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Photosynthesis Research

Hisanori Yamakawa, Ivo H M van Stokkum, Ulrich Heber, Shigeru Itoh
Some mosses stay green and survive long even under desiccation. Dissipation mechanisms of excess excitation energy were studied in two drought-tolerant moss species adapted to contrasting niches: shade-adapted Rhytidiadelphus squarrosus and sun-adapted Rhytidium rugosum in the same family. (1) Under wet conditions, a light-induced nonphotochemical quenching (NPQ) mechanism decreased the yield of photosystem II (PSII) fluorescence in both species. The NPQ extent saturated at a lower illumination intensity in R...
November 18, 2017: Photosynthesis Research
Nuran Çiçek, Abdallah Oukarroum, Reto J Strasser, Gert Schansker
The main objective of this study was to evaluate the effects of salt stress on the photosynthetic electron transport chain using two chickpea lines (Cicer arietinum L.) differing in their salt stress tolerance at the germination stage (AKN 87 and AKN 290). Two weeks after sowing, seedlings were exposed to salt stress for 2 weeks and irrigated with 200 ml of 200 mM NaCl every 2 days. The polyphasic OJIP fluorescence transient and the 820-nm transmission kinetics (photosystem I) were used to evaluate the effects of salt stress on the functionality of the photosynthetic electron transport chain...
November 9, 2017: Photosynthesis Research
Yutaka Shibata, Ahmed Mohamed, Koichiro Taniyama, Kentaro Kanatani, Makiko Kosugi, Hiroshi Fukumura
Some mosses are extremely tolerant of drought stress. Their high drought tolerance relies on their ability to effectively dissipate absorbed light energy to heat under dry conditions. The energy dissipation mechanism in a drought-tolerant moss, Bryum argenteum, has been investigated using low-temperature picosecond time-resolved fluorescence spectroscopy. The results are compared between moss thalli samples harvested in Antarctica and in Japan. Both samples show almost the same quenching properties, suggesting an identical drought tolerance mechanism for the same species with two completely different habitats...
November 9, 2017: Photosynthesis Research
Vaishali Dutt, Shireesh Srivastava
Many freshwater cyanobacteria accumulate polyhydroxybutyrate (PHB) under nitrogen or phosphorus deprivation. While prior literature has shed lights on transcriptomic and metabolomic changes in the model cyanobacterium Synechocystis PCC 6803 cells, the quantitative contributions of the newly fixed carbon following nitrogen deprivation or the externally added acetate to PHB synthesis are not clear. Similarly, it is not clear how photomixotrophy affects precursor contributions. In this study, we show that (i) the pre-growth mode (photoautotrophic or photomixotrophic), while significantly impacting glycogen levels, does not have any significant effect on PHB levels, (ii) the carbon fixed following nitrogen deprivation contributes 26% of C for PHB synthesis in photoautotrophically pre-grown cells and its contribution to the PHB synthesis goes down with the addition of acetate at the resuspension phase or with photomixotrophic pre-growth, (iii) the acetate added at the start of nitrogen deprivation, doubles the intracellular PHB levels and contributes 44-48% to PHB synthesis and this value is not greatly affected by how the cells were pre-grown...
November 9, 2017: Photosynthesis Research
Daisuke Seo, Tomoya Asano
Ferredoxin-NAD(P)(+) reductase ([EC], [EC]) from Chlorobaculum tepidum (CtFNR) is structurally homologous to the bacterial NADPH-thioredoxin reductase (TrxR), but possesses a unique C-terminal extension relative to TrxR that interacts with the isoalloxazine ring moiety of the flavin adenine dinucleotide prosthetic group. In this study, we introduce truncations to the C-terminal residues to examine their role in the reactions of CtFNR with NADP(+) and NADPH by spectroscopic and kinetic analyses...
November 8, 2017: Photosynthesis Research
Cheng Xingxing, Liu Jiuyang, Zhang Huan, Li Fudong, Zhang Shuya, Xu Min, Ruan Ke, Wang Yuhua, Fu Aigen
Proper biogenesis and maintenance of photosynthetic thylakoid membrane complexes are essential for the photosynthetic light reactions. A thylakoid lumenal protein, Psb27, plays a vital role in assembly or/and maintenance of photosystem II (PSII). In cyanobacteria, it is a small lipoprotein docked to the lumenal side of PSII, and functions in the assembly of the Mn4Ca cluster and in the PSII repair cycle. However, Psb27 from Arabidopsis thaliana is not a lipoprotein, and it is involved in PSII repair and acclimation to fluctuating light stress, suggesting a functional divergence between Arabidopsis Psb27 and cyanobacterial Psb27s...
