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Mariya Ostroukhova, Zhanneta Zalutskaya, Elena Ermilova
A feature of the mitochondrial electron transport chain in plants, some protists and many fungi is the presence of two terminal oxidases, the energy-conserving cytochrome oxidase and another termed alternative oxidase (AOX). AOX branches from the main respiratory chain, directly coupling the oxidation of ubiquinol with reduction of oxygen to water. The AOX genes can be divided into two discrete subfamilies, AOX1 and AOX2. Although AOX has been proposed to play essential roles in stress tolerance of organisms, the role of subfamily AOX2 is largely unknown...
December 13, 2016: European Journal of Protistology
Coralie Siebman, Orlin D Velev, Vera I Slaveykova
The capability of alternating current (AC) dielectrophoresis (DEP) for on-chip capture and chaining of the three species representative of freshwater phytoplankton was evaluated. The effects of the AC field intensity, frequency and duration on the chaining efficiency and chain lengths of green alga Chlamydomonas reinhardtii, cyanobacterium Synechocystis sp. and diatom Cyclotella meneghiniana were characterized systematically. C. reinhardtii showed an increase of the chaining efficiency from 100 Hz to 500 kHz at all field intensities; C...
January 5, 2017: Biosensors
Fan Bai, Christian Gusbeth, Wolfgang Frey, Peter Nick
Nanosecond pulsed electric fields (nsPEFs) have great potential for biotechnological and medical applications. However, the biological mechanisms causing the cellular responses are still far from understood. We used the unicellular green algae Chlamydomonas reinhardtii as experimental model to dissect the immediate consequences of electroporation from the developmental cellular responses evoked by nsPEFs. We observe that nsPEFs induce a short-term permeabilization of the membrane, accompanied by swelling and oxidative burst...
January 5, 2017: Biochimica et Biophysica Acta
Lanzhen Wei, Jing Yi, Lianjun Wang, Tingting Huang, Fudan Gao, Quanxi Wang, Weimin Ma
Chlamydomonas reinhardtii is a unicellular green alga that can use light energy to produce H2 from H2O in the background of NaHSO3 treatment. However, the role of light intensity in such H2 production remains elusive. Here, light intensity significantly affected the yield of H2 production in NaHSO3-treated C. reinhardtii, which was consistent with its effects on the content of O2 and the expression and activity of hydrogenase. Further, NaHSO3 was found to be able to remove O2 via a reaction of bisulfite with superoxide anion produced at the acceptor side of PSI, and light intensity affected the reaction rate significantly...
January 7, 2017: Plant & Cell Physiology
Michal Breker, Kristi Lieberman, Frej Tulin, Frederick R Cross
Systematic identification and characterization of genetic perturbations have proven useful to decipher gene function and cellular pathways. However, the conventional approaches of permanent gene deletion cannot be applied to essential genes. We have pioneered a unique collection of ~70 temperature-sensitive (ts) lethal mutants for studying cell cycle regulation in the unicellular green algae Chlamydomonas reinhardtii(1). These mutations identify essential genes, and the ts alleles can be conditionally inactivated by temperature shift, providing valuable tools to identify and analyze essential functions...
December 5, 2016: Journal of Visualized Experiments: JoVE
David A Russo, Andrew P Beckerman, Jagroop Pandhal
Key microalgal species are currently being exploited as biomanufacturing platforms using mass cultivation systems. The opportunities to enhance productivity levels or produce non-native compounds are increasing as genetic manipulation and metabolic engineering tools are rapidly advancing. Regardless of the end product, there are both environmental and industrial risks associated to open pond cultivation of mutant microalgal strains. A mutant escape could be detrimental to local biodiversity and increase the risk of algal blooms...
December 2017: AMB Express
Yuki Hirato, Mayumi Tokuhisa, Minoru Tanigawa, Hiroyuki Ashida, Hiroyuki Tanaka, Katsushi Nishimura
d-Threonine aldolase (DTA) catalyzes the pyridoxal 5'-phosphate (PLP)-dependent interconversion of d-threonine and glycine plus acetaldehyde. The enzyme is a powerful tool for the stereospecific synthesis of various β-hydroxy amino acids in synthetic organic chemistry. In this study, DTA from the green alga Chlamydomonas reinhardtii was discovered and characterized, representing the first report to describe the existence of eukaryotic DTA. DTA was overexpressed in recombinant Escherichia coli BL21 (DE3) cells; the specific activity of the enzyme in the cell-free extract was 0...
