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https://www.readbyqxmd.com/read/28538145/nmr-analysis-of-amide-hydrogen-exchange-rates-in-a-pentapeptide-repeat-protein-from-a-%C3%A2-thaliana
#1
Shenyuan Xu, Shuisong Ni, Michael A Kennedy
At2g44920 from Arabidopsis thaliana is a pentapeptide-repeat protein (PRP) composed of 25 repeats capped by N- and C-terminal α-helices. PRP structures are dominated by four-sided right-handed β-helices typically consisting of mixtures of type II and type IV β-turns. PRPs adopt repeated five-residue (Rfr) folds with an Rfr consensus sequence (STAV)(D/N)(L/F)(S/T/R)(X). Unlike other PRPs, At2g44920 consists exclusively of type II β-turns. At2g44920 is predicted to be located in the thylakoid lumen although its biochemical function remains unknown...
May 23, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28534654/functions-and-substrates-of-plastoglobule-localized-metallopeptidase-pgm48
#2
Nazmul H Bhuiyan, Klaas J van Wijk
Plastoglobules (PGs) in chloroplasts are monolayer lipid-protein particles attached to thylakoids. The size and number of PGs per chloroplast respond dynamically to abiotic environmental stresses and developmental transitions. During senescence, the thylakoid membranes and its constituents are dismantled in controlled fashion. Leaf senescence coincides with a dramatic increase in the size of PGs, which is consistent with a functional role of PG in remobilization of thylakoid membrane components. In a recent publication (1) , we showed that PG-localized metallopeptidase PGM48 promotes natural senescence...
May 23, 2017: Plant Signaling & Behavior
https://www.readbyqxmd.com/read/28533358/role-of-type-2-nad-p-h-dehydrogenase-ndbc-in-regulation-of-carbon-allocation-in-synechocystis-6803
#3
Tuomas Huokko, Dorota Muth-Pawlak, Natalia Battchikova, Yagut Allahverdiyeva, Eva-Mari Aro
NAD(P)H dehydrogenases comprise type 1 (NDH-1) and type 2 (NDH-2s) enzymes. Even though the NDH-1 complex is a well characterized protein complex in the thylakoid membrane of Synechocystis sp. PCC 6803 (hereafter Synechocystis) the exact roles of different NDH2s remain poorly understood. To elucidate this question we studied the function of NdbC, one of the three NDH-2s in Synechocystis, by constructing a deletion mutant (ΔndbC) for corresponding protein and submitting the mutant to physiological and biochemical characterisation as well as to comprehensive proteomics analysis...
May 22, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28526981/rubisco-mutants-of-chlamydomonas-reinhardtii-display-divergent-photosynthetic-parameters-and-lipid-allocation
#4
M G Esquível, A R Matos, J Marques Silva
Photosynthesis and lipid allocation were investigated in Rubisco small subunit mutants of the microalga Chlamydomonas reinhardtii. Comparative analyses were undertaken with cells grown photoheterotrophically under sulphur-replete or sulphur-depleted conditions. The Y67A Rubisco mutant, which has previously demonstrated a pronounced reduction in Rubisco levels and higher hydrogen production rates than the wild type, also shows the following divergences in photosynthetic phenotype and lipid allocation: (i) low Fv/Fm (maximum photochemical efficiency), (ii) low effective quantum yield of photosystem II (ΦPSII), (iii) low effectiveness at protection against high light intensities, (iv) a higher level of total lipids per pigment and (v) changes in the relative proportions of different fatty acids, with a marked decrease in unsaturated fatty acids (FAs)...
May 19, 2017: Applied Microbiology and Biotechnology
https://www.readbyqxmd.com/read/28522455/psa3-a-protein-on-the-stromal-face-of-the-thylakoid-membrane-promotes-photosystem-i-accumulation-in-cooperation-with-the-assembly-factor-pyg7
#5
Jie Shen, Rosalind Williams-Carrier, Alice Barkan
Photosystem I (PSI) is a large protein-pigment complex located in the thylakoid membrane in cyanobacteria, plants, and algae. Although the structure and components of PSI are well characterized, mechanisms that orchestrate its assembly are poorly understood. In this study, we discovered a novel nucleus-encoded protein, Photosystem I Assembly 3 (PSA3), that is required for PSI accumulation. PSA3 is conserved among green photosynthetic eukaryotes but is lacking in cyanobacteria. Mutations in the psa3 gene cause the specific loss of PSI in Arabidopsis and maize...
