Functional Analysis of a Novel Chrysanthemum WRKY Transcription Factor Gene Involved in Salt Tolerance

Plant-specific WRKY transcription factors (TFs) are involved in stress responses such as cold, high salinity, or drought as well as abscisic acid (ABA) signaling. However, their roles in abiotic stresses are still not well known in chrysanthemum. Here, we isolated a novel WRKY gene, DgWRKY1, from chrysanthemum (Dendranthema grandiflorum). DgWRKY1 contains one WRKY domain and one C2H2 zinc-finger motif (C-X-4-C-X-23-H-X-H), and was localized in the nucleus. Expression of DgWRKY1 was up-regulated by drought, salinity, and ABA. The DgWRKY1-overexpression tobacco plants were more tolerant to salt, and seed gerrmination was more sensitive to ABA, than the wild-type (WT). The transgenic lines exhibited less accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) under salt stress, and less antioxidant enzyme activity, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), than the WT under both control conditions and salt stress. In addition, there was greater up-regulation of the ROS-related enzyme genes (NtSOD, NtPOD, and NtCAT) in transgenic lines under normal or salt conditions. These findings suggest that DgWRKY1 plays a positive regulatory role in salt stress response.