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Mauro Bressan, Roberto Bassi, Luca Dall'Osto
LHCI, the peripheral antenna system of Photosystem I, includes four light-harvesting proteins (Lhca1-Lhca4) in higher plants, all of which are devoid in the Arabidopsis thaliana knock-out mutant ΔLhca. PSI absorption cross-section was reduced in the mutant, thus affecting the redox balance of the photosynthetic electron chain and resulting in a more reduced PQ with respect to the wild type. ΔLhca plants developed compensatory response by enhancing LHCII binding to PSI. However, the amplitude of state transitions, as measured from changes of chlorophyll fluorescence in vivo, was unexpectedly low than the high level of PSI-LHCII supercomplex established...
September 16, 2017: Photosynthesis Research
Henry N Chapman, Petra Fromme
Bright and coherent X-ray sources, such free-electron lasers, have spurred large activities in developing new methods to obtain the structures of biological macromolecules. In particular, single-molecule diffraction is highly desired, as it would abolish the need for crystallization. It provides considerably more diffraction intensity information than needed to solve a structure, unlike crystal diffraction, which is usually insufficient for direct phasing. To overcome the challenge of weak scattering signals of single molecules, the direct phasing approaches in coherent diffractive imaging have been combined with crystals in several imaginative ways...
September 13, 2017: Current Opinion in Structural Biology
Adam A Pérez, Bryan H Ferlez, Amanda M Applegate, Karim Walters, Zhihui He, Gaozhong Shen, John H Golbeck, Donald A Bryant
A site-directed C14G mutation was introduced into the stromal PsaC subunit of Synechococcus sp. strain PCC 7002 in vivo in order to introduce an exchangeable coordination site into the terminal FB [4Fe-4S] cluster of Photosystem I (PSI). Using an engineered PSI-less strain (psaAB deletion), psaC was deleted and replaced with recombinant versions controlled by a strong promoter, and the psaAB deletion was complemented. Modified PSI accumulated at lower levels in this strain and supported slower photoautotrophic growth than wild type...
September 15, 2017: Photosynthesis Research
Muhamed Amin, Mikhail Askerka, Victor S Batista, Gary W Brudvig, Marilyn R Gunner
The oxygen-evolving complex (OEC) of photosystem II (PSII) catalyzes water-splitting through a reaction mechanism that cycles the OEC through five redox states, the 'S-state' intermediates. Understanding structure/function relations of the S-state intermediates is crucial for elucidation of the reaction mechanism and the design of biomimetic catalytic systems. Due to the limitations of conventional X-ray crystallography, serial femtosecond X-ray crystallography has been used to minimize the radiation-damage...
September 15, 2017: Journal of Physical Chemistry. B
Jenny Z Zhang, Paolo Bombelli, Katarzyna P Sokol, Andrea Fantuzzi, A William Rutherford, Christopher J Howe, Erwin Reisner
Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, which can lead to energy losses through inefficient electron transfer (ET) processes. Here, we systematically compare the photoe-lectrochemistry of photosystem II (PSII) protein-films to cyano-bacteria biofilms to derive: (i) the losses in light-to-charge con-version efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured elec-trodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp...
September 15, 2017: Journal of the American Chemical Society
Andrea Pannwitz, Oliver S Wenger
The first artificial donor-sensitizer-acceptor compound in which photoinduced long-range electron transfer is coupled to donor deprotonation and acceptor protonation is reported. The long-lived photoproduct stores energy in the form of a radical pair state in which the charges of the donor and the acceptor remain unchanged, much in contrast to previously investigated systems that exhibit charge-separated states comprised of electron-hole pairs. This finding is relevant for light-driven accumulation of redox equivalents, because it exemplifies how the buildup of charge can be avoided yet light energy can be stored...
September 14, 2017: Journal of the American Chemical Society
Etsuko Fujita, David C Grills, Dmitry E Polyansky
Taking inspiration from natural photosystems, the goal of artificial photosynthesis is to harness solar energy to convert abundant materials, such as CO2 and H2O, into solar fuels. Catalysts are required to ensure that the necessary redox half-reactions proceed in the most energy-efficient manner. It is therefore critical to gain a detailed mechanistic understanding of these catalytic reactions in order to develop new and improved catalysts. Many of the key catalytic intermediates are short-lived transient species, requiring time-resolved spectroscopic techniques for their observation...
