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https://www.readbyqxmd.com/read/28817929/oxidized-polymeric-phenolics-could-they-be-considered-photoprotectors
#1
Laura Rustioni
Photooxidative sunburn is the consequence of photosystem overexcitations. It results in tissue color changes due to chlorophyll degradation and accumulation of oxidized polymeric phenolics (OPPs) resulting from scavenging of reactive oxygen species (ROS). From a productive point of view, OPPs should be considered as damages, decreasing the economical and esthetical values of plants and crops. However, from a physiological perspective, OPPs could be also play a screening role against excessive photosynthetically active radiation (PAR), as they follow the criteria proposed for the identification of photoprotectors, as follows: i) Due to the complex conjugated double bond systems, OPPs absorb and, thus, screen the visible photosynthetically active radiation; ii) The accumulation of brown OPPs is well-known to be stimulated by light exposure resulting in sunburn symptoms; iii) OPPs induce PAR resistance: for example, the sunburned brown skin allows the fruit ripening to proceed without further interferences; iv) the screen provided by the accumulated OPPs in death cells protect underlying tissues, demonstrating an increased resistance to radiation when other physiological processes are not functioning...
August 18, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28815613/switching-off-photoprotection-of-photosystem-i-a-novel-tool-for-gradual-psi-photoinhibition
#2
Mikko Tikkanen, Steffen Grebe
Photosystem I (PSI) has evolved in anaerobic atmosphere conditions and until today remains susceptible to oxygen. To minimize the probability of damaging side reactions, plants have evolved sophisticated mechanisms to control electron transfer, and PSI becomes inhibited only when malfunctions of these regulatory mechanisms occur. Due to the complicated induction of PSI photoinhibition, a detailed investigation of the process and following reactions are still largely missing. Here we introduce the theoretical framework and a novel method for an easy and controlled induction of PSI photoinhibition in vivo...
August 16, 2017: Physiologia Plantarum
https://www.readbyqxmd.com/read/28814630/inverted-region-electron-transfer-as-a-mechanism-for-enhancing-photosynthetic-solar-energy-conversion-efficiency
#3
Hiroki Makita, Gary Hastings
In all photosynthetic organisms, light energy is used to drive electrons from a donor chlorophyll species via a series of acceptors across a biological membrane. These light-induced electron-transfer processes display a remarkably high quantum efficiency, indicating a near-complete inhibition of unproductive charge recombination reactions. It has been suggested that unproductive charge recombination could be inhibited if the reaction occurs in the so-called inverted region. However, inverted-region electron transfer has never been demonstrated in any native photosynthetic system...
August 16, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28813504/effect-of-co2-induced-seawater-acidification-on-growth-photosynthesis-and-inorganic-carbon-acquisition-of-the-harmful-bloom-forming-marine-microalga-karenia-mikimotoi
#4
Shunxin Hu, Bin Zhou, You Wang, Ying Wang, Xinxin Zhang, Yan Zhao, Xinyu Zhao, Xuexi Tang
Karenia mikimotoi is a widespread, toxic and non-calcifying dinoflagellate, which can release and produce ichthyotoxins and hemolytic toxins affecting the food web within the area of its bloom. Shifts in the physiological characteristics of K. mikimotoi due to CO2-induced seawater acidification could alter the occurrence, severity and impacts of harmful algal blooms (HABs). Here, we investigated the effects of elevated pCO2 on the physiology of K. mikimotoi. Using semi-continuous cultures under controlled laboratory conditions, growth, photosynthesis and inorganic carbon acquisition were determined over 4-6 week incubations at ambient (390ppmv) and elevated pCO2 levels (1000 ppmv and 2000 ppmv)...
