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

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Articles syndiqués

  • A tribute to Ulrich Heber (1930-2016) for his contribution to photosynthesis research : understanding the interplay between photosynthetic primary reactions, metabolism and the environment.

    26 janvier, par Dietz KJ, Krause GH, Siebke K, Krieger-Liszkay A
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    A tribute to Ulrich Heber (1930-2016) for his contribution to photosynthesis research: understanding the interplay between photosynthetic primary reactions, metabolism and the environment.

    Photosynth Res. 2018 Jan 24;:

    Authors: Dietz KJ, Krause GH, Siebke K, Krieger-Liszkay A

    Abstract
    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.

    PMID: 29368118 [PubMed - as supplied by publisher]

  • Correction to ’Overexpression of plastid terminal oxidase in Synechocystis sp. PCC 6803 alters cellular redox state’.

    8 novembre 2017, par Feilke K, Ajlani G, Krieger-Liszkay A
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    Correction to 'Overexpression of plastid terminal oxidase in Synechocystis sp. PCC 6803 alters cellular redox state'.

    Philos Trans R Soc Lond B Biol Sci. 2017 Dec 19;372(1736):

    Authors: Feilke K, Ajlani G, Krieger-Liszkay A

    PMID: 29109231 [PubMed - in process]

  • The paralogs to the C-terminal domain of the cyanobacterial OCP are carotenoid donors to HCPs.

    23 septembre 2017, par Muzzopappa F, Wilson A, Yogarajah V, Cot S, Perreau F, Montigny C, Bourcier de Carbon C, Kirilovsky D
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    The paralogs to the C-terminal domain of the cyanobacterial OCP are carotenoid donors to HCPs.

    Plant Physiol. 2017 Sep 21;:

    Authors: Muzzopappa F, Wilson A, Yogarajah V, Cot S, Perreau F, Montigny C, Bourcier de Carbon C, Kirilovsky D

    Abstract
    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.

    PMID: 28935842 [PubMed - as supplied by publisher]

  • Carnosic acid and carnosol, two major antioxidants of rosemary, act through different mechanisms.

    17 septembre 2017, par Loussouarn M, Krieger-Liszkay A, Svilar L, Bily A, Birtic S, Havaux M
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    Carnosic acid and carnosol, two major antioxidants of rosemary, act through different mechanisms.

    Plant Physiol. 2017 Sep 15;:

    Authors: Loussouarn M, Krieger-Liszkay A, Svilar L, Bily A, Birtic S, Havaux M

    Abstract
    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.

    PMID: 28916593 [PubMed - as supplied by publisher]