Novel Nuclear-encoded Subunits of the Chloroplast NAD(P)H Dehydrogenase Complex

Abstract

The NAD(P)H dehydrogenase (NDH) complex functions in photosystem I cyclic electron transfer in higher plant chloroplasts and is crucial for plant responses to environmental stress. Chloroplast NDH complex is a close relative to cyanobacterial NDH-1L complex, and all fifteen subunits so far identified in NDH-1L have homologs in the chloroplast NDH complex. Here we report on the identification of two nuclear-encoded proteins NDH48 and NDH45 in higher plant chloroplasts and show their intimate association with the NDH complex. These two membrane proteins are shown to interact with each other and with the NDH complex enriched in stroma thylakoids. Moreover, the deficiency of either the NDH45 protein or the NDH48 protein in respective mutant plants leads to severe defects in both the accumulation and the function of the NDH complex. The NDH48 and NDH45 proteins are not components of the hydrophilic connecting domain of the NDH complex but are strongly attached to the hydrophobic membrane domain. We conclude that NDH48 and NDH45 are novel nuclear-encoded subunits of the chloroplast NDH complex and crucial both for the stable structure and function of the NDH complex.

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

“…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.…”

Subunit Q Is Required to Stabilize the Large Complex of NADPH Dehydrogenase in Synechocystis sp. Strain PCC 6803

“…This approach has been extensively used to monitor NDH-CET activity in cyanobacteria Deng et al, 2003;Ma and Mi, 2005;Battchikova et al, 2011a;Dai et al, 2013;Zhang et al, 2014;Zhao et al, 2014) and higher plants (Burrows et al, 1998;Shikanai et al, 1998;Hashimoto et al, 2003;Wang et al, 2006;Peng et al, 2009Peng et al, , 2011bPeng et al, , 2012Sirpiö et al, 2009;Yamamoto et al, 2011;Armbruster et al, 2013). As shown in Figure 1B, the NDH-CET activity in both mutants was lower than that in the wild type as judged by the height and relative rate of postillumination increase in Chl fluorescence.…”

An Orange Ripening Mutant Links Plastid NAD(P)H Dehydrogenase Complex Activity to Central and Specialized Metabolism during Tomato Fruit Maturation

“…Since it has been well established that the presence of all NDH subunits is required for the assembly and functioning of the complex (Rumeau et al, 2005;Ishihara et al, 2007;Shikanaï, 2007aShikanaï, , 2007bSirpiö et al, 2009;Takabayashi et al, 2009), the presence of the Ndh complex in the different genotypes was investigated using an anti-NDH-H (a different subunit of the Ndh complex) antiserum (Figure 4). Compared with the levels of the wild-type protein, the homozygous line retained <10 and 50% of the protein (NDH-H) in leaves and the immature green fruit, respectively ( Figures 4B and 4D).…”

“…Several Arabidopsis mutants affected in these pathways have been studied (Munekage et al, 2002;Rumeau et al, 2005;Ishihara et al, 2007;Shikanaï, 2007a;DalCorso et al, 2008;Peng et al, 2009;Sirpiö et al, 2009;Takabayashi et al, 2009) and showed no change in their carotenoid content. However, participation of PQ redox state in carotenogenesis in other tissues than leaves cannot be excluded.…”