A CBL4-CIPK6 module confers salt tolerance in cucumber

Soil salinization is a major threat to cucumbers grown under protected cultivation. Under stressful environments, calcineurin B-like proteins (CBLs) can sense and bind Ca²⁺ signals and regulate CBL-interacting protein kinases (CIPKs) to transmit signals and induce cellular responses. Although CBL-CIPK modules play central roles in plant development and response to various abiotic stresses in Arabidopsis, little is known about their functions in cucumber. In this study, we demonstrate that CsCBL4 interacts with CsCIPK6, which exhibited similar responses to salt stress in cucumber. Furthermore, salt stress resulted in greater accumulation of CsCBL4 and CsCIPK6. Comprehensive phenotype analysis demonstrated that silencing CsCBL4 or CsCIPK6 reduced the salt tolerance of cucumber, and overexpression of CsCBL4 increased the salt tolerance of Arabidopsis. Collectively, these results indicate that the CsCBL4-CsCIPK6 module plays an important role in the resistance of cucumber to salt stress. The information provides insights for the genetic breeding of salt tolerance in cucumber in the future.