Abstract
BackgroundPlant glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the reduction of dihydroxyacetone phosphate (DHAP) to produce glycerol-3-phosphate (G-3-P), and plays a key role in glycerolipid metabolism as well as stress responses.ResultsIn this study, we report the cloning, enzymatic and physiological characterization of a cytosolic NAD+-dependent GPDH from maize. The prokaryotic expression of ZmGPDH1 in E.coli showed that the enzyme encoded by ZmGPDH1 was capable of catalyzing the reduction of DHAP in the presence of NADH. The functional complementation analysis revealed that ZmGPDH1 was able to restore the production of glycerol-3-phosphate and glycerol in AtGPDHc-deficient mutants. Furthermore, overexpression of ZmGPDH1 remarkably enhanced the tolerance of Arabidopsis to salinity/osmotic stress by enhancing the glycerol production, the antioxidant enzymes activities (SOD, CAT, APX) and by maintaining the cellular redox homeostasis (NADH/NAD+, ASA/DHA, GSH/GSSG). ZmGPDH1 OE Arabidopsis plants also exhibited reduced leaf water loss and stomatal aperture under salt and osmotic stresses. Quantitative real-time RT-PCR analyses revealed that overexpression of ZmGPDH1 promoted the transcripts accumulation of genes involved in cellular redox homeostasis and ROS-scavenging system.ConclusionsTogether, these data suggested that ZmGPDH1 is involved in conferring salinity and osmotic tolerance in Arabidopsis through modulation of glycerol synthesis, stomatal closure, cellular redox and ROS homeostasis.
Highlights
Plant glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the reduction of dihydroxyacetone phosphate (DHAP) to produce glycerol-3-phosphate (G-3-P), and plays a key role in glycerolipid metabolism as well as stress responses
ZmGPDH1 encodes a cytosol-targeted protein with Oxidized pyridine nucleotides (NAD+)dependent GPDH activity One GPDH gene was originally obtained through BLAST searching against the maize genome utilizing the reported AtGPDHc2 as query [5], the retrieved gene was designated as ZmGPDH1
The sequence alignment revealed that ZmGPDH1 exhibited very high protein sequence identity (77%) to AtGPDHc2, and both proteins consisted of one C-terminal GPD domain (PF07479) that represents DHAP-binding site and one N-terminal NAD-binding domain (PF01210), suggesting that ZmGPDH1 encodes an NAD+-dependent GPDH (Additional file 1: Figure S1)
Summary
Plant glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the reduction of dihydroxyacetone phosphate (DHAP) to produce glycerol-3-phosphate (G-3-P), and plays a key role in glycerolipid metabolism as well as stress responses. Overexpression of ZmGPDH1 remarkably enhanced the tolerance of Arabidopsis to salinity/osmotic stress by enhancing the glycerol production, the antioxidant enzymes activities (SOD, CAT, APX) and by maintaining the cellular redox homeostasis (NADH/NAD+, ASA/DHA, GSH/GSSG). G-3-P can be biosynthesized through two Multiple forms of GPDH have been identified from eukaryotes, and most of them are proved to be key regulators in stress responses [5,6,7]. Plants deficient in plastid-localized GPDH (SFD1/GLY1) exhibited a serious impairment in plastidal glycerolipids pathway of Arabidopsis and overexpression of SFD1/GLY1 could increase the plastidic lipid contents as well as the photosynthetic assimilation rate in transgenic rice plants [11]
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