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https://www.readbyqxmd.com/read/28438997/nucleophilic-water-attack-is-not-a-possible-mechanism-for-o-o-bond-formation-in-photosystem-ii
#1
Per E M Siegbahn
Two different types of mechanisms are at present suggested for the O-O bond-formation step in photosystem II. The first one is a coupling between an oxyl radical and a bridging oxo. The second one is a nucleophilic water attack on a terminal oxo (or oxyl) group. In the present short paper, the six most reasonable versions of the latter mechanism have been studied and compared with the oxo-oxyl mechanism. The barriers are found to be much too high for the water attack, and that mechanism can therefore safely be ruled out...
April 24, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28437448/expression-profiling-of-chrysanthemum-crassum-under-salinity-stress-and-the-initiation-of-morphological-changes
#2
Zhiyong Guan, Yitong Feng, Aiping Song, Xiaomeng Shi, Yachao Mao, Sumei Chen, Jiafu Jiang, Lian Ding, Fadi Chen
Chrysanthemum crassum is a decaploid species of Chrysanthemum with high stress tolerance that allows survival under salinity stress while maintaining a relatively ideal growth rate. We previously recorded morphological changes after salt treatment, such as the expansion of leaf cells. To explore the underlying salinity tolerance mechanisms, we used an Illumina platform and obtained three sequencing libraries from samples collected after 0 h, 12 h and 24 h of salt treatment. Following de novo assembly, 154,944 transcripts were generated, and 97,833 (63...
2017: PloS One
https://www.readbyqxmd.com/read/28432885/from-laboratory-to-field-studies-the-assessment-of-biscutella-laevigata-suitability-to-biological-reclamation-of-areas-contaminated-with-lead-and-cadmium
#3
Ewa Muszyńska, Ewa Hanus-Fajerska, Barbara Piwowarczyk, Joanna Augustynowicz, Krystyna Ciarkowska, Tomasz Czech
The aim of the work was to evaluate the usefulness of the in vitro multiplication of Biscutella laevigata calamine ecotype for in situ reclamation of post-flotation wastes polluted with Pb and Cd. The experiment was conducted on three steps: (i) plant shoots' production under in vitro condition, (ii) establishment of the material in greenhouse experiment, and finally (iii) field cultivation directly on the mining-waste heap of Olkusz Ore-Bearing Region, Poland. This region is known to be one of the most chemically-degraded area in central Europe...
April 19, 2017: Ecotoxicology and Environmental Safety
https://www.readbyqxmd.com/read/28432538/superoxide-generated-in-the-chloroplast-stroma-causes-photoinhibition-of-photosystem-i-in-the-shade-establishing-tree-species-psychotria-henryi
#4
Wei Huang, Ying-Jie Yang, Jiao-Lin Zhang, Hong Hu, Shi-Bao Zhang
Our previous studies indicated that high light induced significant photoinhibition of photosystem I (PSI) in the shade-establishing tree species Psychotria henryi. However, the underlying mechanism has not been fully clarified. In the present study, in order to investigate the mechanism of PSI photoinhibition in P. henryi, we treated detached leaves with constant high light in the presence of methyl viologen (MV) or a soluble α-tocopherol analog, 2,2,5,7,8-pentamethyl-6-chromanol (PMC). We found that MV significantly depressed photochemical quantum yields in PSI and PSII when compared to PMC...
April 21, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28432258/lil3-a-light-harvesting-complex-protein-links-terpenoid-and-tetrapyrrole-biosynthesis
#5
Daniel Hey, Maxi Rothbart, Josephine Herbst, Peng Wang, Jakob Müller, Daniel Wittmann, Kirsten Gruhl, Bernhard Grimm
LIL3 of Arabidopsis thaliana belongs to the light-harvesting complex (LHC) family, which also includes the light-harvesting chlorophyll-binding proteins of photosystems 1 and 2, the early-light-inducible proteins, PsbS involved in non-photochemical quenching, the one-helix-proteins and their cyanobacterial homologs designated high-light-inducible proteins. Each member of this family is characterized by one or two LHC transmembrane domains (referred to as the LHC motif) to which potential functions such as chlorophyll binding, protein interaction and integration of interacting partners into the plastid membranes have been attributed...
