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Accueil > Départements > Biochimie, Biophysique et Biologie Structurale > Diana KIRILOVSKY : Mécanismes régulateurs chez les organismes photosynthétiques

Publications de l’équipe


  • P. I. Calzadilla, F. Muzzopappa, P. Setif, et D. Kirilovsky, « Different roles for ApcD and ApcF in Synechococcus elongatus and Synechocystis sp. PCC 6803 phycobilisomes », Biochimica Et Biophysica Acta-Bioenergetics, vol. 1860, nᵒ 6, p. 488-498, juin 2019.
    Résumé : The phycobilisome, the cyanobacterial light harvesting complex, is a huge phycobiliprotein containing extra membrane complex, formed by a core from which rods radiate. The phycobilisome has evolved to efficiently absorb sun energy and transfer it to the photosystems via the last energy acceptors of the phycobilisome, ApcD and ApcE. ApcF also affects energy transfer by interacting with ApcE. In this work we studied the role of ApcD and ApcF in energy transfer and state transitions in Synechococcus elongatus and Synechocystis PCC6803. Our results demonstrate that these proteins have different roles in both processes in the two strains. The lack of ApcD and ApcF inhibits state transitions in Synechocystis but not in S. elongatus. In addition, lack of ApcF decreases energy transfer to both photosystems only in Synechocystis, while the lack of ApcD alters energy transfer to photosystem I only in S. elongatus. Thus, conclusions based on results obtained in one cyanobacterial strain cannot be systematically transferred to other strains and the putative role(s) of phycobilisomes in state transitions need to be reconsidered.
    Mots-clés : anacystis-nidulans, B3S, chlamydomonas-reinhardtii, Cyanobacteria, Energy transfer, excitation-energy transfer, light, MROP, orange carotenoid protein, photosystem-ii fluorescence, Phycobilisome, porphyridium-cruentum, quenching mechanisms, red alga, State transition, state transitions.

  • P. I. Calzadilla, J. Zhan, P. Sétif, C. Lemaire, D. Solymosi, N. Battchikova, Q. Wang, et D. Kirilovsky, « The cytochrome b6f complex is not involved in cyanobacterial state transitions », The Plant Cell, vol. 31, nᵒ 4, p. 911-931, avr. 2019.
    Résumé : Photosynthetic organisms need to sense and respond to fluctuating environmental conditions to avoid the formation of dangerous reactive oxygen species. The excitation energy arriving at each photosystem permanently changes due to variations of intensity and spectral properties of the absorbed light. Cyanobacteria, like plants and algae, have developed a mechanism, named state transitions, that sense and respond to these fluctuating conditions. In this work, we characterize the role of the cytochrome b6f and phosphorylation reactions in cyanobacterial state transitions using Synechococcus elongatus PCC 7942 and Synechocystis PCC 6803. A large Photosystem II fluorescence quenching was observed in State II which seems not to be related to spillover. This membrane-associated process was inhibited by betaine, sucrose and high concentrations of phosphate. Then, using different chemicals affecting the PQ pool redox state and the activity of the cytochrome b6f, we demonstrated that this complex is not involved in S. elongatus and Synechocystis PCC6803 state transitions. Finally, by constructing and characterizing 21 kinase and phosphatase mutants and using chemical inhibitors, it was clearly shown that phosphorylation reactions are not essential in cyanobacterial state transitions. Thus, signal transduction is completely different in cyanobacteria and plant (green alga) state transitions.
    Mots-clés : B3S, MROP.

  • F. Chauffour, M. Bailly, F. Perreau, G. Cueff, H. Suzuki, B. Collet, A. Frey, G. Clément, L. Soubigou-Taconnat, T. Balliau, A. Krieger-Liszkay, L. Rajjou, et A. Marion-Poll, « Multi-omics analysis reveals sequential roles for ABA during seed maturation », Plant Physiology, vol. 180, nᵒ 2, p. 1198-1218, avr. 2019.
    Résumé : Abscisic acid (ABA) is an important hormone for seed development and germination whose physiological action is modulated by its endogenous levels. Cleavage of carotenoid precursors by 9-cis epoxycarotenoid dioxygenase (NCED) and inactivation of ABA by ABA 8'-hydroxylase (CYP707A) are key regulatory metabolic steps. In Arabidopsis (Arabidopsis thaliana), both enzymes are encoded by multigene families, having distinctive expression patterns. To evaluate the genome-wide impact of ABA deficiency in developing seeds at the maturation stage when dormancy is induced, we used a nced2569 quadruple mutant in which ABA deficiency is mostly restricted to seeds, thus limiting the impact of maternal defects on seed physiology. ABA content was very low in nced2569 seeds, similar to the severe mutant aba2; unexpectedly, ABA glucose ester was detected in aba2 seeds, suggesting the existence of an alternative metabolic route. Hormone content in nced2569 seeds compared with nced259 and wild-type strongly suggested that specific expression of NCED6 in the endosperm is mainly responsible for ABA production. In accordance, transcriptome analyses revealed broad similarities in gene expression between nced2569 and either wild type or nced259 developing seeds. Gene ontology enrichments revealed a large spectrum of ABA activation targets involved in reserve storage and desiccation tolerance, and repression of photosynthesis and cell cycle. Proteome and metabolome profiles in dry nced2569 seeds, compared with wild-type and cyp707a1a2 seeds, also highlighted an inhibitory role of ABA on remobilisation of reserves, ROS production, and protein oxidation. Down-regulation of these oxidative processes by ABA may have an essential role in dormancy control.
    Mots-clés : 9-cis-epoxycarotenoid dioxygenase, abscisic-acid biosynthesis, arabidopsis seeds, B3S, dormancy, drought tolerance, genome-wide analysis, mass-spectrometry, metabolism, MROP, protein oxidation, signaling networks.

  • C. Djediat, K. Feilke, A. Brochard, L. Caramelle, S. K. Tiam, P. Sétif, T. Gauvrit, C. Yéprémian, A. Wilson, L. Talbot, B. Marie, D. Kirilovsky, et C. Bernard, « Light stress in green and red Planktothrix strains: The orange carotenoid protein and its related photoprotective mechanism », Biochimica Et Biophysica Acta. Bioenergetics, juin 2019.
    Résumé : Photosynthetic organisms need to sense and respond to fluctuating environmental conditions, to perform efficient photosynthesis and avoid the formation of harmful reactive oxygen species. Cyanobacteria have developed a photoprotective mechanism that decreases the energy arriving at the reaction centers by increasing thermal energy dissipation at the level of the phycobilisome, the extramembranal light-harvesting antenna. This mechanism is triggered by the photoactive orange carotenoid protein (OCP). In this study, we characterized OCP and the related photoprotective mechanism in non-stressed and light-stressed cells of three different strains of Planktothrix that can form impressive blooms. In addition to changing lake ecosystemic functions and biodiversity, Planktothrix blooms can have adverse effects on human and animal health as they produce toxins (e.g., microcystins). Three Planktothrix strains were selected: two green strains, PCC 10110 (microcystin producer) and PCC 7805 (non-microcystin producer), and one red strain, PCC 7821. The green strains colonize shallow lakes with higher light intensities while red strains proliferate in deep lakes. Our study allowed us to conclude that there is a correlation between the ecological niche in which these strains proliferate and the rates of induction and recovery of OCP-related photoprotection. However, differences in the resistance to prolonged high-light stress were correlated to a better replacement of damaged D1 protein and not to differences in OCP photoprotection. Finally, microcystins do not seem to be involved in photoprotection as was previously suggested.
    Mots-clés : B3S, Cyanobacteria, Fluorescence, Microcystin, MROP, Orange carotenoid protein, Planktothrix.

