A tomato Receptor-like Cytoplasmic Kinase SlZRK1 acts as a negative regulator in wound-induced jasmonic acid accumulation and insect resistance.

Jasmonates accumulate rapidly and act as key regulators in response to mechanical wounding, however few studies link receptor-like cytoplasmic kinases (RLCKs) to wound-induced JA signaling cascades. Here, we identified a novel wounding induced RLCK-XII-2 subfamily member in tomato (SlZRK1) that was closely related to Arabidopsis HOPZ-ETI-DEFICIENT 1 (ZED1)-related kinases 1 based on the phylogenetic analysis. SlZRK1 was targeted to the plasma membrane (PM) of tobacco mesophyll protoplasts as determined by transient co-expressing with PM marker mCherry-H +-ATPase. Catalytic residue sequence analysis and in vitro kinase assay indicated that SlZRK1 may act as a pseudokinase. To further analyze the function of SlZRK1, we developed two stable knock-out mutants by CRISPR/Cas9. Loss of SlZRK1 significantly altered expression of genes involved in jasmonic acid (JA) biosynthesis, salicylic acid (SA) biosynthesis, and ethylene response. Furthermore, after mechanical wounding treatment, slzrk1 mutants increased transcription of early wound inducible genes involved in JA biosynthesis and signaling. In addition, JA accumulation after wounding and plant resistance to herbivorous insects also were enhanced. Our findings expand plant regulatory networks in the wound-induced JA production by adding RLCKs as a new component in wound signal transduction pathway.