April 21, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28429322/photo-and-nutritional-regulation-of-euglena-organelle-development
#6
Steven D Schwartzbach
Euglena can use light and CO2, photosynthesis, as well as a large variety of organic molecules as the sole source of carbon and energy for growth. Light induces the enzymes, in this case an entire organelle, the chloroplast, that is required to use CO2 as the sole source of carbon and energy for growth. Ethanol, but not malate, inhibits the photoinduction of chloroplast enzymes and induces the synthesis of the glyoxylate cycle enzymes that comprise the unique metabolic pathway leading to two carbon, ethanol and acetate, assimilation...
2017: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/28428249/crystal-structure-and-redox-properties-of-a-novel-cyanobacterial-heme-protein-with-a-his-cys-heme-axial-ligation-and-a-per-arnt-sim-pas-like-domain
#7
Taiki Motomura, Michihiro Suga, Rainer Hienerwadel, Akiko Nakagawa, Thanh-Lan Lai, Wolfgang Nitschke, Takahiro Kuma, Miwa Sugiura, Alain Boussac, Jain-Ren Shen
Photosystem II (PSII) catalyzes the light-induced water oxidation leading to the generation of dioxygen indispensable for sustaining aerobic life on Earth. The PSII reaction center is composed of D1 and D2 proteins encoded by the psbA and psbD genes, respectively. In cyanobacteria, different psbA genes are present in the genome. The thermophilic cyanobacterium Thermosynechococcus elongatus contains 3 psbA genes, psbA1, psbA2 and psbA3 and a new c-type heme protein, Tll0287, was found to be expressed in a strain expressing the psbA2 gene only, but the structure and function of Tll0287 are unknown...
April 20, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28427865/dynamics-and-energetics-of-cyanobacterial-photosystem-i-ferredoxin-complexes-in-different-redox-states
#8
Pierre Sétif, Risa Mutoh, Genji Kurisu
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...
April 17, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28426976/alternative-electron-transport-pathways-in-photosynthesis-a-confluence-of-regulation
#9
REVIEW
Jean Alric, Xenie Johnson
Photosynthetic reactions proceed along a linear electron transfer chain linking water oxidation at photosystem II (PSII) to CO2 reduction in the Calvin-Benson-Bassham cycle. Alternative pathways poise the electron carriers along the chain in response to changing light, temperature and CO2 inputs, under prolonged hydration stress and during development. We describe recent literature that reports the physiological functions of new molecular players. Such highlights include the flavodiiron proteins and their important role in the green lineage...
April 17, 2017: Current Opinion in Plant Biology
https://www.readbyqxmd.com/read/28421444/long-term-hyperthermia-impairs-activity-of-both-photosystems
#10
M A Kozuleva, E A Lysenko, A A Klaus, V V Kuznetsov
This is the first study to perform a simultaneous analysis of the activity of photosystem 1 and photosystem 2 after long-term exposure to elevated temperature. It was found that the quantum yield of photochemical reactions decreases in both photosystems. It is shown that, in photosystem 2, the regulated nonphotochemical quenching decreases whereas the unregulated non-photochemical quenching increases. In photosystem 1, limitation on both acceptor and donor sides increases.
