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1. High efficient cyclic electron flow and functional supercomplexes in Chlamydomonas cells

Author

Joliot, Pierre, Sellés, Julien, Wollman, Françis-André, and Verméglio, André

Subjects
Physics - Biological Physics, Quantitative Biology - Subcellular Processes
Abstract

A very high rate for cyclic electron flow (CEF) around PSI (~180 s-1 or 210 s-1 in minimum medium or in the presence of a carbon source respectively) is measured in the presence of methyl viologen (MV) in intact cells of Chlamydomonas reinhardtii under anaerobic conditions. The observation of an efficient CEF in the presence of methyl viologen is in agreement with the previous results reports of Asada et al in broken chloroplasts (Plant Cell Physiol. 31(4) (1990) 557-564). From the analysis of the P700 and PC absorbance changes, we propose that a confinement between 2 PC molecules, 1 PSI and 1 cytb6f corresponding to a functional supercomplex is responsible for these high rates of CEF. Supercomplex formation is also observed in the absence of methyl viologen, but with lower maximal CEF rate (about 100 s-1) suggesting that this compound facilitates the mediation of electron transfer from PSI acceptors to the stromal side of cytb6f. Further analysis of CEF in mutants of Chlamydomonas defective in state transitions shows the requirement of a kinase-driven transition to state 2 to establish this functional supercomplex configuration. However, a movement of the LHCII antennae is not involved in this process. We discuss the possible involvement of auxiliary proteins, among which is a small cytb6f-associated polypeptide, the PETO protein, which is one of the targets of the STT7 kinase.

Published
2023
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6. High efficient cyclic electron flow and functional supercomplexes in Chlamydomonas cells

Author

Pierre, Joliot, Julien, Sellés, Françis-André, Wollman, and André, Verméglio

Subjects
Paraquat, Quantitative Biology - Subcellular Processes, Photosystem I Protein Complex, Chlamydomonas, Biophysics, FOS: Physical sciences, Electrons, Cell Biology, Biochemistry, Carbon, Biological Physics (physics.bio-ph), FOS: Biological sciences, Physics - Biological Physics, Subcellular Processes (q-bio.SC)
Abstract

A very high rate for cyclic electron flow (CEF) around PSI (~180 ssup-/sup1 or 210 ssup-1/supin minimum medium or in the presence of a carbon source respectively) is measured in the presence of methyl viologen (MV) in intact cells of Chlamydomonas reinhardtii under anaerobic conditions. The observation of an efficient CEF in the presence of methyl viologen is in agreement with the previous results reports of Asada et al. in broken chloroplasts (Plant Cell Physiol. 31(4) (1990) 557-564). From the analysis of the P700 and PC absorbance changes, we propose that a confinement between 2 PC molecules, 1 PSI and 1 cytbsub6/subf corresponding to a functional supercomplex is responsible for these high rates of CEF. Supercomplex formation is also observed in the absence of methyl viologen, but with lower maximal CEF rate (about 100 ssup-1/sup) suggesting that this compound facilitates the mediation of electron transfer from PSI acceptors to the stromal side of cytbsub6/subf. Further analysis of CEF in mutants of Chlamydomonas defective in state transitions shows the requirement of a kinase-driven transition to state 2 to establish this functional supercomplex configuration. However, a movement of the LHCII antennae is not involved in this process. We discuss the possible involvement of auxiliary proteins, among which is a small cytbsub6/subf-associated polypeptide, the PETO protein, which is one of the targets of the STT7 kinase.

Published
2023
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14. Legumes Symbioses: Absence of Nod Genes in Photosynthetic Bradyrhizobia

Author

Giraud, Eric, Moulin, Lionel, Vallenet, David, Barbe, Valérie, Cytryn, Eddie, Avarre, Jean-Christophe, Jaubert, Marianne, Simon, Damien, Cartieaux, Fabienne, Prin, Yves, Bena, Gilles, Hannibal, Laure, Fardoux, Joel, Kojadinovic, Mila, Vuillet, Laurie, Lajus, Aurélie, Cruveiller, Stéphane, Rouy, Zoe, Mangenot, Sophie, Segurens, Béatrice, Dossat, Carole, Franck, William L., Chang, Woo-Suk, Saunders, Elizabeth, Bruce, David, Richardson, Paul, Normand, Philippe, Dreyfus, Bernard, Pignol, David, Stacey, Gary, Emerich, David, Verméglio, André, Médigue, Claudine, and Sadowsky, Michael

Published
2007
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28. The cyst-dividing bacterium Ramlibacter tataouinensis TTB310 genome reveals a well-stocked toolbox for adaptation to a desert environment.

