In Silico Cloning and Characterization of the Glycerol-3-Phosphate Dehydrogenase (GPDH) Gene Family in the Green Microalga Chlamydomonas reinhardtii
Glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the conversion of dihydroxyacetone phosphate (DHAP) and NADH to glycerol-3-phosphate (G3P) and NAD+. G3P is important as a precursor for glycerol and glycerolipid synthesis in microalgae. A GPDH enzyme has been previously purified from the green microalga Chlamydomonas reinhardtii, however, no genes coding for GPDH have been characterized before. In this study, we report the in silico characterization of three putative GPDH genes from C. reinhardtii: CrGPDH1, CrGPDH2, and CrGPDH3. These sequences showed a significant similarity to characterized GPDH genes from the microalgae Dunaliella salina and Dunaliella viridis. The prediction of the three-dimensional structure of the proteins showed the characteristic fold topology of GPDH enzymes. Furthermore, the phylogenetic analysis showed that the three CrGPDHs share the same clade with characterized GPDHs from Dunaliella suggesting a common evolutionary origin and a similar catalytic function. In addition, the K a/K s ratios of these sequences suggested that they are under purifying selection. Moreover, the expression analysis showed a constitutive expression of CrGPDH1, while CrGPDH2 and CrGPDH3 were induced in response to osmotic stress, suggesting a possible role for these two sequences in the synthesis of glycerol as a compatible solute in osmoregulation, and perhaps also in lipid synthesis in C. reinhardtii. This study has provided a foundation for further biochemical and genetic studies of the GPDH family in this model microalga, and also opportunities to assess the potential of these genes to enhance the synthesis of TAGs for biodiesel production.
KeywordsMicroalgae Osmotic Stress Chlamydomonas Dunaliella Chloroplast Transit Peptide
This research was supported by the Consejo Nacional de Ciencia y Tecnología (CONACYT, México) Project No. CB-169217 and Centro de Investigación Científica de Yucatán (CICY, Mexico) Project FB0054. Laura Anahi Macario-González, Melissa Lessen Casais-Molina and Anayeli Beltrán Aguilar are grateful to Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico) for the Scholarship Nos. 235997, 228280 and 264772, respectively. Authors are grateful to Ileana C. Borges Argáez for technical support and Miguel Ángel Vallejo Reyna for assistance on the protein modeling.
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