2017: PloS One
https://www.readbyqxmd.com/read/28813042/the-carotenoid-pathway-what-is-important-for-excitation-quenching-in-plant-antenna-complexes
#5
Kieran F Fox, Vytautas Balevičius, Jevgenij Chmeliov, Leonas Valkunas, Alexander V Ruban, Christopher D P Duffy
Plant light-harvesting is regulated by the Non-Photochemical Quenching (NPQ) mechanism involving the reversible formation of excitation quenching sites in the Photosystem II (PSII) antenna in response to high light. While the major antenna complex, LHCII, is known to be a site of NPQ, the precise mechanism of excitation quenching is not clearly understood. A preliminary model of the quenched crystal structure of LHCII implied that quenching arises from slow energy capture by Car pigments. It predicted a thoroughly quenched system but offered little insight into the defining aspects of this quenching...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28813015/transcriptional-responses-of-creeping-bentgrass-to-2-3-butanediol-a-bacterial-volatile-compound-bvc-analogue
#6
Yi Shi, Kuiju Niu, Bingru Huang, Wenhui Liu, Huiling Ma
Bacterial volatile compounds (BVCs) have been reported to enhance plant growth and elicit plant defenses against fungal infection and insect damage. The objective of this study was to determine transcriptomic changes in response to synthetic BVC that could be associated with plant resistance to Rhizoctonia solani in creeping bentgrass. The 2,3-butanediol (BD) (250 µM) was sprayed on creeping bentgrass leaves grown in jam jars. The result showed that synthetic BD induced plant defense against R. solani for creeping bentgrass...
August 16, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28808836/excitation-transfer-and-trapping-kinetics-in-plant-photosystem-i-probed-by-two-dimensional-electronic-spectroscopy
#7
Parveen Akhtar, Cheng Zhang, Zhengtang Liu, Howe-Siang Tan, Petar H Lambrev
Photosystem I is a robust and highly efficient biological solar engine. Its capacity to utilize virtually every absorbed photon's energy in a photochemical reaction generates great interest in the kinetics and mechanisms of excitation energy transfer and charge separation. In this work, we have employed room-temperature coherent two-dimensional electronic spectroscopy and time-resolved fluorescence spectroscopy to follow exciton equilibration and excitation trapping in intact Photosystem I complexes as well as core complexes isolated from Pisum sativum...
August 14, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28808434/continuous-diffraction-of-molecules-and-disordered-molecular-crystals
#8
Henry N Chapman, Oleksandr M Yefanov, Kartik Ayyer, Thomas A White, Anton Barty, Andrew Morgan, Valerio Mariani, Dominik Oberthuer, Kanupriya Pande
The intensities of far-field diffraction patterns of orientationally aligned molecules obey Wilson statistics, whether those molecules are in isolation (giving rise to a continuous diffraction pattern) or arranged in a crystal (giving rise to Bragg peaks). Ensembles of molecules in several orientations, but uncorrelated in position, give rise to the incoherent sum of the diffraction from those objects, modifying the statistics in a similar way as crystal twinning modifies the distribution of Bragg intensities...
August 1, 2017: Journal of Applied Crystallography
https://www.readbyqxmd.com/read/28808384/molecular-authentication-of-the-traditional-medicinal-plant-lakshman-booti-smithia-conferta-sm-and-its-adulterants-through-dna-barcoding
#9
Suraj D Umdale, Parthraj R Kshirsagar, Manoj M Lekhak, Nikhil B Gaikwad
BACKGROUND: Smithia conferta Sm. is an annual herb widely used in Indian traditional medical practice and commonly known as "Lakshman booti" in Sanskrit. Morphological resemblance among the species of genus Smithia Aiton. leads to inaccurate identification and adulteration. This causes inconsistent therapeutic effects and also affects the quality of herbal medicine. AIM: This study aimed to generate potential barcode for authentication of S. conferta and its adulterants through DNA barcoding technique...
July 2017: Pharmacognosy Magazine
https://www.readbyqxmd.com/read/28808108/chloroplast-thioredoxin-systems-prospects-for-improving-photosynthesis
#10
REVIEW
Lauri Nikkanen, Jouni Toivola, Manuel Guinea Diaz, Eevi Rintamäki
Thioredoxins (TRXs) are protein oxidoreductases that control the structure and function of cellular proteins by cleavage of a disulphide bond between the side chains of two cysteine residues. Oxidized thioredoxins are reactivated by thioredoxin reductases (TR) and a TR-dependent reduction of TRXs is called a thioredoxin system. Thiol-based redox regulation is an especially important mechanism to control chloroplast proteins involved in biogenesis, in regulation of light harvesting and distribution of light energy between photosystems, in photosynthetic carbon fixation and other biosynthetic pathways, and in stress responses of plants...