September 12, 2017: ChemSusChem
Misa Takahashi, Jun Shigeto, Atsushi Sakamoto, Hiromichi Morikawa
Exposure of intact Arabidopsis leaves to 40 ppm nitrogen dioxide (NO2) in light resulted almost exclusively in nitration of PsbO1, PsbO2, and PsbP1 of photosystem II (PSII), with minor nitration of four non-PS II proteins, including peroxiredoxin II E, as reported previously. Our previous findings that light-triggered selective nitration of PsbO1 decreased oxygen evolution and that inhibition of photoelectric electron transport inhibited nitration of PsbO1 implied that the nitratable tyrosine residue of PsbO1 is redox-active...
September 12, 2017: Plant Signaling & Behavior
Boris K Semin, Lira N Davletshina, Mahir D Mamedov
Lumenal extrinsic proteins PsbO, PsbP, and PsbQ of photosystem II (PSII) protect the catalytic cluster Mn4CaO5 of oxygen-evolving complex (OEC) from the bulk solution and from soluble compounds in the surrounding medium. Extraction of PsbP and PsbQ proteins by NaCl-washing together with chelator EGTA is followed also by the depletion of Ca(2+) cation from OEC. In this study, the effects of PsbP and PsbQ proteins, as well as Ca(2+) extraction from OEC on the kinetics of the reduced primary electron acceptor (QA(-)) oxidation, have been studied by fluorescence decay kinetics measurements in PSII membrane fragments...
September 11, 2017: Photosynthesis Research
Alberta Pinnola, Matteo Ballottari, Ilaria Bargigia, Marcelo Alcocer, Cosimo D'Andrea, Giulio Cerullo, Roberto Bassi
Light harvesting for oxygenic photosynthesis is regulated to prevent the formation of harmful photoproducts by activation of photoprotective mechanisms safely dissipating the energy absorbed in excess. Lumen acidification is the trigger for the formation of quenching states in pigment binding complexes. With the aim to uncover the photoprotective functional states responsible for excess energy dissipation in green algae and mosses, we compared the fluorescence dynamic properties of the light-harvesting complex stress-related (LHCSR1) protein, which is essential for fast and reversible regulation of light use efficiency in lower plants, as compared to the major LHCII antenna protein, which mainly fulfills light harvesting function...
September 11, 2017: Scientific Reports
Michał Rąpała, Bartosz Pluciński, Paweł Jedynak
Bisphenol A (BPA) is a widely used chemical, that can potentially be toxic to plants. In this study we examined the toxicity of 5-50 mg/l of BPA on Arabidopsis thaliana. Additionally, the effects of 0.5-5 mg/l of BPA were examined after four weeks of development. BPA had no effect on the germination rate and the chlorophyll a/b ratio. The chlorophyll a and carotenoid content was significantly elevated in seedlings treated with 5 mg/l of BPA. In 4-week-old plants there was no change in the chlorophyll and carotenoid content and photosynthetic parameters (Fv/Fm, Fv/F0 and PI) were unaffected, which suggests no photoinhibition...
2017: Acta Biochimica Polonica
Caio A C G Brunharo, Bradley D Hanson
Lolium perenne L. spp. multiflorum (Lam.) Husnot (LOLMU) is a winter annual weed, common to row crops, orchards and roadsides. Glyphosate-resistant populations of LOLMU are widespread in California. In many situations, growers have switched to paraquat or other postemergence herbicides to manage glyphosate-resistant LOLMU populations. Recently, poor control of LOLMU with paraquat was reported in a prune orchard in California where paraquat has been used several times. We hypothesize that the low efficacy observed is due to the selection of a paraquat-resistant biotype of LOLMU...
2017: Frontiers in Plant Science
Fumiya Hamada, Akio Murakami, Seiji Akimoto
The light-harvesting mechanisms in three strains of Prochlorococcus marinus, CCMP1986, CCMP1375, and CCMP2773, grown under blue and red light-emitting diodes (LEDs) at two intensity levels were investigated. The blue LED was divinyl chlorophyll b (DV-Chl b) selective, and the red LED was DV-Chl a selective. Under the red LED, the relative amount of DV-Chl b in CCMP1375 and CCMP2773 decreased, and the relative amount of zeaxanthin increased in CCMP1375. Furthermore, when the red-LED-grown cells of CCMP1375 were transplanted under the blue LED, pigment composition was remodified to that under the blue LED...
September 11, 2017: Journal of Physical Chemistry. B
Martin Bommer, Leighton Coates, Holger Dau, Athina Zouni, Holger Dobbek
The PsbO protein of photosystem II stabilizes the active-site manganese cluster and is thought to act as a proton antenna. To enable neutron diffraction studies, crystals of the β-barrel core of PsbO were grown in capillaries. The crystals were optimized by screening additives in a counter-diffusion setup in which the protein and reservoir solutions were separated by a 1% agarose plug. Crystals were cross-linked with glutaraldehyde. Initial neutron diffraction data were collected from a 0.25 mm(3) crystal at room temperature using the MaNDi single-crystal diffractometer at the Spallation Neutron Source, Oak Ridge National Laboratory...
