Identification and characterization of CBF/DREB1-related genes in Populus hopeiensis

The dehydration-responsive element-binding factor (DREB) is a plant-specific family of transcription factors and plays an important role in plant response and adaptation to abiotic stress. In the present work, two highly similar CBF/DREB1-like genes, designated as PhCBF4a and PhCBF4b, were identified from Populus hopeiensis. These two genes contain all conserved domains known to exist in other CBF/DREB1 genes. In the AP2 domain, there is only one different amino acid residue between PhCBF4a and PhCBF4b, alanine or valine, a nonpolar amino acid, suggesting that PhCBF4a and PhCBF4b may have similar DNA binding ability. Their expression is induced by water-loss treatment and their expression patterns are similar. Moreover, with a genomic DNA as template, the presence of the same bands in PCR products as those in expression pattern analysis indicated that PhCBF4a and PhCBF4b exist in the genome of P. hopeiensis. Their detailed functions are discussed and will need further study.