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Oliver D Caspari, Moritz T Meyer, Dimitri Tolleter, Tyler M Wittkopp, Nik J Cunniffe, Tracy Lawson, Arthur R Grossman, Howard Griffiths
The pyrenoid of the unicellular green alga Chlamydomonas reinhardtii is a microcompartment situated in the centre of the cup-shaped chloroplast, containing up to 90% of cellular Rubisco. Traversed by a network of dense, knotted thylakoid tubules, the pyrenoid has been proposed to influence thylakoid biogenesis and ultrastructure. Mutants that are unable to assemble a pyrenoid matrix, due to expressing a vascular plant version of the Rubisco small subunit, exhibit severe growth and photosynthetic defects and have an ineffective carbon-concentrating mechanism (CCM)...
June 1, 2017: Journal of Experimental Botany
Moritz T Meyer, Charles Whittaker, Howard Griffiths
The confinement of Rubisco in a chloroplast microcompartment, or pyrenoid, is a distinctive feature of most microalgae, and contributes to perhaps ~30 Pg of carbon fixed each year, yet our understanding of pyrenoid composition, regulation, and function remains fragmentary. Recently, significant progress in understanding the pyrenoid has arisen from studies using mutant lines, mass spectrometric analysis of isolated pyrenoids, and advanced ultrastructural imaging of the microcompartment in the model alga Chlamydomonas...
June 1, 2017: Journal of Experimental Botany
Miao Yang, Jun-Peng Jiang, Xi Xie, Ya-Dong Chu, Yan Fan, Xu-Peng Cao, Song Xue, Zhan-You Chi
Triacylglycerols are produced in abundance through chloroplast and endoplasmic reticulum pathways in some microalgae exposed to stress, though the relative contribution of either pathway remains elusive. Characterization of these pathways requires isolation of the organelles. In this study, an efficient and reproducible approach, including homogenous batch cultures of nitrogen-deprived algal cells in photobioreactors, gentle cell disruption using a simple custom-made disruptor with mechanical shear force, optimized differential centrifugation and Percoll density gradient centrifugation, was developed to isolate chloroplasts from Chlamydomonas reinhardtii subjected to nitrogen stress...
2017: Frontiers in Plant Science
Shunsuke Hirooka, Yuu Hirose, Yu Kanesaki, Sumio Higuchi, Takayuki Fujiwara, Ryo Onuma, Atsuko Era, Ryudo Ohbayashi, Akihiro Uzuka, Hisayoshi Nozaki, Hirofumi Yoshikawa, Shin-Ya Miyagishima
Some microalgae are adapted to extremely acidic environments in which toxic metals are present at high levels. However, little is known about how acidophilic algae evolved from their respective neutrophilic ancestors by adapting to particular acidic environments. To gain insights into this issue, we determined the draft genome sequence of the acidophilic green alga Chlamydomonas eustigma and performed comparative genome and transcriptome analyses between Ceustigma and its neutrophilic relative Chlamydomonas reinhardtii The results revealed the following features in Ceustigma that probably contributed to the adaptation to an acidic environment...
September 11, 2017: Proceedings of the National Academy of Sciences of the United States of America
Ryosuke Yamamoto, Jagan M Obbineni, Lea M Alford, Takahiro Ide, Mikito Owa, Juyeon Hwang, Takahide Kon, Kazuo Inaba, Noliyanda James, Stephen M King, Takashi Ishikawa, Winfield S Sale, Susan K Dutcher
Cytoplasmic assembly of ciliary dyneins, a process known as preassembly, requires numerous non-dynein proteins, but the identities and functions of these proteins are not fully elucidated. Here, we show that the classical Chlamydomonas motility mutant pf23 is defective in the Chlamydomonas homolog of DYX1C1. The pf23 mutant has a 494 bp deletion in the DYX1C1 gene and expresses a shorter DYX1C1 protein in the cytoplasm. Structural analyses, using cryo-ET, reveal that pf23 axonemes lack most of the inner dynein arms...
September 11, 2017: PLoS Genetics
Felix Buchert, Benjamin Bailleul, Toru Hisabori
The chloroplast F1Fo-ATP synthase (CF1Fo) drives ATP synthesis and the reverse reaction of ATP hydrolysis. The enzyme evolved in a cellular environment where electron transfer processes and molecular oxygen are abundant, and thiol modulation in the γ-subunit via thioredoxin is important for its ATPase activity regulation. Especially under high light, oxygen can be reduced and forms reactive oxygen species (ROS) which can oxidize CF1Fo among various other biomolecules. Mutation of the conserved ROS targets resulted in a tolerant enzyme, suggesting that ROS might play a regulatory role...
