Molecular cloning and characterization of two novel DREB genes encoding dehydration-responsive element binding proteins in halophyte Suaeda salsa

Abstract

The dehydration-responsive element-binding (DREB) proteins play an important role in regulating expression of stress-inducible genes under abiotic stresses. In this study, two genes encoding putative DREB proteins, named SsDREBa and SsDREBb, were cloned from halophyte Suaeda salsa L. using RACE method. The deduced SsDREBa and SsDREBb proteins contain a typical AP2/ERF domain. Multiple sequence alignments and phylogenetic analysis revealed that the two SsDREB genes of S. salsa were highly similar in AP2/ERF domains at the nucleotide and amino acid levels and belong to the A-6 subgroup of the DREB transcription factor subfamily. A subcellular localization assay showed that both SsDREBs localized to the nucleus. Yeast one-hybrid experiments testified that both proteins were able to specifically bind to the DRE sequence and activate the expression of the down-stream HIS reporter gene in yeast. Quantitative real-time PCR analysis demonstrated that under normal conditions, the expression level of SsDREBa was the most high in the roots and no SsDREBa mRNAs were detected in the stems; SsDREBb expressed at relatively higher levels in the leaves than in the roots and stems. The expression of SsDREa and SsDREBb genes in S. salsa roots and leaves was remarkably induced by high-salt and dehydration treatments, but not by cold and ABA, and exhibited stronger induction in roots and leaves, respectively. These results indicate that the SsDREBa and SsDREBb are novel stress-responsive transcription factors, which are involved in the drought and high-salt stress responses through ABA-independent pathways and could be used for production of stress-tolerant transgenic crops.