title: C2 photosynthesis generates about 3-fold elevated leaf CO2 levels in the C3-C4 intermediate species Flaveria pubescens.
abstract: Formation of a photorespiration-based CO2-concentrating mechanism in C3-C4 intermediate plants is seen as a prerequisite for the evolution of C4 photosynthesis, but it is not known how efficient this mechanism is. Here, using in vivo Rubisco carboxylation-to-oxygenation ratios as a proxy to assess relative intraplastidial CO2 levels is suggested. Such ratios were determined for the C3-C4 intermediate species Flaveria pubescens compared with the closely related C3 plant F. cronquistii and the C4 plant F. trinervia. To this end, a model was developed to describe the major carbon fluxes and metabolite pools involved in photosynthetic-photorespiratory carbon metabolism and used quantitatively to evaluate the labelling kinetics during short-term (14)CO2 incorporation. Our data suggest that the photorespiratory CO2 pump elevates the intraplastidial CO2 concentration about 3-fold in leaves of the C3-C4 intermediate species F. pubescens relative to the C3 species F. cronquistii.
authors.affiliation: Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia hermann.bauwe@uni-rostock.de olav.keerberg@emu.ee.
authors.forename: Olav
authors.initials: O
authors.lastname: Keerberg
authors.affiliation: Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia.
authors.forename: Tiit
authors.initials: T
authors.lastname: Pärnik
authors.affiliation: Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51014 Tartu, Estonia.
authors.forename: Hiie
authors.initials: H
authors.lastname: Ivanova
authors.affiliation: Center for Conservation and Sustainable Development, Missouri Botanical Garden, St. Louis, MO 63166-0299, USA.
authors.forename: Burgund
authors.initials: B
authors.lastname: Bassüner
authors.affiliation: Department of Plant Physiology, University of Rostock, 18051 Rostock, Germany hermann.bauwe@uni-rostock.de olav.keerberg@emu.ee.
authors.forename: Hermann
authors.initials: H
authors.lastname: Bauwe
mesh_terms: D005075:Biological Evolution; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000032:analysis; D019069:Cell Respiration; D037142:Flaveria / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D008954:Models, Biological; D010788:Photosynthesis; D010802:Phylogeny; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D013403:Sugar Phosphates / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D010940:Plant Proteins; D013403:Sugar Phosphates; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase
keywords: 14CO2 labelling; C3–C4 intermediate plants; Flaveria; carbon-concentrating mechanism; glycine decarboxylation; photorespiration; photosynthesis.