Tomato defence against Meloidogyne incognita by jasmonic acid‐mediated fine‐tuning of kaempferol homeostasis

Summary Jasmonic acid (JA) is involved in the modulation of defence and growth activities in plants. The best‐characterized growth‐defence trade‐offs stem from antagonistic crosstalk among hormones. In this study, we first confirmed that JA negatively regulates root‐knot nematode (RKN) susceptibility via the root exudates (REs) of tomato plants. Omics and toxicological analyses implied that kaempferol, a type of flavonol, from REs has a negative effect on RKN infection. We demonstrated that SlMYB57 negatively regulated kaempferol contents in tomato roots, whereas SlMYB108/112 had the opposite effect. We revealed that JA fine‐tuned the homeostasis of kaempferol via SlMYB‐mediated transcriptional regulation and the interaction between SlJAZs and SlMYBs, thus ensuring a balance between lateral root (LR) development and RKN susceptibility. Overall, this work provides novel insights into JA‐modulated LR development and RKN susceptibility mechanisms and elucidates a trade‐off model mediated by JA in plants encountering stress.