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Hexokinase mediates stomatal closure
Author(s) -
Kelly Gilor,
Moshelion Menachem,
DavidSchwartz Rakefet,
Halperin Ofer,
Wallach Rony,
Attia Ziv,
Belausov Eduard,
Granot David
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12258
Subject(s) - guard cell , transpiration , sucrose , hexokinase , abscisic acid , photosynthesis , sugar , chemistry , phloem , osmotic concentration , biophysics , botany , horticulture , microbiology and biotechnology , biology , biochemistry , enzyme , glycolysis , gene
Summary Stomata, composed of two guard cells, are the gates whose controlled movement allows the plant to balance the demand for CO 2 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.