TY - JOUR AU - Böde, Kinga AU - Javornik, Uros AU - Dlouhy, Ondrej AU - Zsíros, Ottó AU - Biswas, Avratanu AU - Racskóné Domonkos, Ildikó AU - Sket, Primoz AU - Karlicky, Vaclav AU - Ughy, Bettina AU - Lambrev, Petar AU - Spunda, Vladimir AU - Plavec, Janez AU - Garab, Győző TI - Role of isotropic lipid phase in the fusion of photosystem II membranes JF - PHOTOSYNTHESIS RESEARCH J2 - PHOTOSYNTH RES PY - 2024 PG - 14 SN - 0166-8595 DO - 10.1007/s11120-024-01097-3 UR - https://m2.mtmt.hu/api/publication/34850122 ID - 34850122 N1 - Funding Agency and Grant Number: National Research Development and Innovation Office of Hungary (OTKA K) [128679]; Czech Science Foundation [GACR 23-07744]; European Union under the LERCO project via the Operational Programme Just Transition [CZ.10.03.01/00/22_003/0000003]; HUN-REN Biological Research Centre, Szeged Funding text: This work was supported by grants from the National Research Development and Innovation Office of Hungary (OTKA K 128679 to G.G.), the Czech Science Foundation (GACR 23-07744 S to G.G.) and the European Union under the LERCO project (CZ.10.03.01/00/22_003/0000003) via the Operational Programme Just Transition. CERIC-ERIC provided financial assistance for travel and lodging. Open access funding provided by HUN-REN Biological Research Centre, Szeged. AB - It has been thoroughly documented, by using P-31-NMR spectroscopy, that plant thylakoid membranes (TMs), in addition to the bilayer (or lamellar, L) phase, contain at least two isotropic (I) lipid phases and an inverted hexagonal (H-II) phase. However, our knowledge concerning the structural and functional roles of the non-bilayer phases is still rudimentary. The objective of the present study is to elucidate the origin of I phases which have been hypothesized to arise, in part, from the fusion of TMs (Garab et al. 2022 Progr Lipid Res 101,163). We take advantage of the selectivity of wheat germ lipase (WGL) in eliminating the I phases of TMs (Dlouh & yacute; et al. 2022 Cells 11: 2681), and the tendency of the so-called BBY particles, stacked photosystem II (PSII) enriched membrane pairs of 300-500 nm in diameter, to form large laterally fused sheets (Dunahay et al. 1984 BBA 764: 179). Our 31P-NMR spectroscopy data show that BBY membranes contain L and I phases. Similar to TMs, WGL selectively eliminated the I phases, which at the same time exerted no effect on the molecular organization and functional activity of PSII membranes. As revealed by sucrose-density centrifugation, magnetic linear dichroism spectroscopy and scanning electron microscopy, WGL disassembled the large laterally fused sheets. These data provide direct experimental evidence on the involvement of I phase(s) in the fusion of stacked PSII membrane pairs, and strongly suggest the role of non-bilayer lipids in the self-assembly of the TM system. LA - English DB - MTMT ER - TY - JOUR AU - Farkas, Attila AU - Pap, Bernadett AU - Zsíros, Ottó AU - Patai, Roland AU - Shetty, Prateek AU - Garab, Győző AU - Bíró, Tibor AU - Ördög, Vince AU - Maróti, Gergely TI - Salinity stress provokes diverse physiological responses of eukaryotic unicellular microalgae JF - ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS J2 - ALGAL RES VL - 73 PY - 2023 PG - 12 SN - 2211-9264 DO - 10.1016/j.algal.2023.103155 UR - https://m2.mtmt.hu/api/publication/33921769 ID - 33921769 N1 - Funding Agency and Grant Number: NKFIH [2020-1.1.2-PIACI-KFI-2020-00020]; Hungarian Academy of Sciences [LP2020-5/2020]; Szechenyi Plan Plus National Laboratory Programme (National Laboratory for Water Science and Water Security) [RRF-2.3.1-21-2022-00008]; Czech Science Foundation [GACR 23-07744S] Funding text: This research was funded by the following international and domestic funds: 2020-1.1.2-PIACI-KFI-2020-00020 (NKFIH), the Lenduelet-Programme (GM) of the Hungarian Academy of Sciences (LP2020-5/2020), the Szechenyi Plan Plus National Laboratory Programme (National Laboratory for Water Science and Water Security, RRF-2.3.1-21-2022-00008) and the Czech Science Foundation (GACR 23-07744S). AB - Highly saline conditions represent a strong challenge for most microorganisms in freshwater ecosystems. Eukaryotic