Aquaporin mediating stomatal closure is associated with water conservation under mild water deficit

SummaryContradictory results indicate that aquaporins might facilitate the diffusion of both water and H2O2during abscisic acid (ABA) triggered stomatal closure. Here, we tested whether maize plasma membrane PIP2;5 aquaporin regulates stomatal closure under water deficit or ABA treatment in intact plants, detached leaves, and peeled epidermis.Transpiration, stomatal conductance and aperture, as well as reactive oxygen species (ROS) in stomatal complexes were studied in maize lines deregulated inPIP2;5gene expression, under water deficit and/or ABA treatments.In well-watered conditions, the PIP2;5 overexpressing (OE) plants transpired more than the wild-type plants (WT), while no significant difference in transpiration was observed betweenpip2;5KO and WT plants. Upon mild-water deficit or low ABA concentration treatment, the transpiration and stomatal conductance decreased more in PIP2;5 OE, and less inpip2;5KO lines, in comparison with WT plants. Using isolated epidermis, ABA treatment induced faster stomatal closing in PIP2;5 OE lines compared to the WT, whilepip2;5KO stomata were ABA insensitive. These phenotypes were associated with guard cell ROS accumulation.Together, these data indicate that maize PIP2;5 regulates early stomatal closure for water conservation upon a water deficit environment.