Suppression of the External Mitochondrial NADPH Dehydrogenase, NDB1, in Arabidopsis thaliana Affects Central Metabolism and Vegetative Growth

Abstract

Ca(2+)-dependent oxidation of cytosolic NADPH is mediated by NDB1, which is an external type II NADPH dehydrogenase in the plant mitochondrial electron transport chain. Using RNA interference, the NDB1 transcript was suppressed by 80% in Arabidopsis thaliana plants, and external Ca(2+)-dependent NADPH dehydrogenase activity became undetectable in isolated mitochondria. This was linked to a decreased level of NADP(+) in rosettes of the transgenic lines. Sterile-grown transgenic seedlings displayed decreased growth specifically on glucose, and respiratory metabolism of (14)C-glucose was increased. On soil, NDB1-suppressing plants had a decreased vegetative biomass, but leaf maximum quantum efficiency of photosystem II and CO2 assimilation rates, as well as total respiration, were similar to the wild-type. The in vivo alternative oxidase activity and capacity were also similar in all genotypes. Metabolic profiling revealed decreased levels of sugars, citric acid cycle intermediates, and amino acids in the transgenic lines. The NDB1-suppression induced transcriptomic changes associated with protein synthesis and glucosinolate and jasmonate metabolism. The transcriptomic changes also overlapped with changes observed in a mutant lacking ABAINSENSITIVE4 and in A. thaliana overexpressing stress tolerance genes from rice. The results thus indicate that A. thaliana NDB1 modulates NADP(H) reduction levels, which in turn affect central metabolism and growth, and interact with defense signaling.

The evolution of substrate specificity‐associated residues and Ca2+‐binding motifs in EF‐hand‐containing type II NAD(P)H dehydrogenases

“…The ancient eukaryotic origin of the non-acidic-motif NDBs further indicates that external NADPH oxidation in plants has an original cellular function that is not connected to photosynthesis. This is consistent with observations that transgenic modification of AtNDB1 and StNDB1 gene expression in A. thaliana and Nicotiana sylvestris affected NADPH/NADP + ratios, growth and development but the changes were not notably associated with photosynthetic processes (Liu et al 2008, Liu et al 2009, Wallström et al 2014a, nor is AtNDB1 gene expression associated with light metabolism (Escobar et al 2004, Liu et al 2009). The inactivation of the gene for NcNDE1 in N. crassa does not affect vegetative growth under normal growth conditions (Melo et al 2001).…”

“…This is consistent with observations that transgenic modification of AtNDB1 and StNDB1 gene expression in A . thaliana and Nicotiana sylvestris affected NADPH/NADP + ratios, growth and development but the changes were not notably associated with photosynthetic processes (Liu et al , Liu et al , Wallström et al ), nor is AtNDB1 gene expression associated with light metabolism (Escobar et al , Liu et al ). The inactivation of the gene for NcNDE1 in N .…”

Decreasing Electron Flux through the Cytochrome and/or Alternative Respiratory Pathways Triggers Common and Distinct Cellular Responses Dependent on Growth Conditions

“…This is largely because of the fact that, with the exception of complex I inactivation, total inactivation of the cytochrome pathway is lethal, and plants lacking cytochrome c, which transfers electrons from complex III to IV, or plants deficient in complex IV are not viable (Gu et al, 1994;Welchen et al, 2012). Thus, although a variety of studies have analyzed the effects of the abolition of complex I activity (Dutilleul et al, 2003a(Dutilleul et al, , 2003bNoctor et al, 2004;Meyer et al, 2009;Braun et al, 2014), AOX (Fiorani et al, 2005;Giraud et al, 2008), or alternative NAD(P)H dehydrogenase activities (Wallström et al, 2014a(Wallström et al, , 2014b, to date, there are a limited number of studies on plants with severely limited electron transport through the cytochrome chain. However, it is possible to decrease the abundance of cytochrome chain components using a surrogate mutant approach (Colas des Francs-Small and Small, 2014), where inactivation of a nuclear gene required for the expression of a mitochondrially encoded subunit can reduce the activity of distinct respiratory chain complexes.…”

Photoperiod Affects the Phenotype of Mitochondrial Complex I Mutants

“…In addition to complex II (succinate dehydrogenase), nonphosphorylating alternative NAD(P)H dehydrogenases (type II dehydrogenases), located on the inner and outer surfaces of the inner mitochondrial membrane, are essential for plant growth and metabolism (Liu et al, 2009;Wallström et al, 2014). Their activity depends on plant metabolic status, such as NADH and Ca 2+ concentration (Rasmusson et al, 2008).…”

“…8A). Overreduction of the NAD pool in mutants might stem from the induction of alternative NAD(P)H dehydrogenase activities (Liu et al, 2009;Rasmusson and Wallström, 2010;Wallström et al, 2014) and/or the activation of redox shuttles (Shen et al, 2006). A redox effect may have then resulted in alterations of the circadian clock (Stangherlin and Reddy, 2013;Shim and Imaizumi, 2015).…”