title: Measuring whole plant CO2 exchange with the environment reveals opposing effects of the gin2-1 mutation in shoots and roots of Arabidopsis thaliana.
abstract: Using a cuvette for simultaneous measurement of net photosynthesis in above ground plant organs and root respiration we investigated the effect of reduced leaf glucokinase activity on plant carbon balance. The gin2-1 mutant of Arabidopsis thaliana is characterized by a 50% reduction of glucokinase activity in the shoot, while activity in roots is about fivefold higher and similar to wild type plants. High levels of sucrose accumulating in leaves during the light period correlated with elevated root respiration in gin2-1. Despite substantial respiratory losses in roots, growth retardation was moderate, probably because photosynthetic carbon fixation was simultaneously elevated in gin2-1. Our data indicate that futile cycling of sucrose in shoots exerts a reduction on net CO2 gain, but this is over-compensated by the prevention of exaggerated root respiration resulting from high sucrose concentration in leaf tissue.
authors.affiliation: a University of Stuttgart ; Institute of Biomaterials and biomolecular Systems; Department of Plant Biotechnology ; Stuttgart , Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Brauner
authors.forename: Simon
authors.initials: S
authors.lastname: Stutz
authors.forename: Martin
authors.initials: M
authors.lastname: Paul
authors.forename: Arnd G
authors.initials: AG
authors.lastname: Heyer
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D018526:Plant Transpiration / Q000235:genetics / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D002245:Carbon Dioxide; D006593:Hexokinase; C473630:ATHXK1 protein, Arabidopsis
keywords: Arabidopsis thaliana; FW, fresh weight; NPS, net photosynthesis; SEM, standard error of mean; WT, wild type; aeroponic culture; gin2; gin2–1, knockout mutant of hexokinase1; hexokinase mutant; net photosynthesis; root respiration; root-shoot ratio