May 18, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28516356/morphology-ultrastructure-and-element-uptake-in-calophyllum-brasiliense-cambess-calophyllaceae-j-agardh-seedlings-under-cadmium-exposure
#6
Alezania Silva Pereira, Priscila Andressa Cortez, Alex-Alan Furtado de Almeida, Majeti Narashima Vara Prasad, Marcel Giovanni Costa França, Maura da Cunha, Raildo Mota de Jesus, Pedro Antônio Oliveira Mangabeira
Cadmium (Cd) is a metal known for its genotoxicity and cytotoxicity, much concerned for its potential environmental and human health impacts. This study evaluates the toxic effect of Cd in Calophyllum brasiliense plants. The plants were cultivated for 30 days in full nutrient solution in order to adapt, and for 15 days in nutrient solution without Cd or with 4, 8, 16, and 32 μmol Cd L(-1). Anatomical analysis of the leaf showed no significant effects of Cd on epidermal thickness in abaxial and adaxial sides, palisade, and spongy parenchyma...
May 17, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28515738/chloroplast-atp-synthase-modulation-of-the-thylakoid-proton-motive-force-implications-for-photosystem-i-and-photosystem-ii-photoprotection
#7
Atsuko Kanazawa, Elisabeth Ostendorf, Kaori Kohzuma, Donghee Hoh, Deserah D Strand, Mio Sato-Cruz, Linda Savage, Jeffrey A Cruz, Nicholas Fisher, John E Froehlich, David M Kramer
In wild type plants, decreasing CO2 lowers the activity of the chloroplast ATP synthase, slowing proton efflux from the thylakoid lumen resulting in buildup of thylakoid proton motive force (pmf). The resulting acidification of the lumen regulates both light harvesting, via the qE mechanism, and photosynthetic electron transfer through the cytochrome b6f complex. Here, we show that the cfq mutant of Arabidopsis, harboring single point mutation in its γ-subunit of the chloroplast ATP synthase, increases the specific activity of the ATP synthase and disables its down-regulation under low CO2...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28515734/plant-growth-under-natural-light-conditions-provides-highly-flexible-short-term-acclimation-properties-toward-high-light-stress
#8
Tobias Schumann, Suman Paul, Michael Melzer, Peter Dörmann, Peter Jahns
Efficient acclimation to different growth light intensities is essential for plant fitness. So far, most studies on light acclimation have been conducted with plants grown under different constant light regimes, but more recent work indicated that acclimation to fluctuating light or field conditions may result in different physiological properties of plants. Thale cress (Arabidopsis thaliana) was grown under three different constant light intensities (LL: 25 μmol photons m(-2) s(-1); NL: 100 μmol photons m(-2) s(-)(1); HL: 500 μmol photons m(-2) s(-1)) and under natural fluctuating light (NatL) conditions...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28499881/spectral-dependence-of-irreversible-light-induced-fluorescence-quenching-chlorophyll-forms-with-maximal-emission-at-700-702-and-705-710nm-as-spectroscopic-markers-of-conformational-changes-in-the-core-complex
#9
Sherzod Nematov, Anna Paola Casazza, William Remelli, Vakhobjon Khuvondikov, Stefano Santabarbara
The spectral dependence of the irreversible non-photochemical fluorescence quenching associated with photoinhibition in vitro has been comparatively investigated in thylakoid membranes, PSII enriched particles and PSII core complexes isolated from spinach. The analysis of the fluorescence emission spectra of dark-adapted and quenched samples as a function of the detection temperature in the 280-80K interval, indicates that Chlorophyll spectral forms having maximal emission in the 700-702nm and 705-710nm ranges gain relative intensity in concomitance with the establishment of irreversible light-induced quenching, acting thereby as spectroscopic markers...
May 9, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28497193/evaluation-of-new-cu-ii-complexes-as-a-novel-class-of-inhibitors-against-plant-carbonic-anhydrase-glutathione-reductase-and-photosynthetic-activity-in-photosystem-ii
#10
Margarita V Rodionova, Sergei K Zharmukhamedov, Mehmet Sayım Karacan, Kubra Begum Venedik, Alexandr V Shitov, Turgay Tunç, Serhat Mamaş, Vladimir D Kreslavski, Nurcan Karacan, Vyacheslav V Klimov, Suleyman I Allakhverdiev
Increasing inefficiency of production of important agricultural plants raises one of the biggest problems in the modern world. Herbicide application is still the best method of weed management. Traditional herbicides blocking only one of the plant metabolic pathways is ineffective due to the rapid growth of herbicide-resistant weeds. The synthesis of novel compounds effectively suppressing several metabolic processes, and therefore achieving the synergism effect would serve as the alternative approach to weed problem...