January 2017: Doklady. Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28421101/hyperspectral-technologies-for-assessing-seed-germination-and-trifloxysulfuron-methyl-response-in-amaranthus-palmeri-palmer-amaranth
#11
Maor Matzrafi, Ittai Herrmann, Christian Nansen, Tom Kliper, Yotam Zait, Timea Ignat, Dana Siso, Baruch Rubin, Arnon Karnieli, Hanan Eizenberg
Weed infestations in agricultural systems constitute a serious challenge to agricultural sustainability and food security worldwide. Amaranthus palmeri S. Watson (Palmer amaranth) is one of the most noxious weeds causing significant yield reductions in various crops. The ability to estimate seed viability and herbicide susceptibility is a key factor in the development of a long-term management strategy, particularly since the misuse of herbicides is driving the evolution of herbicide response in various weed species...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28419460/land-plants-drive-photorespiration-as-higher-electron-sink-comparative-study-of-post-illumination-transient-o2-uptake-rates-from-liverworts-to-angiosperms-through-ferns-and-gymnosperms
#12
Hitomi Hanawa, Kimitsune Ishizaki, Kana Nohira, Daisuke Takagi, Ginga Shimakawa, Takehiro Sejima, Kei-Ichiro Shaku, Amane Makino, Chikahiro Miyake
In higher plants, the electron-sink capacity of photorespiration contributes to alleviation of photoinhibition by dissipating excess energy under conditions when photosynthesis is limited. We addressed the question at what point in the evolution of photosynthetic organisms photorespiration began to function as electron sink and replaced the flavodiiron proteins which catalyze the reduction of O2 at photosystem I in cyanobacteria. Algae do not have a higher activity of photorespiration when CO2 assimilation is limited, and it can therefore not act as an electron sink...
April 17, 2017: Physiologia Plantarum
https://www.readbyqxmd.com/read/28419154/salt-stress-induces-changes-in-the-proteomic-profile-of-micropropagated-sugarcane-shoots
#13
Lucas Z Passamani, Roberta R Barbosa, Ricardo S Reis, Angelo S Heringer, Patricia L Rangel, Claudete Santa-Catarina, Clícia Grativol, Carlos F M Veiga, Gonçalo A Souza-Filho, Vanildo Silveira
Salt stress is one of the most common stresses in agricultural regions worldwide. In particular, sugarcane is affected by salt stress conditions, and no sugarcane cultivar presently show high productivity accompanied by a tolerance to salt stress. Proteomic analysis allows elucidation of the important pathways involved in responses to various abiotic stresses at the biochemical and molecular levels. Thus, this study aimed to analyse the proteomic effects of salt stress in micropropagated shoots of two sugarcane cultivars (CB38-22 and RB855536) using a label-free proteomic approach...
2017: PloS One
https://www.readbyqxmd.com/read/28416696/zeaxanthin-dependent-nonphotochemical-quenching-does-not-occur-in-photosystem-i-in-the-higher-plant-arabidopsis-thaliana
#14
Lijin Tian, Pengqi Xu, Volha U Chukhutsina, Alfred R Holzwarth, Roberta Croce
Nonphotochemical quenching (NPQ) is the process that protects the photosynthetic apparatus of plants and algae from photodamage by dissipating as heat the energy absorbed in excess. Studies on NPQ have almost exclusively focused on photosystem II (PSII), as it was believed that NPQ does not occur in photosystem I (PSI). Recently, Ballottari et al. [Ballottari M, et al. (2014) Proc Natl Acad Sci USA 111:E2431-E2438], analyzing PSI particles isolated from an Arabidopsis thaliana mutant that accumulates zeaxanthin constitutively, have reported that this xanthophyll can efficiently induce chlorophyll fluorescence quenching in PSI...
April 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28413444/functional-photosystem-i-maintains-proper-energy-balance-during-nitrogen-depletion-in-chlamydomonas-reinhardtii-promoting-triacylglycerol-accumulation
#15
Mahmoud Gargouri, Philip D Bates, Jeong-Jin Park, Helmut Kirchhoff, David R Gang
BACKGROUND: Nutrient deprivation causes significant stress to the unicellular microalga, Chlamydomonas reinhardtii, which responds by significantly altering its metabolic program. Following N deprivation, the accumulation of starch and triacylglycerols (TAGs) is significantly altered following massive reprogramming of cellular metabolism. One protein that was found to change dramatically and early to this stress was TAB2, a photosystem I (PSI) translation initiation factor, whose transcript and protein levels increased significantly after only 30 min of N deprivation...