  • M. Grabsztunowicz, P. Mulo, F. Baymann, R. Mutoh, G. Kurisu, P. Sétif, P. Beyer, et A. Krieger-Liszkay, « Electron transport pathways in isolated chromoplasts from Narcissus pseudonarcissus L », The Plant Journal: For Cell and Molecular Biology, vol. 99, nᵒ 2, p. 245-256, mars 2019.
    Résumé : During daffodil flower development, chloroplasts differentiate into photosynthetically inactive chromoplasts having lost functional photosynthetic reaction centers. Chromoplasts exhibit a respiratory activity reducing oxygen to water and generating ATP. Immunoblots revealed the presence of the plastid terminal oxidase (PTOX), the NAD(P)H dehydrogenase (NDH) complex, the cytochrome b6 f complex, ATP synthase and several isoforms of ferredoxin-NADP+ oxidoreductase (FNR) and of ferredoxin (Fd). Fluorescence spectroscopy allowed the detection of chlorophyll a in the cytochrome b6 f complex. Here we characterize the electron transport pathway of chromorespiration by using specific inhibitors for the NDH complex, the cytochrome b6 f complex, FNR and redox-inactive Fd in which the iron was replaced by gallium. Our data suggest an electron flow via two separate pathways, both reducing plastoquinone and using PTOX as oxidase. The first oxidizes NADPH via FNR, Fd, and cytochrome bh of the cytochrome b6 f complex and does not result in the pumping of protons across the membrane. In the second, electron transport takes place via the NDH complex using both, NADH and NADPH, as electron donor. FNR and Fd are not involved in this pathway. The NDH-complex is responsible for the generation of the proton gradient. We propose a model for chromorespiration which may also be relevant for the understanding of chlororespiration and for the characterization of the electron input from Fd to the cytochrome b6 f complex during cyclic electron transport in chloroplasts. This article is protected by copyright. All rights reserved.
    Mots-clés : B3S, chromoplast, chromorespiration, cytochrome b6f complex, electron transport chain, MROP, Narcissus pseudonarcissus, NDH, PTOX.

  • D. Harris, A. Wilson, F. Muzzopappa, N. N. Sluchanko, T. Friedrich, E. G. Maksimov, D. Kirilovsky, et N. Adir, « Structural Rearrangements in the C-Terminal Domain Homolog of Orange Carotenoid Protein are Crucial for Carotenoid Transfer », Biophysical Journal, vol. 116, nᵒ 3, p. 47A-47A, févr. 2019.

  • P. E. Konold, I. H. M. van Stokkum, F. Muzzopappa, A. Wilson, M. - L. Groot, D. Kirilovsky, et J. T. M. Kennis, « Photoactivation Mechanism, Timing of Protein Secondary Structure Dynamics and Carotenoid Translocation in the Orange Carotenoid Protein », Journal of the American Chemical Society, vol. 141, nᵒ 1, p. 520-530, janv. 2019.
    Résumé : The orange carotenoid protein (OCP) is a two-domain photoactive protein that noncovalently binds an echinenone (ECN) carotenoid and mediates photoprotection in cyanobacteria. In the dark, OCP assumes an orange, inactive state known as OCPO; blue light illumination results in the red active state, known as OCPR. The OCPR state is characterized by large-scale structural changes that involve dissociation and separation of C-terminal and N-terminal domains accompanied by carotenoid translocation into the N-terminal domain. The mechanistic and dynamic-structural relations between photon absorption and formation of the OCPR state have remained largely unknown. Here, we employ a combination of time-resolved UV-visible and (polarized) mid-infrared spectroscopy to assess the electronic and structural dynamics of the carotenoid and the protein secondary structure, from femtoseconds to 0.5 ms. We identify a hereto unidentified carotenoid excited state in OCP, the so-called S* state, which we propose to play a key role in breaking conserved hydrogen-bond interactions between carotenoid and aromatic amino acids in the binding pocket. We arrive at a comprehensive reaction model where the hydrogen-bond rupture with conserved aromatic side chains at the carotenoid beta 1-ring in picoseconds occurs at a low yield of <1%, whereby the beta 1-ring retains a trans configuration with respect to the conjugated pi-electron chain. This event initiates structural changes at the N-terminal domain in 1 mu s, which allow the carotenoid to translocate into the N-terminal domain in 10 mu s. We identified infrared signatures of helical elements that dock on the C-terminal domain beta-sheet in the dark and unfold in the light to allow domain separation. These helical elements do not move within the experimental range of 0.5 ms, indicating that domain separation occurs on longer time scales, lagging carotenoid translocation by at least 2 decades of time.
    Mots-clés : B3S, deactivation, domain, energy-transfer, femtosecond, MROP, photoprotection, phycobilisome, proton-transfer, rearrangements, reveals, ultrafast spectroscopy.

  • A. Krieger-Liszkay, K. Krupinska, et G. Shimakawa, « The impact of photosynthesis on initiation of leaf senescence », Physiologia Plantarum, vol. 166, nᵒ 1, p. 148-164, janv. 2019.
    Résumé : Senescence is the last stage of leaf development preceding the death of the organ, and it is important for nutrient remobilization and for feeding sink tissues. There are many reports on leaf senescence but the mechanisms initiating leaf senescence are still poorly understood. Leaf senescence is affected by many environmental factors and seems to vary in different species and even varieties of plants, which makes it difficult to generalize the mechanism. Here, we give an overview on studies reporting about alterations in the composition of the photosynthetic electron transport chain in chloroplasts during senescence. We hypothesize that alternative electron flow and related generation of the proton motive force required for ATP synthesis become increasingly important during progression of senescence. We address the generation of reactive oxygen species (ROS) in chloroplasts in the initiation of senescence, retrograde signaling from the chloroplast to the nucleus and ROS-dependent signaling associated with leaf senescence. Finally, differences between natural senescence and dark-induced senescence are pointed out and a few ideas for increasing crop yields by increasing the chloroplast lifespan are presented. This article is protected by copyright. All rights reserved.
    Mots-clés : a/b-binding proteins, arabidopsis-thaliana, B3S, cyclic electron flow, harvesting complex-ii, hydrogen-peroxide, MROP, oxidative stress, photooxidative-stress, plant photosystem-i, singlet oxygen, superoxide-dismutase.

  • A. Mezzetti, M. T. A. Alexandre, A. Thurotte, A. Wilson, M. Gwizdala, et D. Kirilovsky, « Two-Step Structural Changes in Orange Carotenoid Protein Photoactivation Revealed by Time Resolved FTIR Spectroscopy », The Journal of Physical Chemistry. B, vol. 123, nᵒ 15, p. 3259-3266, avr. 2019.
    Résumé : The Orange Carotenoid Protein (OCP), which is essential in cyanobacterial photoprotection, is the first photoactive protein containing a carotenoid as an active chromophore. Static and time-resolved FTIR difference spectroscopy under continuous illumination at different temperatures was applied to investigate its photoactivation mechanism. Here we demonstrate that in the OCP, the photo-induced conformational change involves at least two different steps, both in the second timescale at 277 K. Each step involves partial reorganization of α-helix domains. At early illumination times the disappearance of a non-solvent exposed α-helix (negative 1651 cm-1 band) is observed. At longer times, a 1644 cm-1 negative band starts to bleach, showing the disappearance of a solvent-exposed α-helix, either the N-terminal extension and/or the C-terminal tail. A kinetic analysis clearly shows that these two events are asynchronous. Minor modifications in the overall FTIR difference spectra confirm that the global protein conformational change consists of - at least - two asynchronous contributions. Comparison of spectra recorded in H2O and D2O suggests that internal water molecules may contribute to the photoactivation mechanism.
    Mots-clés : B3S, domain, forms, MROP, reorganization, water.

