title: Guard cell-specific upregulation of sucrose synthase 3 reveals that the role of sucrose in stomatal function is primarily energetic.
abstract: Isoform 3 of sucrose synthase (SUS3) is highly expressed in guard cells; however, the precise function of SUS3 in this cell type remains to be elucidated. Here, we characterized transgenic Nicotiana tabacum plants overexpressing SUS3 under the control of the stomatal-specific KST1 promoter, and investigated the changes in guard cell metabolism during the dark to light transition. Guard cell-specific SUS3 overexpression led to increased SUS activity, stomatal aperture, stomatal conductance, transpiration rate, net photosynthetic rate and growth. Although only minor changes were observed in the metabolite profile in whole leaves, an increased fructose level and decreased organic acid levels and sucrose to fructose ratio were observed in guard cells of transgenic lines. Furthermore, guard cell sucrose content was lower during light-induced stomatal opening. In a complementary approach, we incubated guard cell-enriched epidermal fragments in (13) C-NaHCO3 and followed the redistribution of label during dark to light transitions; this revealed increased labeling in metabolites of, or associated with, the tricarboxylic acid cycle. The results suggest that sucrose breakdown is a mechanism to provide substrate for the provision of organic acids for respiration, and imply that manipulation of guard cell metabolism may represent an effective strategy for plant growth improvement.
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.|Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, 14476, Germany.
authors.forename: Danilo M
authors.initials: DM
authors.lastname: Daloso
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.|Departamento de Botânica, Universidade de Brasilia, Brasília, DF, 70910-900, Brazil.
authors.forename: Thomas C R
authors.initials: TC
authors.lastname: Williams
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.|Departamento de Biologia, Universidade Estadual de Maringá, Maringá, PR, 87020-900, Brazil.
authors.forename: Werner C
authors.initials: WC
authors.lastname: Antunes
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.
authors.forename: Daniela P
authors.initials: DP
authors.lastname: Pinheiro
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.
authors.forename: Caroline
authors.initials: C
authors.lastname: Müller
authors.affiliation: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.
authors.forename: Marcelo E
authors.initials: ME
authors.lastname: Loureiro
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, 14476, Germany.
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
mesh_terms: D000222:Adaptation, Physiological; D002247:Carbon Isotopes; D002264:Carboxylic Acids / Q000378:metabolism; D055864:Droughts; D005740:Gases / Q000378:metabolism; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D055442:Metabolome; D055432:Metabolomics; D009928:Organ Specificity; D010641:Phenotype; D063245:Plant Development; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000166:cytology*; D018526:Plant Transpiration / Q000502:physiology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011198:Solanum tuberosum / Q000201:enzymology*; D013395:Sucrose / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics; D015854:Up-Regulation
chemical_list: D002247:Carbon Isotopes; D002264:Carboxylic Acids; D005740:Gases; D010940:Plant Proteins; D013395:Sucrose; D005964:Glucosyltransferases; C022699:sucrose synthase
keywords: Nicotiana tabacum; guard cell metabolism; organic acids; stomatal aperture; sucrose; sucrose synthase