Regulation of ion homeostasis under salt stress

When under salt stress, plants maintain a high concentration of K+ and a low concentration of Na+ in the cytosol. They do this by regulating the expression and activity of K+ and Na+ transporters and of H. pumps that generate the driving force for transport. Although salt-stress sensors remain elusive, some of the intermediary signaling components have been identified. Evidence suggests that a protein kinase complex consisting of the myristoylated calcium-binding protein SOS3 and the serine/ threonine protein kinase SOS2 is activated by a salt-stress-elicited calcium signal. The protein kinase complex then phosphorylates and activates various ion transporters, such as the plasma membrane Na+/H+ antiporter SOS1.