A Buckwheat (Fagopyrum esculentum) DRE-Binding Transcription Factor Gene, FeDREB1, Enhances Freezing and Drought Tolerance of Transgenic Arabidopsis

CBF/DREB transcription factors play essential roles in plant stress signaling transduction pathway. We isolated and identified a CBF/DREB homologous gene, FeDREB1, from Fagopyrum esculentum. Protein sequence alignment and phylogenetic analyses revealed that the FeDREB1 was grouped into the DREB (A-1) lineage. Moreover, subcellular localization observations suggested that FeDREB1 localizes in the nucleus. Yeast one-hybrid assays showed that FeDREB1 protein specifically binds to the DRE sequence and could activate the expression of reporter genes in yeast. These results further suggested that the FeRDEB1 protein was a CBF/DREB transcription factor. Expression analysis revealed that the transcript levels of the FeRDEB1 gene increased rapidly following low-/high-temperature treatment, drought stress, and exogenous ABA treatment. Over-expression of the FeDREB1 gene significantly enhanced the drought and freezing tolerance of transgenic Arabidopsis but resulted in its growth retardation. Moreover, the transgenic Arabidopsis lines were also highly sensitive to ABA application. Digital gene expression profiling (DGE) analysis indicated that increased transcript levels of many ABA-independent/-dependent stress-responsive genes in 35S::FeRDEB1 transgenic Arabidopsis, revealing that the FeDREB1 may participate in an ABA-dependent/-independent pathways.