freshwater green algae from the Chlorophyta clade were investigated for their ability to survive in and adapt to increased salt concentration in the growth medium. Striking differences were detected between the responses of the various algae species to the elevated salt concentrations. The investigated Chlamydomonas reinhardtii cc124 and Coelastrella sp. MACC-549 algae showed a moderate resistance to increased salt concentration, while Chlorella sp. MACC-360 exhibited high salt tolerance, showed unaltered growth characteristics and photosynthetic efficiency compared to the saline-free control conditions even at 600 mM NaCl concentration. Diverse physiological responses to elevated salt concentrations were described for the tested algae including variations in their growth capacity, characteristic morphological changes, alterations in the structure and function of the photosynthetic machinery and differences in the production of reactive oxygen species. Special alterations were identified in the lipid and exopolysaccharide production patterns of the tested algal strains in response to high salinity. As a conclusion Chlorella sp. MACC-360 algae showed outstanding salt tolerance features. Together with the concomitant lipid-producing phenotype under highly saline conditions this unicellular green alga is a promising candidate for biotechnological applications. LA - English DB - MTMT ER - TY - JOUR AU - Dlouhy, Ondrej AU - Karlicky, Vaclav AU - Javornik, Uros AU - Kurasova, Irena AU - Zsíros, Ottó AU - Sket, Primoz AU - Kanna, Sai Divya AU - Böde, Kinga AU - Vecerova, Kristyna AU - Urban, Otmar AU - Gasanoff, Edward S. AU - Plavec, Janez AU - Spunda, Vladimir AU - Ughy, Bettina AU - Garab, Győző TI - Structural Entities Associated with Different Lipid Phases of Plant Thylakoid Membranes-Selective Susceptibilities to Different Lipases and Proteases JF - CELLS J2 - CELLS-BASEL VL - 11 PY - 2022 IS - 17 PG - 18 SN - 2073-4409 DO - 10.3390/cells11172681 UR - https://m2.mtmt.hu/api/publication/33117892 ID - 33117892 N1 - Funding Agency and Grant Number: Czech Science Foundation [GACR 19-13637S]; National Research Development and Innovation Office of Hungary [OTKA K 128679, GINOP-2.3.2-15-2016-00058]; Ministry of Education, Youth and Sports of the Czech Republic [CZ.02.1.01/0.0/0.0/16_019/0000797]; Silesian Region [07359/2019/RRC]; European Union [101000501]; University of Ostrava [SGS11/P.rF/2022]; Slovenian Research Agency (ARRS) [P1-242]; Central European Research Infrastructure (CERIC-ERIC) Consortium; Slovenian NMR Center of CERIC-ERIC Consortium at National Institute of Chemistry in Ljubljana [20217148] Funding text: This work was supported by grants from Czech Science Foundation (GACR 19-13637S, to G.G.), National Research Development and Innovation Office of Hungary (OTKA K 128679, to G.G., and GINOP-2.3.2-15-2016-00058, to B.U.), the Ministry of Education, Youth and Sports of the Czech Republic (project "SustES-Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions"; CZ.02.1.01/0.0/0.0/16_019/0000797, to V.S., K.V., O.U., I.K., and V.K.), Silesian Region (07359/2019/RRC, to O.D.), European Union`s Horizon 2020 Research and Innovation Program (No. 101000501, to B.U. and S.D.K), University of Ostrava (SGS11/P.rF/2022, to O.D.) and Slovenian Research Agency (ARRS, grant P1-242 to J.P.). The authors acknowledge Central European Research Infrastructure (CERIC-ERIC) Consortium for the access to experimental facilities and financial support. The 31P-NMR measurements were performed in Slovenian NMR Center of CERIC-ERIC Consortium at National Institute of Chemistry in Ljubljana (project No. 20217148). AB - It is well established that plant thylakoid membranes (TMs), in addition to a bilayer, contain two isotropic lipid phases and an inverted hexagonal (H-II) phase. To elucidate the origin of non-bilayer lipid phases, we recorded the P-31-NMR spectra of isolated spinach plastoglobuli and TMs and tested their susceptibilities to lipases and proteases; the structural and functional characteristics of TMs were monitored using biophysical techniques and CN-PAGE. Phospholipase-A1 gradually destroyed all P-31-NMR-detectable