The SlJMJ15, a Putative Histone Demethylase Gene, Acts as a Negative Regulator of Drought Tolerance in Tomato

JmjC domain proteins play crucial roles in plant growth and development, regulation of epigenetic processes, flowering control, and stress defence. However, these proteins have not been systematically identified or characterised in tomato. Here, we performed a genome-wide identification of JmjC domain-containing genes (JMJ family) in tomato and identified 23 SlJMJ genes within the tomato genome. Expression analysis indicated that SlJMJ15 was responsive to drought stress, prompting us to investigate its functional role in tomato plants. We found that SlJMJ15-RNAi lines displayed a severe dwarf phenotype, whereas SlJMJ15-overexpression lines exhibited increased drought sensitivity compared to wild-type plants, indicating that SlJMJ15 negatively regulates drought tolerance in tomatoes. Further investigation suggests that SlJMJ15 may reduce drought tolerance in tomatoes by modulating the expression of key genes involved in abscisic acid signalling pathways through its demethylation activity. This study deepens our understanding of the roles of SlJMJ family genes in tomato growth and abiotic stress responses, laying the foundation for developing strategies to improve drought stress tolerance in tomatoes.