Involvement of the vacuolar processing enzyme ?VPE in response of Arabidopsis thaliana to water stress

Plant vacuoles play several roles in controlling development, pathogen defence, and stress response. ?VPE is a vacuolar localised cysteine protease with a caspase-1 like activity involved in the activation and maturation of downstream vacuolar hydrolytic enzymes that trigger hypersensitive cell death and tissue senescence. This work provides evidence that ?VPE is strongly expressed in Arabidopsis guard cells and is involved in water stress response. The ?vpe knock-out mutants showed reduced stomatal opening and an increased resistance to desiccation suggesting a new role of ?VPE in control of stomatal movements.