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Cassuriaga APA, Moraes L, Morais MG, Costa JAV. Polyhydroxybutyrate production and increased macromolecule content in Chlamydomonas reinhardtii cultivated with xylose and reduced nitrogen levels. Int J Biol Macromol 2020; 158:875-883. [PMID: 32387355 DOI: 10.1016/j.ijbiomac.2020.04.273] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/21/2020] [Accepted: 04/30/2020] [Indexed: 12/11/2022]
Abstract
The aim of the current study was to evaluate the production of macromolecules such as polyhydroxybutyrate under pentose supplementation and reduced nitrogen levels in Chlamydomonas reinhardtii. Two batches of experiments were carried out: (1) reduction in the nitrogen (NH4Cl) concentration to 6 and 4 g L-1 and (2) supplementation of 10, 20 and 30 mg L-1 D-xylose together with a reduction in the NH4Cl concentration (6 and 4 g L-1). The addition of 20 mg L-1 D-xylose together with 6 g L-1 NH4Cl resulted in polyhydroxybutyrate production (206.0 mg L-1). The reduction of 8 to 6 g L-1 NH4Cl did not trigger a reduction in the production of either proteins (68.3% w w-1) or carbohydrates (23.3% w w-1) in the cells. The current study demonstrated that nutritional modifications, which until now have been unexplored in C. reinhardtii, triggered the production of macromolecules (polymers, carbohydrates and proteins) with high biotechnological potential.
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Affiliation(s)
- Ana Paula Aguiar Cassuriaga
- Laboratory of Biochemical Engineering, College of Chemistry and Food Engineering, Federal University of Rio Grande, Rio Grande, RS, Brazil
| | - Luiza Moraes
- Laboratory of Biochemical Engineering, College of Chemistry and Food Engineering, Federal University of Rio Grande, Rio Grande, RS, Brazil
| | - Michele Greque Morais
- Laboratory of Microbiology and Biochemistry, College of Chemistry and Food Engineering, Federal University of Rio Grande, Rio Grande, RS, Brazil
| | - Jorge Alberto Vieira Costa
- Laboratory of Biochemical Engineering, College of Chemistry and Food Engineering, Federal University of Rio Grande, Rio Grande, RS, Brazil.
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2
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Ivošević DeNardis N, Pletikapić G, Frkanec R, Horvat L, Vernier PT. From algal cells to autofluorescent ghost plasma membrane vesicles. Bioelectrochemistry 2020; 134:107524. [PMID: 32272336 DOI: 10.1016/j.bioelechem.2020.107524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 11/29/2022]
Abstract
Plasma membrane vesicles can be effective, non-toxic carriers for microscale material transport, provide a convenient model for probing membrane-related processes, since intracellular biochemical processes are eliminated. We describe here a fine-tuned protocol for isolating ghost plasma membrane vesicles from the unicellular alga Dunaliella tertiolecta, and preliminary characterization of their structural features and permeability properties, with comparisons to giant unilamellar phospholipid vesicles. The complexity of the algal ghost membrane vesicles reconstructed from the native membrane material released after hypoosmotic stress lies between that of phospholipid vesicles and cells. AFM structural characterization of reconstructed vesicles shows a thick envelope and a nearly empty vesicle interior. The surface of the envelope contains a heterogeneous distribution of densely packed, nanometer-scale globules and pore-like structures which may be derived from surface coat proteins. Confocal fluorescence imaging reveals the highly pigmented photosynthetic apparatus located within the thylakoid membrane and retained in the vesicle membrane. Transport of the fluorescent dye calcein into ghost and giant unilamellar vesicles reveals significant differences in permeability. Expanded knowledge of this unique membrane system will contribute to the design of marine bio-inspired carriers for advanced biotechnological applications.
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Affiliation(s)
| | | | - Ruža Frkanec
- Centre for Research and Knowledge Transfer in Biotechnology, University of Zagreb, Croatia
| | | | - P Thomas Vernier
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, USA
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Gorelova O, Baulina O, Ismagulova T, Kokabi K, Lobakova E, Selyakh I, Semenova L, Chivkunova O, Karpova O, Scherbakov P, Khozin-Goldberg I, Solovchenko A. Stress-induced changes in the ultrastructure of the photosynthetic apparatus of green microalgae. PROTOPLASMA 2019; 256:261-277. [PMID: 30083788 DOI: 10.1007/s00709-018-1294-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 07/25/2018] [Indexed: 05/08/2023]
Abstract
In photosynthetic organisms including unicellular algae, acclimation to and damage by environmental stresses are readily apparent at the level of the photosynthetic apparatus. Phenotypic manifestations of the stress responses include rapid and dramatic reduction of photosynthetic activity and pigment content aimed at mitigating the risk of photooxidative damage. Although the physiological and molecular mechanisms of these events are well known, the ultrastructural picture of the stress responses is often elusive and frequently controversial. We analyzed an extensive set of transmission electron microscopy images of the microalgal cells obtained across species of Chlorophyta and in a wide range of growth conditions. The results of the analysis allowed us to pinpoint distinct ultrastructural changes typical of normal functioning and emergency reduction of the chloroplast membrane system under high light exposure and/or mineral nutrient starvation. We demonstrate the patterns of the stress-related ultrastructural changes including peculiar thylakoid rearrangements and autophagy-like processes and provide an outlook on their significance for implementation of the stress responses.
