Abstract
The opening of stomata, mediated by K+ accumulation in guard cells, is induced by blue light (BL). BL activates the plasma membrane H+-pump in guard cells, and provides driving force for K+ uptake. In this study, we present evidence that the pump is the plasma membrane H+-ATPase, and that the H+-ATPase is activated by phosphorylation of C-terminus in Vicia guard-cell protoplasts. Furthermore, we found that BL induces phosphorylation of Thr950 in the C-terminus of Vicia H+-ATPase isoform1 (VHA1), and that binding of 14-3-3 protein to this site is indispensable to the activation of H+-ATPase. Analysis of BL-responses in stomatal guard cells using Arabidopsis mutants revealed that phot1 and phot2, BL-receptors for phototropism and chloroplast relocation, act redundantly as BL-receptors mediating stomatal opeing. These findings demonstrated that BL, absorbed by phots, activates the plasma membrane H+-ATPase via phosphorylation of the C-terminus with concomitant binding of 14-3-3 protein in stomatal guard-cells.
