Subcellular volume changes in stomata opening: vacuolar vs cytosolic volume changes.

Abstract

Stomata are anatomical structures at the surface of leaves controlling gas exchanges between the plant and the atmosphere. The stomatal pore aperture is regulated by two specialized cells, the guard cells, having the capacity to reversibly change their volume and shape. The changes of the guard cells’ volume are under tight control of signaling cascades regulating the ionic transport processes across the plasma and the vacuolar membranes. In guard cells the vacuole can reversibly change its volume during the opening and closure of stomata. We have used a 3D reconstruction approach to visualize the dynamics changes subcellular compartments volumes in living guard cells. The method we developed allowed us to simultaneously quantify the volumetric modifications of the cytosol and the vacuole. Notably, we could follow modification of the subcellular organization in parallel with the ion transport dynamics at the plasma and vacuolar membranes. Our data show that the vacuole accounts for the whole guard cell volume changes. This suggests that the turgor changes of the guard cells are driven by the vacuole during stomata aperture.