  • T. Motomura, L. Zuccarello, P. Sétif, A. Boussac, Y. Umena, D. Lemaire, J. N. Tripathy, M. Sugiura, R. Hienerwadel, J. - R. Shen, et C. Berthomieu, « An alternative plant-like cyanobacterial ferredoxin with unprecedented structural and functional properties: Ferredoxin with low Em discriminating against FNR », Biochimica Et Biophysica Acta. Bioenergetics, p. 148084, sept. 2019.
    Résumé : Photosynthetic [2Fe-2S] plant-type ferredoxins have a central role in electron transfer between the photosynthetic chain and various metabolic pathways. Several genes are coding for [2Fe2S] ferredoxins in cyanobacteria, with four in the thermophilic cyanobacterium Thermosynechococcus elongatus. The structure and functional properties of the major ferredoxin Fd1 are well known but data on the other ferredoxins are scarce. We report the structural and functional properties of a novel minor type ferredoxin, Fd2 of T. elongatus, homologous to Fed4 from Synechocystis sp. PCC 6803. Remarkably, the midpoint potential of Fd2, Em = -440 mV, is lower than that of Fd1, Em = -372 mV. However, while Fd2 can efficiently react with photosystem I or nitrite reductase, time-resolved spectroscopy shows that Fd2 has a very low capacity to reduce ferredoxin-NADP+ oxidoreductase (FNR). These unique Fd2 properties are discussed in relation with its structure, solved at 1.38 Å resolution. The Fd2 structure significantly differs from other known ferredoxins structures in loop 2, N-terminal region, hydrogen bonding networks and surface charge distributions. UV-Vis, EPR, and Mid- and Far-IR data also show that the electronic properties of the [2Fe2S] cluster of Fd2 and its interaction with the protein differ from those of Fd1 both in the oxidized and reduced states. The structural analysis allows to propose that valine in the motif Cys53ValAsnCys56 of Fd2 and the specific orientation of Phe72, explain the electron transfer properties of Fd2. Strikingly, the nature of these residues correlates with different phylogenetic groups of cyanobacterial Fds. With its low redox potential and its discrimination against FNR, Fd2 exhibits a unique capacity to direct efficiently photosynthetic electrons to metabolic pathways not dependent on FNR.
    Mots-clés : Alternative ferredoxin, B3S, Far-infrared of iron‑sulfur center, MROP, Photosynthetic electron transfer, PS2, Spectro-electrochemistry, UV–vis kinetics, X-ray structure.

  • F. Muzzopappa, A. Wilson, et D. Kirilovsky, « Interdomain interactions reveal the molecular evolution of the orange carotenoid protein », Nature Plants, sept. 2019.
    Résumé : The photoactive orange carotenoid protein (OCP) is a blue-light intensity sensor involved in cyanobacterial photoprotection. Three OCP families co-exist (OCPX, OCP1 and OCP2), having originated from the fusion of ancestral domain genes. Here, we report the characterization of an OCPX and the evolutionary characterization of OCP paralogues focusing on the role of the linker connecting the domains. The addition of the linker with specific amino acids enabled the photocycle of the OCP ancestor. OCPX is the paralogue closest to this ancestor. A second diversification gave rise to OCP1 and OCP2. OCPX and OCP2 present fast deactivation and weak antenna interaction. In OCP1, OCP deactivation became slower and interaction with the antenna became stronger, requiring a further protein to detach OCP from the antenna and accelerate its deactivation. OCP2 lost the tendency to dimerize, unlike OCPX and OCP1, and the role of its linker is slightly different, giving less controlled photoactivation.
    Mots-clés : B3S, MROP.

  • J. M. Schuller, J. A. Birrell, H. Tanaka, T. Konuma, H. Wulflhorst, N. Cox, S. K. Schuller, J. Thiemann, W. Lubitz, P. Setif, T. Ikegamis, B. D. Engel, G. Kurisu, et M. M. Nowaczyk, « Structural adaptations of photosynthetic complex I enable ferredoxin-dependent electron transfer », Science, vol. 363, nᵒ 6424, p. 257-+, janv. 2019.
    Résumé : Photosynthetic complex I enables cyclic electron flow around photosystem I, a regulatory mechanism for photosynthetic energy conversion. We report a 3.3-angstrom-resolution cryo-electron microscopy structure of photosynthetic complex I from the cyanobacterium Thermosynechococcus elongatus. The model reveals structural adaptations that facilitate binding and electron transfer from the photosynthetic electron carrier ferredoxin. By mimicking cyclic electron flow with isolated components in vitro, we demonstrate that ferredoxin directly mediates electron transfer between photosystem I and complex I, instead of using intermediates such as NADPH (the reduced form of nicotinamide adenine dinucleotide phosphate). A large rate constant for association of ferredoxin to complex I indicates efficient recognition, with the protein subunit NdhS being the key component in this process.
    Mots-clés : B3S, crystal-structure, dehydrogenase-like complex, domain-like fold, flash-absorption-spectroscopy, iron-sulfur clusters, mitochondrial nadh, MROP, photosystem-i, quinone oxidoreductase ndh-1, synechocystis sp pcc-6803, ubiquinone oxidoreductase.

  • P. Sétif, A. Boussac, et A. Krieger-Liszkay, « Near-infrared in vitro measurements of photosystem I cofactors and electron-transfer partners with a recently developed spectrophotometer », Photosynthesis Research, sept. 2019.
    Résumé : A kinetic-LED-array-spectrophotometer (Klas) was recently developed for measuring in vivo redox changes of P700, plastocyanin (PCy), and ferredoxin (Fd) in the near-infrared (NIR). This spectrophotometer is used in the present work for in vitro light-induced measurements with various combinations of photosystem I (PSI) from tobacco and two different cyanobacteria, spinach plastocyanin, cyanobacterial cytochrome c6 (cyt. c6), and Fd. It is shown that cyt. c6 oxidation contributes to the NIR absorption changes. The reduction of (FAFB), the terminal electron acceptor of PSI, was also observed and the shape of the (FAFB) NIR difference spectrum is similar to that of Fd. The NIR difference spectra of the electron-transfer cofactors were compared between different organisms and to those previously measured in vivo, whereas the relative absorption coefficients of all cofactors were determined by using single PSI turnover conditions. Thus, the (840 nm minus 965 nm) extinction coefficients of the light-induced species (oxidized minus reduced for PC and cyt. c6, reduced minus oxidized for (FAFB), and Fd) were determined with values of 0.207 ± 0.004, - 0.033 ± 0.006, - 0.036 ± 0.008, and - 0.021 ± 0.005 for PCy, cyt. c6, (FAFB) (single reduction), and Fd, respectively, by taking a reference value of + 1 for P700+. The fact that the NIR P700 coefficient is larger than that of PCy and much larger than that of other contributing species, combined with the observed variability in the NIR P700 spectral shape, emphasizes that deconvolution of NIR signals into different components requires a very precise determination of the P700 spectrum.
    Mots-clés : B3S, Cytochrome c 6, Ferredoxin, Infrared spectral deconvolution, MROP, P700, Photosystem I terminal acceptor, Plastocyanin, PS2.

