New Subunits NDH-M, -N, and -O, Encoded by Nuclear Genes, Are Essential for Plastid Ndh Complex Functioning in Higher Plants

Abstract

In higher plants, the Ndh complex reduces plastoquinones and is involved in cyclic electron flow around photosystem I, supplying extra-ATP for photosynthesis, particularly under environmental stress conditions. Based on plastid genome sequences, the Ndh complex would contain 11 subunits (NDH-A to -K), but homologies with bacterial complex indicate the probable existence of additional subunits. To identify missing subunits, tobacco (Nicotiana tabacum) NDH-H was His tagged at its N terminus using plastid transformation. A functional Ndh subcomplex was purified by Ni 2þ affinity chromatography and its subunit composition analyzed by mass spectrometry. Five plastid encoded subunits (NDH-A, -H, -I, -J, and -K) were identified as well as three new subunits (NDH-M, -N, and -O) homologous to cyanobacterial and higher plant proteins. Arabidopsis thaliana mutants missing one of these new subunits lack a functional Ndh complex, and NDH-M and NDH-N are not detected in a tobacco transformant lacking the Ndh complex. We discuss the involvement of these three nuclear-encoded subunits in the functional integrity of the plastidial complex.

Supercomplex Formation with Photosystem I Is Required for the Stabilization of the Chloroplast NADH Dehydrogenase-Like Complex in Arabidopsis

“…S2A), as often suggested in the mutants defective in NDH activity (Rumeau et al, 2005). NPQ induction was affected severely in pgr5, as reported previously (Munekage et al, 2002).…”

“…1C). So far, a total of 25 NDH subunits have been identified by various approaches (Rumeau et al, 2005;Ishihara et al, 2007;Ishikawa et al, 2008;Majeran et al, 2008;Shimizu et al, 2008;Peng et al, 2009;Sirpiö et al, 2009aSirpiö et al, , 2009bTakabayashi et al, 2009;Suorsa et al, 2010;Yabuta et al, 2010). If we assume that only one copy of each subunit is included in the complex, the calculated molecular mass of NDH is approximately 690 kD, which is almost identical to that of the NDH complex detected in lhca5 lhca6.…”

Evidence for a Role for NAD(P)H Dehydrogenase in Concentration of CO2 in the Bundle Sheath Cell of Zea mays

“…At least 11 plastid and 25 nuclear genes encode NDH subunits and related protein factors in Arabidopsis (Ifuku et al, 2011. Serial disruption of several nuclear genes encoding structural subunits or assembly factors resulted in failed NDH supercomplex assembly and disrupted electron flow to PQ (plastoquinone) in the dark (Rumeau et al, 2005, Munshi et al, 2006, Ishihara et al, 2007, Ishikawa et al, 2008, Takabayashi et al, 2009, Peng et al, 2010, Suorsa et al, 2010, Yabuta et al, 2010, Armbruster et al, 2013. Chloroplastic NDH has been assigned to a redundant NAD(P)H-dependent PSI cyclic electron transport pathway in C 3 plants (Nixon 2000).…”

Plant respiration under low oxygen

“…There have been studies on the importance of environmental changes in chlororespiration, with an increase in the activity and expression of a protein complex called NDH (homologous to complex I) (Peltier and Cournac, 2002). This complex catalyzes the transfer of electrons from NAD(P)H to plastoquinones (Rumeau et al, 2005). According to some authors, this complex is key in chlororespiration because it has an NADH dehydrogenase function in mitochondria.…”

“…According to some authors, this complex is key in chlororespiration because it has an NADH dehydrogenase function in mitochondria. In turn, the Ndh complex regulates the proton gradient produced in the stroma, suggesting a role in the control of oxidative stress produced in the chloroplast stroma (Rumeau et al, 2005).…”