title: Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration.
abstract: Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species.
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Nitsan
authors.initials: N
authors.lastname: Lugassi
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Gilor
authors.initials: G
authors.lastname: Kelly
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Lena
authors.initials: L
authors.lastname: Fidel
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Yossi
authors.initials: Y
authors.lastname: Yaniv
authors.affiliation: The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem Rehovot, Israel.
authors.forename: Ziv
authors.initials: Z
authors.lastname: Attia
authors.affiliation: Institute of Agricultural Engineering, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Asher
authors.initials: A
authors.lastname: Levi
authors.affiliation: Institute of Agricultural Engineering, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Victor
authors.initials: V
authors.lastname: Alchanatis
authors.affiliation: The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem Rehovot, Israel.
authors.forename: Menachem
authors.initials: M
authors.lastname: Moshelion
authors.affiliation: Department of Fruit Tree Sciences, Institute of Plant Sciences, Agricultural Research Organization, Gilat Research Center Negev, Israel.
authors.forename: Eran
authors.initials: E
authors.lastname: Raveh
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: Nir
authors.initials: N
authors.lastname: Carmi
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center Bet Dagan, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Granot
keywords: citrus rooted leaves; hexokinase; humidity; light intensity; stomata; sugar; transpiration; water-use efficiency