  • Y. B. Slonimskiy, F. Muzzopappa, E. G. Maksimov, A. Wilson, T. Friedrich, D. Kirilovsky, et N. N. Sluchanko, « Light-controlled carotenoid transfer between water-soluble proteins related to cyanobacterial photoprotection », Febs Journal, vol. 286, nᵒ 10, p. 1908-1924, mai 2019.
    Résumé : Carotenoids are lipophilic pigments with multiple biological functions from coloration to vision and photoprotection. Still, the number of water-soluble carotenoid-binding proteins described to date is limited, and carotenoid transport and carotenoprotein maturation processes are largely underexplored. Recent studies revealed that CTDHs, which are natural homologs of the C-terminal domain (CTD) of the orange carotenoid protein (OCP), a photoswitch involved in cyanobacterial photoprotection, are able to bind carotenoids, with absorption shifted far into the red region of the spectrum. Despite the recent discovery of their participation in carotenoid transfer processes, the functional roles of the diverse family of CTDHs are not wellunderstood. Here, we characterized CTDH carotenoproteins from Anabaenavariabilis (AnaCTDH) and Thermosynechococcuselongatus and examined their ability to participate in carotenoid transfer processes with a set of OCP-derived proteins. This revealed that carotenoid transfer occurs in several directions guided by different affinities for carotenoid and specific protein-protein interactions. We show that CTDHs have higher carotenoid affinity compared to the CTD of OCP from Synechocystis, which results in carotenoid translocation from the CTD into CTDH via a metastable heterodimer intermediate. Activation of OCP by light, or mutagenesis compromising the OCP structure, provides AnaCTDH with an opportunity to extract carotenoid from the full-length OCP, either from Synechocystis or Anabaena. These previously unknown reactions between water-soluble carotenoproteins demonstrate multidirectionality of carotenoid transfer, allowing for efficient and reversible control over the carotenoid-mediated protein oligomerization by light, which gives insights into the physiological regulation of OCP activity by CTDH and suggests multiple applications.
    Mots-clés : B3S, carotenoid transfer, diversity, evolution, fluorescence recovery protein, MROP, oligomeric structure, Orange carotenoid protein.


  • R. R. Choubeh, E. Wientjes, P. C. Struik, D. Kirilovsky, et H. van Amerongen, « State transitions in the cyanobacterium Synechococcus elongatus 7942 involve reversible quenching of the photosystem II core », Biochimica Et Biophysica Acta-Bioenergetics, vol. 1859, nᵒ 10, p. 1059-1066, oct. 2018.
    Résumé : Cyanobacteria use chlorophyll and phycobiliproteins to harvest light. The resulting excitation energy is delivered to reaction centers (RCs), where photochemistry starts. The relative amounts of excitation energy arriving at the RCs of photosystem I (PSI) and II (PSII) depend on the spectral composition of the light. To balance the excitations in both photosystems, cyanobacteria perform state transitions to equilibrate the excitation energy. They go to state I if PSI is preferentially excited, for example after illumination with blue light (light I), and to state II after illumination with green-orange light (light II) or after dark adaptation. In this study, we performed 77-K time-resolved fluorescence spectroscopy on wild-type Synechococcus elongatus 7942 cells to measure how state transitions affect excitation energy transfer to PSI and PSII in different light conditions and to test the various models that have been proposed in literature. The time-resolved spectra show that the PSII core is quenched in state II and that this is not due to a change in excitation energy transfer from PSII to PSI (spill-over), either direct or indirect via phycobilisomes.
    Mots-clés : B3S, cells, Cyanobacteria, excitation-energy, less mutant, MROP, photosynthesis, Photosystem II, phycobilisome, picosecond fluorescence spectroscopy, porphyridium-cruentum, State transitions, synechococcus sp, synechocystis pcc 6803, Time-resolved fluorescence spectroscopy, wild-type.

  • K. - J. Dietz, G. H. Krause, K. Siebke, et A. Krieger-Liszkay, « A tribute to Ulrich Heber (1930-2016) for his contribution to photosynthesis research: understanding the interplay between photosynthetic primary reactions, metabolism and the environment », Photosynthesis Research, vol. 137, nᵒ 1, p. 17-28, juill. 2018.
    Résumé : The dynamic and efficient coordination of primary photosynthetic reactions with leaf energization and metabolism under a wide range of environmental conditions is a fundamental property of plants involving processes at all functional levels. The present historical perspective covers 60 years of research aiming to understand the underlying mechanisms, linking major breakthroughs to current progress. It centers on the contributions of Ulrich Heber who had pioneered novel concepts, fundamental methods, and mechanistic understanding of photosynthesis. An important first step was the development of non-aqueous preparation of chloroplasts allowing the investigation of chloroplast metabolites ex vivo (meaning that the obtained results reflect the in vivo situation). Later on, intact chloroplasts, retaining their functional envelope membranes, were isolated in aqueous media to investigate compartmentation and exchange of metabolites between chloroplasts and external medium. These studies elucidated metabolic interaction between chloroplasts and cytoplasm during photosynthesis. Experiments with isolated intact chloroplasts clarified that oxygenation of ribulose-1.5-bisphosphate generates glycolate in photorespiration. The development of non-invasive optical methods enabled researchers identifying mechanisms that balance electron flow in the photosynthetic electron transport system avoiding its over-reduction. Recording chlorophyll a (Chl a) fluorescence allowed one to monitor, among other parameters, thermal energy dissipation by means of 'nonphotochemical quenching' of the excited state of Chl a. Furthermore, studies both in vivo and in vitro led to basic understanding of the biochemical mechanisms of freezing damage and frost tolerance of plant leaves, to SO2 tolerance of tree leaves and dehydrating lichens and mosses.
    Mots-clés : B3S, Carbon metabolism, Chlorophyll a fluorescence, Chloroplast, Chloroplasts, Cyclic electron transport, Fluorometry, Freezing, History, 20th Century, History, 21st Century, Lichen, Light scattering, MROP, Photorespiration, Photosynthesis, Plant Physiological Phenomena, Xanthophylls.

  • M. Gwizdala, J. L. Botha, A. Wilson, D. Kirilovsky, R. van Grondelle, et T. P. J. Krüger, « Switching an Individual Phycobilisome Off and On », The Journal of Physical Chemistry Letters, vol. 9, nᵒ 9, p. 2426-2432, mai 2018.
    Résumé : Photosynthetic organisms have found various smart ways to cope with unexpected changes in light conditions. In many cyanobacteria, the lethal effects of a sudden increase in light intensity are mitigated mainly by the interaction between phycobilisomes (PBs) and the orange carotenoid protein (OCP). The latter senses high light intensities by means of photoactivation and triggers thermal energy dissipation from the PBs. Due to the brightness of their emission, PBs can be characterized at the level of individual complexes. Here, energy dissipation from individual PBs was reversibly switched on and off using only light and OCP. We reveal the presence of quasistable intermediate states during the binding and unbinding of OCP to PB, with a spectroscopic signature indicative of transient decoupling of some of the PB rods during docking of OCP. Real-time control of emission from individual PBs has the potential to contribute to the development of new super-resolution imaging techniques.
    Mots-clés : B3S, MROP.

