[show abstract][hide abstract] ABSTRACT: A region of the mitochondrial (mt) DNA of wheat was studied because of its homology with other plant mtDNAs. Sequence analysis revealed an open reading frame encoding a polypeptide of 247 amino acids. Comparison of the sequence of the putative polypeptide with the protein sequence data of the Swiss-Prot library reveals homology with subunit 6 of the NADH-ubiquinone complex of mitochondria from Marchantia polymorpha, Podospora anserina, Chlamydomonas reinhardtii and of chloroplasts from M. polymorpha and Oryza sativa. No similarity was detected when compared with the subunit 6 of animal mitochondria, probably due to the rapid evolution of the sequence. A single 1.2 kb transcript appears in northern RNA blots. We found 15 edited sites of which only 13 give amino acid changes. This is the first report of a mt nad6 gene in higher plants.
[show abstract][hide abstract] ABSTRACT: The mitochondrial single-copy gene nad5 of wheat and maize consists of 5 exons located on three widely separated regions of the genome that are independently transcribed. The first region contains exons I and II separated by an atypical group II intron; in the second region is exon III (only 22 bp long), which is flanked upstream by a maturase-related open reading frame (ORF) and exon e of the nad1 gene, and downstream by a previously unidentified ORF (ORF143); in the third region are exons IV and V separated by a group II intron. In maize, this last domain is flanked upstream by the genes rps12, nad3, and tRNA(Ser) and downstream by a chloroplast tRNA(Cys). RNA editing occurs in wheat exons IV and V as C-to-U changes. A detailed analysis of the transcription of the nad5 gene in wheat and maize reveals that the exons are assembled into a 2.4-kb mRNA after two cis-splicing (between exons I and II and exons IV and V) and two trans-splicing events. The trans-splicing process involves the sequences flanking exons II, III, and IV that feature group II introns. A model is proposed for the assembly and maturation of the nad5 transcripts.
The Plant Cell 01/1992; 3(12):1363-78. · 9.25 Impact Factor