November 2, 2017: Photosynthesis Research
Gábor Bernát, Gábor Steinbach, Radek Kaňa, Govindjee, Amarendra N Misra, Ondřej Prašil
The slow kinetic phases of the chlorophyll a fluorescence transient (induction) are valuable tools in studying dynamic regulation of light harvesting, light energy distribution between photosystems, and heat dissipation in photosynthetic organisms. However, the origin of these phases are not yet fully understood. This is especially true in the case of prokaryotic oxygenic photoautotrophs, the cyanobacteria. To understand the origin of the slowest (tens of minutes) kinetic phase, the M-T fluorescence decline, in the context of light acclimation of these globally important microorganisms, we have compared spectrally resolved fluorescence induction data from the wild type Synechocystis sp...
October 31, 2017: Photosynthesis Research
Dorota Kowalska, Marcin Szalkowski, Khuram Ashraf, Justyna Grzelak, Heiko Lokstein, Joanna Niedziolka-Jonsson, Richard Cogdell, Sebastian Mackowski
A polyhistidine tag (His-tag) present on Chlorobaculum tepidum reaction centers (RCs) was used to immobilize photosynthetic complexes on a silver nanowire (AgNW) modified with nickel-chelating nitrilo-triacetic acid (Ni-NTA). The optical properties of conjugated nanostructures were studied using wide-field and confocal fluorescence microscopy. Plasmonic enhancement of RCs conjugated to AgNWs was observed as their fluorescence intensity dependence on the excitation wavelength does not follow the excitation spectrum of RC complexes in solution...
October 31, 2017: Photosynthesis Research
Ekaterina Sukhova, Maxim Mudrilov, Vladimir Vodeneev, Vladimir Sukhov
Local damage (mainly burning, heating, and mechanical wounding) induces propagation of electrical signals, namely, variation potentials, which are important signals during the life of plants that regulate different physiological processes, including photosynthesis. It is known that the variation potential decreases the rate of CO2 assimilation by the Calvin-Benson cycle; however, its influence on light reactions has been poorly investigated. The aim of our work was to investigate the influence of the variation potential on the light energy flow that is absorbed, trapped and dissipated per active reaction centre in photosystem II and on the flow of electrons through the chloroplast electron transport chain...
October 31, 2017: Photosynthesis Research
P P Pashkovskiy, T N Soshinkova, D V Korolkova, A V Kartashov, I E Zlobin, V Yu Lyubimov, V D Kreslavski, Vl V Kuznetsov
The antioxidant balance, photochemical activity of photosystem II (PSII), and photosynthetic pigment content, as well as the expression of genes involved in the light signalling of callus lines of Eutrema salsugineum plants (earlier Thellungiella salsuginea) under different spectral light compositions were studied. Growth of callus in red light (RL, maximum 660 nm), in contrast to blue light (BL, maximum 450 nm), resulted in a lower H2O2 content and thiobarbituric acid reactive substances (TBARS). The BL increased the activities of key antioxidant enzymes in comparison with the white light (WL) and RL and demonstrated the minimum level of PSII photochemical activity...
October 25, 2017: Photosynthesis Research
Gábor Sipka, Péter Maróti
Upon high light excitation in photosynthetic bacteria, various triplet states of pigments can accumulate leading to harmful effects. Here, the generation and lifetime of flash-induced carotenoid triplets ((3)Car) have been studied by observation of the quenching of bacteriochlorophyll (BChl) fluorescence in different strains of photosynthetic bacteria including Rvx. gelatinosus (anaerobic and semianaerobic), Rsp. rubrum, Thio. roseopersicina, Rba. sphaeroides 2.4.1 and carotenoid- and cytochrome-deficient mutants Rba...
October 24, 2017: Photosynthesis Research
Anjali Pandit, Ivo H M van Stokkum, Herbert van Amerongen, Roberta Croce
No abstract text is available yet for this article.
October 17, 2017: Photosynthesis Research
Sebastian Szewczyk, Wojciech Giera, Rafał Białek, Gotard Burdziński, Krzysztof Gibasiewicz
Femtosecond transient absorption was used to study excitation decay in monomeric and trimeric cyanobacterial Photosystem I (PSI) being prepared in three states: (1) in aqueous solution, (2) deposited and dried on glass surface (either conducting or non-conducting), and (3) deposited on glass (conducting) surface but being in contact with aqueous solvent. The main goal of this contribution was to determine the reason of the acceleration of the excitation decay in dried PSI deposited on the conducting surface relative to PSI in solution observed previously using time-resolved fluorescence (Szewczyk et al...