September 26, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28808107/structure-of-psb29-thf1-and-its-association-with-the-ftsh-protease-complex-involved-in-photosystem-ii-repair-in-cyanobacteria
#11
Martina Bec Ková, Jianfeng Yu, Vendula Krynická, Amanda Kozlo, Shengxi Shao, Peter Koník, Josef Komenda, James W Murray, Peter J Nixon
One strategy for enhancing photosynthesis in crop plants is to improve their ability to repair photosystem II (PSII) in response to irreversible damage by light. Despite the pivotal role of thylakoid-embedded FtsH protease complexes in the selective degradation of PSII subunits during repair, little is known about the factors involved in regulating FtsH expression. Here we show using the cyanobacterium Synechocystis sp. PCC 6803 that the Psb29 subunit, originally identified as a minor component of His-tagged PSII preparations, physically interacts with FtsH complexes in vivo and is required for normal accumulation of the FtsH2/FtsH3 hetero-oligomeric complex involved in PSII repair...
September 26, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28808104/interaction-between-photosynthetic-electron-transport-and-chloroplast-sinks-triggers-protection-and-signalling-important-for-plant-productivity
#12
Peter J Gollan, Yugo Lima-Melo, Arjun Tiwari, Mikko Tikkanen, Eva-Mari Aro
The photosynthetic light reactions provide energy that is consumed and stored in electron sinks, the products of photosynthesis. A balance between light reactions and electron consumption in the chloroplast is vital for plants, and is protected by several photosynthetic regulation mechanisms. Photosystem I (PSI) is particularly susceptible to photoinhibition when these factors become unbalanced, which can occur in low temperatures or in high light. In this study we used the pgr5 Arabidopsis mutant that lacks ΔpH-dependent regulation of photosynthetic electron transport as a model to study the consequences of PSI photoinhibition under high light...
September 26, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28808100/hacking-the-thylakoid-proton-motive-force-for-improved-photosynthesis-modulating-ion-flux-rates-that-control-proton-motive-force-partitioning-into-%C3%AE-%C3%AF-and-%C3%AE-ph
#13
REVIEW
Geoffry A Davis, A William Rutherford, David M Kramer
There is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the 'energy-dependent' form of non-photochemical quenching (qE), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce field recombination-induced photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δψ) induce photosystem II recombination reactions that produce damaging singlet oxygen ((1)O2)...
September 26, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28808098/overexpression-of-plastid-terminal-oxidase-in-synechocystis-sp-pcc-6803-alters-cellular-redox-state
#14
Kathleen Feilke, Ghada Ajlani, Anja Krieger-Liszkay
Cyanobacteria are the most ancient organisms performing oxygenic photosynthesis, and they are the ancestors of plant plastids. All plastids contain the plastid terminal oxidase (PTOX), while only certain cyanobacteria contain PTOX. Many putative functions have been discussed for PTOX in higher plants including a photoprotective role during abiotic stresses like high light, salinity and extreme temperatures. Since PTOX oxidizes PQH2 and reduces oxygen to water, it is thought to protect against photo-oxidative damage by removing excess electrons from the plastoquinone (PQ) pool...
September 26, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28805493/pathways-for-external-alkalinization-in-intact-and-in-microwounded-chara-cells-are-differentially-sensitive-to-wortmannin
#15
Alexander A Bulychev, Ilse Foissner
Proton flows across the plant cell membranes play a major role in electrogenesis and regulation of photosynthesis and ion balance. The profiles of external pH along the illuminated internodal cells of characean algae consist of alternating high- and low-pH zones that are spatially coordinated with the distribution of photosynthetic activity of chloroplasts underlying these zones. The results based on confocal laser scanning fluorescence microscopy, pH microsensors, and pulse-amplitude-modulated chlorophyll microfluorometry revealed that the coordination of H(+) transport and photosynthesis is disrupted by the two different environmental cues (low light and wounding) and by a chemical, wortmannin interfering with the inositol phospholipid metabolism...