May 11, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28489071/exchange-pathways-of-plastoquinone-and-plastoquinol-in-the-photosystem-ii-complex
#11
Floris J Van Eerden, Manuel N Melo, Pim W J M Frederix, Xavier Periole, Siewert J Marrink
Plastoquinone (PLQ) acts as an electron carrier between photosystem II (PSII) and the cytochrome b6f complex. To understand how PLQ enters and leaves PSII, here we show results of coarse grained molecular dynamics simulations of PSII embedded in the thylakoid membrane, covering a total simulation time of more than 0.5 ms. The long time scale allows the observation of many spontaneous entries of PLQ into PSII, and the unbinding of plastoquinol (PLQol) from the complex. In addition to the two known channels, we observe a third channel for PLQ/PLQol diffusion between the thylakoid membrane and the PLQ binding sites...
May 10, 2017: Nature Communications
https://www.readbyqxmd.com/read/28488221/photosynthetic-electron-and-proton-transport-in-chloroplasts-epr-study-of-%C3%AE-ph-generation-an-overview
#12
Alexander N Tikhonov
This is a brief overview focused on the electron paramagnetic resonance applications to the study of the proton transport processes in chloroplasts. After brief description of structural and functional organization of the chloroplast electron transport chain, our attention is focused on the measurements of trans-thylakoid pH difference (ΔpH) with pH-sensitive spin-probes. The use of spin-probes is based either (i) on measuring the ΔpH-partitioning of spin-probes between the thylakoid lumen and external volume, or (ii) on monitoring changes in the electron paramagnetic resonance spectra of pH-sensitive nitroxide radicals located in the lumen...
May 9, 2017: Cell Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28483636/sublocalization-of-cytochrome-b6f-complexes-in-photosynthetic-membranes
#13
REVIEW
Helmut Kirchhoff, Meng Li, Sujith Puthiyaveetil
It is well established that the majority of energy-converting photosynthetic protein complexes in plant thylakoid membrane are nonhomogenously distributed between stacked and unstacked membrane regions. Yet, the sublocalization of the central cytochrome b6f complex remains controversial. We present a structural model that explains the variation in cytochrome b6f sublocalization data. Small changes in the distance between adjacent membranes in stacked grana regions either allow or restrict access of cytochrome b6f complexes to grana...
May 5, 2017: Trends in Plant Science
https://www.readbyqxmd.com/read/28481319/salinity-response-in-chloroplasts-insights-from-gene-characterization
#14
REVIEW
Jinwei Suo, Qi Zhao, Lisa David, Sixue Chen, Shaojun Dai
Salinity is a severe abiotic stress limiting agricultural yield and productivity. Plants have evolved various strategies to cope with salt stress. Chloroplasts are important photosynthesis organelles, which are sensitive to salinity. An understanding of molecular mechanisms in chloroplast tolerance to salinity is of great importance for genetic modification and plant breeding. Previous studies have characterized more than 53 salt-responsive genes encoding important chloroplast-localized proteins, which imply multiple vital pathways in chloroplasts in response to salt stress, such as thylakoid membrane organization, the modulation of photosystem II (PS II) activity, carbon dioxide (CO₂) assimilation, photorespiration, reactive oxygen species (ROS) scavenging, osmotic and ion homeostasis, abscisic acid (ABA) biosynthesis and signaling, and gene expression regulation, as well as protein synthesis and turnover...
May 8, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28450383/the-complex-effects-of-ocean-acidification-on-the-prominent-n2-fixing-cyanobacterium-trichodesmium
#15
Haizheng Hong, Rong Shen, Futing Zhang, Zuozhu Wen, Siwei Chang, Wenfang Lin, Sven A Kranz, Ya-Wei Luo, Shuh-Ji Kao, François M M Morel, Dalin Shi
Acidification of seawater caused by anthropogenic carbon dioxide (CO2) is anticipated to influence the growth of dinitrogen (N2)-fixing phytoplankton, which contribute a large fraction of primary production in the tropical and subtropical ocean. We found that growth and N2-fixation of the ubiquitous cyanobacterium Trichodesmium decreased under acidified conditions, notwithstanding a beneficial effect of high CO2 Acidification resulted in low cytosolic pH and reduced N2-fixation rates despite elevated nitrogenase concentrations...
