RNA editing at a splicing site of NADH dehydrogenase subunit IV gene transcript in wheat mitochondria

Comparison between the sequence of the gene coding for the wheat mitochondrial NADH dehydrogenase subunit IV (nad4) and the cDNA sequence obtained by reverse transcription, using total wheat mtRNA as template, has shown the presence of a uridine residue, not encoded by the genomic sequence, at the exon2-exon3 junction of the spliced transcript. This U creates a non-encoded CUG leucine codon which is essential for maintaining the reading frame, as shown by the conservation of the amino acid sequence of the NAD4 protein in various species. The addition of a U or the specific post-transcriptional conversion of a C to a U could explain this phenomenon.