  • D. Harris, A. Wilson, F. Muzzopappa, N. N. Sluchanko, T. Friedrich, E. G. Maksimov, D. Kirilovsky, et N. Adir, « Structural rearrangements in the C-terminal domain homolog of Orange Carotenoid Protein are crucial for carotenoid transfer », Communications Biology, vol. 1, nᵒ 1, p. 1-11, août 2018.
    Résumé : Dvir Harris et al. present the structure of a homolog of the orange carotenoid protein&nbsp;(OCP) C-terminal domain, elaborating on this protein family’s carotenoid transfer mechanism. They observed major structural shifts&nbsp;in the homolog&nbsp;compared to that of the OCP C-terminal domain, with a strong positive impact on carotenoid uptake and delivery.
    Mots-clés : B3S, MROP.
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  • F. Kong, A. Burlacot, Y. Liang, B. Legeret, S. Alseekh, Y. Brotman, A. R. Fernie, A. Krieger-Liszkay, F. Beisson, G. Peltier, et Y. Li-Beisson, « Interorganelle Communication: Peroxisomal MALATE DEHYDROGENASE 2 Connects Lipid Catabolism to Photosynthesis through Redox Coupling in Chlamydomonas », The Plant Cell, juill. 2018.
    Résumé : Plants and algae must tightly coordinate photosynthetic electron transport and metabolic activities given that they often face fluctuating light and nutrient conditions. The exchange of metabolites and signaling molecules between organelles is thought to be central to this regulation but evidence for this is still fragmentary. Here we show that knocking out the peroxisome-located MALATE DEHYDROGENASE 2 (MDH2) of Chlamydomonas reinhardtii results in dramatic alterations not only in peroxisomal fatty acid breakdown but also in chloroplast starch metabolism and photosynthesis. mdh2 mutants accumulated 50% more storage lipid and two-fold more starch than wild type during nitrogen deprivation. In parallel, mdh2 showed increased PSII yield and photosynthetic CO2 fixation. Metabolite analyses revealed a &gt;60% reduction in malate, together with increased levels of NADPH and H2O2 in mdh2. Similar phenotypes were found upon high light exposure. Furthermore, based on the lack of starch accumulation in a knock-out mutant of the H2O2-producing peroxisomal ACYL-COA OXIDASE 2 and on the effects of H2O2 supplementation, we propose that peroxisome-derived H2O2 acts as a regulator of chloroplast metabolism. We conclude that peroxisomal MDH2 helps photoautotrophs cope with nitrogen scarcity and high light by transmitting the redox state of the peroxisome to the chloroplast by means of malate shuttle- and H2O2-based redox signaling.
    Mots-clés : B3S, MROP.

  • A. Krieger-Liszkay et S. Thomine, « Importing Manganese into the Chloroplast: Many Membranes to Cross », Molecular Plant, vol. 11, nᵒ 9, p. 1109-1111, août 2018.
    Mots-clés : arabidopsis, B3S, BIOCELL, cells, homeostasis, MINION, MROP, photosynthesis, photosystem-ii, protein.

  • H. Kubota-Kawai, R. Mutoh, K. Shinmura, P. Sétif, M. M. Nowaczyk, M. Rögner, T. Ikegami, H. Tanaka, et G. Kurisu, « X-ray structure of an asymmetrical trimeric ferredoxin–photosystem I complex », Nature Plants, vol. 4, nᵒ 4, p. 218-224, 2018.

  • M. Messant, S. Timm, A. Fantuzzi, W. Weckwerth, H. Bauwe, B. Rutherford, et A. Krieger-Liszkay, « Glycolate induces redox tuning of photosystem II in vivo: study of a photorespiration mutant », Plant Physiology, mai 2018.
    Résumé : Bicarbonate removal from the non-heme iron at the acceptor side of photosystem II (PSII) was recently shown to shift the midpoint potential of the primary quinone acceptor QA to a more positive potential and lowers the yield of singlet oxygen (1O2) production. The presence of QA- results in weaker binding of bicarbonate, suggesting a redox-based regulatory and protective mechanism where loss of bicarbonate or exchange of bicarbonate by other small carboxylic acids may protect PSII against 1O2 in vivo under photorespiratory conditions. Here we compared the properties of QA in the Arabidopsis (Arabidopsis thaliana) photorespiration mutant hpr1-1, deficient in NADH-dependent, peroxisomal hydroxypyruvate reductase 1 (HPR1), which accumulates glycolate in leaves, to the wild type. Photosynthetic electron transport was affected in the mutant, and chlorophyll fluorescence showed slower electron transport between QA and QB in the mutant. Glycolate induced an increase in the temperature maximum of thermoluminescence emission indicating a shift of the midpoint potential of QA to a more positive value. The yield of 1O2 production was lowered in thylakoid membranes isolated from hpr1-1 compared to the wild type, consistent with a higher potential of QA/QA-. In addition, electron donation to photosystem I was affected in hpr1-1 at higher light intensities consistent with diminished electron transfer out of photosystem II. This study indicates that replacement of bicarbonate at the non-heme iron by a small carboxylate anion occurs in plants in vivo. These findings suggested that replacement of the bicarbonate on the non-heme iron by glycolate may represent a regulatory mechanism that protects PSII against photo-oxidative stress under low CO2 conditions.
    Mots-clés : B3S, MROP.

  • A. Swida-Barteczka, A. Krieger-Liszkay, W. Bilger, U. Voigt, G. Hensel, Z. Szweykowska-Kulinska, et K. Krupinska, « The plastid-nucleus located DNA/RNA binding protein WHIRLY1 regulates microRNA-levels during stress in barley (Hordeum vulgare L.) », RNA biology, juin 2018.
    Résumé : In this article a novel mechanism of retrograde signaling by chloroplasts during stress is described. This mechanism involves the DNA/RNA binding protein WHIRLY1 as a regulator of microRNA levels. By virtue of its dual localization in chloroplasts and the nucleus of the same cell, WHIRLY1 was proposed as an excellent candidate coordinator of chloroplast function and nuclear gene expression. Comparison of wild-type and transgenic plants with an RNAi-mediated knockdown of WHIRLY1 showed, that the transgenic plants were unable to cope with continuous high light conditions. They were impaired in production of several microRNAs mediating post-transcriptional responses during stress. The results support a central role of WHIRLY1 in retrograde signaling and also underpin a so far underestimated role of microRNAs in this process.
    Mots-clés : B3S, MROP, retrograde signaling, small RNA, stress response.


  • P. Cardol et A. Krieger-Liszkay, « From light capture to metabolic needs, oxygenic photosynthesis is an ever-expanding field of study in plants, algae and cyanobacteria », Physiologia Plantarum, mai 2017.
    Résumé : Understanding of the molecular mechanisms of photosynthetic electron and proton transports and their regulation in plants and algae in response to changes in environmental conditions is an important issue for fundamental research on photosynthesis, and may extend even to practical applications by identifying important sites for improvement of photosynthesis. The significance and often centrality of regulatory mechanisms of photosynthetic electron transport is well established for processes in plant acclimation. In recent years, significant advancements have been achieved in understanding of regulatory processes such as dissipation of excess energy in the antenna systems, state transitions, cyclic electron flow, oxygen reduction by flavodiiron enzymes and many others.
    Mots-clés : B3S, MROP.

  • K. Feilke, G. Ajlani, et A. Krieger-Liszkay, « Correction to ‘Overexpression of plastid terminal oxidase in <i>Synechocystis</i> sp. PCC 6803 alters cellular redox state’ », Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 372, nᵒ 1736, p. 20170277, déc. 2017.

