Functional characterization of CtWRKY70 transcription factor from Cynanchum thesioides in salt and drought stress resistance.

The WRKY transcription factor CtWRKY70 from Cynanchum thesioides was functionally characterized to explore its role in abiotic stress responses. CtWRKY70, encoding a 340-amino acid protein from the WRKY Group III subfamily, localizes to the nucleus and exhibits transcriptional activation activity. Its expression is significantly induced by salt and drought stress. Overexpression of CtWRKY70 in Arabidopsis improved tolerance to both stresses, as evidenced by enhanced survival rates, maintained biomass, and preserved chlorophyll content. Transgenic lines exhibited elevated antioxidant enzyme activities (SOD, CAT, POD) and increased proline accumulation, with CtWRKY70 directly bound to the promoter of the AtSOD1 gene as confirmed by electrophoretic mobility shift assay (EMSA) and yeast one-hybrid (Y1H) assays, indicating enhanced ROS scavenging and osmoregulation. In contrast, CtWRKY70-silenced plants showed heightened stress sensitivity, characterized by greater wilting, increased stomatal aperture, and accelerated water loss. Y2H and BiFC assays confirmed the interaction of CtWRKY70 with another stress-responsive WRKY protein, CtWRKY41. These results demonstrate that CtWRKY70 positively regulates drought and salt tolerance by coordinating antioxidant defense and osmotic adjustment. This study provides valuable insights into the molecular mechanisms of WRKY-mediated stress adaptation in horticultural species, positioning CtWRKY70 as a potential genetic target for improving crop resilience.