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.

• Published in: Plant, Cell & Environment
• Main Authors: Laureau, Constance, De Paepe, Rosine, Latouche, Gwendal, Moreno-Chacón, Maria, Finazzi, Giovanni, Kuntz, Marcel, Cornic, Gabriel, Streb, Peter
• Other Authors: Ecologie Systématique et Evolution (ESE), Université Paris-Sud - Paris 11 (UP11)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS), Institut de biotechnologie des plantes (IBP), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physiologie cellulaire végétale (LPCV), Université Joseph Fourier - Grenoble 1 (UJF)-Institut National de la Recherche Agronomique (INRA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Institut de Biosciences et de Biotechnologies de Grenoble (ex-IRTSV) (BIG), Institut National de la Santé et de la Recherche Médicale (INSERM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: alternative electron flow; photorespiration; alpine plant; Ranunculus glacialis; photosynthesis; carbon assimilation; stress tolerance; sun-leaves; shade-leaves; enzymatic activity; plastid terminal oxidase; NADPH dehydrogenase; [SDV.BBM]Life Sciences [q-bio]/Biochemistry; Molecular Biology
• Online Access: https://hal.archives-ouvertes.fr/hal-00789674; https://doi.org/10.1111/pce.12059

International audience 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 C(i) 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.