September 7, 2017: Biochimica et Biophysica Acta
Md Saiful Islam, Kazuto Sazawa, Noriko Hata, Kazuharu Sugawara, Hideki Kuramitz
We developed an electrochemical microalgal bioassay for the determination of heavy metal toxicity in water on the basis of the alkaline phosphatase (ALP) enzyme inhibition of Chlamydomonas reinhardtii. Five heavy metals were chosen as toxicants: Hg, Cd, Pb, Zn, and Cu. The induced ALP activity of C. reinhardtii was inhibited using the phosphate starvation method, and the results were evaluated by measuring the electrochemical oxidation of p-aminophenol (PAP) following the enzymatic conversion of p-aminophenyl phosphate (PAPP) as a substrate...
September 4, 2017: Chemosphere
Dario Leister
The term 'experimental evolution' refers to short-term evolutionary experiments with microorganisms under controlled conditions in which selection is expected to occur. In combination with whole-genome sequencing and genetic engineering, the method has become a powerful tool to study evolutionary mechanisms and engineer new microbial variants. It has been most extensively used in the model species Escherichia coli and Saccharomyces cerevisiae, but more recently photosynthetic microorganisms have been subjected to experimental evolution...
September 7, 2017: Essays in Biochemistry
Susanne Kraemer, Katharina B Böndel, Robert W Ness, Peter D Keightley, Nick Colegrave
Although all genetic variation ultimately stems from mutations, their properties are difficult to study directly. Here, we used multiple mutation accumulation (MA) lines derived from five genetic backgrounds of the green algae Chlamydomonas reinhardtii that have been previously subjected to whole genome sequencing to investigate the relationship between the number of spontaneous mutations and change in fitness from a non-evolved ancestor. MA lines were on average less fit than their ancestors and we detected a significantly negative correlation between the change in fitness and the total number of accumulated mutations in the genome...
September 8, 2017: Evolution; International Journal of Organic Evolution
Elly Spijkerman, Marcus Lukas, Alexander Wacker
Mixing events in stratified lakes result in microalgae being exposed to varying conditions in light and organic carbon concentrations. Stratified lakes consist of an upper illuminated strata and a lower, darker strata where organic carbon accumulates. Therefore, in this contribution we explore the importance of dissolved organic carbon for growth under various light intensities by measuring some ecophysiological adaptations in two green microalgae. We compared the non-motile Chlorella vulgaris with the flagellated Chlamydomonas acidophila under auto-, mixo-, and heterotrophic growth conditions...
September 4, 2017: Phytochemistry
Fabian Ries, Yvonne Carius, Marina Rohr, Karin Gries, Sandro Keller, C Roy D Lancaster, Felix Willmund
A considerably small fraction of approximately 60-100 proteins of all chloroplast proteins are encoded by the plastid genome. Many of these proteins are major subunits of complexes with central functions within plastids. In comparison with other subcellular compartments and bacteria, many steps of chloroplast protein biogenesis are not well understood. We report here on the first study of chloroplast-localised trigger factor. In bacteria, this molecular chaperone is known to associate with translating ribosomes to facilitate the folding of newly synthesized proteins...
September 6, 2017: Scientific Reports
Xiaoyan Zhu, Emiliya Poghosyan, Radhika Gopal, Yi Liu, Kristine S Ciruelas, Yousif Maizy, Dennis R Diener, Stephen M King, Takashi Ishikawa, Pinfen Yang
Nucleoside diphosphate kinases (NDKs) play a central role in diverse cellular processes using the canonical NDK activity or alternative mechanisms that remain poorly defined. Our study of dimeric NDK5 in a flagellar motility control complex, the radial spoke (RS), has revealed new modalities. The flagella in Chlamydomonas ndk5 mutant were paralyzed, albeit only deficient in three RS subunits. RS morphology appeared severely changed in averaged cryo-electron tomograms, suggesting that NDK5 is crucial for the intact spokehead formation as well as RS structural stability...
September 6, 2017: Molecular Biology of the Cell
Yi Liu, Mike Visetsouk, Michelle Mynlieff, Hongmin Qin, Karl F Lechtreck, Pinfen Yang
Although microtubules are known for dynamic instability, the dynamicity is considered to be tightly controlled to support a variety of cellular processes. Yet diverse evidence suggests that this is not applicable to Chlamydomonas, a biflagellate fresh water green alga, but intense autofluorescence from photosynthesis pigments has hindered the investigation. By expressing a bright fluorescent reporter protein at the endogenous level, we demonstrate in real time discreet sweeping changes in algal microtubules elicited by rises of intracellular H(+) and Na(+)...
