Phosphorylation-dependent interaction between plant plasma membrane H+-ATPase and 14-3-3 proteins

The H+-ATPase is a key enzyme for the establishment and maintenance of plasma membrane potential and energization of secondary active transport in the plant cell. The phytotoxin fusicoccin induces H+-ATPase activation by promoting the association of 14-3-3 proteins. It is still unclear whether 14-3-3 proteins can represent natural regulators of the proton pump, and factors regulating 14-3-3 binding to the H+-ATPase under physiological conditions are unknown as well. In the present study in vivo and in, vitro evidence is provided that 14-3-3 proteins can associate with the H+-ATPase from maize roots also in a fusicoccin-independent manner and that the interaction depends on the phosphorylation status of the proton pump. Furthermore, results indicate that phosphorylation of H+-ATPase influences also the fusicoccin-dependent interaction of 14-3-3 proteins. Finally, a protein phosphatase 2A able to impair the interaction between H+-ATPase and 14-3-3 proteins was identified and partially purified from maize root.