  • K. Feilke, G. Ajlani, et A. Krieger-Liszkay, « Overexpression of plastid terminal oxidase in Synechocystis sp. PCC 6803 alters cellular redox state », Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, vol. 372, nᵒ 1730, sept. 2017.
    Résumé : Cyanobacteria are the most ancient organisms performing oxygenic photosynthesis, and they are the ancestors of plant plastids. All plastids contain the plastid terminal oxidase (PTOX), while only certain cyanobacteria contain PTOX. Many putative functions have been discussed for PTOX in higher plants including a photoprotective role during abiotic stresses like high light, salinity and extreme temperatures. Since PTOX oxidizes PQH2 and reduces oxygen to water, it is thought to protect against photo-oxidative damage by removing excess electrons from the plastoquinone (PQ) pool. To investigate the role of PTOX we overexpressed rice PTOX fused to the maltose-binding protein (MBP-OsPTOX) in Synechocystis sp. PCC 6803, a model cyanobacterium that does not encode PTOX. The fusion was highly expressed and OsPTOX was active, as shown by chlorophyll fluorescence and P700 absorption measurements. The presence of PTOX led to a highly oxidized state of the NAD(P)H/NAD(P)(+) pool, as detected by NAD(P)H fluorescence. Moreover, in the PTOX overexpressor the electron transport capacity of PSI relative to PSII was higher, indicating an alteration of the photosystem I (PSI) to photosystem II (PSII) stoichiometry. We suggest that PTOX controls the expression of responsive genes of the photosynthetic apparatus in a different way from the PQ/PQH2 ratio.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'.
    Mots-clés : B3S, cellular redox state, chlorophyll fluorescence, LBMS, MROP, NAD(P)H fluorescence, P700 absorption, plastid terminal oxidase, Synechocystis sp. PCC 6803.

  • M. Loussouarn, A. Krieger-Liszkay, L. Svilar, A. Bily, S. Birtic, et M. Havaux, « Carnosic acid and carnosol, two major antioxidants of rosemary, act through different mechanisms », Plant Physiology, sept. 2017.
    Résumé : Carnosic acid, a phenolic diterpene specific of the Lamiaceae family, is highly abundant in rosemary species. Despite numerous industrial and medicinal/pharmaceutical applications of its antioxidative features, this compound in planta and its antioxidant mechanism have received little attention, except a few studies of rosemary plants under natural conditions. In vitro analyses, using HPLC-UV and luminescence imaging, revealed that carnosic acid and its major oxidized derivative, carnosol, protect lipids from oxidation. Both compounds preserved linolenic acid and monogalactosyldiacylglycerol from singlet oxygen and from hydroxyl radical. When applied exogenously, they were both able to protect thylakoid membranes prepared from Arabidopsis leaves against lipid peroxidation. Different levels of carnosic acid and carnosol in two contrasted rosemary varieties correlated with tolerance to lipid peroxidation. Upon ROS oxidation of lipids, carnosic acid was consumed and oxidized into various derivatives, including into carnosol, while carnosol resisted, suggesting that carnosic acid is a chemical quencher of ROS. The antioxidative function of carnosol relies on another mechanism, occurring directly in lipid oxidation process. Under oxidative conditions that did not involve ROS generation, carnosol inhibited lipid peroxidation, contrary to carnosic acid. Using spin probes and EPR detection, we confirmed that carnosic acid, rather than carnosol, is a ROS quencher. Various oxidized derivatives of carnosic acid were detected in rosemary leaves in low light, indicating chronic oxidation of this compound, and accumulated in plants exposed to stress conditions, in parallel with a loss of carnosic acid, confirming that chemical quenching of ROS by carnosic acid takes place in planta.
    Mots-clés : B3S, MROP.

  • C. Mignée, R. Mutoh, A. Krieger-Liszkay, G. Kurisu, et P. Sétif, « Gallium ferredoxin as a tool to study the effects of ferredoxin binding to photosystem I without ferredoxin reduction », Photosynthesis Research, févr. 2017.

  • F. Muzzopappa, A. Wilson, V. Yogarajah, S. Cot, F. Perreau, C. Montigny, C. Bourcier de Carbon, et D. Kirilovsky, « The paralogs to the C-terminal domain of the cyanobacterial OCP are carotenoid donors to HCPs », Plant Physiology, sept. 2017.
    Résumé : The photoactive Orange Carotenoid Protein photoprotects cyanobacteria cells by quenching singlet oxygen and excess excitation energy. Its N-terminal domain (NTD) is the active part of the protein and the C-terminal domain (CTD) regulates the activity. Recently, the characteristics of a family of soluble carotenoid-binding proteins (Helical Carotenoid Proteins or HCPs), paralogs of NTD-OCP, were described. Bioinformatics studies also revealed the existence of genes coding for homologs of CTD. Here, we show that the latter genes encode carotenoid proteins (CTDHs). This family of proteins contains two subgroups with distinct characteristics. One CTDH of each clade was further characterized and proved to be very good singlet oxygen quenchers. When synthesized in E. coli or Synechocystis PCC 6803, CTDHs form dimers that share a carotenoid molecule and are able to transfer their carotenoid to apo-HCPs and apo-OCP. The CTDHs from clade 2 have a cysteine in position 103. A disulfide bond is easily formed between the monomers of the dimer preventing carotenoid transfer. This suggests that the transfer of the carotenoid could be redox regulated in clade 2 CTDH. We also demonstrate here that apo-OCPs and apo CTDHs are able to take the carotenoid directly from membranes, while HCPs are unable. HCPs need the presence of CTDH to become holo-proteins. We propose that in cyanobacteria the CTDHs are carotenoid donors to HCPs.
    Mots-clés : B3S, LPSM, MROP.

  • P. Pétriacq, L. de Bont, L. Genestout, J. Hao, C. Laureau, I. Florez-Sarasa, T. Rzigui, G. Queval, F. Gilard, C. Mauve, F. Guérard, M. Lamothe-Sibold, J. Marion, C. Fresneau, S. Brown, A. Danon, A. Krieger-Liszkay, R. Berthomé, M. Ribas-Carbo, G. Tcherkez, G. Cornic, B. Pineau, B. Gakière, et R. De Paepe, « Photoperiod Affects the Phenotype of Mitochondrial Complex I Mutants », Plant Physiology, vol. 173, nᵒ 1, p. 434-455, 2017.

  • T. Roach, T. Baur, W. Stöggl, et A. Krieger-Liszkay, « Chlamydomonas reinhardtii responding to high light: A role for 2-propenal (acrolein) », Physiologia Plantarum, 2017.

  • Á. Sánchez-Corrionero, I. Sánchez-Vicente, S. González-Pérez, A. Corrales, A. Krieger-Liszkay, Ó. Lorenzo, et J. B. Arellano, « Singlet oxygen triggers chloroplast rupture and cell death in the zeaxanthin epoxidase defective mutant aba1 of Arabidopsis thaliana under high light stress », Journal of Plant Physiology, vol. 216, p. 188-196, juill. 2017.
    Résumé : The two Arabidopsis thaliana mutants, aba1 and max4, were previously identified as sharing a number of co-regulated genes with both the flu mutant and Arabidopsis cell suspension cultures exposed to high light (HL). On this basis, we investigated whether aba1 and max4 were generating high amounts of singlet oxygen ((1)O2) and activating (1)O2-mediated cell death. Thylakoids of aba1 produced twice as much (1)O2 as thylakoids of max4 and wild type (WT) plants when illuminated with strong red light. (1)O2 was measured using the spin probe 2,2,6,6-tetramethyl-4-piperidone hydrochloride. 77-K chlorophyll fluorescence emission spectra of thylakoids revealed lower aggregation of the light harvesting complex II in aba1. This was rationalized as a loss of connectivity between photosystem II (PSII) units and as the main cause for the high yield of (1)O2 generation in aba1. Up-regulation of the (1)O2 responsive gene AAA-ATPase was only observed with statistical significant in aba1 under HL. Two early jasmonate (JA)-responsive genes, JAZ1 and JAZ5, encoding for two repressor proteins involved in the negative feedback regulation of JA signalling, were not up-regulated to the WT plant levels. Chloroplast aggregation followed by chloroplast rupture and eventual cell death was observed by confocal imaging of the fluorescence emission of leaf cells of transgenic aba1 plants expressing the chimeric fusion protein SSU-GFP. Cell death was not associated with direct (1)O2 cytotoxicity in aba1, but rather with a delayed stress response. In contrast, max4 did not show evidence of (1)O2-mediated cell death. In conclusion, aba1 may serve as an alternative model to other (1)O2-overproducing mutants of Arabidopsis for investigating (1)O2-mediated cell death.
    Mots-clés : AAA-ATPase, aba1, B3S, Cell Death, Chloroplast rupture, JAZ repressors, MROP, Singlet oxygen.

