The Chloroplast NAD(P)H Dehydrogenase Complex Interacts with Photosystem I in Arabidopsis

Abstract

The chloroplast NAD(P)H dehydrogenase (NDH) complex is involved in photosystem I (PSI) cyclic and chlororespiratory electron transport in higher plants. Although biochemical and genetic evidence for its subunit composition has accumulated, it is not enough to explain the complexes putative activity of NAD(P)H-dependent plastoquinone reduction. We analyzed the NDH complex by using blue native PAGE and found that it interacts with PSI to form a novel supercomplex. Mutants lacking NdhL and NdhM accumulated a pigment-protein complex with a slightly lower molecular mass than that of the NDH-PSI supercomplex; this may be an intermediate supercomplex including PSI. This intermediate is unstable in mutants lacking NdhB, NdhD, or NdhF, implying that it includes some NDH subunits. Analysis of thylakoid membrane complexes using sucrose density gradient centrifugation supported the presence of the NDH-PSI supercomplex in vivo. Although the NDH complex exists as a monomer in etioplasts, it interacts with PSI to form a supercomplex within 48 h during chloroplast development. The chloroplast NAD(P)H dehydrogenase (NDH)3 complex is localized to the stroma thylakoids (1) and is involved in chlororespiration and photosystem I (PSI) cyclic electron transport in higher plants (2, 3). The NDH complex is essential for preventing over-reduction of the stroma in the pgr5 (proton gradient regulation 5) mutant, which is defective in the main pathway of PSI cyclic electron transport (4). This function suggests that NDH alleviates oxidative stress under certain conditions even in wild-type (WT) plants (3, 5). So far, 11 plastid-encoded and 4 nuclear-encoded subunits of chloroplast NDH have been identified, and all subunits are conserved in cyanobacteria. It is generally accepted that chloroplast NDH is more closely related to the cyanobacterial NDH-1 complex than to the mitochondrial complex

N-Terminal Structure of Maize Ferredoxin:NADP+ Reductase Determines Recruitment into Different Thylakoid Membrane Complexes

“…By contrast, mesophyll cells must have the capacity to adjust electron flow between LET and CET, depending on environmental conditions (Munekage et al, 2004). There is evidence for FNR recruitment to several different thylakoid complexes (Andersen et al, 1992;Jose Quiles and Cuello, 1998;Zhang et al, 2001;Peng et al, 2008;Benz et al, 2009;Juric et al, This model summarizes structural and transgenic results indicating that both FNR N-terminal structure and amino acid composition of the interaction site with TROL contribute to membrane recruitment of FNR in maize and is based on the assumption that FNR:FNR binding protein interactions are dependent on FNR dimerization. The structure of Zm-FNR1 shows N termini of adjacent FNR molecules helping to coordinate dimer formation.…”

“…These roles in different electron transport pathways have led to intense research interest in the mechanism and location of FNR binding to the thylakoid membrane (Andersen et al, 1992;Jose Quiles and Cuello, 1998;Zhang et al, 2001;Peng et al, 2008;Benz et al, 2009;Juric et al, 2009;Alte et al, 2010;Baniulis et al, 2011). Two thylakoid FNR binding proteins named TROL and Tic62 have been identified in Arabidopsis thaliana.…”

A Study of New Arabidopsis Chloroplast RNA Editing Mutants Reveals General Features of Editing Factors and Their Target Sites

“…To assess whether the subunits affected in otp84 and otp85 stably accumulate in vivo, protein blots were analyzed using antibodies against NdhH and PsbZ (Figure 4). The NDH complex is unstable without NdhB and NdhD (Peng et al, 2008), and an antibody against NdhH can be used to monitor accumulation of the complex. In otp84, the level of NdhH is reduced to 50 to 25% of the wild type.…”

Phylogenetic viewpoints on regulation of light harvesting and electron transport in eukaryotic photosynthetic organisms

“…Another suspected role for the NDH-like complex is in chlororespiration, where the plastoquinone (PQ) pool becomes oxidized via transfer of electrons to molecular oxygen, serving as a safety valve during stress to protect the PQ pool from over-reduction (Niyogi 2000;Peltier and Cournac 2002). The functional role of the NDH-like complex in C3 plants becomes even more puzzling due to its presence in etioplasts prior to greening and thylakoid biogenesis with the assembly of the major photosynthetic pigment-protein complexes (Kanervo et al 2008;Peng et al 2008). During de-etiolation, the NDH-like complex rapidly starts to interact with PSI, and after just 48 h in light, the PSI-NDH supercomplex is assembled (Peng et al 2008).…”

“…Of these, the subcomplex B as well as the lumenal subcomplex are specific to higher plants, and composed entirely of nuclear-encoded subunits ). Furthermore, in higher plants NDH forms a supercomplex with PSI (Peng et al 2008;, and the minor LHCI proteins Lhca5 and Lhca6 are involved in binding the NDH complex to PSI (Peng et al 2009). …”