Involvement of a Glycerol-3-Phosphate Dehydrogenase in Modulating the NADH/NAD+ Ratio Provides Evidence of a Mitochondrial Glycerol-3-Phosphate Shuttle in Arabidopsis

Abstract

A mitochondrial glycerol-3-phosphate (G-3-P) shuttle that channels cytosolic reducing equivalent to mitochondria for respiration through oxidoreduction of G-3-P has been extensively studied in yeast and animal systems. Here, we report evidence for the operation of such a shuttle in Arabidopsis thaliana. We studied Arabidopsis mutants defective in a cytosolic G-3-P dehydrogenase, GPDHc1, which, based on models described for other systems, functions as the cytosolic component of a G-3-P shuttle. We found that the gpdhc1 T-DNA insertional mutants exhibited increased NADH/NAD þ ratios compared with wild-type plants under standard growth conditions, as well as impaired adjustment of NADH/NAD þ ratios under stress simulated by abscisic acid treatment. The altered redox state of the NAD(H) pool was correlated with shifts in the profiles of metabolites concerning intracellular redox exchange. The impairment in maintaining cellular redox homeostasis was manifest by a higher steady state level of reactive oxygen species under standard growth conditions and by a significantly augmented hydrogen peroxide production under stress. Loss of GPDHc1 affected mitochondrial respiration, particularly through a diminished capacity of the alternative oxidase respiration pathway. We propose a model that outlines potential involvements of a mitochondrial G-3-P shuttle in plant cells for redox homeostasis.

The malate–aspartate NADH shuttle components are novel metabolic longevity regulators required for calorie restriction-mediated life span extension in yeast

“…Lin, unpubl.). The gut2⌬ mutants in plants also showed reduced mitochondrial respiration rates (Shen et al 2006). Finally, Gut2 overexpression required a functional mitochondrial respiratory chain to extend life span (Fig.…”

TheArabidopsis onset of leaf death5Mutation of Quinolinate Synthase Affects Nicotinamide Adenine Dinucleotide Biosynthesis and Causes Early Ageing

“…Pyridine nucleotides have well-characterized roles as redox carriers in processes such as oxidative phosphorylation, the TCA cycle, and as electron acceptors in photosynthesis (Hunt et al, 2004). Next to their role in metabolism, they play a part during several stress conditions, including oxidative stress (Moller, 2001;Hayashi et al, 2005), wound response (Sinclair et al, 2000), and ABA signaling and salt stress (Shen et al, 2006;Wang and Pichersky, 2007). Recently, it was found that the NADdependent histone deacetylase SIR2 influences the lifespan for several model organisms, including yeast, Caenorhabditis The relative expression of several genes was determined by real-time PCR and calculated relative to the wild type.…”

“…ROS production in the chloroplast has been clearly demonstrated to be under the influence of NADP/NADPH ratios in this compartment (Asada, 2006). Production of mitochondrial ROS by the electron transport chain is largely dependent on NAD(P) status as well (Dutilleul et al, 2005;Shen et al, 2006;Sweetlove et al, 2006). The turnover of antioxidant pools such as those of glutathione and ascorbate are maintained by NAD(P)H .…”

“…Since previous studies have shown that alterations in NAD/ NADH levels can have dramatic consequences on cellular metabolism (Dutilleul et al, 2005;Shen et al, 2006), we next performed a comprehensive metabolite profiling using an established gas chromatography-mass spectrometry protocol capable of quantifying the relative levels of >80 metabolites (Lisec et al, 2006). For this purpose, leaves were harvested, in the middle of the light period, from both the old5 mutant and the wild type at days 21 and 27 and metabolites were measured (see Supplemental Table 1 online).…”

Defining Core Metabolic and Transcriptomic Responses to Oxygen Availability in Rice Embryos and Young Seedlings

“…The accumulations of urate and glycolate in anaerobic tissues are readily explained by the oxygen requirement of their respective catabolic enzymes, urate oxidase (EC 1.7.3.3) and glycolate oxidase (EC 1.1.3.15), as suggested for anaerobic glycolate accumulation by Dubinina (1961). Similarly, major catabolic pathways of succinate and glycerol-3-phosphate are linked to oxygen availability via the mitochondrial respiratory chain-associated enzymes succinate dehydrogenase and glycerol-3-phosphate dehydrogenase (Shen et al, 2003(Shen et al, , 2006Rasmusson et al, 2008), respectively. In rice, coumarate may be formed from Tyr via Tyr ammonia lyase activity (Kishor, 1989), thus avoiding an oxygen-dependent step required for its synthesis from Phe.…”