  • P. Sétif, R. Mutoh, et G. Kurisu, « Dynamics and energetics of cyanobacterial photosystem I:ferredoxin complexes in different redox states », Biochimica Et Biophysica Acta, avr. 2017.
    Résumé : Fast turnover of ferredoxin/Fd reduction by photosystem-I/PSI requires that it dissociates rapidly after it has been reduced by PSI:Fd intracomplex electron transfer. The rate constants of Fd dissociation from PSI have been determined by flash-absorption spectroscopy with different combinations of cyanobacterial PSIs and Fds, and different redox states of Fd and of the terminal PSI acceptor (FAFB). Newly obtained values were derived firstly from the fact that the dissociation constant between PSI and redox-inactive gallium-substituted Fd increases upon (FAFB) reduction and secondly from the characterization and elucidation of a kinetic phase following intracomplex Fd reduction to binding of oxidized Fd to PSI, a process which is rate-limited by the foregoing dissociation of reduced Fd from PSI. By reference to the complex with oxidized partners, dissociation rate constants were found to increase moderately with (FAFB) single reduction and by about one order of magnitude after electron transfer from (FAFB)(-) to Fd, therefore favoring turnover of Fd reduction by PSI. With Thermosynechococcus elongatus partners, values of 270, 730 and >10000 s(-1) were thus determined for (FAFB)Fdoxidized, (FAFB)(-)Fdoxidized and (FAFB)Fdreduced, respectively. Moreover, assuming a conservative upper limit for the association rate constant between reduced Fd and PSI, a significant negative shift of the Fd midpoint potential upon binding to PSI has been calculated (<-60 mV for Thermosynechococcus elongatus). From the present state of knowledge, the question is still open whether this redox shift is compatible with a large (>10) equilibrium constant for intracomplex reduction of Fd from (FAFB)(-).
    Mots-clés : association and dissociation kinetics, B3S, binding-induced shift of midpoint potential, Electron transfer, ferredoxin binding, gallium-substituted ferredoxin, MROP, photosynthesis, redox potential.

  • V. Šlouf, V. Kuznetsova, M. Fuciman, C. B. de Carbon, A. Wilson, D. Kirilovsky, et T. Polívka, « Ultrafast spectroscopy tracks carotenoid configurations in the orange and red carotenoid proteins from cyanobacteria », Photosynthesis Research, vol. 131, nᵒ 1, p. 105-117, janv. 2017.
    Résumé : A quenching mechanism mediated by the orange carotenoid protein (OCP) is one of the ways cyanobacteria protect themselves against photooxidative stress. Here, we present a femtosecond spectroscopic study comparing OCP and RCP (red carotenoid protein) samples binding different carotenoids. We confirmed significant changes in carotenoid configuration upon OCP activation reported by Leverenz et al. (Science 348:1463-1466. doi: 10.1126/science.aaa7234 , 2015) by comparing the transient spectra of OCP and RCP. The most important marker of these changes was the magnitude of the transient signal associated with the carotenoid intramolecular charge-transfer (ICT) state. While OCP with canthaxanthin exhibited a weak ICT signal, it increased significantly for canthaxanthin bound to RCP. On the contrary, a strong ICT signal was recorded in OCP binding echinenone excited at the red edge of the absorption spectrum. Because the carbonyl oxygen responsible for the appearance of the ICT signal is located at the end rings of both carotenoids, the magnitude of the ICT signal can be used to estimate the torsion angles of the end rings. Application of two different excitation wavelengths to study OCP demonstrated that the OCP sample contains two spectroscopically distinct populations, none of which is corresponding to the photoactivated product of OCP.
    Mots-clés : B3S, Carotenoids, Cyanobacteria, Intramolecular charge-transfer state, MROP, Non-photochemical quenching, Orange carotenoid protein, Red carotenoid protein, Spectrum Analysis, Ultrafast spectroscopy.

  • A. Thurotte, C. Bourcier de Carbon, A. Wilson, L. Talbot, S. Cot, R. López-Igual, et D. Kirilovsky, « The cyanobacterial Fluorescence Recovery Protein has two distinct activities: Orange Carotenoid Protein amino acids involved in FRP interaction », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1858, nᵒ 4, p. 308-317, 2017.


  • A. M. Acuña, R. Kaňa, M. Gwizdala, J. J. Snellenburg, P. van Alphen, B. van Oort, D. Kirilovsky, R. van Grondelle, et I. H. M. van Stokkum, « A method to decompose spectral changes in Synechocystis PCC 6803 during light-induced state transitions », Photosynthesis Research, vol. 130, nᵒ 1-3, p. 237-249, déc. 2016.
    Résumé : Cyanobacteria have developed responses to maintain the balance between the energy absorbed and the energy used in different pigment-protein complexes. One of the relatively rapid (a few minutes) responses is activated when the cells are exposed to high light intensities. This mechanism thermally dissipates excitation energy at the level of the phycobilisome (PB) antenna before it reaches the reaction center. When exposed to low intensities of light that modify the redox state of the plastoquinone pool, the so-called state transitions redistribute energy between photosystem I and II. Experimental techniques to investigate the underlying mechanisms of these responses, such as pulse-amplitude modulated fluorometry, are based on spectrally integrated signals. Previously, a spectrally resolved fluorometry method has been introduced to preserve spectral information. The analysis method introduced in this work allows to interpret SRF data in terms of species-associated spectra of open/closed reaction centers (RCs), (un)quenched PB and state 1 versus state 2. Thus, spectral differences in the time-dependent fluorescence signature of photosynthetic organisms under varying light conditions can be traced and assigned to functional emitting species leading to a number of interpretations of their molecular origins. In particular, we present evidence that state 1 and state 2 correspond to different states of the PB-PSII-PSI megacomplex.
    Mots-clés : B3S, Cyanobacteria, MROP, Singular value decomposition, Spectrally resolved fluorometry, Time-resolved spectroscopy.

  • A. M. Acuña, J. J. Snellenburg, M. Gwizdala, D. Kirilovsky, R. van Grondelle, et I. H. M. van Stokkum, « Resolving the contribution of the uncoupled phycobilisomes to cyanobacterial pulse-amplitude modulated (PAM) fluorometry signals », Photosynthesis Research, vol. 127, nᵒ 1, p. 91-102, janv. 2016.
    Résumé : Pulse-amplitude modulated (PAM) fluorometry is extensively used to characterize photosynthetic organisms on the slow time-scale (1-1000 s). The saturation pulse method allows determination of the quantum yields of maximal (F(M)) and minimal fluorescence (F(0)), parameters related to the activity of the photosynthetic apparatus. Also, when the sample undergoes a certain light treatment during the measurement, the fluorescence quantum yields of the unquenched and the quenched states can be determined. In the case of cyanobacteria, however, the recorded fluorescence does not exclusively stem from the chlorophyll a in photosystem II (PSII). The phycobilins, the pigments of the cyanobacterial light-harvesting complexes, the phycobilisomes (PB), also contribute to the PAM signal, and therefore, F(0) and F(M) are no longer related to PSII only. We present a functional model that takes into account the presence of several fluorescent species whose concentrations can be resolved provided their fluorescence quantum yields are known. Data analysis of PAM measurements on in vivo cells of our model organism Synechocystis PCC6803 is discussed. Three different components are found necessary to fit the data: uncoupled PB (PB(free)), PB-PSII complexes, and free PSI. The free PSII contribution was negligible. The PB(free) contribution substantially increased in the mutants that lack the core terminal emitter subunits allophycocyanin D or allophycocyanin F. A positive correlation was found between the amount of PB(free) and the rate constants describing the binding of the activated orange carotenoid protein to PB, responsible for non-photochemical quenching.
    Mots-clés : B3S, Computer Simulation, Cyanobacteria, Fluorescence, Fluorescence quantum yield, Fluorometry, Models, Biological, MROP, Mutation, Non-photochemical quenching, Photosystem I Protein Complex, Photosystem II Protein Complex, Phycobilisome, Phycobilisomes, Phycocyanin, Protein Subunits, Pulse-amplitude modulated (PAM) fluorometry, Synechocystis, Time Factors.