2017: Biotechnology for Biofuels
https://www.readbyqxmd.com/read/28409634/calcium-ammonia-redox-active-tyrosine-yz-and-proton-coupled-electron-transfer-in-the-photosynthetic-oxygen-evolving-complex
#16
Zhanjun Guo, Bridgette A Barry
A redox-active tyrosine, YZ (Y161 in the D1 polypeptide), is essential in photosystem II (PSII), which conducts photosynthetic oxygen evolution. On each step of the light-driven oxygen evolving reaction, YZ radical is formed by a chlorophyll cation radical. YZ radical is then reduced by a Mn4CaO5 cluster in a proton coupled electron transfer (PCET) reaction. YZ is hydrogen bonded to His190-D1 and to water molecules in a hydrogen-bonding network, involving calcium. This network is sensitive to disruption with ammonia and to removal and replacement of calcium...
April 14, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28405863/high-light-acclimation-of-chromera-velia-points-to-photoprotective-npq
#17
Erica Belgio, Eliška Trsková, Eva Kotabová, Daniela Ewe, Ondřej Prášil, Radek Kaňa
It has previously been shown that the long-term treatment of Arabidopsis thaliana with the chloroplast inhibitor lincomycin leads to photosynthetic membranes enriched in antennas, strongly reduced in photosystem II reaction centers (PSII) and with enhanced nonphotochemical quenching (NPQ) (Belgio et al. Biophys J 102:2761-2771, 2012). Here, a similar physiological response was found in the microalga Chromera velia grown under high light (HL). In comparison to cells acclimated to low light, HL cells displayed a severe re-organization of the photosynthetic membrane characterized by (1) a reduction of PSII but similar antenna content; (2) partial uncoupling of antennas from PSII; (3) enhanced NPQ...
April 12, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28405862/isolation-and-characterization-of-psi-lhci-super-complex-and-their-sub-complexes-from-a-red-alga-cyanidioschyzon-merolae
#18
Lirong Tian, Zheyi Liu, Fangjun Wang, Liangliang Shen, Jinghua Chen, Lijing Chang, Songhao Zhao, Guangye Han, Wenda Wang, Tingyun Kuang, Xiaochun Qin, Jian-Ren Shen
Photosystem I (PSI)-light-harvesting complex I (LHCI) super-complex and its sub-complexes PSI core and LHCI, were purified from a unicellular red alga Cyanidioschyzon merolae and characterized. PSI-LHCI of C. merolae existed as a monomer with a molecular mass of 580 kDa. Mass spectrometry analysis identified 11 subunits (PsaA, B, C, D, E, F, I, J, K, L, O) in the core complex and three LHCI subunits, CMQ142C, CMN234C, and CMN235C in LHCI, indicating that at least three Lhcr subunits associate with the red algal PSI core...
April 12, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28401734/photoswitchable-sn-cyt-c-solid-state-devices
#19
Satoshi Nakamaru, Frank Scholz, William E Ford, Yoshio Goto, Florian von Wrochem
Electron transfer across proteins plays an important role in many biological processes, including those relevant for the conversion of solar photons to chemical energy. Previous studies demonstrated the generation of photocurrents upon light irradiation in a number of photoactive proteins, such as photosystem I or bacteriorhodopsin. Here, it is shown that Sn-cytochrome c layers act as reversible and efficient photoelectrochemical switches upon integration into large-area solid-state junctions. Photocurrents are observed both in the Soret band (λ = 405 nm) and in the Q band (λ = 535 nm), with current on/off ratios reaching values of up to 25...
April 12, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28400776/translation-and-co-translational-membrane-engagement-of-plastid-encoded-chlorophyll-binding-proteins-are-not-influenced-by-chlorophyll-availability-in-maize
#20
Reimo Zoschke, Prakitchai Chotewutmontri, Alice Barkan
Chlorophyll is an indispensable constituent of the photosynthetic machinery in green organisms. Bound by apoproteins of photosystems I and II, chlorophyll performs light-harvesting and charge separation. Due to the phototoxic nature of free chlorophyll and its precursors, chlorophyll synthesis is regulated to comply with the availability of nascent chlorophyll-binding apoproteins. Conversely, the synthesis and co-translational insertion of such proteins into the thylakoid membrane have been suggested to be influenced by chlorophyll availability...
2017: Frontiers in Plant Science
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