Isolation and Functional Characterization of a Novel Gene Encoding a Dehydration Responsive Element Binding Transcription Factor from Populus euphratica

Dehydration responsive element binding (DREB) transcription factors (TFs) play a key role in regulating abiotic stress related genes. A new gene (PeDREB2b) encoding an unidentified DRE-binding protein was isolated from 20% PEG6000 treated Populus euphratica Oliv. seedlings by RT-PCR and RACE. Full length of PeDREB2b cDNA was 1110 bp, and an ORF of 870 bp, which encoded 289-amino-acids polypeptide, were included. The deduced amino acid sequence analysis revealed that this protein was a putative AP2/EREBP transcription factor with a conserved AP2/EREBP domain of 64 amino acids and a potential nuclear localization signal (NLS). Based on phylogenetic characterization, PeDREB2b was classified as a member of A-5 group belonged to the DREB family. The PeDREB2b gene is induced by salinization, low temperature, drought and phytohormones GA3, NAA and 6BA, but not by ABA treatment. The fact that the product of PeDREB2b as a DREB transcription factor was verified in our further experiment: the nuclear localization of the gene when it was expressed transiently as a GFP fusion in onion epidermal cells. In addition, PeDREB2b was capable of activating reporter gene expression. To study the salt and drought stress responses for PeDREB2b transgenic Arabidopsis thaliana in detail, integrated physiological, biochemical and genetic approach methods were used. Results indicated that the PeDREB2b gene was over-expressed under stress-inducible rd29A promotor in transgenic plants alleviates the adverse effects of environmental stresses. Keywords: DREB transcription factor, Environmental stresses, Phylogenetic analysis, Populus euphratica, Subcellular localization, Yeast expression.