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Affiliation(s)
- Olga Gorelova
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Olga Baulina
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Tatiana Ismagulova
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Kamilya Kokabi
- Microalgal Biotechnology Laboratory, The French Associates Institute for Agriculture and Biotechnology for Drylands, The J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede-Boqer Campus, 8499000, Midreshet Ben Gurion, Israel
| | - Elena Lobakova
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Irina Selyakh
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Larisa Semenova
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Olga Chivkunova
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Olga Karpova
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Pavel Scherbakov
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia
| | - Inna Khozin-Goldberg
- Microalgal Biotechnology Laboratory, The French Associates Institute for Agriculture and Biotechnology for Drylands, The J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede-Boqer Campus, 8499000, Midreshet Ben Gurion, Israel
| | - Alexei Solovchenko
- Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, 119234, Russia.
- Peoples Friendship University of Russia (RUDN University), Moscow, 117198, Russia.
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Cassuriaga APA, Freitas BCB, Morais MG, Costa JAV. Innovative polyhydroxybutyrate production by Chlorella fusca grown with pentoses. BIORESOURCE TECHNOLOGY 2018; 265:456-463. [PMID: 29935455 DOI: 10.1016/j.biortech.2018.06.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/08/2018] [Accepted: 06/10/2018] [Indexed: 06/08/2023]
Abstract
The current study aimed to evaluate if the addition of pentoses along with variations in light intensity and photoperiod can stimulate the production of polyhydroxybutyrate (PHB) and other biomolecules by Chlorella fusca LEB 111. The variables evaluated were the addition of xylose and arabinose as sources of organic carbon, different photoperiods (18 h, 12 h and 6 h light) and variations in light intensities (58, 28 and 9 μmolphotons m-2 s-1). The highest PHB accumulation (17.4% w w-1) and protein production (53.2% ww-1) were observed in assays with xylose addition and a photoperiod of 6 h of light provided at 28 and 58 μmolphotons m-2 s-1, respectively. The highest lipid content (24.7% w w-1) was obtained with 18 h of light. The current study contributes to the development of sustainable alternatives for the use of wastes and the production of biomolecules from algae.
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Affiliation(s)
- A P A Cassuriaga
- College of Chemistry and Food Engineering, Federal University of Rio Grande, Laboratory of Biochemical Engineering, Rio Grande, RS, Brazil
| | - B C B Freitas
- College of Chemistry and Food Engineering, Federal University of Rio Grande, Laboratory of Biochemical Engineering, Rio Grande, RS, Brazil
| | - M G Morais
- College of Chemistry and Food Engineering, Federal University of Rio Grande, Laboratory of Microbiology and Biochemistry, Rio Grande, RS, Brazil
| | - J A V Costa
- College of Chemistry and Food Engineering, Federal University of Rio Grande, Laboratory of Biochemical Engineering, Rio Grande, RS, Brazil.
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Lynch M, Marinov GK. Membranes, energetics, and evolution across the prokaryote-eukaryote divide. eLife 2017; 6:20437. [PMID: 28300533 PMCID: PMC5354521 DOI: 10.7554/elife.20437] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 01/17/2017] [Indexed: 12/19/2022] Open
Abstract
The evolution of the eukaryotic cell marked a profound moment in Earth’s history, with most of the visible biota coming to rely on intracellular membrane-bound organelles. It has been suggested that this evolutionary transition was critically dependent on the movement of ATP synthesis from the cell surface to mitochondrial membranes and the resultant boost to the energetic capacity of eukaryotic cells. However, contrary to this hypothesis, numerous lines of evidence suggest that eukaryotes are no more bioenergetically efficient than prokaryotes. Thus, although the origin of the mitochondrion was a key event in evolutionary history, there is no reason to think membrane bioenergetics played a direct, causal role in the transition from prokaryotes to eukaryotes and the subsequent explosive diversification of cellular and organismal complexity. Over time, life on Earth has evolved into three large groups: archaea, bacteria, and eukaryotes. The most familiar forms of life – such as fungi, plants and animals – all belong to the eukaryotes. Bacteria and archaea are simpler, single-celled organisms and are collectively referred to as prokaryotes. The hallmark feature that distinguishes eukaryotes from prokaryotes is that eukaryotic cells contain compartments called organelles that are surrounded by membranes. Each organelle supports different activities in the cell. Mitochondria, for example, are organelles that provide eukaryotes with most of their energy by producing energy-rich molecules called ATP. Prokaryotes lack mitochondria and instead produce their ATP on their cell surface membrane. Some researchers have suggested that mitochondria might actually be one of the reasons that eukaryotic cells are typically larger than prokaryotes and more varied in their shape and structure. The thinking is that producing ATP on dedicated membranes inside the cell, rather than on the cell surface, boosted the amount of energy available to eukaryotic cells and allowed them to diversify more. However, other researchers are not convinced by this view. Moreover, some recent evidence suggested that eukaryotes are no more efficient in producing energy than prokaryotes. Lynch and Marinov have now used computational and comparative analysis to compare the energy efficiency of different organisms including prokaryotes and eukaryotes grown under defined conditions. To do the comparison, the results were scaled based on cell volume and the total surface area deployed in energy production. From their findings, Lynch and Marinov concluded that mitochondria did not enhance how much energy eukaryotes could produce per unit of cell volume in any substantial way. Although the origin of mitochondria was certainly a key event in evolutionary history, it is unlikely to have been responsible for the diversity and complexity of today’s life forms.