lipid phases of isolated TMs, but the weak signal of isolated plastoglobuli was not affected. Parallel with the destabilization of their lamellar phase, TMs lost their impermeability; other effects, mainly on Photosystem-II, lagged behind the destruction of the original phases. Wheat-germ lipase selectively eliminated the isotropic phases but exerted little or no effect on the structural and functional parameters of TMs-indicating that the isotropic phases are located outside the protein-rich regions and might be involved in membrane fusion. Trypsin and Proteinase K selectively suppressed the H-II phase-suggesting that a large fraction of TM lipids encapsulate stroma-side proteins or polypeptides. We conclude that-in line with the Dynamic Exchange Model-the non-bilayer lipid phases of TMs are found in subdomains separated from but interconnected with the bilayer accommodating the main components of the photosynthetic machinery. LA - English DB - MTMT ER - TY - JOUR AU - Kanna, Sai Divya AU - Racskóné Domonkos, Ildikó AU - Kóbori, T.O. AU - Dergez, Ágnes Karolina AU - Böde, Kinga AU - Nagyapáti, Sarolta AU - Zsíros, Ottó AU - Ünnep, Renáta AU - Nagy, Gergely AU - Garab, Győző AU - Szilák, László AU - Solymosi, Katalin AU - Kovács, László AU - Ughy, Bettina TI - Salt Stress Induces Paramylon Accumulation and Fine-Tuning of the Macro-Organization of Thylakoid Membranes in Euglena gracilis Cells JF - FRONTIERS IN PLANT SCIENCE J2 - FRONT PLANT SCI VL - 12 PY - 2021 PG - 15 SN - 1664-462X DO - 10.3389/fpls.2021.725699 UR - https://m2.mtmt.hu/api/publication/32823174 ID - 32823174 LA - English DB - MTMT ER - TY - JOUR AU - Dlouhy, Ondrej AU - Javornik, Uros AU - Zsíros, Ottó AU - Sket, Primoz AU - Karlicky, Vaclav AU - Spunda, Vladimir AU - Plavec, Janez AU - Garab, Győző TI - Lipid Polymorphism of the Subchloroplast-Granum and Stroma Thylakoid Membrane-Particles. I. P-31-NMR Spectroscopy JF - CELLS J2 - CELLS-BASEL VL - 10 PY - 2021 IS - 9 PG - 16 SN - 2073-4409 DO - 10.3390/cells10092354 UR - https://m2.mtmt.hu/api/publication/32293664 ID - 32293664 N1 - Funding Agency and Grant Number: Czech Science FoundationGrant Agency of the Czech Republic [GACR 19-13637S]; National Research Development and Innovation Office of HungaryNational Research, Development & Innovation Office (NRDIO) - Hungary [OTKA K 128679]; project "SustES-Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions" [CZ.02.1.01/0.0/0.0/16_019/0000797]; Silesian Region [07359/2019/RRC]; University of Ostrava [SGS02/PrF/2021] Funding text: This work was supported by grants from the Czech Science Foundation (GAC R 19-13637S to G.G., V.S., V.K. and O.D.), the National Research Development and Innovation Office of Hungary (OTKA K 128679 to G.G.), the project "SustES-Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions" (CZ.02.1.01/0.0/0.0/16_019/0000797, to V.S. and V.K.), the Silesian Region (07359/2019/RRC to O.D.) and the University of Ostrava (SGS02/PrF/2021 to O.D.). The 31P-NMR measurements were carried out in the NMR Center of CERIC-ERIC; this organization also provided financial assistance in shipping samples from Szeged to Ljubljana. AB - Build-up of the energized state of thylakoid membranes and the synthesis of ATP are warranted by organizing their bulk lipids into a bilayer. However, the major lipid species of these membranes, monogalactosyldiacylglycerol, is a non-bilayer lipid. It has also been documented that fully functional thylakoid membranes, in addition to the bilayer, contain an inverted hexagonal (H-II) phase and two isotropic phases. To shed light on the origin of these non-lamellar phases, we performed P-31-NMR spectroscopy experiments on sub-chloroplast particles of spinach: stacked, granum and unstacked, stroma thylakoid membranes. These membranes exhibited similar lipid polymorphism as the whole thylakoids. Saturation transfer experiments, applying saturating pulses at characteristic frequencies at 5 degrees C, provided evidence for distinct lipid phases-with component spectra very similar to those derived from mathematical deconvolution of the P-31-NMR spectra. Wheat-germ lipase treatment of samples selectively eliminated the phases