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Michael Saur, Raoul Hennig, Phoebe Young, Kristiane Rusitzka, Nadja Hellmann, Jennifer Heidrich, Nina Morgner, Jürgen Markl, Dirk Schneider
Biogenesis and dynamics of thylakoid membranes likely involves membrane fusion events. Membrane attachment of the inner membrane-associated protein of 30 kDa (IM30) affects the structure of the lipid bilayer, finally resulting in membrane fusion. Yet, how IM30 triggers membrane fusion is largely unclear. IM30 monomers pre-assemble into stable tetrameric building blocks, which further align to form oligomeric ring structures, and differently sized IM30 rings bind to membranes. Based on a 3D reconstruction of IM30 rings, we locate the IM30 loop 2 region at the bottom of the ring and show intact membrane binding but missing fusogenic activity of loop 2 mutants...
August 2, 2017: Structure
Chi-Chu Tsai, Yu-Jen Wu, Chiou-Rong Sheue, Pei-Chun Liao, Ying-Hao Chen, Shu-Ju Li, Jian-Wei Liu, Han-Tsung Chang, Wen-Lin Liu, Ya-Zhu Ko, Yu-Chung Chiang
Leaf variegation is often the focus of plant breeding. Here, we studied a variegated mutant of Phalaenopsis aphrodite subsp. formosana, which is usually used as a parent of horticultural breeding, to understand its anatomic and genetic regulatory mechanisms in variegation. Chloroplasts with well-organized thylakoids and starch grains were found only in the mesophyll cells of green sectors but not of yellow sectors, confirming that the variegation belongs to the chlorophyll type. The two-dimensional electrophoresis and LC/MS/MS also reveal differential expressions of PsbP and PsbO between the green and yellow leaf sectors...
2017: Frontiers in Plant Science
Stéphane T Gabilly, Patrice P Hamel
Cytochromes c are hemoproteins, with the prosthetic group covalently linked to the apoprotein, which function as electron carriers. A class of cytochromes c is defined by a CXXCH heme-binding motif where the cysteines form thioether bonds with the vinyl groups of heme. Plastids are known to contain up to three cytochromes c. The membrane-bound cytochrome f and soluble cytochrome c6 operate in photosynthesis while the activity of soluble cytochrome c6A remains unknown. Conversion of apo- to holocytochrome c occurs in the thylakoid lumen and requires the independent transport of apocytochrome and heme across the thylakoid membrane followed by the stereospecific attachment of ferroheme via thioether linkages...
2017: Frontiers in Plant Science
Alessio Fini, Cecilia Brunetti, Francesco Loreto, Mauro Centritto, Francesco Ferrini, Massimiliano Tattini
The functional reasons for isoprene emission are still a matter of hot debate. It was hypothesized that isoprene biosynthesis evolved as an ancestral mechanism in plants adapted to high water availability, to cope with transient and recurrent oxidative stresses during their water-to-land transition. There is a tight association between isoprene emission and species hygrophily, suggesting that isoprene emission may be a favorable trait to cope with occasional exposure to stresses in mesic environments. The suite of morpho-anatomical traits does not allow a conservative water use in hygrophilic mesophytes challenged by the environmental pressures imposed or exacerbated by drought and heat stress...
2017: Frontiers in Plant Science
Kaori Kohzuma, John E Froehlich, Geoffry A Davis, Joshua A Temple, Deepika Minhas, Amit Dhingra, Jeffrey A Cruz, David M Kramer
The chloroplast ATP synthase catalyzes the light-driven synthesis of ATP and is activated in the light and inactivated in the dark by redox-modulation through the thioredoxin system. It has been proposed that this down-regulation is important for preventing wasteful hydrolysis of ATP in the dark. To test this proposal, we compared the effects of extended dark exposure in Arabidopsis lines expressing the wild-type and mutant forms of ATP synthase that are redox regulated or constitutively active. In contrast to the predictions of the model, we observed that plants with wild-type redox regulation lost photosynthetic capacity rapidly in darkness, whereas those expressing redox-insensitive form were far more stable...
2017: Frontiers in Plant Science
James Kevin McCarthy, Sarah R Smith, John P McCrow, Maxine Tan, Hong Zheng, Karen Beeri, Robyn A Roth, Christiane Lichtle, Ursula Goodenough, Chris Bowler, Cristopher L Dupont, Andrew E Allen
The ecological prominence of diatoms in the ocean environment largely results from their superior competitive ability for dissolved nitrate (NO3-). To investigate the cellular and genetic basis of diatom NO3- assimilation, we generated a knockout in the nitrate reductase gene (NR-KO) of the model pennate diatom Phaeodactylum tricornutum. In NR-KO cells, N assimilation was abolished although NO3-transport remained intact. Unassimilated NO3- accumulated in NR-KO cells, resulting in swelling and associated changes in biochemical composition and physiology...