August 14, 2017: Plant Signaling & Behavior
https://www.readbyqxmd.com/read/28805492/roles-of-rice-phytochrome-interacting-factor-like1-ospil1-in-leaf-senescence
#16
Yasuhito Sakuraba, Eun-Young Kim, Nam-Chon Paek
Rice (Oryza sativa) Phytochrome-Interacting Factor-Like1 (OsPIL1), a basic helix-loop-helix transcription factor, plays an important role in the elongation of internode cells. Recently, we found that OsPIL1 participates in chlorophyll biosynthesis by directly upregulating several genes encoding components of the photosystem apparatus. Here, we show that OsPIL1 negatively regulates leaf senescence in rice. During dark-induced senescence (DIS), ospil1 mutants senesced earlier than wild type; this is opposite to mutants of Arabidopsis PIF4 and PIF5, the closest homologs of OsPIL1...
August 14, 2017: Plant Signaling & Behavior
https://www.readbyqxmd.com/read/28803071/responses-of-szarvasi-1-energy-grass-to-sewage-sludge-treatments-in-hydroponics
#17
Ambrus Rév, Brigitta Tóth, Ádám Solti, Gyula Sipos, Ferenc Fodor
Sewage sludge (SS) originating from communal wastewater is a hazardous material but have a potentially great nutritive value. Its disposal after treatment in agricultural lands can be a very economical and safe way of utilization once fast growing, high biomass, perennial plants of renewable energy production are cultivated. Szarvasi-1 energy grass (Elymus elongatus subsp. ponticus cv. Szarvasi-1), a good candidate for this application, was grown in hydroponics in order to assess its metal accumulation and tolerance under increasing SS amendments...
August 1, 2017: Plant Physiology and Biochemistry: PPB
https://www.readbyqxmd.com/read/28801049/a-four-state-parametric-model-for-the-kinetics-of-the-non-photochemical-quenching-in-photosystem-ii
#18
Joris J Snellenburg, Matthew P Johnson, Alexander V Ruban, Rienk van Grondelle, Ivo H M van Stokkum
The phenomenon of non-photochemical quenching (NPQ) was studied in spinach chloroplasts using pulse amplitude modulated (PAM) fluorometry. We present a new analysis method which describes the observed fluorescence quantum yield as the sum of the product of four different states of PSII and their corresponding quantum yields. These four distinct states are PSII in the quenched or unquenched state, and with its reaction center either open or closed depending upon the reduction of the QA site. With this method we can describe the dynamics of the NPQ induction and recovery as well as quantify the percentage of photoinactivated RC throughout the measurement...
August 8, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28798298/the-algicidal-mechanism-of-prodigiosin-from-hahella-sp-ka22-against-microcystis-aeruginosa
#19
Ke Yang, Qiuliang Chen, Danyang Zhang, Huajun Zhang, Xueqian Lei, Zhangran Chen, Yi Li, Yaling Hong, Xiaohong Ma, Wei Zheng, Yun Tian, Tianling Zheng, Hong Xu
In recent years, Microcystis aeruginosa blooms have occurred throughout the world, causing huge economic losses and destroying aquatic ecosystems. It is necessary to develop effective and ecofriendly methods to control M. aeruginosa blooms. Here, we report a high algicidal activity of prodigiosin (PG) against M. aeruginosa as well as the algicidal mechanism. PG showed high algicidal activity against M. aeruginosa, with a 50% lethal dose (LD50) of 5.87 μg/mL in 72 h. A combination of methods, including propidium iodide and Annexin V-fluorescein staining assays and light and electron microscopy indicated the existence of two modes of cell death with features similar to those in eukaryotic programmed cell death: necrotic-like and apoptotic-like...
August 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28797596/an-update-on-aureochromes-phylogeny-mechanism-function
#20
REVIEW
Peter G Kroth, Christian Wilhelm, Tilman Kottke
Light is important for algae, as it warrants metabolic independence via photosynthesis. In addition to the absorption of light by the photosystems, algae possess a variety of specific photoreceptors that allow the quantification of the light fluxes as well as the assessment of light qualities. About a decade ago, aureochromes have been described in the xanthophyte alga Vaucheria frigida. These proteins represent a new type of blue light photoreceptor as they possess both a light-oxygen-voltage (LOV) domain for light reception as well as a basic region leucine zipper (bZIP) domain for DNA binding, indicating that they represent light-driven transcription factors...
July 11, 2017: Journal of Plant Physiology
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