Abstract: It is well know that the DREB (dehydration responsive element binding protein) transcription factors in the AP2/ERF family play important roles in the regulation of plant stress responses, hormone responses and so on. GmDREB5, a novel DREB homologous gene, was isolated from soybean (Glycine max) and transferred into tobacco in our previous study. To investigate its function, the T₂ transgenic tobacco plants with GmDREB5 and the wild type plants were inoculated on MS medium with 100 mmol L^-1 NaCl and 2% PEG, and their phenotypes were observed 40 days later. The results showed that the growth of the transgenic plants was more vigorous, and their roots were longer on the medium containing 2% PEG than those of wild type plants. The germination rate of transgenic plants (75%) was five-fold higher than that of the wild type plants (15%) on the medium containing NaCl, indicating that the over-expression of GmDREB5 improved the tolerances to both drought and salt stresses. The interacting proteins of GmDREB5 was attained by screening the cDNA library of soybean under drought and identified by yeast-two-hybrid system. It was found that there existed conservative domain WD40 in the interacting proteins,and which shared 61% and 52% similarity of the amino acid sequence with G protein β subunit in cotton (Gossypium hirsutum) and rice (Oryza sativa), respectively, The interacting protein with GmDREB5, named GmGβ1, was isolated and proven to be a G protein β subunit in soybean. The prey vector containing GmGβ1 and bait vector pGBKT7-IIR were co-transformed into yeast AH109, then incubated on mediums with shortage of four components (SD/ trp- leu- his- ade-) for 3–5 days, and the results showed that the thansformants but the contorol grew normally ,and could activate the expression of the downstream reporter gene LacZ, which performed interaction between GmDREB5 and GmGβ1. Further analyses showed that the expression of GmGβ1 gene in soybean was induced by drought, high salt, cold stresses and ABA treatment. These results suggested that GmGβ1 might involve in not only response to abiotic stress but also regulation of GmDREB5 by interacting in soybean.

Key words: Soybean, DREB gene, Yeast two-hybrid system, Interaction protein, G protein β subunit