Drought, high salinity and low temperature are major abiotic stresses that influence survival, productivity and geographical distribution of many important crops across the globe. Plants respond to these environmental challenges via physiological, cellular and molecular processes, which results in adjusted metabolic and structural alterations. The dehydration-responsiveelement-binding (DREB) protein / C-repeat binding factors (CBFs) belong to APETALA2 (AP2) family transcription factors that bind to DRE/CRT cis-element and regulate the expression of stress-responsive genes. DREB1/CBF genes, therefore, play an important role in increasing stress tolerance in plants and their deployment using transgenic technology seems to be a potential alternative in management of abiotic stresses in crop plants. This review is mainly focussed on the structural characteristics as well as transcriptional regulation of gene expression in response to various abiotic stresses, with particular emphasis on the role of DREB1/CBF regulon in stress-responsive gene expression. The recent progress related to genetic engineering of DREB1/CBF transcription factors in various crops and model plants is also summarized.

The dehydration-responsive element-binding (DREB) protein/C-Repeat Binding Factors (CBFs) belongs to APETALA2 (AP2) family transcription factors that binds to DRE/CRT cis-element in cold-responsive (COR) genes and induce COR genes. CBFs have been isolated and characterized from evolutionarily diverse plant species. CBF pathway is conserved by CBF regulon and the size or the number and kind of target genes vary among freezing sensitive and tolerant plants. Hence, cloning of CBFs from highly freezing tolerant plants such as Lepidium latifolium L. will be useful in understanding the freezing tolerance of this species. In this study, LlCBF, a CBF1 family gene from L. Latifolium L., was cloned using RT-PCR and RACE-PCR. The full length mRNA of LlCBF is 948 bp with an open reading frame of 642 bp, encoding a protein of 213 amino acids with a molecular weight of 23.92 kDa and a theoretical isoelectric point of 4.80. Amino acid sequence analysis showed that LlCBF has an AP2 DNA binding domain, a potential CBF type nuclear localization signal (NLS) and C-terminal acidic domain. Semi-quantitative RT-PCR analysis of LlCBF revealed that this gene is up-regulated by high salt, dehydration and low temperature stresses. The investigation is therefore successful in cloning of a gene having strong homology with CBF transcription factors and responsive to low temperature, high salt and dehydration conditions.