Plant Molecular Biology

, Volume 71, Issue 1, pp 193–205

Cloning and characterization of two novel chloroplastic glycerol-3-phosphate dehydrogenases from Dunaliella viridis

Authors

  • Yunxia He
    • Shanghai Key Laboratory of Bio-Energy Crops, School of Life SciencesShanghai University
  • Xiangzong Meng
    • Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological SciencesChinese Academy of Sciences
  • Qianlan Fan
    • Shanghai Key Laboratory of Bio-Energy Crops, School of Life SciencesShanghai University
  • Xiaoliang Sun
    • Shanghai Key Laboratory of Bio-Energy Crops, School of Life SciencesShanghai University
  • Zhengkai Xu
    • Shanghai Key Laboratory of Bio-Energy Crops, School of Life SciencesShanghai University
    • Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological SciencesChinese Academy of Sciences
    • Shanghai Key Laboratory of Bio-Energy Crops, School of Life SciencesShanghai University
Article

DOI: 10.1007/s11103-009-9517-7

Cite this article as:
He, Y., Meng, X., Fan, Q. et al. Plant Mol Biol (2009) 71: 193. doi:10.1007/s11103-009-9517-7

Abstract

Dunaliella, a unicellular green alga, has the unusual ability to survive dramatic osmotic stress by accumulating high concentrations of intracellular glycerol as a compatible solute. The chloroplastic glycerol-3-phosphate dehydrogenase (GPDH) has been considered to be the key enzyme that produces glycerol for osmoregulation in Dunaliella. In this study, we cloned the two most prominent GPDH cDNAs (DvGPDH1 and DvGPDH2) from Dunaliella viridis, which encode two polypeptides of 695 and 701 amino acids, respectively. Unlike higher plant GPDHs, both proteins contained extra phosphoserine phosphatase (SerB) domains at their N-termini in addition to C-terminal GPDH domains. Such bi-domain GPDHs represent a novel type of GPDH and are found exclusively in the chlorophyte lineage. Transient expression of EGFP fusion proteins in tobacco leaf cells demonstrated that both DvGPDH1 and DvGPDH2 are localized in the chloroplast. Overexpression of DvGPDH1 or DvGPDH2 could complement a yeast GPDH mutant (gpd1Δ), but not a yeast SerB mutant (ser2Δ). In vitro assays with purified DvGPDH1 and DvGPDH2 also showed apparent GPDH activity for both, but no SerB activity was detected. Surprisingly, unlike chloroplastic GPDHs from plants, DvGPDH1 and DvGPDH2 could utilize both NADH and NADPH as coenzymes and exhibited significantly higher GPDH activities when NADH was used as the coenzyme. Q-PCR analysis revealed that both genes exhibited transient transcriptional induction of gene expression upon hypersalinity shock, followed by a negative feedback of gene expression. These results shed light on the regulation of glycerol synthesis during salt stress in Dunaliella.

Keywords

DunaliellaGlycerol-3-phosphate dehydrogenaseFunctional characterizationGene expressionGlycerol synthesis

Abbreviations

GPDH

Glycerol-3-phosphate dehydrogenase

SerB/PSP

Phosphoserine phosphatase

DHAP

Dihydroxyacetone phosphate

GPP

Glycerol-3-phosphate phosphatase

ORF

Open reading frame

Supplementary material

11103_2009_9517_MOESM1_ESM.doc (54 kb)
(DOC 52 kb)
11103_2009_9517_MOESM2_ESM.tif (125 kb)
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Copyright information

© Springer Science+Business Media B.V. 2009