The MYC2-PUB22-JAZ4 module plays a crucial role in jasmonate signaling in tomato

Jasmonates(JAs),a class of lipid-derived stress hormones,play a crucial role across an array of plant physiological processes and stress responses.Although JA signaling is thought to rely predominantly on the degradation of specific JAZ proteins by SCF^(COI1),it remains unclear whether other pathways are involved in the regulation of JAZ protein stability.Here,we report that PUB22,a plant U-box type E3 ubiquitin ligase,plays a critical role in the regulation of plant resistance against Helicoverpa armigera and other JA responses in tomato.Whereas COI1 physically interacts with JAZ1/2/5/7,PUB22 physically interacts with JAZ1/3/4/6.PUB22 ubiquitinates JAZ4 to promote its degradation via the 26S proteasome pathway.Importantly,we observed that pub22 mutants showreduced resistance to H.armigera,whereas jaz4 single mutants and jaz1 jaz3 jaz4 jaz6 quadruple mutants have enhanced resistance.The hypersensitivity of pub22 mutants to herbivores could be partially rescued by JAZ4 mutation.Moreover,we found that expression of PUB22 can be transcriptionally activated by MYC2,thus forming a positive feedback circuit in JA signaling.We noticed that the PUB22-JAZ4 module also regulates other JA responses,including defense against B.cinerea,inhibition of root elongation,and anthocyanin accumulation.Taken together,these results indicate that PUB22 plays a crucial role in plant growth and defense responses,together with COI1-regulated JA signaling,by targeting specific JAZs.

CHARACTERISTICS OF HERBIVORY/WOUND-ELICITED ELECTRICAL SIGNAL TRANSDUCTION IN TOMATO

Electrical signals commonly occur in plants in response to various environmental changes and have a dominant function in plant acclimation.The transduction of wound-elicited electrical signals in the model plant spedes Arabidopsis has been characterized but the characteristics of electrical signal transduction in response to herbivory or wounding in crop species remain unknown.Here,the features of electrical signals elicited by insect herbivory and wounding in tomato were investigated.Unlike those in Arabidopsis,wounding tomato leaves did not cause leaf-to-leaf electrical signal transduction.In contrast,electrical signals elicited in response to petiole wounding were stronger and more strongly transduced.Leaflet wounding also activated electrical signal transduction and jasmonic acid(JA)signaling within the whole compound leaf.It was also demonstrated that tomato glutamate receptor-like 3.3(GLR3.3)and GLR3.5 mediated leaflet-to-leaflet electrical signal transduction.Herbivory-induced JA accumulation and Helicoverpa armigera resistance were reduced in glr3.3/3.5 plants.This work reveals the nature of electrical signal transduction in tomato and emphasizes the key roles of GLR3.3 and GLR3.5 in electrical signal transduction and JA signaling activation.