Disease relevance of nad7

• RNA gel blot data confirm the absence of nad7 expression, strongly suggesting that the molecular basis for the CMSII abnormal phenotype, poor growth and male sterility, is the altered complex I structure [1].

High impact information on nad7

• The nad7 sequence was transcribed and translated and the NAD7 protein directed to mitochondria in CMSnad7 transgenic plants, which recovered both wild type morphology and growth features [2].
• The Nicotiana sylvestris mutant, CMS, lacks the mitochondrial gene nad7 and functional complex I, and respires using low-affinity NADH (alternative) mitochondrial dehydrogenases [3].
• We have previously shown that in Nicotiana sylvestris cytoplasmic male-sterile (CMS) mutants where the mtDNA lacks the nad7 gene coding for a subunit of respiratory Complex I (NADH:ubiquinone oxidoreductase, EC 1.6.5.3), glycine (Gly) oxidation was lower than in the wild type and insensitive to rotenone, suggesting Complex I dysfunction [4].
• However, due to the presence of large duplications in the progenitor mitochondrial genome, the only unique gene that appears to be deleted is nad7 [1].
• Here, we show by cosmid mapping that the deletion is 60 kb in length and contains several mitochondrial genes or ORFs, including the complex I nad7 gene [1].

Biological context of nad7

• Targeting the NAD7 subunit to mitochondria restores a functional complex I and a wild type phenotype in the Nicotiana sylvestris CMS II mutant lacking nad7 [2].
• Although the N. sylvestris nad7 gene shows strong homology with its wheat counterpart, it contains only three introns instead of four [5].
• Deletion of the last two exons of the mitochondrial nad7 gene results in lack of the NAD7 polypeptide in a Nicotiana sylvestris CMS mutant [5].
• A mitochondrial region of 16.2 kb deleted from both CMS mutants was found to contain the last two exons of the nad7 gene coding for a subunit of the mitochondrial respiratory chain complex I, which is encoded in the nucleus in fungi and animals but was recently found to be encoded by the mitochondrial genome in wheat [5].

Other interactions of nad7

• Moreover, the editing status within nad1 intron 1 and nad7 intron 4 was seen to differ among plant species, so that homologous intron sequences shared lower similarity at the RNA level than at the DNA level [6].

References