Isolation and functional analysis of transcription factor GmWRKY57B from soybean

WRKY proteins are a large family of transcriptional regulators in higher plants involved in many biological processes, such as responses to biotic and abiotic stress, plant development and metabolism. In this study, a soybean cDNA library was constructed and screened by yeast one-hybrid system using the 3xW-box element as a bait, and consequently a transcription factor, named GmWRKY57B, a member of group 3 of WRKY family, was obtained. GmWRKY57B specifically binds to the W-box of the Arabidopsis NPR1 （AtNPR1） promoter in yeast cells. This specific binding was further confirmed with an in vitro electrophoretic mobility shift assay. RT-PCR analysis showed that GmWRKY57B was expressed at a similar level in root, stem and leaf of the soybean plant. Overexpression of the GmWRKY57B gene in tobacco conferred the transgenics tolerance to drought stress. This result indicated that the GmWRKY57B gene plays a role in plant tolerance to abiotic stress.