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Kotaro Kosuge, Ryutaro Tokutsu, Eunchul Kim, Seiji Akimoto, Makio Yokono, Yoshifumi Ueno, Jun Minagawa
Photosynthetic organisms are frequently exposed to light intensities that surpass the photosynthetic electron transport capacity. Under these conditions, the excess absorbed energy can be transferred from excited chlorophyll in the triplet state (3Chl*) to molecular O2 , which leads to the production of harmful reactive oxygen species. To avoid this photooxidative stress, photosynthetic organisms must respond to excess light. In the green alga Chlamydomonas reinhardtii , the fastest response to high light is nonphotochemical quenching, a process that allows safe dissipation of the excess energy as heat...
March 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
Sa Geng, Ayano Miyagi, James G Umen
Volvocine algae comprise a unique comparative model for investigating the evolution of distinct male and female sexes (oogamy) from an isogamous ancestral state with mating types. The mating-type or sex-determining gene MID encodes a putative RWP-RK family transcription factor, and orthologs of MID are present throughout the volvocine algal lineage in either the MT- or male mating locus of dioecious species. It was previously found that ectopic expression of isogamous Chlamydomonas reinhardtii MID ( CrMID ) in a C...
March 16, 2018: Development
Teresa Morales-Ruiz, Álvaro C Romero-Valenzuela, Vanessa M Vázquez-Grande, Teresa Roldán-Arjona, Rafael R Ariza, Dolores Córdoba-Cañero
Base excision repair (BER) is a major defense pathway against spontaneous DNA damage. This multistep process is initiated by DNA glycosylases that recognise and excise the damaged base, and proceeds by the concerted action of additional proteins that perform incision of the abasic site, gap filling and ligation. BER has been extensively studied in bacteria, yeasts and animals. Although knowledge of this pathway in land plants is increasing, there are no reports detecting BER in algae. We describe here an experimental in vitro system allowing the specific analysis of BER in the model alga Chlamydomonas reinhardtii...
March 5, 2018: DNA Repair
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
Dhivya Kumar, Rebecca T Thomason, Maya Yankova, Jonathan D Gitlin, Richard E Mains, Betty A Eipper, Stephen M King
The assembly of membranous extensions such as microvilli and cilia in polarized cells is a tightly regulated, yet poorly understood, process. Peptidylglycine α-amidating monooxygenase (PAM), a membrane enzyme essential for the synthesis of amidated bioactive peptides, was recently identified in motile and non-motile (primary) cilia and has an essential role in ciliogenesis in Chlamydomonas, Schmidtea and mouse. In mammalian cells, changes in PAM levels alter secretion and organization of the actin cytoskeleton...
March 14, 2018: Scientific Reports
Tomohiro Kubo, Yuqing Hou, Deborah A Cochran, George B Witman, Toshiyuki Oda
Motility of cilia/flagella is generated by a coordinated activity of thousands of dyneins. Inner dynein arms (IDAs) are particularly important for the formation of ciliary/flagellar waveforms, but the molecular mechanism of IDA regulation is poorly understood. Here, we show using cryo-electron tomography and biochemical analyses of Chlamydomonas flagella that a conserved protein FAP44 forms a complex that tethers IDA f (I1 dynein) head domains to the A-tubule of the axonemal outer doublet microtubule. In wild-type flagella, IDA f showed little nucleotide-dependent movement except for a tilt in the f β head perpendicular to the microtubule-sliding direction...
March 14, 2018: Molecular Biology of the Cell
Ashok Aspatwar, Susanna Haapanen, Seppo Parkkila
Carbonic anhydrases (CAs) are metalloenzymes that are omnipresent in nature. CAs catalyze the basic reaction of the reversible hydration of CO₂ to HCO₃- and H⁺ in all living organisms. Photosynthetic organisms contain six evolutionarily different classes of CAs, which are namely: α-CAs, β-CAs, γ-CAs, δ-CAs, ζ-CAs, and θ-CAs. Many of the photosynthetic organisms contain multiple isoforms of each CA family. The model alga Chlamydomonas reinhardtii contains 15 CAs belonging to three different CA gene families...
March 13, 2018: Metabolites
Zhen Yu, Rui Hao, Liang Zhang, Yi Zhu
Nanoparticles (NPs) are inevitably released into the aquatic environment for being widely used and may affect the toxicity of other contaminants already present in the environment, such as trace metals. However, the effects of NPs on the ecotoxicity of cadmium (Cd), a common environmental trace metal pollutant, are not well explored. In this study, effects of four widely used NPs TiO2 (n-TiO2 ), SiO2 (n-SiO2 ), Ag (n-Ag) and CdTe/CdS core/shell quantum dots (QD) on the toxicity of Cd to the freshwater algae Chlamydomonas reinhardtii were assessed respectively...
