Arabidopsis Genes Encoding Mitochondrial Type II NAD(P)H Dehydrogenases Have Different Evolutionary Origin and Show Distinct Responses to Light

Abstract

In addition to proton-pumping complex I, plant mitochondria contain several type II NAD(P)H dehydrogenases in the electron transport chain. The extra enzymes allow the nonenergy-conserving electron transfer from cytoplasmic and matrix NAD(P)H to ubiquinone. We have investigated the type II NAD(P)H dehydrogenase gene families in Arabidopsis. This model plant contains two and four genes closely related to potato (Solanum tuberosum) genes nda1 and ndb1, respectively. A novel homolog, termed ndc1, with a lower but significant similarity to potato nda1 and ndb1, is also present. All genes are expressed in several organs of the plant. Among the nda genes, expression of nda1, but not nda2, is dependent on light and circadian regulation, suggesting separate roles in photosynthesis-associated and other respiratory NADH oxidation. Genes from all three gene families encode proteins exclusively targeted to mitochondria, as revealed by expression of green fluorescent fusion proteins and by western blotting of fractionated cells. Phylogenetic analysis indicates that ndc1 affiliates with cyanobacterial type II NADH dehydrogenase genes, suggesting that this gene entered the eukaryotic cell via the chloroplast progenitor. The ndc1 should then have been transferred to the nucleus and acquired a signal for mitochondrial targeting of the protein product. Although they are of different origin, the nda, ndb, and ndc genes carry an identical intron position.Plant and fungal mitochondria have highly branched electron transport chains. The protonpumping respiratory complexes I, III, and IV work to a varying extent in parallel with non-protonpumping enzymes, i.e. type II NAD(P)H dehydrogenases and alternative oxidase. Thus, the coupling of electron transport to ATP formation varies depending on the electron path (Siedow and Umbach, 1995;Joseph-Horne et al., 2001).Complex I, the proton-pumping (type I) NAD(P)H dehydrogenase, is a multisubunit enzyme that is inhibited by rotenone in most organisms. It is present in ␣-proteobacteria and mitochondria of all eukaryotes except fermenting yeasts e.g. Saccharomyces cerevisiae. A homologous complex with unclear enzymatic properties is also present in chloroplasts (Yagi, 1991;Friedrich et al., 1995;Rasmusson et al., 1998).Type II, or rotenone-insensitive, NAD(P)H dehydrogenases have been found in several bacterial species and in plant and fungal mitochondria. The most studied enzymes, Escherichia coli NDH and S. cerevisiae NDI1, are FAD-containing single-polypeptide enzymes of 45 to 50 kD de Vries and Grivell, 1988). The S. cerevisiae NDI1 is located on the inner surface of the inner mitochondrial membrane, where it catalyzes the oxidation of matrix NADH (de Vries et al., 1992). Two homologous S. cerevisiae proteins, NDE1 and NDE2, are located on the external side of the inner membrane, where they oxidize cytoplasmic NADH (Luttik et al., 1998;Small and McAlister-Henn, 1998). An NADPHspecific type II dehydrogenase, NDE1, is present on the external surface of the inner membrane of Neurospora crassa ...

The mitochondrial respiratory chain of the secondary green alga Euglena gracilis shares many additional subunits with parasitic Trypanosomatidae

“…Except for CII, these complexes couple electron transfer with translocation of protons from the matrix to the intermembrane space, generating a proton gradient used by a fifth complex (CV or F 1 F o -ATP synthase, EC 3.6.3.14) for ATP synthesis. Many organisms however have alternative pathways that transfer electrons without concomitant proton translocation, such as type-II NAD(P)H dehydrogenases (from NAD(P)H to ubiquinone) and alternative oxidases (AOX; from ubiquinol to molecular oxygen) (Michalecka et al, 2003;Van Aken et al, 2009). …”

Role of Type 2 NAD(P)H Dehydrogenase NdbC in Redox Regulation of Carbon Allocation in Synechocystis

“…Plant-type NDH-2s fall into three distinct groups: NDA and NDB relating to fungal sequences and NDC of cyanobacterial origin (Michalecka et al, 2003). Most of these NDH-2s are targeted to mitochondria or peroxisomes, but some also are targeted to plastids.…”

“…The genome of Arabidopsis (Arabidopsis thaliana) contains seven open reading frames encoding NDH-2 homologs, of which at least five have a mitochondrial localization (Michalecka et al, 2003). NDC1, the only NDH-2 of cyanobacterial origin (Michalecka et al, 2003), has dual targeting to both mitochondria and chloroplasts (Carrie et al, 2008), being involved in prenylquinone and vitamin K 1 metabolism in the chloroplast (Piller et al, 2011).…”

Characterization of Nda2, a Plastoquinone-reducing Type II NAD(P)H Dehydrogenase in Chlamydomonas Chloroplasts

“…Numerous sequences encoding putative NDH-2 have been found in various organisms, including bacteria, yeasts, and plants (12)(13)(14). The Arabidopsis thaliana genome contains three gene families, in total seven reading frames, encoding NDH-2 homologs (15). Based on GFP localization studies and in vitro protein import assays, six of these putative A. thaliana NDH-2 were located in mitochondria (15,16).…”