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Affiliation(s)
- Michael Lynch
- Department of Biology, Indiana University, Bloomington, United States
| | - Georgi K Marinov
- Department of Biology, Indiana University, Bloomington, United States
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Xu Y, Ibrahim IM, Harvey PJ. The influence of photoperiod and light intensity on the growth and photosynthesis of Dunaliella salina (chlorophyta) CCAP 19/30. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 106:305-15. [PMID: 27231875 PMCID: PMC5250801 DOI: 10.1016/j.plaphy.2016.05.021] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 05/16/2016] [Accepted: 05/16/2016] [Indexed: 05/03/2023]
Abstract
The green microalga Dunaliella salina survives in a wide range of salinities via mechanisms involving glycerol synthesis and degradation and is exploited for large amounts of nutraceutical carotenoids produced under stressed conditions. In this study, D. salina CCAP 19/30 was cultured in varying photoperiods and light intensities to study the relationship of light with different growth measurement parameters, with cellular contents of glycerol, starch and carotenoids, and with photosynthesis and respiration. Results show CCAP 19/30 regulated cell volume when growing under light/dark cycles: cell volume increased in the light and decreased in the dark, and these changes corresponded to changes in cellular glycerol content. The decrease in cell volume in the dark was independent of cell division and biological clock and was regulated by the photoperiod of the light/dark cycle. When the light intensity was increased to above 1000 μmol photons m(-2) s(-1), cells displayed evidence of photodamage. However, these cells also maintained the maximum level of photosynthesis efficiency and respiration possible, and the growth rate increased as light intensity increased. Significantly, the intracellular glycerol content also increased, >2-fold compared to the content in light intensity of 500 μmol photons m(-2) s(-1), but there was no commensurate increase in the pool size of carotenoids. These data suggest that in CCAP 19/30 glycerol stabilized the photosynthetic apparatus for maximum performance in high light intensities, a role normally attributed to carotenoids.
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Affiliation(s)
- Yanan Xu
- University of Greenwich, Faculty of Engineering and Science, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Iskander M Ibrahim
- University of Greenwich, Faculty of Engineering and Science, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Patricia J Harvey
- University of Greenwich, Faculty of Engineering and Science, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK.
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Baulina O, Gorelova O, Solovchenko A, Chivkunova O, Semenova L, Selyakh I, Scherbakov P, Burakova O, Lobakova E. Diversity of the nitrogen starvation responses in subarcticDesmodesmussp. (Chlorophyceae) strains isolated from symbioses with invertebrates. FEMS Microbiol Ecol 2016; 92:fiw031. [DOI: 10.1093/femsec/fiw031] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2016] [Indexed: 12/28/2022] Open
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8
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Di Gregorio E, Ferrauto G, Gianolio E, Aime S. Gd loading by hypotonic swelling: an efficient and safe route for cellular labeling. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 8:475-86. [PMID: 24375903 DOI: 10.1002/cmmi.1574] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 09/10/2013] [Accepted: 09/23/2013] [Indexed: 11/12/2022]
Abstract
Cells incubated in hypo-osmotic media swell and their membranes become leaky. The flow of water that enters the cells results in the net transport of molecules present in the incubation medium directly into the cell cytoplasm. This phenomenon has been exploited to label cells with MRI Gd-containing contrast agents. It has been found that, in the presence of 100 mM Gd-HPDO3A in an incubation medium characterized by an overall osmolarity of 160 mOsm l⁻¹, each cell is loaded with amounts of paramagnetic complex ranging from 2 × 10⁹ to 2 × 10¹⁰ depending on the cell type. To obtain more insight into the determinants of cellular labeling by the 'hypo-osmotic shock' methodology, a study on cell viability, proliferation rate and cell morphology was carried out on J774A.1 and K562 cells as representative of cells grown in adhesion and suspended ones, respectively. Moreover a comparison of the efficiency of the proposed method with established cell labeling procedures such as pinocytosis and electroporation was carried out. Finally, the effects of the residual electric charge, the size and some structural features of the metal complex were investigated. In summary, the 'hypotonic shock' methodology appears to be an efficient and promising tool to pursue cellular labeling with paramagnetic complexes. Its implementation is straightforward and one may foresee that it will be largely applied in in vitro cellular labeling of many cell types.