March 13, 2018: Ecotoxicology and Environmental Safety
María Jesús García-Murria, Hemanth P K Sudhani, Julia Marín-Navarro, Manuel M Sánchez Del Pino, Joaquín Moreno
Oxidation of the cysteines from ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) leads to inactivation and promotes structural changes that increase the proteolytic sensitivity and membrane association propensity related to its catabolism. To uncover the individual role of the different cysteines, the sequential order of modification under increasing oxidative conditions was determined using chemical labeling and mass spectrometry. Besides, site-directed RubisCO mutants were obtained in Chlamydomonas reinhardtii replacing single conserved cysteines (Cys84, Cys172, Cys192, Cys247, Cys284, Cys427, Cys459 from the large and sCys41, sCys83 from the small subunit) and the redox properties of the mutant enzymes were determined...
March 10, 2018: Photosynthesis Research
Sigrun Rumpel, Constanze Sommer, Edward Reijerse, Christophe Farès, Wolfgang Lubitz
Hydride state intermediates are known to occur in various hydrogen conversion enzymes, including the highly efficient [FeFe] hydrogenases. The intermediate state involving a terminal iron-bound hydride has been recognized as crucial for the catalytic mechanism, but its occurrence has up to now eluded unequivocal proof under (near) physiological conditions. Here we show that the terminal hydride in the [FeFe] hydrogenase from Chlamydomonas reinhardtii can be directly detected using solution 1H NMR spectroscopy at room temperature, opening new avenues for detailed in-situ investigations under catalytic conditions...
March 9, 2018: Journal of the American Chemical Society
Huawen Lin, Zhengyan Zhang, Carlo Iomini, Susan K Dutcher
Intraflagellar transport moves proteins in and out of flagella/cilia and it is essential for the assembly of these organelles. Using whole-genome sequencing, we identified splice site mutations in two IFT genes, IFT81 ( fla9 ) and IFT121 ( ift121-2 ), which lead to flagellar assembly defects in the unicellular green alga Chlamydomonas reinhardtii The splicing defects in these ift mutants are partially corrected by mutations in two conserved spliceosome proteins, DGR14 and FRA10. We identified a dgr14 deletion mutant, which suppresses the 3' splice site mutation in IFT81 , and a frameshift mutant of FRA10 , which suppresses the 5' splice site mutation in IFT121 Surprisingly, we found dgr14-1 and fra10 mutations suppress both splice site mutations...
March 2018: Open Biology
Helene Launay, Patrick Barre, Carine Puppo, Yizhi Zhang, Stéphanie Manneville, Brigitte Gontero, Véronique Receveur-Brechot
Among intrinsically disordered proteins, conditionally disordered proteins undergo dramatic structural disorder rearrangements upon environmental changes and/or post-translational modifications that directly modulate their function. Quantifying the dynamics of these fluctuating proteins is extremely challenging but paramount to understanding the regulation of their function. The chloroplast protein CP12 is a model of such proteins, and acts as a redox switch by formation/disruption of its two disulfide bridges...
February 28, 2018: Journal of Molecular Biology
Sakina Bensalem, Filipa Lopes, Pierre Bodénès, Dominique Pareau, Olivier Français, Bruno Le Pioufle
One way envisioned to overcome part of the issues biodiesel production encounters today is to develop a simple, economically viable and eco-friendly process for the extraction of lipids from microalgae. This study investigates the lipid extraction efficiency from the microalga Chlamydomonas reinhardtii as well as the underlying mechanisms. We propose a new methodology combining a pulsed electric field (PEF) application and mechanical stresses as a pretreatment to improve lipid extraction with solvents. Cells enriched in lipids are therefore submitted to electric field pulses creating pores on the cell membrane and then subjected to a mechanical stress by applying cyclic pressures on the cell wall (using a microfluidic device)...
February 10, 2018: Bioresource Technology
Yu Zhan, Christophe H Marchand, Alexandre Maes, Adeline Mauries, Yi Sun, James S Dhaliwal, James Uniacke, Simon Arragain, Heng Jiang, Nicholas D Gold, Vincent J J Martin, Stéphane D Lemaire, William Zerges
Organelles are intracellular compartments which are themselves compartmentalized. Biogenic and metabolic processes are localized to specialized domains or microcompartments to enhance their efficiency and suppress deleterious side reactions. An example of intra-organellar compartmentalization is the pyrenoid in the chloroplasts of algae and hornworts. This microcompartment enhances the photosynthetic CO2-fixing activity of the Calvin-Benson cycle enzyme Rubisco, suppresses an energetically wasteful oxygenase activity of Rubisco, and mitigates limiting CO2 availability in aquatic environments...