Author

Gilles De Luca, Mohamed Barakat, Philippe Ortet, Sylvain Fochesato, Cécile Jourlin-Castelli, Mireille Ansaldi, Béatrice Py, Gwennaele Fichant, Pedro M Coutinho, Romé Voulhoux, Olivier Bastien, Eric Maréchal, Bernard Henrissat, Yves Quentin, Philippe Noirot, Alain Filloux, Vincent Méjean, Michael S DuBow, Frédéric Barras, Valérie Barbe, Jean Weissenbach, Irina Mihalcescu, André Verméglio, Wafa Achouak, and Thierry Heulin

Subjects
Medicine, Science
Abstract

Ramlibacter tataouinensis TTB310(T) (strain TTB310), a betaproteobacterium isolated from a semi-arid region of South Tunisia (Tataouine), is characterized by the presence of both spherical and rod-shaped cells in pure culture. Cell division of strain TTB310 occurs by the binary fission of spherical "cyst-like" cells ("cyst-cyst" division). The rod-shaped cells formed at the periphery of a colony (consisting mainly of cysts) are highly motile and colonize a new environment, where they form a new colony by reversion to cyst-like cells. This unique cell cycle of strain TTB310, with desiccation tolerant cyst-like cells capable of division and desiccation sensitive motile rods capable of dissemination, appears to be a novel adaptation for life in a hot and dry desert environment. In order to gain insights into strain TTB310's underlying genetic repertoire and possible mechanisms responsible for its unusual lifestyle, the genome of strain TTB310 was completely sequenced and subsequently annotated. The complete genome consists of a single circular chromosome of 4,070,194 bp with an average G+C content of 70.0%, the highest among the Betaproteobacteria sequenced to date, with total of 3,899 predicted coding sequences covering 92% of the genome. We found that strain TTB310 has developed a highly complex network of two-component systems, which may utilize responses to light and perhaps a rudimentary circadian hourglass to anticipate water availability at the dew time in the middle/end of the desert winter nights and thus direct the growth window to cyclic water availability times. Other interesting features of the strain TTB310 genome that appear to be important for desiccation tolerance, including intermediary metabolism compounds such as trehalose or polyhydroxyalkanoate, and signal transduction pathways, are presented and discussed.

Published
2011
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43. Tribute in memory of Jacques Breton (1942–2018)

Author

Eliane Nabedryk, André Verméglio, Paul Mathis, Section de Bioénergétique Département de Biologie Cellulaire et Moléculaire, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Microbiologie Environnementale et Moléculaire (MEM), Institut de Biosciences et Biotechnologies d'Aix-Marseille (ex-IBEB) (BIAM), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
0106 biological sciences, [SDV]Life Sciences [q-bio], Photosynthetic Reaction Center Complex Proteins, Biophysics, Tribute, Plant Science, 01 natural sciences, Biochemistry, History, 21st Century, Atomic energy commission, Visual arts, 03 medical and health sciences, Professional life, Sociology, Photosynthesis, 030304 developmental biology, 0303 health sciences, Bacteria, Cell Biology, General Medicine, Pigments, Biological, History, 20th Century, Plants, Energy Transfer, Photosynthetic bacteria, 010606 plant biology & botany
Abstract

International audience; Jacques Breton spent his 39 years of professional life at Saclay, a center of the French Atomic Energy Commission. He studied photosynthesis with various advanced biophysical tools, often developed by himself and his numerous coworkers, obtaining a large number of new information on the structure and the functioning of antenna and of reaction centers of plants and bacteria: excitation migration in the antenna, orientation of molecules, rate of primary reactions, binding of pigments and electron transfer cofactors. Although it is much too short to illustrate his impressive work, we hope that this contribution will help maintaining the souvenir of Jacques Breton as an active and enthusiastic person, full of qualities, devoted to research and to his family as well. We include personal comments from N. E. Geacintov, A. Dobek, W. Leibl, M. Vos and W. W. Parson.

Published
2019

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