Cytokinin response induces immunity and fungal pathogen resistance, and modulates trafficking of the PRR LeEIX2 in tomato

Abstract

Plant immunity is often defined by the immunity hormones: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). These hormones are well known for differentially regulating defence responses against pathogens. In recent years, the involvement of other plant growth hormones such as auxin, gibberellic acid, abscisic acid, and cytokinins (CKs) in biotic stresses has been recognized. Previous reports have indicated that endogenous and exogenous CK treatment can result in pathogen resistance. We show here that CK induces systemic immunity in tomato (Solanum lycopersicum), modulating cellular trafficking of the pattern recognition receptor (PRR) LeEIX2, which mediates immune responses to Xyn11 family xylanases, and promoting resistance to Botrytis cinerea and Oidium neolycopersici in an SA‐ and ET‐dependent mechanism. CK perception within the host underlies its protective effect. Our results support the notion that CK promotes pathogen resistance by inducing immunity in the host.

Cytokinin inhibits fungal development and virulence by targeting the cytoskeleton and cellular trafficking

“…As reported previously by us and others, CK was shown to promote fungal disease resistance in plants (21,24). Direct effects of CK on fungal growth and development have not been investigated in depth in plant-free systems, and although a few studies have discussed some effects of CK on fungal pathogen growth (9,10), no mechanisms for CK antifungal activity have yet been reported.…”

“…CK showed no effect on leakage of nucleic acids and proteins from It has been previously suggested that certain classes of fungi possess CK receptors to be able to "sense plants", a trait posited to have been required for land colonization by fungi (69). We and others have previously demonstrated that plants activate CK signaling upon pathogen attack, and that CK serves as a cue to activate defense responses (21,24,65) (Fig. 7), or S. cerevisiae (Fig.…”

“…Us and others (24,43) have previously shown that CK can influence cellular trafficking in plants. We therefore examined the effect of CK on endocytosis in Bc.…”

“…High levels of CKs were found to increase the plants' resistance to bacterial and fungal pathogens (19)(20)(21)(22)(23)(24). Different mechanisms have been suggested for this enhanced resistance.…”

Cytokinin induces bacterial pathogen resistance in tomato

“…fungi, in a mechanism dependent on SA and ET signalling (Gupta et al, 2020). We showed that fungal pathogens cause activation of the tomato CK machinery, and that CK-mediated disease resistance requires pattern recognition receptors.…”