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Justine Marchand, Parisa Heydarizadeh, Benoît Schoefs, Cornelia Spetea
Chloroplasts are endosymbiotic organelles and play crucial roles in energy supply and metabolism of eukaryotic photosynthetic organisms (algae and land plants). They harbor channels and transporters in the envelope and thylakoid membranes, mediating the exchange of ions and metabolites with the cytosol and the chloroplast stroma and between the different chloroplast subcompartments. In secondarily evolved algae, three or four envelope membranes surround the chloroplast, making more complex the exchange of ions and metabolites...
March 14, 2018: Cellular and Molecular Life Sciences: CMLS
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
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
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
Guangwei Li, Danyang Chen, Xiaofeng Tang, Yongsheng Liu
Constitutive expression of AchGLK from A. chinensis in transgenic tomato (S. lycopersicum) confers fruits an elevated plastid biogenesis with intensified granule thylakoid stacks and increased content of nutritional compounds. Plastid development is regulated by multiple environmental and genetic factors. Golden2-like (GLK) genes, members from GARP subfamily of the MYB transcription factors, have been shown to regulate plastid biogenesis and development in several species. In tomato (S. lycopersicum), SlGLK2 gene is expressed in the fruit in a manner of latitudinal gradient and determines the green shoulder phenotype...
March 8, 2018: Planta
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
Biao Jin
Ginkgo biloba is grown worldwide as an ornamental plant for its golden leaf color. However, the regulatory mechanism of leaf coloration in G. biloba remains unclear. Here, we compared G. biloba gold-colored mutant leaves and normal green leaves in cytological, physiological and transcriptomic terms. We found that chloroplasts of the mutant were fewer and smaller, and exhibited ruptured thylakoid membranes, indistinct stromal lamellae and irregularly arranged vesicles. Physiological experiments also showed that the mutant had a lower chlorophyll, lower flavonoid and higher carotenoid contents (especially lutein)...
2018: Horticulture Research
Hongyu Chen, Shuqin Li, Lu Li, Hengjin Hu, Jie Zhao
In higher plants, embryo development originated from fertilized egg cell is the first step of the life cycle. The chloroplast participates in many essential metabolic pathways, and its function is highly associated with embryo development. However, the mechanisms and relevant genetic components by which the chloroplast functions in embryogenesis are largely uncharacterized. In this paper, we describe the Arabidopsis EMB1990 gene, encoding a plastid-targeted YlmG protein which is required for chloroplast biogenesis and embryo development...
2018: Frontiers in Plant Science
Kaori Kohzuma, Kouki Hikosaka
Non-photochemical quenching (NPQ) is the most important photoprotective system in higher plants. NPQ can be divided into several steps according to the timescale of relaxation of chlorophyll fluorescence after reaching a steady state (i.e., the fast phase, qE; middle phase, qZ or qT; and slow phase, qI). The dissipation of excess energy as heat during the xanthophyll cycle, a large component of NPQ, is detectable during the fast to middle phase (sec to min). Although thermal dissipation is primarily investigated using indirect methods such as chlorophyll a fluorescence measurements, such analyses require dark adaptation or the application of a saturating pulse during measurement, making it difficult to continuously monitor this process...
February 28, 2018: Biochemical and Biophysical Research Communications
Shang-Hung Pao, Ping-Yun Tsai, Ching-I Peng, Pei-Ju Chen, Chi-Chu Tsai, En-Cheng Yang, Ming-Chih Shih, Jiannyeu Chen, Jun-Yi Yang, Peter Chesson, Chiou-Rong Sheue
Iridoplasts (modified plastids in adaxial epidermal cells) reported from Begonia were originally hypothesized to cause iridescence, which was broadly accepted for decades. However, several species of Begonia with iridoplasts are not iridescent causing confusion. Here chloroplast ultrastructure was observed in 40 taxa of Begoniaceae to explore the phenomenon of iridescence. However, 22 Begonias and Hillebrandia were found to have iridoplasts, but only nine display visually iridescent blue to blue-green leaves...
March 2, 2018: Journal of Plant Research
Ewa Niewiadomska, Kathleen Brückner, Maria Mulisch, Jerzy Kruk, Aleksandra Orzechowska, Maria Pilarska, Rafał Luchowski, Wiesław I Gruszecki, Karin Krupinska
As tocopherols are expected to protect PSII against toxic singlet oxygen it is surprising that the null tocopherol mutant vte1 has been reported to show only a weak enhancement of photosystem II photoinhibition under high irradiance. Based on the view that singlet oxygen is formed also in unstressed conditions, such as low light (LL), we hypothesized that some defense strategies are activated in vte1 in these light conditions. In support for that we noted several symptoms of stress at PSII in the mutant under LL, by means of parameters of fast and slow kinetics of chlorophyll fluorescence and of changes in the relative contribution of PSII antenna in comparison to those of PSI...
February 21, 2018: Journal of Plant Physiology
Rabia Ghaffar, Marieluise Weidinger, Barbara Mähnert, Michael Schagerl, Irene Lichtscheidl
Deep-shade plants have adapted to low-light conditions by varying morphology and physiology of cells and chloroplasts, but it still remains unclear, if prolonged periods of high-light or darkness induce additional modifications in chloroplasts' anatomy and pigment patterns. We studied giant chloroplasts (bizonoplasts) of the deep-shade lycopod Selaginella erythropus in epidermal cells of mature fully developed microphylls and subjected them to prolonged darkness and high-light conditions. Chloroplast size and ultrastructure were investigated by light and electron microscopy...
