title: Plastid terminal oxidase (PTOX) has the potential to act as a safety valve for excess excitation energy in the alpine plant species Ranunculus glacialis L.
abstract: Ranunculus glacialis leaves were tested for their plastid terminal oxidase (PTOX) content and electron flow to photorespiration and to alternative acceptors. In shade-leaves, the PTOX and NAD(P)H dehydrogenase (NDH) content were markedly lower than in sun-leaves. Carbon assimilation/light and Ci response curves were not different in sun- and shade-leaves, but photosynthetic capacity was the highest in sun-leaves. Based on calculation of the apparent specificity factor of ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco), the magnitude of alternative electron flow unrelated to carboxylation and oxygenation of Rubisco correlated to the PTOX content in sun-, shade- and growth chamber-leaves. Similarly, fluorescence induction kinetics indicated more complete and more rapid reoxidation of the plastoquinone (PQ) pool in sun- than in shade-leaves. Blocking electron flow to assimilation, photorespiration and the Mehler reaction with appropriate inhibitors showed that sun-leaves were able to maintain higher electron flow and PQ oxidation. The results suggest that PTOX can act as a safety valve in R. glacialis leaves under conditions where incident photon flux density (PFD) exceeds the growth PFD and under conditions where the plastoquinone pool is highly reduced. Such conditions can occur frequently in alpine climates due to rapid light and temperature changes.
authors.affiliation: Ecologie, Systématique et Evolution, Université Paris-Sud 11, UMR-CNRS 8079, Bâtiment 362, 91405 Orsay cedex, France.
authors.forename: Constance
authors.initials: C
authors.lastname: Laureau
authors.affiliation: Institut de Biologie des Plantes, Université Paris-Sud 11, UMR-CNRS 8618, Bâtiment 630, 91405, Orsay cedex, France.
authors.forename: Rosine
authors.initials: R
authors.lastname: De Paepe
authors.affiliation: Ecologie, Systématique et Evolution, Université Paris-Sud 11, UMR-CNRS 8079, Bâtiment 362, 91405, Orsay cedex, France.
authors.forename: Gwendal
authors.initials: G
authors.lastname: Latouche
authors.affiliation: Ecologie, Systématique et Evolution, Université Paris-Sud 11, UMR-CNRS 8079, Bâtiment 362, 91405, Orsay cedex, France.
authors.forename: Maria
authors.initials: M
authors.lastname: Moreno-Chacón
authors.affiliation: Unité Mixte Recherche 5168, Laboratoire Physiologie Cellulaire et Végétale, Centre National Recherche Scientifique, F-38054, Grenoble, France.|Commissariat à l'Energie Atomique et Energies Alternatives, l'Institut de Recherches en Technologies et Sciences pour le Vivant, F-38054, Grenoble, France.|Université Grenoble 1, F-38041, Grenoble, France.|Institut National Recherche Agronomique, UMR1200, F-38054, Grenoble, France.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Finazzi
authors.affiliation: Unité Mixte Recherche 5168, Laboratoire Physiologie Cellulaire et Végétale, Centre National Recherche Scientifique, F-38054, Grenoble, France.|Commissariat à l'Energie Atomique et Energies Alternatives, l'Institut de Recherches en Technologies et Sciences pour le Vivant, F-38054, Grenoble, France.|Université Grenoble 1, F-38041, Grenoble, France.|Institut National Recherche Agronomique, UMR1200, F-38054, Grenoble, France.
authors.forename: Marcel
authors.initials: M
authors.lastname: Kuntz
authors.affiliation: Ecologie, Systématique et Evolution, Université Paris-Sud 11, UMR-CNRS 8079, Bâtiment 362, 91405, Orsay cedex, France.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cornic
authors.affiliation: Ecologie, Systématique et Evolution, Université Paris-Sud 11, UMR-CNRS 8079, Bâtiment 362, 91405, Orsay cedex, France.
authors.forename: Peter
authors.initials: P
authors.lastname: Streb
mesh_terms: D010088:Oxidoreductases / Q000378:metabolism / Q000502:physiology*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism / Q000502:physiology*; D018087:Plastids / Q000201:enzymology* / Q000378:metabolism; D031947:Ranunculus / Q000201:enzymology*; D013312:Stress, Physiological; D013472:Sunlight
chemical_list: D010940:Plant Proteins; D010088:Oxidoreductases
keywords: alternative electron flow; photorespiration; photosynthesis; stress tolerance