Tendril length is determined by gibberellin deactivation during thigmo response in cucumber

Changes in plant morphology due to mechanical stimulation are known as thigmo responses. As climbing organs in plants, tendrils can sense mechanical stimulation after attaching to a support and then change their morphology within a short time. Here, the thigmo responses of cucumber tendril were investigated. Our results showed that mechanical stimulation stopped tendril elongation and that tendril length was determined by the distance from the support in cucumber. The mimicry touch treatment indicated that mechanical stimulation stopped tendril elongation by inhibiting cell expansion. RNA-seq data showed that three gibberellin (GA) metabolic genes (CsGA2ox3, CsCYP714A2, and CsCYP714A3) were upregulated in mechanically stimulated tendrils, and a major endogenous bio-active GA (GA₄) was reduced in mechanically stimulated tendrils. The roles of CsGA2ox3, CsCYP714A2, and CsCYP714A3 in GA deactivation were confirmed by their overexpression in transgenic Arabidopsis. Moreover, exogenous GA treatment recovered tendril elongation under mechanical stimulation, whereas exogenous uniconazole treatment inhibited tendril elongation without mechanical stimulation, suggesting that mechanical stimulation stopped tendril elongation, depending on GA deactivation. In summary, our results suggest that GA deactivation plays an important role in tendril thigmo response, ensuring that tendrils obtain a suitable final length according to their distance from the support in cucumber.