March 2, 2018: Plant, Cell & Environment
Muhammad Moman Khan, Ejazul Islam, Samra Irem, Kalsoom Akhtar, Muhammad Yasin Ashraf, Javed Iqbal, Dan Liu
Hydroponics experiment was conducted to investigate the effects of different levels of Pb on Para Grass (Brachiaria mutica) and Castorbean (Ricinus communis L). Generally, Para Grass exhibited higher tolerance to excessive concentrations of Pb in nutrient solution, whereas a consistent decline was observed in growth of Castorbean plants exposed to similar Pb levels. Malondialdehyde (MDA) and H2 O2 contents exhibited contrasting results with a general decrease in Para Grass and a linear increase in case of Castorbean...
February 20, 2018: Chemosphere
Jian Zhou, Zhaopei Zhang, Yichuan Zhang, Yuan Wei, Zeping Jiang
In this study, we investigated the effects of different lead (Pb) concentrations (0, 200, 600, 1000, 1400 mg kg-1 soil) on the growth, ion enrichment in the tissues, photosynthetic and physiological characteristics, and cellular structures of privet seedlings. We observed that with the increase in the concentrations of Pb, the growth of privet seedlings was restricted, and the level of Pb ion increased in the roots, stem, and leaves of the seedlings; however, most of the ions were concentrated in the roots...
2018: PloS One
Makio Yokono, Seiji Akimoto
Traditionally, two types of photosystem reaction centers (PSI and PSII) are thought to be spatially dispersed in the plant thylakoid membrane. In this model, PSI and PSII independently accept excitation energy from their own peripheral light-harvesting complexes, LHCI and LHCII, respectively, and form supercomplexes (PSI-LHCI and PSII-LHCII). However, recent studies using a combination of mild detergent treatment and spectroscopic analysis have revealed the existence of various megacomplexes such as a PSI-PSII megacomplex and a PSII megacomplex...
February 20, 2018: Current Opinion in Biotechnology
Joana Rocha, Milène Nitenberg, Agnès Girard-Egrot, Juliette Jouhet, Eric Maréchal, Maryse A Block, Christelle Breton
A unique feature of chloroplasts is their high content of the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), which constitute up to 80% of their lipids. These galactolipids are synthesized in the chloroplast envelope membrane through the concerted action of galactosyltransferases, the so-called 'MGDG synthases (MGDs)' and 'DGDG synthases (DGDs),' which use uridine diphosphate (UDP)-galactose as donor. In Arabidopsis leaves, under standard conditions, the enzymes MGD1 and DGD1 provide the bulk of galactolipids, necessary for the massive expansion of thylakoid membranes...
2018: Frontiers in Plant Science
Koichi Kobayashi
The article "Role of membrane glycerolipids in photosynthesis, thylakoid biogenesis and chloroplast development", written by "Koichi Kobayashi", was originally published Online First without open access. After publication in volume 129, issue 4, page 565-580 the Botanical Society of Japan decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to
February 21, 2018: Journal of Plant Research
Alexander N Tikhonov
This chapter presents an overview of structural properties of the cytochrome (Cyt) b6 f complex and its functioning in chloroplasts. The Cyt b6 f complex stands at the crossroad of photosynthetic electron transport pathways, providing connectivity between Photosystem (PSI) and Photosysten II (PSII) and pumping protons across the membrane into the thylakoid lumen. After a brief review of the chloroplast electron transport chain, the consideration is focused on the structural organization of the Cyt b6 f complex and its interaction with plastoquinol (PQH2 , reduced form of plastoquinone), a mediator of electron transfer from PSII to the Cyt b6 f complex...
2018: Sub-cellular Biochemistry
Roman Kouřil, Lukáš Nosek, Dmitry Semchonok, Egbert J Boekema, Petr Ilík
In nature, plants are continuously exposed to varying environmental conditions. They have developed a wide range of adaptive mechanisms, which ensure their survival and maintenance of stable photosynthetic performance. Photosynthesis is delicately regulated at the level of the thylakoid membrane of chloroplasts and the regulatory mechanisms include a reversible formation of a large variety of specific protein-protein complexes, supercomplexes or even larger assemblies known as megacomplexes. Revealing their structures is crucial for better understanding of their function and relevance in photosynthesis...
2018: Sub-cellular Biochemistry
Lenka Bučinská, Eva Kiss, Peter Konik, Jana Knoppova, Josef Komenda, Roman Sobotka
Photosystem II (PSII) is a large enzyme complex embedded in the thylakoid membrane of oxygenic phototrophs. The biogenesis of PSII requires the assembly of more than 30 subunits, with the assistance of number of auxiliary proteins. In plants and cyanobacteria, the Pam68 (Photosynthesis affected mutant 68) is important for PSII assembly. However, its mechanisms of action remain unknown. Using a Synechocystis PCC 6803 strain expressing Flag-tagged Pam68, we purified a large protein complex containing ribosomes, SecY translocase, and the chlorophyll-binding PSII inner antenna CP47...
February 20, 2018: Plant Physiology
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