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Beatrycze Nowicka, Andrzej Żądło, Bartosz Pluciński, Jerzy Kruk, Paulina Kuczyńska
Allelopathy is a phenomenon, where one species releases compounds able to inhibit the growth of other species. Juglone, 5-hydroxy-1,4-naphtoquinone, is an allelochemical produced by walnut trees. The main mode of juglone toxicity is the formation of semiquinone radicals, able to reduce O2 to superoxide. Prenyllipid antioxidants such as tocopherol and plastoquinone are important for antioxidant defense in photosynthetic organisms. Here we assess their participation in the response to juglone. The impact of 20 μM juglone on the content of photosynthetic pigments and prenyllipid antioxidants in green microalga Chlamydomonas reinhardtii was measured over an incubation period of 7...
September 21, 2017: Phytochemistry
Elizabeth S Freeman Rosenzweig, Bin Xu, Luis Kuhn Cuellar, Antonio Martinez-Sanchez, Miroslava Schaffer, Mike Strauss, Heather N Cartwright, Pierre Ronceray, Jürgen M Plitzko, Friedrich Förster, Ned S Wingreen, Benjamin D Engel, Luke C M Mackinder, Martin C Jonikas
Approximately 30%-40% of global CO2 fixation occurs inside a non-membrane-bound organelle called the pyrenoid, which is found within the chloroplasts of most eukaryotic algae. The pyrenoid matrix is densely packed with the CO2-fixing enzyme Rubisco and is thought to be a crystalline or amorphous solid. Here, we show that the pyrenoid matrix of the unicellular alga Chlamydomonas reinhardtii is not crystalline but behaves as a liquid that dissolves and condenses during cell division. Furthermore, we show that new pyrenoids are formed both by fission and de novo assembly...
September 21, 2017: Cell
Luke C M Mackinder, Chris Chen, Ryan D Leib, Weronika Patena, Sean R Blum, Matthew Rodman, Silvia Ramundo, Christopher M Adams, Martin C Jonikas
Approximately one-third of global CO2 fixation is performed by eukaryotic algae. Nearly all algae enhance their carbon assimilation by operating a CO2-concentrating mechanism (CCM) built around an organelle called the pyrenoid, whose protein composition is largely unknown. Here, we developed tools in the model alga Chlamydomonas reinhardtii to determine the localizations of 135 candidate CCM proteins and physical interactors of 38 of these proteins. Our data reveal the identity of 89 pyrenoid proteins, including Rubisco-interacting proteins, photosystem I assembly factor candidates, and inorganic carbon flux components...
September 21, 2017: Cell
Qian Lu, Yi-Fan Bu, Jian-Zhong Liu
Astaxanthin is a carotenoid of significant commercial value due to its superior antioxidant potential and wide applications in the aquaculture, food, cosmetic and pharmaceutical industries. A higher ratio of astaxanthin to the total carotenoids is required for efficient astaxanthin production. β-Carotene ketolase and hydroxylase play important roles in astaxanthin production. We first compared the conversion efficiency to astaxanthin in several β-carotene ketolases from Brevundimonas sp. SD212, Sphingomonas sp...
September 22, 2017: Marine Drugs
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
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
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
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
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
Isabel B Oliveira, Ksenia J Groh, Rene Schönenberger, Carlos Barroso, Kevin V Thomas, Marc J-F Suter
Antifouling (AF) systems provide the most cost-effective protection against biofouling. Several AF biocides have, however, caused deleterious effects in the environment. Subsequently, new compounds have emerged that claim to be more environment-friendly, but studies on their toxicity and environmental risk are necessary in order to ensure safety. This work aimed to assess the toxicity of three emerging AF biocides, tralopyril, triphenylborane pyridine (TPBP) and capsaicin, towards non-target freshwater organisms representing three trophic levels: algae (Chlamydomonas reinhardtii), crustacean (Daphnia magna) and fish (Danio rerio)...
August 1, 2017: Aquatic Toxicology
Md Abdur Razzak, Dong Wook Lee, Yun-Joo Yoo, Inhwan Hwang
Chloroplasts evolved from a free-living cyanobacterium acquired by the ancestor of all photosynthetic eukaryotes, including algae and plants, through a single endosymbiotic event. During endosymbiotic conversion, the majority of genes in the endosymbiont were transferred to the host nucleus and many of the proteins encoded by these genes must therefore be transported into the chloroplast after translation in the cytosol. Chloroplast-targeted proteins contain a targeting signal, named the transit peptide (TP), at the N-terminus...
August 24, 2017: Scientific Reports
Bin Dong, Song Wu, Jing Wang, Yan-Xia Liu, Zhao Peng, De-Mei Meng, Kaiyao Huang, Mingfu Wu, Zhen-Chuan Fan
Intraflagellar transport (IFT) particles are composed of polyprotein complexes IFT-A and IFT-B as well as cargo adaptors such as the BBSome. As two IFT-B subunits, IFT25 and IFT27 were found to form a heterodimer, which is essential in exporting the BBSome out of the cilium but not involved in flagellar assembly and cytokinesis in vertebrates. Controversial results were, however, recorded to show that defects in IFT, flagellar assembly and even cytokinesis were caused by IFT27 knockdown in C. reinhardtii By using C...
August 24, 2017: Biology Open
Luke C M Mackinder
Contents I. II. III. IV. V. VI. References SUMMARY: To meet the food demands of a rising global population, innovative strategies are required to increase crop yields. Improvements in plant photosynthesis by genetic engineering show considerable potential towards this goal. One prospective approach is to introduce a CO2 -concentrating mechanism into crop plants to increase carbon fixation by supplying the central carbon-fixing enzyme, Rubisco, with a higher concentration of its substrate, CO2 . A promising donor organism for the molecular machinery of this mechanism is the eukaryotic alga Chlamydomonas reinhardtii...
August 21, 2017: New Phytologist
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