Functional Characterisation of the Transcription Factor GsWRKY23 Gene from Glycine soja in Overexpressed Soybean Composite Plants and Arabidopsis under Salt Stress.

WRKY proteins are a superfamily of transcription factors (TFs) that play multiple roles in plants' growth, development, and environmental stress response. In this study, a novel WRKY gene called that is specifically upregulated in salt-tolerant accession BB52 seedlings was identified by transcriptomic analysis under salt stress. How the physiological functions and mechanisms of the gene affect salt tolerance was investigated using transformations of soybean hairy roots and , including wild-type (WT) and -mutant plants. The results showed that in the roots, stems, and leaves of BB52, along with its promoter in the cotyledons and root tips of ::GUS seedlings, displayed enhanced induction under salt stress. GsWRKY23 localises to the nucleus and shows transcriptional activation ability in yeast cells. Compared to -RNAi wild soybean hairy-root composite plants under salt stress, obvious improvements, such as superior growth appearance, plant height and fresh weight (FW), and leaf chlorophyll and relative water content (RWC), were displayed by -overexpressing (OE) composite plants. Moreover, their relative electrolytic leakage (REL) values and malondialdehyde (MDA) contents in the roots and leaves declined significantly. Most of the contents of Na and Cl in the roots, stems, and leaves of -OE plants decreased significantly, while the content of K in the roots increased, and the content of NO displayed no obvious change. Ultimately, the Na/K ratios of roots, stems, and leaves, along with the Cl/NO ratios of roots and stems, decreased significantly. In the transgenic WT- and - seedlings, the salt-induced reduction in seed germination rate and seedling growth was markedly ameliorated; plant FW, leaf chlorophyll content, and RWC increased, and the REL value and MDA content in shoots decreased significantly. In addition, the accumulation of Na and Cl decreased, and the K and NO levels increased markedly to maintain lower Na/K and Cl/NO ratios in the roots and shoots. Taken together, these results highlight the role of in regulating ionic homeostasis in NaCl-stressed overexpressed soybean composite plants and seedlings to maintain lower Na/K and Cl/NO ratios in the roots and shoots, thus conferring improved salt tolerance.