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Affiliation(s)
- Enza Di Gregorio
- Molecular Imaging Center, Department of Molecular Biotechnologies and Health Sciences, University of Torino, Via Nizza 52, 10126-, Torino, Italy
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Lin H, Fang L, Low CS, Chow Y, Lee YK. Occurrence of glycerol uptake in Dunaliella tertiolecta under hyperosmotic stress. FEBS J 2013; 280:1064-72. [PMID: 23279806 DOI: 10.1111/febs.12100] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 12/06/2012] [Accepted: 12/12/2012] [Indexed: 11/29/2022]
Abstract
The unicellular halotolerant green alga species Dunaliella are able to proliferate in extremely varied salinities by synthesizing intracellular glycerol and adjusting the cell shape and volume. However, some marine Dunaliella species such as Dunaliella tertiolecta are not able to regulate cell volume as an immediate response to counter external osmotic shock. Here we report that a rapid shock-response mechanism is present in Dunaliella tertiolecta, involving uptake of exogenous glycerol in response to hyperosmotic shock without changing cell volume, and this glycerol uptake activity is associated with the Dunaliella tertiolecta glycerol uptake protein 1 (DtGUP1) gene, which belongs to the membrane-bound O-acyltransferase. The mutant DtGUP1-E, in which the DtGUP1 gene is silenced, displayed an inability to take up glycerol from the medium and showed cell death under hyperosmotic shock. To our knowledge, this is the first time a gene product has been reported in Dunaliella tertiolecta that is involved in glycerol uptake activity under hyperosmotic stress.
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Affiliation(s)
- Huixin Lin
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Guermazi W, Sellami-Kammoun A, Elloumi J, Drira Z, Aleya L, Marangoni R, Ayadi H, Maalej S. Microalgal cryo-preservation using dimethyl sulfoxide (Me2SO) coupled with two freezing protocols: Influence on the fatty acid profile. J Therm Biol 2010. [DOI: 10.1016/j.jtherbio.2010.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Downs CA, Kramarsky-Winter E, Woodley CM, Downs A, Winters G, Loya Y, Ostrander GK. Cellular pathology and histopathology of hypo-salinity exposure on the coral Stylophora pistillata. THE SCIENCE OF THE TOTAL ENVIRONMENT 2009; 407:4838-4851. [PMID: 19515401 DOI: 10.1016/j.scitotenv.2009.05.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2009] [Revised: 04/25/2009] [Accepted: 05/01/2009] [Indexed: 05/27/2023]
Abstract
Coral reefs can experience extreme salinity changes, particularly hypo-salinity, as a result of storms, heavy rainy seasons (e.g., monsoons), and coastal runoff. Field and laboratory observations have documented that corals exposed to hypo-saline conditions can undergo extensive bleaching and mortality. There is controversy in the literature as to whether hypo-saline conditions induce a pathological response in corals, and if there is a relationship between decreasing salinity treatment and pathological responses. To test the hypothesis that hypo-salinity exposure does not have a pathological effect on coral, we used histological and cellular diagnostic methods to characterize the pathology in hypo-salinity-exposed corals. Colonies of Stylophora pistillata were exposed to five salinity concentrations [39 parts per thousand (ppt), 32 ppt, 28 ppt, 24 ppt, and 20 ppt] that may realistically occur on a reef. Histological examination indicated an increasing severity of pathomorphologies associated with decreasing salinity, including increased tissue swelling, degradation and loss of zooxanthellae, and tissue necrosis. Pulse-amplitude modulated chlorophyll fluorimetry kinetics demonstrated a decreasing photosynthetic efficiency with decreasing salinity conditions. Cytochrome P450 levels were affected by even slight changes in salinity concentration suggesting that detoxification pathways, as well as several endocrine pathways, may be adversely affected. Finally, these studies demonstrated that hypo-saline conditions can induce an oxidative-stress response in both the host and in its algal symbiont, and in so doing, may synergistically increase oxidative-stress burdens. As with other types of environmental stresses, exposure to hypo-saline conditions may have long-term consequences on coral physiology.
