The PHD transcription factor ThPHD5 regulates antioxidant enzyme activity to increase salt tolerance in Tamarix hispida.

PHD proteins are an important class of transcription factors (TFs) that are widely distributed in eukaryotes and play crucial roles in many aspects of plant growth, development and response to stress. We identified a transcription factor, ThPHD5, from the PHD family in Tamarix hispida based on its potential involvement in abiotic stress response processes. In this study, the salt tolerance function of ThPHD5 from T. hispida was further characterized. The qRTPCR results showed ThPHD5 was expressed in response to NaCl, PEG and ABA treatments. Transient transformation analysis revealed that ThPHD5 improved salt tolerance in T. hispida by increasing POD and SOD activity and decreasing the MDA, total ROS content and electrolyte leakage. To explore the salt tolerance mechanism of the ThPHD5 TF, its binding DNA motifs and potential downstream regulatory genes were analyzed. The results showed that ThPHD5 affect the expression of 7 antioxidant enzyme-related genes. The Yeast one-hybrid (Y1H) and Electrophoretic Mobility Shift Assay (EMSA) results indicated ThPHD5 could bind to ABRE, MYB and Dof cis-acting elements. ChIP-PCR further confirmed ThPHD5 exercise its regulatory function by directly binding motifs on the ThPOD16, ThSOD and ThSOD1 promoters. Taken together, these findings indicate the ThPHD5 TF improves salt tolerance in T. hispida by regulating the expression of antioxidant enzyme-related genes to increase antioxidant enzyme activity, enhance the ROS scavenge ability, reduce ROS accumulation and cellular damage.