FIGURE 1.

Proposed model for CBL10 function. CBL10 functions as a crucial regulator in Na⁺ homeostasis under salt stress conditions, interacting with CIPK24 (SOS2) and CIPK8, and activating SOS1 pathway at plasma membrane for Na⁺ extrusion to apoplast and may be interacting with vacuolar H⁺ pumps (AVP1, VHA) facilitating Na⁺ sequestration into the vacuole. CBL10 also plays a key role in Ca²⁺ homeostasis, which in turn hints at this Ca²⁺ -sensor protein as a key master regulator of stress signaling in plants, involved in generation and fine tuning of Ca²⁺ signatures in the cytoplasm, through the coordination of different Ca²⁺ channels at different cellular localizations, such as plasma membrane (AtANN4) and probably tonoplast (TPC1), as well as in the cross-talk between Ca²⁺ and ROS, through regulation of RBOHs activity, for a rapid long-distance transmission of signals. CBL10 seems also to be involved in mobilizing Ca²⁺ stored in vacuole toward demanding tissues to compensate for Ca²⁺ deficiency caused by salinity and thus allowing development of the meristem and reproductive organs. Finally, functions of CBL10 in root have been associated with K⁺ uptake by negative regulation of AKT1 channel. Green arrows indicate activation by phosphorylation; red line indicates repression by direct interaction; gray arrows indicate activation by Ca²⁺, and question mark indicates hypothesized signaling processes that have not been verified yet.