  • C. Biniek, E. Heyno, J. Kruk, F. Sparla, P. Trost, et A. Krieger-Liszkay, « Role of the NAD(P)H quinone oxidoreductase NQR and the cytochrome b AIR12 in controlling superoxide generation at the plasma membrane », Planta, déc. 2016.

  • K. Brinkert, S. De Causmaecker, A. Krieger-Liszkay, A. Fantuzzi, et A. W. Rutherford, « Bicarbonate-induced redox tuning in Photosystem II for regulation and protection », Proceedings of the National Academy of Sciences of the United States of America, vol. 113, nᵒ 43, p. 12144-12149, oct. 2016.
    Résumé : The midpoint potential (Em) of [Formula: see text], the one-electron acceptor quinone of Photosystem II (PSII), provides the thermodynamic reference for calibrating PSII bioenergetics. Uncertainty exists in the literature, with two values differing by ∼80 mV. Here, we have resolved this discrepancy by using spectroelectrochemistry on plant PSII-enriched membranes. Removal of bicarbonate (HCO3(-)) shifts the Em from ∼-145 mV to -70 mV. The higher values reported earlier are attributed to the loss of HCO3(-) during the titrations (pH 6.5, stirred under argon gassing). These findings mean that HCO3(-) binds less strongly when QA(-•) is present. Light-induced QA(-•) formation triggered HCO3(-) loss as manifest by the slowed electron transfer and the upshift in the Em of QA HCO3(-)-depleted PSII also showed diminished light-induced (1)O2 formation. This finding is consistent with a model in which the increase in the Em of [Formula: see text] promotes safe, direct [Formula: see text] charge recombination at the expense of the damaging back-reaction route that involves chlorophyll triplet-mediated (1)O2 formation [Johnson GN, et al. (1995) Biochim Biophys Acta 1229:202-207]. These findings provide a redox tuning mechanism, in which the interdependence of the redox state of QA and the binding by HCO3(-) regulates and protects PSII. The potential for a sink (CO2) to source (PSII) feedback mechanism is discussed.
    Mots-clés : B3S, CO2 fixation, MROP, photoassembly, photoinhibition, photosynthesis, water oxidation.

  • Q. Bruggeman, C. Mazubert, F. Prunier, R. Lugan, K. X. Chan, S. Y. Phua, B. J. Pogson, A. Krieger-Liszkay, M. Delarue, M. Benhamed, C. Bergounioux, et C. Raynaud, « Chloroplasts activity and PAP-signaling regulate programmed cell death in Arabidopsis », Plant Physiology, p. pp.01872.2015, janv. 2016.

  • K. - J. Dietz, I. Turkan, et A. Krieger-Liszkay, « Redox- and Reactive Oxygen Species-Dependent Signaling into and out of the Photosynthesizing Chloroplast », Plant Physiology, vol. 171, nᵒ 3, p. 1541-1550, 2016.

  • K. Feilke, P. Streb, G. Cornic, F. Perreau, J. Kruk, et A. Krieger-Liszkay, « Effect of Chlamydomonas plastid terminal oxidase 1 expressed in tobacco on photosynthetic electron transfer », The Plant Journal: For Cell and Molecular Biology, vol. 85, nᵒ 2, p. 219-228, janv. 2016.
    Résumé : The plastid terminal oxidase PTOX is a plastohydroquinone:oxygen oxidoreductase that is important for carotenoid biosynthesis and plastid development. Its role in photosynthesis is controversially discussed. Under a number of abiotic stress conditions, the protein level of PTOX increases. PTOX is thought to act as a safety valve under high light protecting the photosynthetic apparatus against photodamage. However, transformants with high PTOX level were reported to suffer from photoinhibition. To analyze the effect of PTOX on the photosynthetic electron transport, tobacco expressing PTOX-1 from Chlamydomonas reinhardtii (Cr-PTOX1) was studied by chlorophyll fluorescence, thermoluminescence, P700 absorption kinetics and CO2 assimilation. Cr-PTOX1 was shown to compete very efficiently with the photosynthetic electron transport for PQH2 . High pressure liquid chromatography (HPLC) analysis confirmed that the PQ pool was highly oxidized in the transformant. Immunoblots showed that, in the wild-type, PTOX was associated with the thylakoid membrane only at a relatively alkaline pH value while it was detached from the membrane at neutral pH. We present a model proposing that PTOX associates with the membrane and oxidizes PQH2 only when the oxidation of PQH2 by the cytochrome b6 f complex is limiting forward electron transport due to a high proton gradient across the thylakoid membrane.
    Mots-clés : B3S, Chlamydomonas, Chlamydomonas reinhardtii PTOX1, Electron Transport, MROP, Nicotiana tabacum, Oxidoreductases, photooxidative stress, photosynthesis, photosynthetic electron transport, Plants, Genetically Modified, plastid terminal oxidase, Plastids, regulation, Tobacco.

  • M. Gwizdala, R. Berera, D. Kirilovsky, R. van Grondelle, et T. P. J. Krüger, « Controlling Light Harvesting with Light », Journal of the American Chemical Society, vol. 138, nᵒ 36, p. 11616-11622, sept. 2016.

  • D. Harris, O. Tal, D. Jallet, A. Wilson, D. Kirilovsky, et N. Adir, « Orange carotenoid protein burrows into the phycobilisome to provide photoprotection », Proceedings of the National Academy of Sciences, vol. 113, nᵒ 12, p. E1655-E1662, mars 2016.

  • D. Kirilovsky et C. A. Kerfeld, « Cyanobacterial photoprotection by the orange carotenoid protein », Nature Plants, vol. 2, nᵒ 12, p. 16180, déc. 2016.

  • A. Krieger-Liszkay et K. Feilke, « The Dual Role of the Plastid Terminal Oxidase PTOX: Between a Protective and a Pro-oxidant Function », Frontiers in Plant Science, vol. 6, janv. 2016.

  • R. López-Igual, A. Wilson, R. L. Leverenz, M. R. Melnicki, C. Bourcier de Carbon, M. Sutter, A. Turmo, F. Perreau, C. A. Kerfeld, et D. Kirilovsky, « Different Functions of the Paralogs to the N-Terminal Domain of the Orange Carotenoid Protein in the Cyanobacterium Anabaena sp. PCC 7120 », Plant Physiology, vol. 171, nᵒ 3, p. 1852-1866, 2016.

  • M.  R. Melnicki, R.  L. Leverenz, M. Sutter, R. López-Igual, A. Wilson, E.  G. Pawlowski, F. Perreau, D. Kirilovsky, et C.  A. Kerfeld, « Structure, Diversity, and Evolution of a New Family of Soluble Carotenoid-Binding Proteins in Cyanobacteria », Molecular Plant, vol. 9, nᵒ 10, p. 1379-1394, 2016.

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