In plants, Calcineurin B-like proteins (CBLs) and their interacting kinases (CIPKs) are essential for mediating responses to various environmental stresses. This study functionally characterized LjCIPK1 from Lonicera japonica and verified its role in salt stress responses. Ectopic expression of LjCIPK1 in Arabidopsis thaliana significantly increased tolerance to salt stress, allowing transgenic plants to bolt, flower, and set seed normally under stress conditions. Subcellular localization assays indicated that LjCIPK1 is distributed in both the cytoplasm and nucleus, and this pattern remains unchanged under salt stress. Mechanistically, Y2H and BiFC assays revealed that LjCIPK1 interacts with the Ca 2+ sensors LjCBL1/3/6 and the Na + /H + antiporter LjNHX3/6/7. Overexpression of LjNHX3 also conferred salt tolerance, supporting a role for LjCIPK1 in maintaining intracellular ion homeostasis. In parallel, LjCIPK1 overexpression significantly enhanced flavonoid content and upregulated key biosynthetic genes, leading to reduced ROS accumulation and oxidative damage. Furthermore, LjCIPK1 was found to interact with diverse stress regulators, including the transcription factor MYB42, protein phosphatase AIP1, glycosyltransferase UGT75B1, and kinase regulatory subunit KINB2. These results demonstrate that the LjCBL1/3/6–LjCIPK1 complex enhances salt tolerance by coordinating multiple pathways: regulating LjNHX3 to compartmentalize Na + into the vacuole, activating antioxidant defense systems through flavonoid biosynthesis, and recruiting diverse downstream stress regulators to orchestrate a multifaceted stress response.
Huang et al. (Wed,) studied this question.