title: Tobacco guard cells fix CO2 by both Rubisco and PEPcase while sucrose acts as a substrate during light-induced stomatal opening.
abstract: Transcriptomic and proteomic studies have improved our knowledge of guard cell function; however, metabolic changes in guard cells remain relatively poorly understood. Here we analysed metabolic changes in guard cell-enriched epidermal fragments from tobacco during light-induced stomatal opening. Increases in sucrose, glucose and fructose were observed during light-induced stomatal opening in the presence of sucrose in the medium while no changes in starch were observed, suggesting that the elevated fructose and glucose levels were a consequence of sucrose rather than starch breakdown. Conversely, reduction in sucrose was observed during light- plus potassium-induced stomatal opening. Concomitant with the decrease in sucrose, we observed an increase in the level as well as in the (13) C enrichment in metabolites of, or associated with, the tricarboxylic acid cycle following incubation of the guard cell-enriched preparations in (13) C-labelled bicarbonate. Collectively, the results obtained support the hypothesis that sucrose is catabolized within guard cells in order to provide carbon skeletons for organic acid production. Furthermore, they provide a qualitative demonstration that CO2 fixation occurs both via ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPcase). The combined data are discussed with respect to current models of guard cell metabolism and function.
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.|Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, 14476, Germany.
authors: Danilo M
authors: DM
authors: Daloso
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.|Departamento de Biologia, Universidade Estadual de Maringá, Maringá, Paraná, 87020-900, Brazil.
authors: Werner C
authors: WC
authors: Antunes
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.
authors: Daniela P
authors: DP
authors: Pinheiro
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.
authors: Jardel P
authors: JP
authors: Waquim
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.
authors: Wagner L
authors: WL
authors: Araújo
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.
authors: Marcelo E
authors: ME
authors: Loureiro
authors: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, 14476, Germany.
authors: Alisdair R
authors: AR
authors: Fernie
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, Minas Gerais, Brazil.|Departamento de Botânica, Universidade de Brasilia, Brasilia, Distrito Federal, 70910-900, Brazil.
authors: Thomas C R
authors: TC
authors: Williams
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D007700:Kinetics; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism*; D059828:Plant Cells / Q000378:metabolism / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology* / Q000528:radiation effects; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide; D013395:Sucrose; D010730:Phosphoenolpyruvate Carboxylase; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Stable isotope labelling; guard cell metabolism; organic acids