Hexokinase mediates stomatal closure

• DOI: 10.1111/tpj.12258
• Publication Date: 2013-06-06T08:56:48Z
• Authors: Gilor Kelly; Menachem Moshelion; Rakefet David‐Sch...; Ofer Halperin; Rony Wallach; Ziv Attia; Eduard Belausov; David Granot
• Keywords: 0301 basic medicine; Sucrose; 0303 health sciences; 03 medical and health sciences; Solanum lycopersicum; Arabidopsis Proteins; Hexokinase; Plant Stomata; Plant Transpiration; Nitric Oxide; Plants, Genetically Modified; Abscisic Acid

SummaryStomata, composed of two guard cells, are the gates whose controlled movement allows the plant to balance the demand for CO2 for photosynthesis with the loss of water through transpiration. Increased guard‐cell osmolarity leads to the opening of the stomata and decreased osmolarity causes the stomata to close. The role of sugars in the regulation of stomata is not yet clear. In this study, we examined the role of hexokinase (HXK), a sugar‐phosphorylating enzyme involved in sugar‐sensing, in guard cells and its effect on stomatal aperture. We show here that increased expression of HXK in guard cells accelerates stomatal closure. We further show that this closure is induced by sugar and is mediated by abscisic acid. These findings support the existence of a feedback‐inhibition mechanism that is mediated by a product of photosynthesis, namely sucrose. When the rate of sucrose production exceeds the rate at which sucrose is loaded into the phloem, the surplus sucrose is carried toward the stomata by the transpiration stream and stimulates stomatal closure via HXK, thereby preventing the loss of precious water.