. The co-transcript promoter carries the consensus motif of plant mitochondrial promoters. Analysis of transcript sequences reveals the presence of editing sites in analogous positions in both nad1e and nad5III trans-introns, suggesting that RNA editing is necessary for the trans-splicing process.
Farré
J C
JC
Laboratoire de Réplication et Expression des Gènes Eucaryotes et Rétroviraux, EP-630, Centre National de la Recherche Scientifique and Université Victor Segalen-Bordeaux II, France.
Araya
A
A
D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics; D005091:Exons; D007438:Introns; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics*; D024101:Mitochondrial Proteins; D016366:Open Reading Frames; D010940:Plant Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017393:RNA Editing; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic; D014908:Triticum / Q000201:enzymology / Q000235:genetics*
D004272:DNA, Mitochondrial; C091699:MAT-R protein, plant; D024101:Mitochondrial Proteins; D010940:Plant Proteins; D029701:Saccharomyces cerevisiae Proteins; C066564:aI2 protein, S cerevisiae; D012194:RNA-Directed DNA Polymerase