Cytokinin induces bacterial pathogen resistance in tomato

Abstract

Phytohormones are involved in the regulation of plant responses to biotic stress. How a limited number of hormones differentially regulate defence responses and influence the outcome of plant–biotic interactions is not fully understood. In recent years, cytokinin (CK) was shown to induce plant resistance against several pathogens. In the present study, we investigated the effect of CK in inducing tomato resistance against the hemibiotrophic pathogenic bacteria Xanthomonas campestris pv. vesicatoria (Xcv) and Pseudomonas syringae pv. tomato (Pst). We demonstrate that CK enhances tomato resistance to Xcv and Pst through a process that relies on salicylic acid and ethylene signalling. CK did not directly affect the growth or biofilm formation ability of these pathogens in vitro. Overall, our work provides insight into the underlying mechanisms of CK‐induced immune responses against bacterial pathogens in tomato.

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

“…Why does CK directly inhibit growth and virulence of fungal pathogens from different classes (ascomycetes, basidiomycetes), different lifestyles (hemibiotrophs, necrotrophs), different modes of plant infection (air borne, soil borne, vascular or not) and different host target organs (leaves, stems, roots)? Of note is that us and others have found that CK has no direct inhibitory effect on bacterial pathogens (23, 40). Our results demonstrate that CK inhibits fungal growth and development ( Figs.…”

“…Given that CK can induce plant immunity and restrict phytopathogen growth in certain cases, direct effects of CK against phytopathogens are an intriguing possibility. A direct effect of CK on bacterial pathogens was ruled out in previous works (23, 25). Interestingly, CK did not affect germination and elongation of germ tubes, but strongly inhibited appressorium formation of Erysiphe graminis , an obligate biotrophic powdery mildew causing barley pathogen (14).…”

“…However, in tobacco, an SA-Independent, phytoalexin-dependent mechanism was suggested (22). We recently reported that CK induces systemic immunity in tomato ( Solanum lycopersicum ), promoting resistance to fungal and bacterial pathogens (23, 24) including Botrytis cinerea, in an SA and ethylene dependent mechanism.…”

Cytokinin Modulates Cellular Trafficking and the Cytoskeleton, Enhancing Defense Responses

“…We and others have previously demonstrated that pathogenesis processes can activate the CK pathway [ 17 , 18 , 19 ], raising the possibility that CK pathway activation might be required for pathogen resistance. Interestingly, we previously found that B. cinerea infection activates the synthetic CK response promoter TCSv2 [ 18 ].…”

“…In tobacco, an SA-independent, phytoalexin-dependent mechanism was reported [ 16 ]. We recently reported that CK induces systemic immunity in tomato, promoting resistance to fungal and bacterial pathogens in an SA- and ethylene (ET)-dependent mechanism [ 18 , 19 ]. Until recently, other than the evidence that SA is required for CK-induced immunity [ 14 , 15 , 17 ], and that phytoalexins are involved [ 16 ], no additional cellular mechanisms related to CK-mediated immunity had been reported.…”