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Jan Paulo T Zaragoza, Maxime A Siegler, David P Goldberg
High-valent metal-hydroxide species are invoked as critical intermediates in both catalytic, metal-mediated O2 activation (e.g., by Fe porphyrin in Cytochrome P450) and O2 production (e.g., by the Mn cluster in Photosystem II). However, well-characterized mononuclear MIV (OH) complexes remain a rarity. Herein we describe the synthesis of MnIV (OH)(ttppc) (3) (ttppc = tris(2,4,6-triphenylphenyl) corrole), which has been characterized by X-ray diffraction (XRD). The large steric encumbrance of the ttppc ligand allowed for isolation of 3...
March 15, 2018: Journal of the American Chemical Society
Andreas Carstensen, Andrei Herdean, Sidsel Birkelund Schmidt, Anurag Sharma, Cornelia Spetea, Mathias Pribil, Søren Husted
Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency disrupts the photosynthetic machinery and the electron transport chain through a series of sequential events in barley (Hordeum vulgare). Phosphorus deficiency reduces the orthophosphate (Pi) concentration in the chloroplast stroma to levels that inhibit ATP synthase activity...
March 14, 2018: Plant Physiology
Joshua H Marks, Timothy B Ward, Michael A Duncan
Manganese oxide cluster cations are produced by laser vaporization in a pulsed nozzle source, and detected with time-of-flight mass spectrometry. The mass spectrum contains intense peaks for stoichiometries corresponding to (MnO)n+. Multiphoton photodissociation of these clusters yields smaller ions with the same stoichiometric ratio, either by sequential elimination of MnO units or by various fission processes with roughly equal efficiencies. Fragmentation of clusters containing excess oxygen also yields (MnO)n+ fragments...
March 14, 2018: Journal of Physical Chemistry. A
Wei Huang, Ying-Jie Yang, Shi-Bao Zhang, Tao Liu
In higher plants, moderate photoinhibition of photosystem II (PSII) leads to a stimulation of cyclic electron flow (CEF) at low light, which is accompanied by an increase in the P700 oxidation ratio. However, the specific role of CEF stimulation at low light is not well known. Furthermore, the mechanism underlying this increase in P700 oxidation ratio at low light is unclear. To address these questions, intact leaves of the shade-adapted plant Panax notoginseng were treated at 2258 μmol photons m-2 s-1 for 30 min to induce PSII photoinhibition...
2018: Frontiers in Plant Science
Trevor S Kashey, Dustin D Luu, John C Cowgill, Patricia L Baker, Kevin E Redding
Photosynthetic reaction centers (RCs) evolved > 3 billion years ago and have diverged into Type II RCs reducing quinones and Type I RCs reducing soluble acceptors via iron-sulfur clusters. Photosystem I (PSI), the exemplar Type I RC, uses modified menaquinones as intermediate electron transfer cofactors, but it has been controversial if the Type I RC of heliobacteria (HbRC) uses its two bound menaquinones in the same way. The sequence of the quinone-binding site in PSI is not conserved in the HbRC, and the recently solved crystal structure of the HbRC does not reveal a quinone in the analogous site...
March 12, 2018: Photosynthesis Research
Mizue Asada, Taishi Nishimura, Kentaro Ifuku, Hiroyuki Mino
The binding site of the extrinsic protein PsbP in plant photosystem II was mapped by pulsed electron-electron double resonance, using mutant spinach PsbP (Pro20Cys, Ser82Cys, Ala111Cys, and Ala186Cys) labeled with 4-maleimido-TEMPO (MSL) spin label. The distances between the spin label and the Tyr160 neutral radical (YD ) in PsbD, the D2 subunit of plant photosystem II, were 50.8 ± 3.5 Å, 54.9 ± 4.0 Å, 57.8 ± 4.9 Å, and 58.4 ± 14.1 Å, respectively. The geometry inferred from these distances was fitted to the PsbP crystal structure (PDB: 4RTI) to obtain the coordinates of YD relative to PsbP...
March 7, 2018: Biochimica et Biophysica Acta
Yu-Ting Li, Ying Liang, Yue-Nan Li, Xing-Kai Che, Shi-Jie Zhao, Zi-Shan Zhang, Hui-Yuan Gao
Bisphenol A (BPA), a widely distributed pollutant, suppresses photosynthesis in leaves. In previous studies on higher plants, the plants were treated by BPA through irrigation to root. This method cannot distinguish whether the BPA directly suppresses photosynthesis in leaves, or indirectly influences photosynthesis through affecting the function of root. Here, only the leaves but not the roots of cucumber were infiltrated with BPA solution. The photosystem II and I (PSII, PSI) were insensitive to BPA under darkness...