August 1, 2017: Plant Cell
Qi Huang, Tracy Palmer
The general secretory pathway (Sec) and twin-arginine translocase (Tat) operate in parallel to export proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Substrates are targeted to their respective machineries by N-terminal signal peptides that share a tripartite organization; however, Tat signal peptides harbor a conserved and almost invariant arginine pair that is critical for efficient targeting to the Tat machinery. Tat signal peptides interact with a membrane-bound receptor complex comprised of TatB and TatC components, with TatC containing the twin-arginine recognition site...
August 1, 2017: MBio
Stephanie P Mueller, Melissa Unger, Lena Guender, Agnes Fekete, Martin J Mueller
High temperatures rapidly induce a genetically programmed heat shock response (HSR) that is essential to establish short-term acquired thermotolerance. In addition, an immediate HSR-independent metabolic response is triggered resulting in an accumulation of unsaturated triacylglycerols (TAGs) in the cytosol. The metabolic processes involved in heat-induced TAG formation in plants and their physiological significance remain to be clarified. Lipidomic analyses of Arabidopsis thaliana seedlings indicated that during heat stress polyunsaturated fatty acids from thylakoid galactolipids are incorporated into cytosolic TAGs...
July 21, 2017: Plant Physiology
Manish Singh Kaushik, Meenakshi Srivastava, Anumeha Singh, Arun Kumar Mishra
Iron deficiency ends up into several unavoidable consequences including damaging oxidative stress in cyanobacteria. NtcA is a global nitrogen regulator controls wide range of metabolisms in addition to regulation of nitrogen metabolism. In present communication, NtcA based regulation of iron homeostasis, ROS production and cellular phenotype under iron deficiency in Anabaena 7120 has been investigated. NtcA regulates the concentration dependent iron uptake by controlling the expression of furA gene. NtcA also regulated pigment synthesis and phenotypic alterations in Anabaena 7120...
August 2017: World Journal of Microbiology & Biotechnology
Yusuke Matsuda, Brian M Hopkinson, Kensuke Nakajima, Christopher L Dupont, Yoshinori Tsuji
Diatoms are one of the most successful marine eukaryotic algal groups, responsible for up to 20% of the annual global CO2 fixation. The evolution of a CO2-concentrating mechanism (CCM) allowed diatoms to overcome a number of serious constraints on photosynthesis in the marine environment, particularly low [CO2]aq in seawater relative to concentrations required by the CO2 fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), which is partly due to the slow diffusion rate of CO2 in water and a limited CO2 formation rate from [Formula: see text] in seawater...
September 5, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Nancy R Hofmann
No abstract text is available yet for this article.
July 2017: Plant Cell
Shota Kato, Mika Soshino, Shinichi Takaichi, Takahiro Ishikawa, Noriko Nagata, Masashi Asahina, Tomoko Shinomura
BACKGROUND: Photosynthetic organisms utilize carotenoids for photoprotection as well as light harvesting. Our previous study revealed that high-intensity light increases the expression of the gene for phytoene synthase (EgcrtB) in Euglena gracilis (a unicellular phytoflagellate), the encoded enzyme catalyzes the first committed step of the carotenoid biosynthesis pathway. To examine carotenoid synthesis of E. gracilis in response to light stress, we analyzed carotenoid species and content in cells grown under various light intensities...
July 17, 2017: BMC Plant Biology
Claudia Büchel, Christian Wilhelm, Volker Wagner, Maria Mittag
Comparative proteome analysis of subcellular compartments like thylakoid membranes and their associated supercomplexes can deliver important in-vivo information on the molecular basis of physiological functions which go far beyond to that what can be learnt from transcriptional-based gene expression studies. For instance, the finding that light intensity influences mainly the relative stoichiometry of subunits could be obtained only by high resolution proteome analysis. The high sensitivity of LC-ESI-MS/MS based proteome analysis allows the determination of proteins in very small subfractions along with their non-labeled semi quantitative analysis...