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Affiliation(s)
- Craig A Downs
- Pacific Biosciences Research Center, University of Hawaii at Manoa, 2500 Campus Rd., Hawaii Hall 211, Honolulu, HI 96822, USA
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Chen H, Jiang JG. Osmotic responses ofDunaliellato the changes of salinity. J Cell Physiol 2009; 219:251-8. [DOI: 10.1002/jcp.21715] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ye ZW, Jiang JG, Wu GH. Biosynthesis and regulation of carotenoids in Dunaliella: progresses and prospects. Biotechnol Adv 2008; 26:352-60. [PMID: 18486405 DOI: 10.1016/j.biotechadv.2008.03.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Revised: 03/25/2008] [Accepted: 03/27/2008] [Indexed: 10/22/2022]
Abstract
Natural carotenoids are high in demand in global market owing to their widespread applications in nutrition, medicine, food coloring agent and cosmetic, as well as to the natural and healthy preference of consumers today. Some strains of Dunaliella are well known for their talent of massive beta-carotene accumulation. Content of the high bioavailability stereoisomer of beta-carotene, the 9-cis stereoisomer, is highest in Dunaliella among all the natural carotenoids sources. These valuable algae have been exploited commercially for beta-carotene-rich Dunaliella powder and natural beta-carotene in many countries since 1980s. However, drawbacks of traditional production methods have hampered the worldwide promotion of carotenoids production with Dunaliella. To shake off the dilemma, complete understanding of carotenogenic mechanism is urgent. Carotenogenic mechanism in Dunaliella is described in present paper, including carotenogenic pathway and its regulation. Generally, it seems that carotenogenic pathway in Dunaliella is close to the one of higher plants. It is known that reactive oxygen species (ROS) were involved in signal transduction for gene activation. Induction of ROS is in parallel with the enhanced beta-carotene accumulation in Dunaliella. It is suggested that ROS trigger massive carotenoids accumulation in Dunaliella. It also revealed that relation may exist between enhanced beta-carotene accumulation and lipid metabolism. For the talent of beta-carotene synthesis, it is possible that Dunaliella massively accumulates beta-carotene and other high-value carotenoids by genetic technologies.
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Affiliation(s)
- Zhi-Wei Ye
- College of Food and Bioengineering, South China University of Technology, Guangzhou, 510640, China
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Katz A, Waridel P, Shevchenko A, Pick U. Salt-induced changes in the plasma membrane proteome of the halotolerant alga Dunaliella salina as revealed by blue native gel electrophoresis and nano-LC-MS/MS analysis. Mol Cell Proteomics 2007; 6:1459-72. [PMID: 17569891 DOI: 10.1074/mcp.m700002-mcp200] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The halotolerant alga Dunaliella salina is a recognized model photosynthetic organism for studying plant adaptation to high salinity. The adaptation mechanisms involve major changes in the proteome composition associated with energy metabolism and carbon and iron acquisition. To clarify the molecular basis for the remarkable resistance to high salt, we performed a comprehensive proteomics analysis of the plasma membrane. Plasma membrane proteins were recognized by tagging intact cells with a membrane-impermeable biotin derivative. Proteins were resolved by two-dimensional blue native/SDS-PAGE and identified by nano-LC-MS/MS. Of 55 identified proteins, about 60% were integral membrane or membrane-associated proteins. We identified novel surface coat proteins, lipid-metabolizing enzymes, a new family of membrane proteins of unknown function, ion transporters, small GTP-binding proteins, and heat shock proteins. The abundance of 20 protein spots increased and that of two protein spots decreased under high salt. The major salt-regulated proteins were implicated in protein and membrane structure stabilization and within signal transduction pathways. The migration profiles of native protein complexes on blue native gels revealed oligomerization or co-migration of major surface-exposed proteins, which may indicate mechanisms of stabilization at high salinity.
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Affiliation(s)
- Adriana Katz
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel.
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15
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Liu XD, Hu FH, Shen YG. Transient decrease of light-harvesting complex II phosphorylation level by hypoosmotic shock in dark-adapted Dunaliella salina. Acta Biochim Biophys Sin (Shanghai) 2006; 38:104-9. [PMID: 16474901 DOI: 10.1111/j.1745-7270.2006.00139.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
This study investigated the regulation of major light harvesting chlorophyll a/b protein (LHCII) phosphorylation by hypoosmotic shock in dark-adapted Dunaliella salina cells. When the external NaCl concentration decreased in darkness, D. salina LHCII phosphorylation levels transiently dropped within 20 min and then restored gradually to basal levels. The transient decrease in LHCII phosphorylation levels was insensitive to NaF, a phosphatase inhibitor. Inhibition of intracellular ATP production by addition of an uncoupler or an ATP synthase inhibitor increased LHCII phosphorylation levels in D. salina cells exposed to hypoosmotic shock. Taken together, these results indicate that hypoosmotic shock inhibits the LHCII phosphorylation process. The related mechanism and physiological significance are discussed.