December 27, 2016: Phytochemistry
Matthew R Preimesberger, Ananya Majumdar, Juliette T J Lecomte
Nitrate metabolism in Chlamydomonas reinhardtii involves THB1, a monomeric hemoglobin thought to function as a nitric oxide dioxygenase (NOD). NOD activity requires dioxygen and nitric oxide binding followed by a one-electron oxidation of the heme iron and nitrate release. Unlike pentacoordinate flavohemoglobins, which are efficient NODs, THB1 uses two iron axial ligands: the conserved proximal histidine and a distal lysine (Lys53). As a ligand in both the oxidized (ferric) and reduced (ferrous) states, Lys53 is expected to lower the reorganization energy associated with electron transfer and therefore facilitate reduction of the ferric enzyme...
January 18, 2017: Biochemistry
Atsushi Takabayashi, Saeka Takabayashi, Kaori Takahashi, Mai Watanabe, Hiroko Uchida, Akio Murakami, Tomomichi Fujita, Masahiko Ikeuchi, Ayumi Tanaka
The identification of protein complexes is important to understand protein structure and function, and the regulation of cellular processes. We used blue-native PAGE and tandem mass spectrometry to identify protein complexes systematically, and built a web database, the protein co-migration database (PCoM-DB,, to provide prediction tools for protein complexes. PCoM-DB provides migration profiles for any given protein of interest, and allows users to compare them with migration profiles of other proteins, showing the oligomeric states of proteins and thus identifying potential interaction partners...
December 22, 2016: Plant & Cell Physiology
Robert VAN Lis, Marion Popek, Yohann Coute, Artemis Kosta, Dominique Drapier, Wolfgang Nitschke, Ariane Atteia
Aldehyde/alcohol dehydrogenases (ADHEs) are bifunctional enzymes that commonly produce ethanol from acetyl-CoA with acetaldehyde as intermediate, and play a key role in anaerobic redox balance in many fermenting bacteria. ADHEs are also present in photosynthetic unicellular eukaryotes, where their physiological role and regulation are however largely unknown. Herein we provide the first molecular and enzymatic characterization of the ADHE from the photosynthetic microalga Chlamydomonas reinhardtii. Purified recombinant ADHE catalyzed the reversible NADH-mediated interconversions of acetyl-CoA, acetaldehyde and ethanol, but seemed to be poised towards the production of ethanol from acetaldehyde...
December 22, 2016: Journal of Biological Chemistry
Pilar Carbonero, Raquel Iglesias-Fernández, Jesús Vicente-Carbajosa
Seed development follows zygotic embryogenesis; during the maturation phase reserves accumulate and desiccation tolerance is acquired. This is tightly regulated at the transcriptional level and the AFL (ABI3/FUS3/LEC2) subfamily of B3 transcription factors (TFs) play a central role. They alter hormone biosynthesis, mainly in regards to abscisic acid and gibberellins, and also regulate the expression of other TFs and/or modulate their downstream activity via protein-protein interactions. This review deals with the origin of AFL TFs, which can be traced back to non-vascular plants such as Physcomitrella patens and achieves foremost expansion in the angiosperms...
December 21, 2016: Journal of Experimental Botany
Laura Girolomoni, Paola Ferrante, Silvia Berteotti, Giovanni Giuliano, Roberto Bassi, Matteo Ballottari
In eukaryotic autotrophs, photosystems are composed of a core moiety, hosting charge separation and electron transport reactions, and an antenna system, enhancing light harvesting and photoprotection. In Chlamydomonas reinhardtii, the major antenna of PSII is a heterogeneous trimeric complex made up of LHCBM1-LHCBM9 subunits. Despite high similarity, specific functions have been reported for several members including LHCBM1, 2, 7, and 9. In this work, we analyzed the function of LHCBM4 and LHCBM6 gene products in vitro by synthesizing recombinant apoproteins from individual sequences and refolding them with pigments...
December 21, 2016: Journal of Experimental Botany
James D Vasta, Amit Choudhary, Katrina H Jensen, Nicholas A McGrath, Ronald T Raines
Collagen prolyl 4-hydroxylases (CP4Hs) catalyze a prevalent posttranslational modification, the hydroxylation of (2S)-proline residues in protocollagen strands. The ensuing (2S,4R)-4-hydroxyproline residues are necessary for the conformational stability of the collagen triple helix. Prolyl peptide bonds isomerize between cis and trans isomers, and the preference of the enzyme is unknown. We synthesized alkene isosteres of the cis and trans isomers to probe the conformational preferences of human CP4H1. We discovered that the presence of a prolyl peptide bond is necessary for catalysis...