March 9, 2018: Scientific Reports
Ricarda Höhner, Joaquim V Marques, Tetsuro Ito, Yoshiaki Amakura, Alan D Budgeon, Karl Weitz, Kim K Hixson, Laurence B Davin, Helmut Kirchhoff, Norman G Lewis
Arogenate dehydratase (ADT) catalyzes the final step of phenylalanine (Phe) biosynthesis. Previous work showed that ADT-deficient Arabidopsis thaliana mutants had significantly reduced lignin contents, with stronger reductions in lines that had deficiencies in more ADT isoforms. Here, by analyzing Arabidopsis ADT mutants using our phenomics facility and UPLC-MS based metabolomics, we describe the effects of modulation of ADT on photosynthetic parameters and secondary metabolism. Our data indicate that a reduced carbon flux into Phe biosynthesis in ADT mutants impairs the consumption of photosynthetically produced ATP leading to an increased ATP/ADP ratio, the over-accumulation of transitory starch, and lower electron transport rates...
March 9, 2018: Plant Physiology
N N Sluchanko, Y B Slonimskiy, E G Maksimov
Photoprotective mechanisms of cyanobacteria are characterized by several features associated with the structure of their water-soluble antenna complexes - the phycobilisomes (PBs). During energy transfer from PBs to chlorophyll of photosystem reaction centers, the "energy funnel" principle is realized, which regulates energy flux due to the specialized interaction of the PBs core with a quenching molecule capable of effectively dissipating electron excitation energy into heat. The role of the quencher is performed by ketocarotenoid within the photoactive orange carotenoid protein (OCP), which is also a sensor for light flux...
December 2017: Biochemistry. Biokhimii︠a︡
Momchil Paunov, Lyubka Koleva, Andon Vassilev, Jaco Vangronsveld, Vasilij Goltsev
A comparative study of the effects of exposure to high Cd2+ (50 µM) and excess Zn2+ (600 µM) on photosynthetic performance of hydroponically-grown durum wheat seedlings was performed. At day 8, Cd and Zn were added to the nutrient solution. After 7-days exposure, the chosen concentrations of both metals resulted in similar relative growth rate (RGR) inhibitions of about 50% and comparable retardations of the CO₂ assimilation rates (about 30%) in the second developed leaf of wheat seedlings. Analysis of chlorophyll a fluorescence indicated that both metals disturbed photosynthetic electron transport processes which led to a 4- to 5-fold suppression of the efficiency of energy transformation in Photosystem II...
March 9, 2018: International Journal of Molecular Sciences
Ginga Shimakawa, Chikahiro Miyake
Oxygenic phototrophs are vulnerable to damage by reactive oxygen species (ROS) that are produced in photosystem I (PSI) by excess photon energy over the demand of photosynthetic CO2 assimilation. In plant leaves, repetitive short-pulse (rSP) illumination produces ROS to inactivate PSI. The production of ROS is alleviated by oxidation of the reaction center chlorophyll in PSI, P700, during the illumination with the short-pulse light, which is supported by flavodiiron protein (FLV). In this study, we found that in the cyanobacterium Synechocystis sp...
March 8, 2018: Photosynthesis Research
Satomi Arisaka, Haruna Sukigara, Takashi Osanai
Cyanobacteria are a group of prokaryotic organisms that perform oxygenic photosynthesis using a similar photosynthetic apparatus as is used in higher plants and eukaryotic algae. Cyanobacteria are also known to have a circadian rhythm. Here, we evaluated the effects on photosynthesis caused by the genetic manipulation of RpaA, which is a response regulator of a two-component regulatory system responsible for the signal output from circadian clocks. Using the unicellular cyanobacterium Synechocystis sp. PCC 6803, photosynthetic activities and transcript levels of photosystem I and photosystems II in the rpaA-overexpressing strain were measured, and it was found that the parameters, such as Fv /Fm , Fv '/Fm ', qP, and ϕII, obtained from chlorophyll fluorescence analysis were decreased by rpaA overexpression...
March 5, 2018: Journal of Bioscience and Bioengineering
Navish Kumar Batchu, Shradha Khater, Sonal Patil, Vinod Nagle, Gautam Das, Bhaskar Bhadra, Ajit Sapre, Santanu Dasgupta
A filamentous cyanobacteria, Geitlerinema sp. FC II, was isolated from marine algae culture pond at Reliance Industries Limited (RIL), India. The 6.7 Mb draft genome of FC II encodes for 6697 protein coding genes. Analysis of the whole genome sequence revealed presence of nif gene cluster, supporting its capability to fix atmospheric nitrogen. FC II genome contains two variants of sulfide:quinone oxidoreductases (SQR), which is a crucial elector donor in cyanobacterial metabolic processes. FC II is characterized by the presence of multiple CRISPR- Cas (Clustered Regularly Interspaced Short Palindrome Repeats - CRISPR associated proteins) clusters, multiple variants of genes encoding photosystem reaction centres, biosynthetic gene clusters of alkane, polyketides and non-ribosomal peptides...