exhibiting sharp isotropic peaks, suggesting easier accessibility of these lipids compared to the bilayer and the H-II phases. Gradually increasing lipid exchanges were observed between the bilayer and the two isotropic phases upon gradually elevating the temperature from 5 to 35 degrees C, suggesting close connections between these lipid phases. Data concerning the identity and structural and functional roles of different lipid phases will be presented in the accompanying paper. LA - English DB - MTMT ER - TY - JOUR AU - Dlouhý, Ondřej AU - Karlický, Václav AU - Arshad, Rameez AU - Zsíros, Ottó AU - Racskóné Domonkos, Ildikó AU - Kurasová, Irena AU - Wacha, András Ferenc AU - Morosinotto, Tomas AU - Bóta, Attila AU - Kouřil, Roman AU - Špunda, Vladimír AU - Garab, Győző TI - Lipid Polymorphism of the Subchloroplast—Granum and Stroma Thylakoid Membrane–Particles. II. Structure and Functions JF - CELLS J2 - CELLS-BASEL VL - 10 PY - 2021 IS - 9 PG - 19 SN - 2073-4409 DO - 10.3390/cells10092363 UR - https://m2.mtmt.hu/api/publication/32258462 ID - 32258462 N1 - Funding Agency and Grant Number: Czech Science FoundationGrant Agency of the Czech Republic [GACR 19-13637S]; National Research Development and Innovation Office of HungaryNational Research, Development & Innovation Office (NRDIO) - Hungary [OTKA K 128679]; Hungarian Ministry for National Economy [GINOP-2.3.2-152016-00058]; project "SustES-Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions" [CZ.02.1.01/0.0/0.0/16_019/0000797]; Ministry of Education, Youth and Sports of CR within the CzeCOS program [LM2018123]; European Regional Development Fund (ERDF) project 'Plants as a tool for sustainable global development' [CZ.02.1.01/0.0/0.0/16_019/0000827]; Silesian Region [07359/2019/RRC]; University of Ostrava [SGS02/P.rF/2021]; MEYS CR [LM2015043]; CF Cryo-electron Microscopy and Tomography Funding text: This work was supported by grants from the Czech Science Foundation (GAC. R 19-13637S to G.G., V.S., V.K., I.K. and O.D.), the National Research Development and Innovation Office of Hungary (OTKA K 128679 to G.G.), the Hungarian Ministry for National Economy (GINOP-2.3.2-152016-00058 to I.D.), the project "SustES-Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions" (CZ.02.1.01/0.0/0.0/16_019/0000797, to V.S. and V.K.), by the Ministry of Education, Youth and Sports of CR within the CzeCOS program (no. LM2018123 to I.K. and V.K.), by the European Regional Development Fund (ERDF) project `Plants as a tool for sustainable global development' (no. CZ.02.1.01/0.0/0.0/16_019/0000827), the Silesian Region (07359/2019/RRC to O.D.) and the University of Ostrava (SGS02/P.rF/2021 to O.D.). The 31P-NMR measurements were performed in the NMR Center of CERIC-ERIC. We thank CIISB research infrastructure project LM2015043, funded by MEYS CR; financial support of the measurements at the CF Cryo-electron Microscopy and Tomography is gratefully acknowledged. AB - In Part I, by using P-31-NMR spectroscopy, we have shown that isolated granum and stroma thylakoid membranes (TMs), in addition to the bilayer, display two isotropic phases and an inverted hexagonal (H-II) phase; saturation transfer experiments and selective effects of lipase and thermal treatments have shown that these phases arise from distinct, yet interconnectable structural entities. To obtain information on the functional roles and origin of the different lipid phases, here we performed spectroscopic measurements and inspected the ultrastructure of these TM fragments. Circular dichroism, 77 K fluorescence emission spectroscopy, and variable chlorophyll-a fluorescence measurements revealed only minor lipase- or thermally induced changes in the photosynthetic machinery. Electrochromic absorbance transients showed that the TM fragments were re-sealed, and the vesicles largely retained their impermeabilities after lipase treatments-in line with the low susceptibility of the bilayer against the same treatment, as reflected by our P-31-NMR spectroscopy. Signatures of H-II-phase could not be discerned with small-angle X-ray scattering-but traces of H-II structures, without long-range order, were found by freeze-fracture electron