Phosphorylation of plasma membrane aquaporin PIP2;1 in C-terminal affects light-induced stomatal opening in Arabidopsis.

Guard cells undergo quick volume changes during stomatal movements. However, the contribution of aquaporins to stomatal movements has not been well understood. The plasma membrane aquaporin PIP2;1in Arabidopsis has been found to mediate abscisic acid-induced or flag22-induced stomatal closure. In this research, we investigated the role of PIP2;1 in light-induced stomatal opening by measuring the stomatal apertures of the mutant and overexpression lines after light treatment. mutant exhibited a larger stomatal aperture, and the overexpression lines displayed a smaller stomatal aperture. It has been reported that the phosphorylation at Ser-280 and Ser-283 of PIP2;1 in rosette tissue increased in response to darkness, whereas osmotic water permeability () in mesophyll protoplasts in darkness was lower than that under light, suggesting that phosphorylation at Ser-280 and Ser-283 of PIP2;1 affected in mesophyll protoplasts. Therefore, we obtained the mutant expressing phosphorylation-deficient () or phosphomimetic () forms of . The lines exhibited a larger stomatal aperture as mutant, whereas lines exhibited a smaller stomatal aperture as overexpression lines under light. These results suggest that PIP2;1 plays a negative role in light-induced stomatal opening, and phosphorylation of PIP2;1 at Ser-280 and Ser-283 causes reduced water absorption in guard cells and decreased stomatal opening.