March 5, 2018: Genomics
Vasily V Ptushenko, Tatiana V Zhigalova, Olga V Avercheva, Alexander N Tikhonov
In plants, the short-term regulation (STR, seconds to minute time scale) of photosynthetic apparatus is associated with the energy-dependent control in the chloroplast electron transport, the distribution of light energy between photosystems (PS) II and I, activation/deactivation of the Calvin-Benson cycle (CBC) enzymes, and relocation of chloroplasts within the plant cell. In this work, using a dual-PAM technique for measuring the time-courses of P700 photooxidation and Chl a fluorescence, we have investigated the STR events in Tradescantia fluminensis leaves...
March 7, 2018: Photosynthesis Research
Padmavathi A V Thangella, Srinivas N B S Pasumarti, Raghu Pullakhandam, Bhanuprakash Reddy Geereddy, Manohar Rao Daggu
Drought is a major constraint to the productivity of many crops affecting various physiological and biochemical processes. Seventy percent of the peanuts are grown in semiarid tropics that are frequently prone to drought stress. So, we analyzed its effect in 4 cultivars of peanut, with different degrees of drought tolerance, under 10 and 20 days of water stress using two-dimensional gel electrophoresis and mass spectrometry. A total of 189 differentially expressed protein spots were identified in the leaf proteome of all the 4 cultivars using PD Quest Basic software; 74 in ICGV 91114, 41 in ICGS 76, 44 in J 11 and 30 in JL 24...
March 2018: 3 Biotech
Neelam Soda, Brijesh K Gupta, Khalid Anwar, Ashutosh Sharan, Govindjee, Sneh L Singla-Pareek, Ashwani Pareek
Cytoskeleton plays a vital role in stress tolerance; however, involvement of intermediate filaments (IFs) in such a response remains elusive in crop plants. This study provides clear evidence about the unique involvement of IFs in cellular protection against abiotic stress in rice. Transcript abundance of Oryza sativa intermediate filament (OsIF) encoding gene showed 2-10 fold up-regulation under different abiotic stress. Overexpression of OsIF in transgenic rice enhanced tolerance to salinity and heat stress, while its knock-down (KD) rendered plants more sensitive thereby indicating the role of IFs in promoting survival under stress...
March 6, 2018: Scientific Reports
Katarzyna Głowacka, Johannes Kromdijk, Katherine Kucera, Jiayang Xie, Amanda P Cavanagh, Lauriebeth Leonelli, Andrew D B Leakey, Donald R Ort, Krishna K Niyogi, Stephen P Long
Insufficient water availability for crop production is a mounting barrier to achieving the 70% increase in food production that will be needed by 2050. One solution is to develop crops that require less water per unit mass of production. Water vapor transpires from leaves through stomata, which also facilitate the influx of CO2 during photosynthetic assimilation. Here, we hypothesize that Photosystem II Subunit S (PsbS) expression affects a chloroplast-derived signal for stomatal opening in response to light, which can be used to improve water-use efficiency...
March 6, 2018: Nature Communications
Marcela Brandão Costa, Francesca Valêncio Tavares, Claudia Bueno Martinez, Ioni Gonçalves Colares, Camila de Martinez Gaspar Martins
This study investigated the ability of Potamogeton pectinatus L. to accumulate copper and its effects on plants. In accumulation tests, macrophytes were exposed (96 h) to different copper concentrations (0-1000 µM) and the metal was measured in media and plant tissues (roots, stems and leaves) to determine the bioconcentration factor (BCF). Plants accumulated high concentrations of copper in a dose-dependent manner and roots was the main organ for copper accumulation. However, the more copper increased in water, the more BCF values decreased...
March 3, 2018: Ecotoxicology and Environmental Safety
Travis C Korosh, Andrew Dutcher, Brian F Pfleger, Katherine D McMahon
Sidestreams in wastewater treatment plants can serve as concentrated sources of nutrients (i.e., nitrogen and phosphorus) to support the growth of photosynthetic organisms that ultimately serve as feedstock for production of fuels and chemicals. However, other chemical characteristics of these streams may inhibit growth in unanticipated ways. Here, we evaluated the use of liquid recovered from municipal anaerobic digesters via gravity belt filtration as a nutrient source for growing the cyanobacterium Synechococcus sp...
January 2018: MSphere
Michal Gwizdala, Tjaart P J Krüger, Md Wahadoszamen, J Michael Gruber, Rienk van Grondelle
Solar energy captured by pigments embedded in light-harvesting complexes can be either transferred to neighboring pigments, dissipated or emitted as fluorescence. Only when it reaches a reaction center the excitation energy is stabilized in the form of a charge separation and converted into chemical energy. Well directed and regulated energy transfer within the network of pigments is therefore of crucial importance for the success of the photosynthetic process. Using single molecule spectroscopy, we show that phycocyanin can dynamically switch between two spectrally distinct states originating from two different conformations...
March 5, 2018: Journal of Physical Chemistry Letters
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