2018: PloS One
Tanya Ostapenko, Fabian Jan Schwarzendahl, Thomas J Böddeker, Christian Titus Kreis, Jan Cammann, Marco G Mazza, Oliver Bäumchen
Microorganisms, such as bacteria and microalgae, often live in habitats consisting of a liquid phase and a plethora of interfaces. The precise ways in which these motile microbes behave in their confined environment remain unclear. Using experiments and Brownian dynamics simulations, we study the motility of a single Chlamydomonas microalga in an isolated microhabitat with controlled geometric properties. We demonstrate how the geometry of the habitat controls the cell's navigation in confinement. The probability of finding the cell swimming near the boundary increases with the wall curvature, as seen for both circular and elliptical chambers...
February 9, 2018: Physical Review Letters
Xiao Han, Haibo Xie, Yadong Wang, Chengtian Zhao
Radial spokes are structurally conserved, macromolecular complexes that are essential for the motility of 9 + 2 motile cilia. In Chlamydomonas species, mutations in radial spoke proteins result in ciliary motility defects. However, little is known about the function of radial spoke proteins during embryonic development. Here, we investigated the role of a novel radial spoke protein, leucine-rich repeat containing protein 23 (Lrrc23), during zebrafish embryonic development. Mutations in lrrc23 resulted in a selective otolith formation defect during early ear development...
February 22, 2018: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
Valéria Nagy, André Vidal-Meireles, Anna Podmaniczki, Klára Szentmihályi, Gábor Rákhely, Laura Zsigmond, László Kovács, Szilvia Z Tóth
Sulphur limitation may restrain cell growth and viability. In the green alga, Chlamydomonas reinhardtii, sulphur limitation may induce H2 production lasting for several days, to be exploited as a renewable energy source. Sulphur limitation causes a large number of physiological changes, including the inactivation of photosystem II (PSII), leading to the establishment of hypoxia, essential for the increase in hydrogenase expression and activity. The inactivation of PSII has been long assumed to be caused by the sulphur-limited turnover of its reaction center protein, PsbA...
February 23, 2018: Plant Journal: for Cell and Molecular Biology
Thilo Rühle, Bennet Reiter, Dario Leister
Measurements of chlorophyll fluorescence provide an elegant and non-invasive means of probing the dynamics of photosynthesis. Advances in video imaging of chlorophyll fluorescence have now made it possible to study photosynthesis at all levels from individual cells to entire crop populations. Since the technology delivers quantitative data, is easily scaled up and can be readily combined with other approaches, it has become a powerful phenotyping tool for the identification of factors relevant to photosynthesis...
2018: Frontiers in Plant Science
Emily L Hunter, Karl Lechtreck, Gang Fu, Juyeon Hwang, Huawen Lin, Avanti Gokhale, Lea M Alford, Brian Lewis, Ryosuke Yamamoto, Ritsu Kamiya, Fan Yang, Daniela Nicastro, Susan K Dutcher, Maureen Wirschell, Winfield S Sale
Axonemal dyneins, including inner dynein arm I1, assemble in the cytoplasm prior to transport into cilia by intraflagellar transport (IFT). How I1 dynein interacts with IFT is not understood. We take advantage of the Chlamydomonas reinhardtii ida3 mutant that assembles the inner arm I1 dynein complex in the cytoplasm but fails to transport I1 into the cilium, resulting in I1 dynein-deficient axonemes with abnormal motility. The IDA3 gene encodes a ∼115 kDa coiled-coil protein that primarily enters the cilium during ciliary growth but is not an axonemal protein...
February 21, 2018: Molecular Biology of the Cell
Ayswarya Ravi, Shengchun Guo, Beth Rasala, Miller Tran, Stephen Mayfield, Zivko L Nikolov
Correct folding and post-translational modifications are vital for therapeutic proteins to elicit their biological functions. Osteopontin (OPN), a bone regenerative protein present in a range of mammalian cells, is an acidic phosphoprotein with multiple potential phosphorylation sites. In this study, the ability of unicellular microalgae, Chlamydomonas reinhardtii , to produce phosphorylated recombinant OPN in its chloroplast is investigated. This study further explores the impact of phosphorylation and expression from a "plant-like" algae on separation of OPN...
February 16, 2018: International Journal of Molecular Sciences
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