Chrysanthemum DgWRKY2 Gene Enhances Tolerance to Salt Stress in Transgenic Chrysanthemum

Abstract

WRKY transcription factors (TFs) play a vital part in coping with different stresses. In this study, <i>DgWRKY2</i> was isolated from <i>Dendranthema grandiflorum</i>. The gene encodes a 325 amino acid protein, belonging to the group II WRKY family, and contains one typical WRKY domain (WRKYGQK) and a zinc finger motif (C-X4-5-C-X22-23-H-X1-H). Overexpression of <i>DgWRKY2</i> in chrysanthemum enhanced tolerance to high-salt stress compared to the wild type (WT). In addition, the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (<i>CAT</i>)), proline content, soluble sugar content, soluble protein content, and chlorophyll content of transgenic chrysanthemum, as well as the survival rate of the transgenic lines, were on average higher than that of the WT. On the contrary, hydrogen peroxide (H₂O₂), superoxide anion (O₂^-), and malondialdehyde (MDA) accumulation decreased compared to WT. Expression of the stress-related genes <i>DgCAT</i>, <i>DgAPX</i>, <i>DgZnSOD</i>, <i>DgP5CS</i>, <i>DgDREB1A</i>, and <i>DgDREB2A</i> was increased in the <i>DgWRKY2</i> transgenic chrysanthemum compared with their expression in the WT. In conclusion, our results indicate that <i>DgWRKY2</i> confers salt tolerance to transgenic chrysanthemum by enhancing antioxidant and osmotic adjustment. Therefore, this study suggests that <i>DgWRKY2</i> could be used as a reserve gene for salt-tolerant plant breeding.