Roles of Aquaporins in Stomata

Stomata can be regarded as tightly regulated hydraulically driven valves that control the fluxes of water vapor and carbon dioxide between the plant and the atmosphere. In this chapter, we will focus on the mechanisms and regulation of the movement of fully developed stomata, which requires rapid and controlled fluxes of ions and water. Guard cells are symplastically isolated from their neighboring cells, implying that the regulation of transmembrane water movement is central to the control of their aperture/closure mechanism. Such hydraulic regulation of stomatal movement can be modulated by the activity of aquaporins, acting as water and small uncharged solute facilitators. Despite the existence of a wide range of transcriptomic and proteomic data showing that multiple plasma membrane aquaporins are expressed in these structures, there is currently only a limited number of experimental data supporting a functional involvement of these water channels in stomatal movements. The present review will highlight the main reverse genetics data linking the modulation of aquaporin activity to the control of the aperture of stomata.