Overexpression of SlWRKY30 reduces drought stress tolerance in tomato.

The WRKY transcription factors play an important role in regulating plant response to drought stress. The results show that SlWRKY30 acts as a negative regulator of drought tolerance, and that overexpressing SlWRKY30 (SlWRKY30OE) promotes vegetative growth. Moreover, the expression of SlWRKY30 was induced by drought stress, and SlWRKY30OE plants exhibited more severe wilting than WT under drought conditions. SlWRKY30 overexpression led to high relative electrolyte leakage, MDA content, and ROS levels in tomatoes under drought stress. In SlWRKY30OE plants, the activities of SOD, POD, CAT and APX were lower than those of WT plants; further, the expression levels of SlFe-SOD, SlCAT1 and SlcAPX were also lower than in WT plants under drought stress. Further analysis of RNA sequencing indicated that the transcription level of the encoding photosystem I and II genes was almost down-regulated, while the degree of SlWRKY30OE plants downregulation was stronger than in WT plants. Consistently, the Pn and Fv/Fm were lower in SlWRKY30OE plants during drought stress. These results indicate that SlWRKY30 reduces drought resistance in tomato by weakening antioxidant capacity, promoting ROS accumulation and membrane damage, and impairing photosynthetic performance under drought stress.