CBL–CIPK pathway for maintaining ion homeostasis under high salinity and low-K+ conditions. Salt and low-K+ environmental conditions are perceived by unknown sensors, triggering different cytosolic Ca2+ signals. CBL4, CBL10, CBL1, and CBL9 perceive related Ca2+ signals; the first two proteins interact with CIPK24, while CBL1 and CBL9 interact with CIPK23. Plasma membrane Na+/H+ antiporter SOS1 is phosphorylated and activated by CBL4–CIPK24 in roots and by CBL10–CIPK24 in shoots, subsequently transporting Na+ out of the cell. The CBL1/9–CIPK23 complex phosphorylates K+ channel AKT1, which enhances K+ uptake under K+ deficient conditions. Only CBL4–CIPK24 pathway has been confirmed in rice. At, Arabidopsis; Os, rice.