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Affiliation(s)
- Xian-De Liu
- Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200032, China
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16
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Ishida T, Li W, Liu Z, Kiwada H. Stimulatory effect of polyethylene glycol (PEG) on gene expression in mouse liver following hydrodynamics-based transfection. J Gene Med 2006; 8:324-34. [PMID: 16288498 DOI: 10.1002/jgm.850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Rapid intravenous injection of a large volume of plasmid DNA (pDNA), i.e. a transfection procedure based on hydrodynamics, is known to be an efficient and liver-specific method of in vivo gene delivery. However, the gene expression is transient. METHODS We investigated the effect of addition of polyethylene glycol (PEG) to a solution of naked pDNA (luciferase) on the expression of the gene in mouse liver following transfection by the hydrodynamics-based technique. In addition, the mechanism leading to the enhancement of the gene expression was studied. RESULTS The addition of 1% (w/v) PEG2000 to the pDNA solution enhanced the resulting gene expression in the liver. Increasing the PEG2000 concentration to more than 1 and up to 10% (w/v) rather diminished the gene expression level. By contrast, increasing the molecular weight of PEG to over 2000 up to 10 000 did not affect the level of gene expression. Histopathological and serum-chemistry examinations indicated that hydrostatic or osmotic pressure increased tissue and hepatocellular damage in a PEG-concentration-dependent manner, and resulted in a decrease in gene expression. Quantitative evaluation showed that the enhanced gene expression resulted from stabilization of the pDNA introduced into the hepatocytes and an enhancement of the transport of intact pDNA to the nucleus. CONCLUSIONS For most gene therapy applications and gene function studies, sustained expression of the introduced gene(s) is necessary. This simple method to achieve enhanced gene expression in liver may have a great potential for a wide variety of laboratory studies in molecular and cellular biology as well as possibly for future clinical applications in humans.
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Affiliation(s)
- Tatsuhiro Ishida
- Department of Pharmacokinetics and Biopharmaceutics, Faculty of Pharmaceutical Sciences, The University of Tokushima, 1-78-1 Sho-machi, Tokushima 770-8505, Japan
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Hypoosmotic shock induces a state I transition of photosynthetic apparatus inDunaliella salina. CHINESE SCIENCE BULLETIN-CHINESE 2004. [DOI: 10.1007/bf03184263] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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18
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Organic Compatible Solutes. CELLULAR ORIGIN, LIFE IN EXTREME HABITATS AND ASTROBIOLOGY 2003. [DOI: 10.1007/0-306-48053-0_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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19
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Pinontoan R, Yuasa T, Anderca MI, Matsuoka T, Uozumi N, Mori H, Muto S. CLONING OF A cDNA ENCODING A 66-kDa Ca 2 +-DEPENDENT PROTEIN KINASE (CDPK) FROM DUNALIELLA TERTIOLECTA (CHLOROPHYTA). JOURNAL OF PHYCOLOGY 2000; 36:545-552. [PMID: 29544003 DOI: 10.1046/j.1529-8817.2000.99185.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A cDNA clone encoding a Ca2 +-dependent protein kinase (DtCPK1) with a calculated molecular mass of 65,746 Da was isolated by sequential immuno- and hybridization-screening from a cDNA library of the halotolerant green alga, Dunaliella tertiolecta Butcher (Chlorophyceae). Primary structure analysis of DtCPK1 revealed a long variable domain preceding a catalytic domain, an autoinhibitory junction domain, and a C-terminal calmodulin-like domain containing 4 EF-hand motifs. Database searches showed that DtCPK1 has a high similarity to CCK1, a CDPK from the green alga, Chlamydomonas eugamentos Moewus. The N-terminal long variable domain of DtCPK1 contains neither the N-myristoylation motif, which is found in many CDPKs, nor the PEST motif, which is associated with rapid protein turnover and found in one CDPK subfamily. However, a putative Ca2 +-dependent lipid binding domain that might be responsible for the association of cytosolic DtCPK1 with the cell membrane was identified in the variable domain. Three CDPKs, with molecular masses of 62, 54, and 47 kDa respectively, were observed in an in-gel protein kinase assay of D. tertiolecta cells extract. No change in the activities of these CDPKs were observed for up to 30 min after D. tertiolecta cells had been subjected to a hypoosmotic shock. An antibody raised against a CDPK purified from D. tertiolecta and used to isolate the DtCPK1 cDNA clone cross-reacted strongly with the 62-kDa CDPK but weakly with the 54-kDa CDPK in a Western blot, indicating that the 62-kDa CDPK is identical to DtCPK1. There was no change in the intensity of these bands after hypoosmotic shock, implying that the cellular level of the enzyme protein is not associated with hypoosmotic shock. These results indicate that CDPK is activated only by the increase in cytosolic-free Ca2 + concentration in vivo.