microscopy (FF-EM) and cryo-electron tomography (CET). EM and CET images also revealed the presence of small vesicles and fusion of membrane particles, which might account for one of the isotropic phases. Interaction of VDE (violaxanthin de-epoxidase, detected by Western blot technique in both membrane fragments) with TM lipids might account for the other isotropic phase. In general, non-bilayer lipids are proposed to play role in the self-assembly of the highly organized yet dynamic TM network in chloroplasts. LA - English DB - MTMT ER - TY - JOUR AU - Ünnep, Renáta AU - Paul, S. AU - Zsíros, Ottó AU - Kovács, László AU - Székely, Noémi Kinga AU - Steinbach, Gábor AU - Appavou, M.-S. AU - Porcar, L. AU - Holzwarth, A.R. AU - Garab, Győző AU - Nagy, Gergely TI - Thylakoid membrane reorganizations revealed by small-angle neutron scattering of Monstera deliciosa leaves associated with non-photochemical quenching JF - OPEN BIOLOGY J2 - OPEN BIOL VL - 10 PY - 2020 IS - 9 PG - 12 SN - 2046-2441 DO - 10.1098/rsob.200144 UR - https://m2.mtmt.hu/api/publication/31614001 ID - 31614001 N1 - Neutron Spectroscopy Department, Centre for Energy Research, H-1121 Budapest, Konkoly-Thege Miklós út, 29-33, Hungary Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen PSI, CH-5232, Switzerland Max-Planck-Institute for Chemical Energy Conversion, Stiftstr. 34-36, Mülheim a.d. Ruhr, 45470, Germany Biological Research Centre, Institute of Plant Biology, Szeged, 6726, Hungary Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, Garching, 85748, Germany Biological Research Centre, Institute of Biophysics, Temesvári körút 62, Szeged, 6726, Hungary Institut Laue-Langevin, BP 156, Grenoble Cedex 9, 38042, France Department of Physics, Faculty of Science, Ostrava University, Chittussiho 10, Ostrava, 710 00, Czech Republic European Spallation Source ESS ERIC, PO Box 176, Lund, 221 00, Sweden Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, 1121, Hungary Cited By :8 Export Date: 10 May 2024 Correspondence Address: Garab, G.; Biological Research Centre, Hungary; email: garab.gyozo@brc.hu AB - Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants and algae. Although the process is extensively studied, little is known about its relationship with ultrastructural changes of the thylakoid membranes. In order to better understand this relationship, we studied the effects of illumination on the organization of thylakoid membranes in Monstera deliciosa leaves. This evergreen species is known to exhibit very large NPQ and to possess giant grana with dozens of stacked thylakoids. It is thus ideally suited for small-angle neutron scattering measurements (SANS) - a non-invasive technique, which is capable of providing spatially and statistically averaged information on the periodicity of the thylakoid membranes and their rapid reorganizations in vivo. We show that NPQ-inducing illumination causes a strong decrease in the periodic order of granum thylakoid membranes. Development of NPQ and light-induced ultrastructural changes, as well as the relaxation processes, follow similar kinetic patterns. Surprisingly, whereas NPQ is suppressed by diuron, it impedes only the relaxation of the structural changes and not its formation, suggesting that structural changes do not cause but enable NPQ. We also demonstrate that the diminishment of SANS peak does not originate from light-induced redistribution and reorientation of chloroplasts inside the cells. © 2020 The Authors. LA - English DB - MTMT ER - TY - JOUR AU - Zsíros, Ottó AU - Ünnep, Renáta AU - Nagy, Gergely AU - Almásy, László AU - Patai, Roland AU - Szekely, NK AU - Kohlbrecher, J AU - Garab, Győző AU - Dér, András AU - Kovács, László TI - Role of Protein-Water Interface in the Stacking Interactions of Granum Thylakoid Membranes-As Revealed by the Effects of Hofmeister Salts JF - FRONTIERS IN PLANT SCIENCE J2 - FRONT PLANT SCI VL - 11 PY - 2020 PG - 14 SN - 1664-462X DO - 10.3389/fpls.2020.01257 UR - https://m2.mtmt.hu/api/publication/31605569 ID - 31605569 N1 - Export Date: 18 April 2024 LA - English DB - MTMT ER - TY - JOUR AU - Zsíros, Ottó AU - Nagy, Gergely AU - Patai, Roland AU - Solymosi, Katalin