September 6, 2017: ELife
Mark Rütgers, Ligia Segatto Muranaka, Miriam Schulz-Raffelt, Sylvia Thoms, Juliane Schurig, Felix Willmund, Michael Schroda
A conserved reaction of all organisms exposed to heat stress is an increased expression of heat shock proteins (HSPs). Several studies have proposed that HSP expression in heat-stressed plant cells is triggered by an increased fluidity of the plasma membrane. Among the main lines of evidence in support of this model are (i) the degree of membrane lipid saturation was higher in cells grown at elevated temperatures and correlated with a lower amplitude of HSP expression upon a temperature upshift; (ii) membrane fluidizers induce HSP expression at physiological temperatures; (iii) membrane rigidifier dimethylsulfoxide dampens heat-induced HSP expression...
September 6, 2017: Plant, Cell & Environment
Ben Lucker, Eliezer Schwartz, Sebastian Kuhlgert, Elisabeth Ostendorf, David M Kramer
Photosynthetic organisms rapidly adjust the capture, transfer and utilization of light energy to optimize the efficiency of photosynthesis and avoid photodamage. These adjustments involve fine tuning of expression levels and mutual interactions among electron/proton transfer components and their associated light harvesting antenna. Detailed studies of these interactions and their dynamics have been hindered by the low throughput and resolution of currently available research tools, which involve laborious isolation, separation and characterization steps...
September 2, 2017: Plant Journal: for Cell and Molecular Biology
Chun-Yen Chen, Ai-Ling Kao, Zheng-Chia Tsai, Yu-Mei Shen, Pei-Hsun Kao, I-Son Ng, Jo-Shu Chang
β-carotene is a valuable pigment abundant in some microalgal species but the low β-carotene productivity of microalgae has become the major obstacles against its commercialization. This work aims to improve the productivity of algae-based β-carotene via genetic engineering approaches. First, a synthetic psy gene construct (891 bp) encoding 297 amino acids was expressed in Scenedesmus sp. CPC2 host to enhance the β-carotene production. The synthetic psy gene was designed by considering the highest consensus of amino acids (i...
September 2, 2017: Biotechnology Journal
Gaëtan Vanier, Pierre-Louis Lucas, Corinne Loutelier-Bourhis, Jessica Vanier, Carole Plasson, Marie-Laure Walet-Balieu, Philippe Chan Tchi-Song, Isabelle Remy-Jouet, Vincent Richard, Sophie Bernard, Azeddine Driouich, Carlos Afonso, Patrice Lerouge, Elodie Mathieu-Rivet, Muriel Bardor
Eukaryotic N-glycosylation pathways are dependent of N-acetylglucosaminyltransferase I (GnTI), a key glycosyltransferase opening the door to the formation of complex-type N-glycans by transferring a N-acetylglucosamine residue onto the Man5GlcNAc2 intermediate. In contrast, glycans N-linked to Chlamydomonas reinhardtii proteins arise from a GnTI-independent Golgi processing of oligomannosides giving rise to Man5GlcNAc2 substituted eventually with one or two xylose(s). Here, complementation of C. reinhardtii with heterologous GnTI was investigated by expression of GnTI cDNAs originated from Arabidopsis and the diatom Phaeodactylum tricornutum...
August 31, 2017: Scientific Reports
S Massoz, M Hanikenne, B Bailleul, N Coosemans, M Radoux, H Miranda-Astudillo, P Cardol, V Larosa, C Remacle
The qualitative screening method to select complex I mutants in the microalga Chlamydomonas, based on reduced growth under heterotrophic condition, is not suited for high throughput screening. In order to develop a fast screening method based on measurements of chlorophyll fluorescence, we first demonstrated that complex I mutants displayed decreased photosystem II efficiency in the genetic background of a photosynthetic mutation leading to reduced formation of the electrochemical proton gradient in the chloroplast (pgrl1 mutation)...
August 30, 2017: Plant Journal: for Cell and Molecular Biology
Karel Horňák, Vojtěch Kasalický, Karel Šimek, Hans-Peter Grossart
We investigated changes in quality and quantity of extracellular and biomass-derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass-derived OM concentrations from each alga were approximately 20 and 1 mg l(-1) , respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids...
August 30, 2017: Environmental Microbiology
Johannes Vierock, Christiane Grimm, Noam Nitzan, Peter Hegemann
Channelrhodopsins are light-gated ion channels of green algae used for the precise temporal and spatial control of transmembrane ion fluxes. The channelrhodopsin Chrimson from Chlamydomonas noctigama allows unprecedented deep tissue penetration due to peak absorption at 590 nm. We demonstrate by electrophysiological recordings and imaging techniques that Chrimson is highly proton selective causing intracellular acidification in HEK cells that is responsible for slow photocurrent decline during prolonged illumination...
August 30, 2017: Scientific Reports
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