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Affiliation(s)
- Reinhard Pinontoan
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Takashi Yuasa
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Marinela I Anderca
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Takashi Matsuoka
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Nobuyuki Uozumi
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Hitoshi Mori
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Shoshi Muto
- Nagoya University Bioscience Center, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 JapanGraduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan Nagoya University Bioscience Center and Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
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Effect of Ca2+ channel blockers on glycerol levels in Dunaliella tertiolecta under hypoosmotic stress. J Biotechnol 1999. [DOI: 10.1016/s0168-1656(99)00076-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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21
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Possible role of inositol phospholipid signal transduction system inDunaliella salina under hypoosmotic shock. CHINESE SCIENCE BULLETIN-CHINESE 1997. [DOI: 10.1007/bf03182791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Abstract
Transmembrane osmotic gradients applied on large unilamellar 1-palmitoyl-2-oleoyl-phosphatidylcholine vesicles were used to modulate the potency of melittin to induce leakage. Melittin, an amphipathic peptide, changes the permeability of vesicles, as studied using the release of entrapped calcein, a fluorescent marker. A promotion of the ability of melittin to induce leakage was observed when a hyposomotic gradient (i.e., internal salt concentration higher than the external one) was imposed on the vesicles. It is proposed that structural perturbations caused by the osmotic pressure loosen the compactness of the outer leaflet, which facilitates the melittin-induced change in membrane permeability. Additionally, we have shown that this phenomenon is not due to enhanced binding of melittin to the vesicles using intrinsic fluorescence of the melittin tryptophan. Furthermore, we investigated the possibility of using a transmembrane pH gradient to control the lytic activity of melittin. The potency of melittin in inducing release is known to be inhibited by increased negative surface charge density. A transmembrane pH gradient causing an asymmetric distribution of unprotonated palmitic acid in the bilayer is shown to be an efficient way to modulate the lytic activity of melittin, without changing the overall lipid composition of the membrane. We demonstrate that the protective effect of negatively charged lipids is preserved for asymmetric membranes.
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Affiliation(s)
- T Benachir
- Département de chimie, Université de Montréal, Québec, Canada
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23
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Coté GG, Yueh YG, Crain RC. Phosphoinositide turnover and its role in plant signal transduction. Subcell Biochem 1996; 26:317-43. [PMID: 8744270 DOI: 10.1007/978-1-4613-0343-5_11] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- G G Coté
- Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269-3125, USA
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Zelazny AM, Shaish A, Pick U. Plasma Membrane Sterols Are Essential for Sensing Osmotic Changes in the Halotolerant Alga Dunaliella. PLANT PHYSIOLOGY 1995; 109:1395-1403. [PMID: 12228675 PMCID: PMC157674 DOI: 10.1104/pp.109.4.1395] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The halotolerant alga Dunaliella responds to hyperosmotic stress by synthesis of massive amounts of glycerol. The trigger for this osmotic response is the change in cell volume, but the mechanism that senses volume changes is not known. Preincubation of Dunaliella salina with tridemorph, a specific inhibitor of sterol biosynthesis, inhibits glycerol synthesis and volume recovery. The inhibition is associated with suppression of [14C]bicarbonate incorporation into sterols and is correlated with pronounced depletion of plasma membrane sterols. Incubation of sterol-depleted cells with cholesterol hemisuccinate restores the capacity for volume regulation in response to hyperosmotic stress. Tridemorph as well as lovastatin also inhibit volume changes that are induced by high light in Dunaliella bardawil, a species that responds to high light intensity by synthesis of large amounts of [beta]-carotene. These volume changes result from accumulation of glycerol and are associated with de novo synthesis of sterols. The major plasma membrane sterol in D. salina and the high-light-induced sterol in D. bardawil co-migrate with ergosterol on thin-layer chromatography and on reversed-phase high-performance liquid chromatography. These results suggest that the osmosensory mechanism in Dunaliella resides in the plasma membrane, and that sterols have an important role in sensing osmotic changes.
