The NADH dehydrogenase subunit 7 gene is interrupted by four group II introns in the wheat mitochondrial genome

We have characterized a wheat mitochondrial gene, designated nad7, capable of encoding a 394-amino acid subunit of the respiratory chain NADH dehydrogenase complex. It contains four introns possessing group II features and their positions differ from those in both the liverwort mitochondrial nad7 pseudogene and the nuclear gene encoding the homologous 49 kDa subunit of complex I in Neurospora. The derived amino acid sequence of the wheat nad7 gene is strongly conserved relative to its nuclear or organellar counterparts in other organisms. C-to-U type RNA editing, which is observed at 32 positions within the coding region of wheat nad7 transcripts, strengthens protein sequence similarity. RNA editing is also predicted to improve base-pairing within the domain V/VI regions of all four introns.