July 4, 2017: Journal of Plant Physiology
Álvaro Sánchez-Corrionero, Inmaculada Sánchez-Vicente, Sergio González-Pérez, Ascensión Corrales, Anja Krieger-Liszkay, Óscar Lorenzo, Juan B Arellano
The two Arabidopsis thaliana mutants, aba1 and max4, were previously identified as sharing a number of co-regulated genes with both the flu mutant and Arabidopsis cell suspension cultures exposed to high light (HL). On this basis, we investigated whether aba1 and max4 were generating high amounts of singlet oxygen ((1)O2) and activating (1)O2-mediated cell death. Thylakoids of aba1 produced twice as much (1)O2 as thylakoids of max4 and wild type (WT) plants when illuminated with strong red light. (1)O2 was measured using the spin probe 2,2,6,6-tetramethyl-4-piperidone hydrochloride...
September 2017: Journal of Plant Physiology
Vivek Dogra, Jianli Duan, Keun Pyo Lee, Shanshan Lv, Renyi Liu, Chanhong Kim
Photosystem II reaction center (PSII RC) and light-harvesting complex inevitably generate highly reactive singlet oxygen ((1)O2) that can impose photo-oxidative damage, especially when the rate of generation exceeds the rate of detoxification. Besides being toxic, (1)O2 has also been ascribed to trigger retrograde signaling, which leads to nuclear gene expression changes. Two distinctive molecular components appear to regulate (1)O2 signaling: a volatile signaling molecule β-cyclocitral (β-CC) generated upon oxidation of β-carotene by (1)O2 in PSII RC assembled in grana core, and a thylakoid membrane-bound FtsH2 metalloprotease that promotes (1)O2-triggered signaling through the proteolysis of EXECUTER1 (EX1) proteins associated with PSII in grana margin...
2017: Frontiers in Plant Science
Dennis Seiwert, Hannes Witt, Andreas Janshoff, Harald Paulsen
In the photosynthetic apparatus of plants a high proportion of LHCII protein is needed to integrate 50% non-bilayer lipid MGDG into the lamellar thylakoid membrane, but whether and how the stability of the protein is also affected is not known. Here we use single-molecule force spectroscopy to map the stability of LHCII against mechanical unfolding along the polypeptide chain as a function of oligomerization state and lipid composition. Comparing unfolding forces between monomeric and trimeric LHCII demonstrates that the stability does not increase significantly upon trimerization but can mainly be correlated with specific contact sites between adjacent monomers...
July 11, 2017: Scientific Reports
Weimin Pan, Junchao Wang, Ye Yang, Lin Liu, Min Zhang
Thioredoxins (Trxs) play important roles in chloroplasts by linking photosynthetic light reactions to a series of plastid functions. They execute their function by regulating the oxidation and reduction of disulfide bonds. ACHT1 (atypical cysteine/histidine-rich Trx1) is a thylakoid-associated thioredoxin-type protein found in the Arabidopsis thaliana chloroplast. Recombinant ACHT1 protein was overexpressed in Escherichia coli, purified and crystallized by the vapour-diffusion method. The crystal diffracted to 1...
July 1, 2017: Acta Crystallographica. Section F, Structural Biology Communications
Kun Wang, John E Froehlich, Agnieszka Zienkiewicz, Hope Lynn Hersh, Christoph Benning
The lipid composition of thylakoid membranes inside chloroplasts is conserved from leaves to developing embryos. A finely tuned lipid assembly machinery is required to build these membranes during Arabidopsis thaliana development. Contrary to thylakoid lipid biosynthetic enzymes, the functions of most predicted chloroplast lipid-degrading enzymes remain to be elucidated. Here, we explore the biochemistry and physiological function of an Arabidopsis thylakoid membrane-associated lipase, PLASTID LIPASE1 (PLIP1)...
July 2017: Plant Cell
(no author information available yet)
No abstract text is available yet for this article.
July 2017: Plant Cell
Jocelyn Bédard, Raphael Trösch, Feijie Wu, Qihua Ling, Úrsula Flores-Pérez, Mats Töpel, Fahim Nawaz, Paul Jarvis
To extend our understanding of chloroplast protein import and the role played by the import machinery component Tic40, we performed a genetic screen for suppressors of chlorotic tic40 knockout mutant Arabidopsis thaliana plants. As a result, two suppressor of tic40 loci, stic1 and stic2, were identified and characterized. The stic1 locus corresponds to the gene ALBINO4 (ALB4), which encodes a paralog of the well-known thylakoid protein targeting factor ALB3. The stic2 locus identified a previously unknown stromal protein that interacts physically with both ALB4 and ALB3...
July 2017: Plant Cell
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