September 1, 2017: Acta Crystallographica. Section F, Structural Biology Communications
Jun Liu, Robert L Last
Despite our increasingly sophisticated understanding of mechanisms ensuring efficient photosynthesis under laboratory-controlled light conditions, less is known about the regulation of photosynthesis under fluctuating light. This is important because-in nature-photosynthetic organisms experience rapid and extreme changes in sunlight, potentially causing deleterious effects on photosynthetic efficiency and productivity. Here we report that the chloroplast thylakoid lumenal protein MAINTENANCE OF PHOTOSYSTEM II UNDER HIGH LIGHT 2 (MPH2; encoded by At4g02530) is required for growth acclimation of Arabidopsis thaliana plants under controlled photoinhibitory light and fluctuating light environments...
September 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
Masakazu Katsumata, Ichiro Takeuchi
We examined the effect of two herbicides (Irgarol 1051 and Diuron) on symbiotic dinoflagellates in the hard coral Acropora digitifera using delayed fluorescence (DF), specifically assessing changes in molecular membrane transport, i.e. inflow and outflow rates, and the binding of the herbicides to target proteins in photosystem II. The DF approach is rapid (e.g. measurement time, 60 s) and non-invasive, and can provide data on the extent of a photosynthetic system and the activity of its electron carriers. The DF of A...
August 30, 2017: Marine Pollution Bulletin
S Massoz, M Hanikenne, B Bailleul, N Coosemans, M Radoux, H Miranda-Astudillo, P Cardol, V Larosa, C Remacle
The qualitative screening method to select complex I mutants in the microalga Chlamydomonas, based on reduced growth under heterotrophic condition, is not suited for high throughput screening. In order to develop a fast screening method based on measurements of chlorophyll fluorescence, we first demonstrated that complex I mutants displayed decreased photosystem II efficiency in the genetic background of a photosynthetic mutation leading to reduced formation of the electrochemical proton gradient in the chloroplast (pgrl1 mutation)...
August 30, 2017: Plant Journal: for Cell and Molecular Biology
Ikumi Umetani, Motoshi Kunugi, Makio Yokono, Atsushi Takabayashi, Ayumi Tanaka
Diverse light-harvesting complexes (LHCs) have been found in photosynthetic microalgae that originated from secondary endosymbiosis involving primary red algae. However, the associations between LHCs and photosystem I (PSI) and photosystem II (PSII) in these microalgae are not fully understood. Eustigmatophyta is a red algal lineage that appears to have a unique organization in its photosynthetic machinery, consisting of only chlorophyll a and carotenoids that are atypical compared with other closely related groups...
August 30, 2017: Photosynthesis Research
Pascal Albanese, Roberto Melero, Benjamin D Engel, Alessandro Grinzato, Paola Berto, Marcello Manfredi, Angelica Chiodoni, Javier Vargas, Carlos Óscar Sánchez Sorzano, Emilio Marengo, Guido Saracco, Giuseppe Zanotti, Jose-Maria Carazo, Cristina Pagliano
In higher plant thylakoids, the heterogeneous distribution of photosynthetic protein complexes is a determinant for the formation of grana, stacks of membrane discs that are densely populated with Photosystem II (PSII) and its light harvesting complex (LHCII). PSII associates with LHCII to form the PSII-LHCII supercomplex, a crucial component for solar energy conversion. Here, we report a biochemical, structural and functional characterization of pairs of PSII-LHCII supercomplexes, which were isolated under physiologically-relevant cation concentrations...
August 30, 2017: Scientific Reports
Sha Tang, Lin Li, Yongqiang Wang, Qiannan Chen, Wenying Zhang, Guanqing Jia, Hui Zhi, Baohua Zhao, Xianmin Diao
Understanding drought-tolerance mechanisms and identifying genetic dominance are important for crop improvement. Setaria italica, which is extremely drought-tolerant, has been regarded as a model plant for studying stress biology. Moreover, different genotypes of S. italica have evolved various drought-tolerance/avoidance mechanisms that should be elucidated. Physiological and transcriptomic comparisons between drought-tolerant S. italica cultivar 'Yugu1' and drought-sensitive 'An04' were conducted. 'An04' had higher yields and more efficient photosystem activities than 'Yugu1' under well-watered conditions, and this was accompanied by positive brassinosteroid regulatory actions...
August 30, 2017: Scientific Reports
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