January 10, 2017: Biochemistry
Andrew R Durney, Leah C Frenette, Elizabeth C Hodvedt, Todd D Krauss, Hitomi Mukaibo
A template-synthesis method that enables fabrication of tapered microtube arrays is reported. Track-etched poly(ethylene terephthalate) membranes are used as the template, with closed-tipped conical pores having length and base diameter of 6.27 ± 0.28 and 1.21 ± 0.05 μm, respectively. A conductive layer of Pt is deposited by atomic layer deposition (ALD) to enable the successive electrodeposition of Ni. By decreasing the Pt precursor pulse duration from 10 to 1 s during the ALD step, the heights of the microtubes are controlled from the maximal full length (∼6 μm) to only a fraction (1-2 μm) of the template pore...
December 21, 2016: ACS Applied Materials & Interfaces
Tânia Gomes, Li Xie, Dag Brede, Ole-Christian Lind, Knut Asbjørn Solhaug, Brit Salbu, Knut Erik Tollefsen
The aquatic environment is continuously exposed to ionizing radiation from both natural and anthropogenic sources, making the characterization of ecological and health risks associated with radiation of large importance. Microalgae represent the main source of biomass production in the aquatic ecosystem, thus becoming a highly relevant biological model to assess the impacts of gamma radiation. However, little information is available on the effects of gamma radiation on microalgal species, making environmental radioprotection of this group of species challenging...
December 5, 2016: Aquatic Toxicology
David Adam, Lisa Bösche, Leonardo Castaneda-Losada, Martin Winkler, Ulf-Peter Apfel, Thomas Happe
Herein we report a sustainable in vitro system for an enzyme-based photohydrogen production. The [FeFe]-hydrogenase HydA1 from Chlamydomonas reinhardtii was tested for photohydrogen production as a proton reducing catalyst in combination with eight different photosensitizers. Using the organic dye 5-carboxyeosin (5CE) as photosensitizer and plant type ferredoxin PetF as electron mediator, HydA1 achieves the highest light-driven turnover number (TONHydA1) yet reported for an enzyme-based in vitro system (2.9 x 106 mol H2 mol-1 catalyst) and a maximum turnover frequency (TOFHydA1) of 550 mol H2 mol-1 HydA1 sec-1...
December 15, 2016: ChemSusChem
David W Mulder, Yisong Guo, Michael W Ratzloff, Paul W King
Hydrogenases couple electrochemical potential to the reversible chemical transformation of H2 and protons, yet the reaction mechanism and composition of intermediates are not fully understood. In this Communication we describe the biophysical properties of a hydride-bound state (Hhyd) of the [FeFe]-hydrogenase from Chlamydomonas reinhardtii. The catalytic H-cluster of [FeFe]-hydrogenase consists of a [4Fe-4S] subcluster ([4Fe-4S]H) linked by a cysteine thiol to an azadithiolate-bridged 2Fe subcluster ([2Fe]H) with CO and CN(-) ligands...
December 21, 2016: Journal of the American Chemical Society
Anna Ophelia Müller, Katharina Franziska Blersch, Anna Lena Gippert, Till Ischebeck
Lipid droplets have emerged in recent years as dynamic organelles rather than inactive storage sites of triacylglycerol. The number of proteins known to be associated with lipid droplets has increased, but remains small in comparison to other organelles. Also the mechanisms how lipid droplets are recognized and bound by proteins need deeper investigation. Here, we present a fast, simple and inexpensive approach to assay proteins for their association with lipid droplets in vivo that can help to screen protein candidates or mutated variants of proteins for their association in an efficient manner...
December 10, 2016: Plant Journal: for Cell and Molecular Biology
Jasmin Krismer, Manu Tamminen, Simone Fontana, Renato Zenobi, Anita Narwani
Phenotypic variation is vital for microbial populations to survive environmental perturbations. Both genetic and non-genetic factors contribute to an organism's phenotypic variation and therefore its fitness. To investigate the correlation between genetic diversity and phenotypic variation, we applied our recently developed mass spectrometry method that allows for the simultaneous measurement of more than 25 different lipids and pigments with high throughput in the unicellular microalga Chlamydomonas reinhardtii...
December 9, 2016: ISME Journal
Guillaume Allorent, Linnka Lefebvre-Legendre, Richard Chappuis, Marcel Kuntz, Thuy B Truong, Krishna K Niyogi, Roman Ulm, Michel Goldschmidt-Clermont
Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown...
December 20, 2016: Proceedings of the National Academy of Sciences of the United States of America
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