May 5, 2017: Science
https://www.readbyqxmd.com/read/28448865/glycolipids-from-spinach-suppress-lps-induced-vascular-inflammation-through-enos-and-nk-%C3%AE%C2%BAb-signaling
#16
Masakazu Ishii, Tatsuo Nakahara, Daisuke Araho, Juri Murakami, Masahiro Nishimura
Glycolipids are the major constituent of the thylakoid membrane of higher plants and have a variety of biological and pharmacological activities. However, anti-inflammatory effects of glycolipids on vascular endothelial cells have not been elucidated. Here, we investigated the effect of glycolipids extracted from spinach on lipopolysaccharides (LPS)-induced endothelial inflammation and evaluated the underlying molecular mechanisms. Treatment with glycolipids from spinach had no cytotoxic effects on cultured human umbilical vein endothelial cells (HUVECs) and significantly blocked the expression of LPS-induced interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1), and intracellular adhesion molecule-1 (ICAM-1) in them...
April 24, 2017: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
https://www.readbyqxmd.com/read/28429526/sll1783-a-monooxygenase-associated-with-polysaccharide-processing-in-the-unicellular-cyanobacterium-synechocystis-pcc-6803
#17
Hélder Miranda, Peter Immerzeel, Lorenz Gerber, Katarina Hörnaeus, Sara Bergström Lind, Bagmi Pattanaik, Pia Lindberg, Fikret Mamedov, Peter Lindblad
Cyanobacteria play a pivotal role as the primary producer in many aquatic ecosystems. The knowledge on the interacting processes of cyanobacteria with its environment - abiotic and biotic factors - is still very limited. Many potential exocytoplasmic proteins in the model unicellular cyanobacterium Synechocystis PCC 6803 have unknown functions and their study is essential to improve our understanding of this photosynthetic organism and its potential for biotechnology use. Here we characterize a deletion mutant of Synechocystis PCC 6803, ∆sll1783, a strain that showed a remarkably high light resistance which is related with its lower thylakoid membrane formation...
April 21, 2017: Physiologia Plantarum
https://www.readbyqxmd.com/read/28429323/protein-targeting-to-the-plastid-of-euglena
#18
Dion G Durnford, Steven D Schwartzbach
The lateral transfer of photosynthesis between kingdoms through endosymbiosis is among the most spectacular examples of evolutionary innovation. Euglena, which acquired a chloroplast indirectly through an endosymbiosis with a green alga, represents such an example. As with other endosymbiont-derived plastids from eukaryotes, there are additional membranes that surround the organelle, of which Euglena has three. Thus, photosynthetic genes that were transferred from the endosymbiont to the host nucleus and whose proteins are required in the new plastid, are now faced with targeting and plastid import challenges...
2017: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/28426975/the-regulation-of-the-chloroplast-proton-motive-force-plays-a-key-role-for-photosynthesis-in-fluctuating-light
#19
REVIEW
Ute Armbruster, Viviana Correa Galvis, Hans-Henning Kunz, Deserah D Strand
Plants use sunlight as their primary energy source. During photosynthesis, absorbed light energy generates reducing power by driving electron transfer reactions. These are coupled to the transfer of protons into the thylakoid lumen, generating a proton motive force (pmf) required for ATP synthesis. Sudden alterations in light availability have to be met by regulatory mechanisms to avoid the over-accumulation of reactive intermediates and maximize energy efficiency. Here, the acidification of the lumen, as an intermediate product of photosynthesis, plays an important role by regulating photosynthesis in response to excitation energy levels...
April 17, 2017: Current Opinion in Plant Biology
https://www.readbyqxmd.com/read/28405745/lethal-albinic-seedling-encoding-a-threonyl-trna-synthetase-is-involved-in-development-of-plastid-protein-synthesis-system-in-rice
#20
Yuan-Yan Zhang, Yuan-Yuan Hao, Yi-Hua Wang, Chun-Ming Wang, Yun-Long Wang, Wu-Hua Long, Di Wang, Xi Liu, Ling Jiang, Jian-Min Wan
An albinic rice is caused by mutation of threonyl-tRNA synthetase, which is essential for plant development by stabilizing of NEP and PEP gene expressions and chloroplast protein synthesis. Chloroplast biogenesis and development depend on complex genetic mechanisms. Apart from their function in translation, aminoacyl-tRNA synthetases (aaRSs) play additional role in gene expression regulation, RNA splicing, and cytokine activity. However, their detailed functions in plant development are still poorly understood...
April 12, 2017: Plant Cell Reports
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