AU - Gasser, U. AU - Polgár, Tamás Ferenc AU - Garab, Győző AU - Kovács, László AU - Hörcsik, Tibor Zsolt TI - Similarities and Differences in the Effects of Toxic Concentrations of Cadmium and Chromium on the Structure and Functions of Thylakoid Membranes in Chlorella variabilis JF - FRONTIERS IN PLANT SCIENCE J2 - FRONT PLANT SCI VL - 11 PY - 2020 PG - 13 SN - 1664-462X DO - 10.3389/fpls.2020.01006 UR - https://m2.mtmt.hu/api/publication/31395462 ID - 31395462 LA - English DB - MTMT ER - TY - JOUR AU - Ughy, Bettina AU - Karlický, Václav AU - Dlouhý, Ondřej AU - Javornik, Uroš AU - Materová, Zuzana AU - Zsíros, Ottó AU - Šket, Primož AU - Plavec, Janez AU - Špunda, Vladimír AU - Garab, Győző TI - Lipid-polymorphism of plant thylakoid membranes. Enhanced non-bilayer lipid phases associated with increased membrane permeability. JF - PHYSIOLOGIA PLANTARUM J2 - PHYSIOL PLANTARUM VL - 166 PY - 2019 IS - 1 SP - 278 EP - 287 PG - 10 SN - 0031-9317 DO - 10.1111/ppl.12929 UR - https://m2.mtmt.hu/api/publication/30619359 ID - 30619359 N1 - A közlemény a Bolyai János Kutatási Ösztöndíj támogatásával jött létre Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, Szeged, H-6726, Hungary Department of Physics, Faculty of Science, University of Ostrava, Ostrava, CZ-710 00, Czech Republic Global Change Research Institute, Czech Academy of Sciences, Brno, 603 00, Czech Republic Slovenian NMR Center, National Institute of Chemistry, Ljubljana, Slovenia EN-FIST Center of Excellence, Ljubljana, Slovenia Faculty of Chemistry and Chemical Technology, Ljubljana, Slovenia Cited By :1 Export Date: 27 September 2019 CODEN: PHPLA Correspondence Address: Ughy, B.; Institute of Plant Biology, Biological Research Center, Hungarian Academy of SciencesHungary; email: ughy.bettina@brc.mta.hu Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, Szeged, H-6726, Hungary Department of Physics, Faculty of Science, University of Ostrava, Ostrava, CZ-710 00, Czech Republic Global Change Research Institute, Czech Academy of Sciences, Brno, 603 00, Czech Republic Slovenian NMR Center, National Institute of Chemistry, Ljubljana, Slovenia EN-FIST Center of Excellence, Ljubljana, Slovenia Faculty of Chemistry and Chemical Technology, Ljubljana, Slovenia Cited By :1 Export Date: 17 February 2020 CODEN: PHPLA Correspondence Address: Ughy, B.; Institute of Plant Biology, Biological Research Center, Hungarian Academy of SciencesHungary; email: ughy.bettina@brc.mta.hu AB - Earlier experiments, using 31 P-NMR and time-resolved merocyanine fluorescence spectroscopy, have shown that isolated intact, fully functional plant thylakoid membranes, in addition to the bilayer phase, contain three non-bilayer (or non-lamellar) lipid phases. It has also been shown that the lipid polymorphism of thylakoid membranes can be characterized by remarkable plasticity, i.e. by significant variations in 31 P-NMR signatures. However, changes in the lipid-phase behaviour of thylakoids could not be assigned to changes in the overall membrane organization and the photosynthetic activity, as tested by circular dichroism and 77 K fluorescence emission spectroscopy and the magnitude of the variable fluorescence of photosystem II, which all showed only marginal variations. In this work, we investigated in more detail the temporal stability of the different lipid phases by recording 31 P-NMR spectra on isolated thylakoid membranes that were suspended in sorbitol- or NaCl-based media. We observed, at 5°C during 8 h in the dark, substantial gradual enhancement of the isotropic lipid phases and diminishment of the bilayer phase in the sorbitol-based medium. These changes compared well with the gradually increasing membrane permeability, as testified by the gradual acceleration of the decay of flash-induced electrochromic absorption changes and characteristic changes in the kinetics of fast chlorophyll a-fluorescence transients; all variations were much less pronounced in the NaCl-based medium. These observations suggest that non-bilayer lipids and non-lamellar lipid phases play significant roles in the structural dynamics and functional plasticity of thylakoid membranes. LA - English DB - MTMT ER -