Isolation And Characterization Of DREB-type Transcription Factor Genes From Soybean

Abiotic stresses such as drought, salt, cold and freezing exert severe influences on growth and development of plant. Under stress conditions, a series of physiological and biochemical reactions will occur in plants. Plants sense the environmental changes through many ways, and then transform these changes into the cell signals. The transcription factors accepting this signal after a series of actions will act with cis-acting element and promote the expression of stress-responsive genes, resulting in an enhance of stress-tolerance in plants. In plants, the expression of many genes is regulated at transcriptional level, and mostly by cis- and trans-acting elements. Therefore, transcription factors function pivotally during stress signaling in plants. DREB-type transcription factors can accept stress signals from environment and promote the expression of stress-tolerant genes.Four DREB homolog genes, GmDREBa, GmDREBb, GmDREBc and OsDREB4-2 were isolated from soybean [Glycine max (L.) Merr.] and rice (Oryza sativa L.), respectively. Each of deduced proteins contains an AP2 domain of 64 amino acids. Yeast one-hybrid assay revealed that all of the four DREB proteins specifically bound to the DRE element. Analysis of transcriptional activation abilities of three GmDREB proteins in yeast indicated that GmDREBa and GmDREBb could activate the expression of a reporter gene, whereas GmDREBc could not. The GmDREBa, GmDREBb and GmDREBc genes were expressed at different level in aerial parts of soybean, but undetectable in root. In rice, OsDREB4-2 gene had a higher expression in spike, a lower expression in root and stem, but undetectable in leave and sheath. The transcripts of GmDREBa were induced by salt, drought, ABA and cold stresses in leaves of soybean seedlings. GmDREBb was induced by salt, drought, and cold stresses, but not by ABA. The expression of GmDREBc was only induced in roots by salt, drought and ABA treatments. OsDREB4-2 was not induced by salt, drought, cold and ABA in leaves of rice seedlings. Transgenic Arabidopsis plants overexpressioning GmDREBb display different phenotypes when compared to wild type.These results suggest that these four genes may function specially in response to abiotic stresses in plants.