October 13, 2017: Photosynthesis Research
Alonso M Acuña, Claire Lemaire, Rienk van Grondelle, Bruno Robert, Ivo H M van Stokkum
Excitation energy transfer (EET) and trapping in Synechococcus WH 7803 whole cells and isolated photosystem I (PSI) complexes have been studied by time-resolved emission spectroscopy at room temperature (RT) and at 77 K. With the help of global and target analysis, the pathways of EET and the charge separation dynamics have been identified. Energy absorbed in the phycobilisome (PB) rods by the abundant phycoerythrin (PE) is funneled to phycocyanin (PC645) and from there to the core that contains allophycocyanin (APC660 and APC680)...
October 13, 2017: Photosynthesis Research
Rodrigo Gómez, Néstor Carrillo, María P Morelli, Suresh Tula, Fahimeh Shahinnia, Mohammad-Reza Hajirezaei, Anabella F Lodeyro
Plants grown in the field experience sharp changes in irradiation due to shading effects caused by clouds, other leaves, etc. The excess of absorbed light energy is dissipated by a number of mechanisms including cyclic electron transport, photorespiration, and Mehler-type reactions. This protection is essential for survival but decreases photosynthetic efficiency. All phototrophs except angiosperms harbor flavodiiron proteins (Flvs) which relieve the excess of excitation energy on the photosynthetic electron transport chain by reducing oxygen directly to water...
October 11, 2017: Photosynthesis Research
Viktor A Anashkin, Yulia V Bertsova, Adalyat M Mamedov, Mahir D Mamedov, Alexander M Arutyunyan, Alexander A Baykov, Alexander V Bogachev
Light-driven H(+), Cl(-) and Na(+) rhodopsin pumps all use a covalently bound retinal molecule to capture light energy. Some H(+)-pumping rhodopsins (xanthorhodopsins; XRs) additionally contain a carotenoid antenna for light absorption. Comparison of the available primary and tertiary structures of rhodopsins pinpointed a single Thr residue (Thr216) that presumably prevents carotenoid binding to Na(+)-pumping rhodopsins (NaRs). We replaced this residue in Dokdonia sp. PRO95 NaR with Gly, which is found in the corresponding position in XRs, and produced a variant rhodopsin in a ketocarotenoid-synthesising Escherichia coli strain...
October 5, 2017: Photosynthesis Research
Mikael Kim, Kasper Elgetti Brodersen, Milán Szabó, Anthony W D Larkum, John A Raven, Peter J Ralph, Mathieu Pernice
Seagrasses are a diverse group of angiosperms that evolved to live in shallow coastal waters, an environment regularly subjected to changes in oxygen, carbon dioxide and irradiance. Zostera muelleri is the dominant species in south-eastern Australia, and is critical for healthy coastal ecosystems. Despite its ecological importance, little is known about the pathways of carbon fixation in Z. muelleri and their regulation in response to environmental changes. In this study, the response of Z. muelleri exposed to control and very low oxygen conditions was investigated by using (i) oxygen microsensors combined with a custom-made flow chamber to measure changes in photosynthesis and respiration, and (ii) reverse transcription quantitative real-time PCR to measure changes in expression levels of key genes involved in C4 metabolism...
October 4, 2017: Photosynthesis Research
Eliezer M Schwarz, Stephanie Tietz, John E Froehlich
Photosystem II is known to be a highly dynamic multi-protein complex that participates in a variety of regulatory and repair processes. In contrast, photosystem I (PSI) has, until quite recently, been thought of as relatively static. We report the discovery of plant PSI-LHCII megacomplexes containing multiple LHCII trimers per PSI reaction center. These PSI-LHCII megacomplexes respond rapidly to changes in light intensity, as visualized by native gel electrophoresis. PSI-LHCII megacomplex formation was found to require thylakoid stacking, and to depend upon growth light intensity and leaf age...
October 3, 2017: Photosynthesis Research
Agu Laisk, Vello Oja
The OJDIP rise in chlorophyll fluorescence during induction at different light intensities was mathematically modeled using 24 master equations describing electron transport through photosystem II (PSII) plus ordinary differential equations for electron budgets in plastoquinone, cytochrome f, plastocyanin, photosystem I, and ferredoxin. A novel feature of the model is consideration of electron in- and outflow budgets resulting in changes in redox states of Tyrosine Z, P680, and QA as sole bases for changes in fluorescence yield during the transient...
September 21, 2017: Photosynthesis Research
Marcus Moldenhauer, Nikolai N Sluchanko, Neslihan N Tavraz, Cornelia Junghans, David Buhrke, Mario Willoweit, Leonardo Chiappisi, Franz-Josef Schmitt, Vladana Vukojević, Evgeny A Shirshin, Vladimir Y Ponomarev, Vladimir Z Paschenko, Michael Gradzielski, Eugene G Maksimov, Thomas Friedrich
In Fig. 1a in the original article, the amino acid side chains were incorrectly labeled in the structure representation of the orange carotenoid protein (OCP). The corrected figure is printed in this erratum.
September 19, 2017: Photosynthesis Research
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