A Group III WRKY Transcription Factor, SlWRKY52, Positively Regulates Drought Tolerance in Tomato

Drought severely limits crop growth and development, reducing productivity. WRKY transcription factors play crucial roles in regulating diverse aspects of plant growth, development, and responses to stress. Despite this, the functions of tomato WRKYs (SlWRKYs) in response to drought stress remain incompletely understood. Thus, we isolated SlWRKY52, a member of the group III SlWRKYs from the tomato variety ‘Ailsa Craig’, and investigated its role in drought stress responses. SlWRKY52 is an unstable hydrophilic protein chiefly located in the nucleus, which promoter region features cis-acting elements engaged in drought stress response. It was expressed in all tomato tissues and its expression was rapidly induced by drought stress. SlWRKY52 overexpression lines conferred enhanced drought stress resistance in tomato: its involved in abscisic acid (ABA) synthesis, resulted in rapid, ABA-dependent stomatal closure, reduced leaf water loss, lessened photosynthetic damage, higher antioxidant enzyme activity, decreased oxidative damage parameters, increased osmoregulatory substance content, accelerated reactive oxygen species scavenging, and increased expression of regulatory interaction, ABA biosynthesis, and abiotic stress response-related genes. Conversely, the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 nuclease mutant lines of SlWRKY52 reduced drought stress tolerance. In conclusion, our findings suggest that SlWRKY52 acts as a positive regulator of drought tolerance in tomato and has the potential to be used as a target gene for further molecular breeding.