Cloning and expression studies of the Dunaliella salina UDP-glucose dehydrogenase cDNA

Abstract

The enzyme UDP-glucose dehydrogenase (EC 1.1.1.22) converts UDP-glucose to UDP-glucuronate. Plant UDP-glucose dehydrogenase (UGDH) is an important enzyme in the formation of hemicellulose and pectin, the components of primary cell walls. A cDNA, named DsUGDH, (GeneBank accession number: AY795899) corresponding to UGDH was cloned by RT-PCR approach from Dunaliella salina. The cDNA is 1941-bp long and has an open reading frame encoded a protein of 483 amino acids with a calculated molecular weight of 53 kDa. The derived amino acids sequence shows high homology with reported plants UGDHs, and has highly conserved amino acids motifs believed to be NAD binding site and catalytic site. Although UDP-glucose dehydrogenase is a comparatively well characterized enzyme, the cloning and characterization of the green alga Dunaliella salina UDP-glucose dehydrogenase gene is very important to understand the salt tolerance mechanism of Dunaliella salina. Northern analyses indicate that NaCl can induce the expression the DsUGDH.

Plant Nucleotide Sugar Formation, Interconversion, and Salvage by Sugar Recycling*

“…In plants, the gene encoding UGD activity was first described in soybean (76,148). Subsequently, numerous UDP-GlcDH genes encoding proteins with high amino acid sequence similarity to one another were identified in Arabidopsis, poplar (68), tobacco (15), maize (72), and Dunaliella (122). Each plant has multiple UGD isoforms and their specific activities are of interest because studies with sugar cane revealed that CTP-glucose and TDPglucose were also oxidized, albeit less effectively than UDP-Glc (154).…”

Cell Wall Polysaccharide Synthesis

“…The enzyme is well characterized from numerous organisms and crystal structures are available. In plants, the gene encoding this activity was first described in soybean (460), and soon after, as genome sequence became available, numerous UDPGDH gene isoforms that share high amino acid sequence similarity to each other were identified in Arabidopsis (461), poplar (462), tobacco (463), maize (464), and Dunaliella (465). In Arabidopsis, four UDPGDH isozymes are present and, likewise, multiple UDPGDH isoforms are found in the genome of every plant species that has been sequenced.…”