Complex I of the respiratory chain is a proton-pumping, NADH ubiquinone oxidoreductase that oxidises NADH in the electron transport pathway. Plants contain the series of 14 highly conserved complex I subunits found in other eukaryotic and related prokaryotic enzymes [1].

1: Mitochondrial complex I from Arabidopsis and rice: orthologs of mammalian and fungal components coupled with plant-specific subunits. Heazlewood JL, Howell KA, Millar AH; Biochim Biophys Acta. 2003;1604:159-169. PMID:12837548