The Mulberry WRKY Transcription Factor MaWRKYIIc7 Participates in Regulating Plant Drought Stress Tolerance

The sericulture industry is an important component of the agricultural industry. Drought stress can cause yellowing, premature ageing, and the shrinkage of mulberry (Morus alba L.) leaves, greatly damaging their quality and restricting the high-quality development of the sericulture industry. WRKY transcription factors play important roles in the plant drought stress response. In this study, we found that MaWRKYIIc7 of the mulberry WRKY TFs, had significantly higher expression levels in leaves than in other tissues and was induced to be expressed under drought stress. The MaWRKYIIc7 protein is located in the nucleus and plasma membrane, and its transcriptional activity depends mainly on the N-terminal sequence. The overexpression of MaWRKYIIc7 in Arabidopsis resulted in better drought tolerance. An analysis of the transient overexpression of MaWRKYIIc7 in mulberry seedlings under drought stress revealed that the transgenic seedlings presented decreased stomatal opening, decreased MDA content, increased ROS clearance ability, and increased the expression of ABA biosynthesis-related genes. The Y1H and Dual-luc results indicate that MaWRKYIIc7 can bind W-boxes to positively regulate MaNCED1 and MaRD29A, synergistically regulating the drought tolerance of mulberry. Overall, our research suggests that MaWRKYIIc7 can increase plant drought tolerance by promoting ROS clearance, adjusting stomatal opening, and activating the ABA signalling pathway.