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Affiliation(s)
- A. M. Zelazny
- Department of Biochemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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25
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Lehtonen JY, Kinnunen PK. Poly(ethylene glycol)-induced and temperature-dependent phase separation in fluid binary phospholipid membranes. Biophys J 1995; 68:525-35. [PMID: 7696506 PMCID: PMC1281717 DOI: 10.1016/s0006-3495(95)80214-6] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Exclusion of the strongly hygroscopic polymer, poly(ethylene glycol) (PEG), from the surface of phosphatidylcholine liposomes results in an osmotic imbalance between the hydration layer of the liposome surface and the bulk polymer solution, thus causing a partial dehydration of the phospholipid polar headgroups. PEG (average molecular weight of 6000 and in concentrations ranging from 5 to 20%, w/w) was added to the outside of large unilamellar liposomes (LUVs). This leads to, in addition to the dehydration of the outer monolayer, an osmotically driven water outflow and shrinkage of liposomes. Under these conditions phase separation of the fluorescent lipid 1-palmitoyl-2[6-(pyren-1-yl)]decanoyl-sn-glycero-3-phosphocholine (PPDPC) embedded in various phosphatidylcholine matrices was observed, evident as an increase in the excimer-to-monomer fluorescence intensity ratio (IE/IM). Enhanced segregation of the fluorescent lipid was seen upon increasing and equal concentrations of PEG both inside and outside of the LUVs, revealing that osmotic gradient across the membrane is not required, and phase separation results from the dehydration of the lipid. Importantly, phase separation of PPDPC could be induced by PEG also in binary mixtures with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), for which temperature-induced phase segregation of the fluorescent lipid below Tm was otherwise not achieved. In the different lipid matrices the segregation of PPDPC caused by PEG was abolished above characteristic temperatures T0 well above their respective main phase transition temperatures Tm. For 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), DMPC, SOPC, and POPC, T0 was observed at approximately 50, 32, 24, and 20 degrees C, respectively. Notably, the observed phase separation of PPDPC cannot be accounted for the 1 degree C increase in Tm for DMPC or for the increase by 0.5 degrees C for DPPC observed in the presence of 20% (w/w) PEG. At a given PEG concentration maximal increase in IE/IM (correlating to the extent of segregation of PPDPC in the different lipid matrices) decreased in the sequence 1,2-dihexadecyl-sn-glycero-3-phosphocholine (DHPC) > DPPC > DMPC > SOPC > POPC, whereas no evidence for phase separation in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) LUV was observed (Lehtonen and Kinnunen, 1994, Biophys. J. 66: 1981-1990). Our results indicate that PEG-induced dehydration of liposomal membranes provides the driving force for the segregation of the pyrene lipid. In brief, phase separation of PPDPC from the matrix lipid could be attributed to the diminishing effective size of the phosphatidylcholine polar headgroup resulting from its partial dehydration by PEG. This in turn would allow for enhanced van der Waals interactions between the acyl chains of the matrix lipid, which then caused the exclusion of PPDPC due to the perturbing bulky pyrene moiety. Phase separation in DMPC/PPDPC liposomes was abolished by the inclusion of 25 mol % cholesterol and to a lesser extent by epicholesterol.
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Affiliation(s)
- J Y Lehtonen
- Department of Medical Chemistry, University of Helsinki, Finland
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26
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Lehtonen JY, Kinnunen PK. Changes in the lipid dynamics of liposomal membranes induced by poly(ethylene glycol): free volume alterations revealed by inter- and intramolecular excimer-forming phospholipid analogs. Biophys J 1994; 66:1981-90. [PMID: 8075332 PMCID: PMC1275923 DOI: 10.1016/s0006-3495(94)80991-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Influence of osmotic shrinkage, swelling, and dehydration on large unilamellar liposomes (LUVs) of 1,2-dioleoylsn-glycero-3-phosphocholine (DOPC) was investigated using the fluorescent lipid probes 1-palmitoyl-2-[10-(pyren-1-yl)]-decanoyl-sn-glycero-3-phosphocholi ne (PPDPC) and 1,2-bis[10-(pyren-1-yl)]decanoyl-sn-glycero-3-phosphocholine (bisPDPC). Increasing concentrations of poly(ethylene glycol) (PEG, average molecular weight of 6000) producing osmotic gradients delta omega up to 250 mOsm/kg were first added to the outside of LUV labeled with 0.1 mol% of either of the above fluorescent phospholipids. The resulting osmotic shrinkage was accompanied by a progressive reduction in the lateral diffusion of the membrane-incorporated PPDPC, evident as a decrease in the rate of its intermolecular excimer formation. In contrast, under the same conditions the rate of intramolecular excimer formation by bisPDPC increased. Notably, signals opposite to those described above were observed for both of the fluorescent probes upon osmotic swelling of DOPC liposomes with encapsulated PEG. The lateral diffusion of PPDPC became progressively reduced upon membrane dehydration due to increasing concentrations of symmetrically distributed PEG (with equal polymer concentrations inside and outside of the liposomes) when neither shrinkage nor swelling occurs while enhanced excimer formation by bisPDPC was evident. The later results were interpreted in terms of osmotically induced changes in the hydration of lipids. In brief, the removal of water from the phospholipid hydration shell diminishes the effective size of the polar headgroup, which subsequently allows for an enhanced lateral packing of the phospholipid acyl chains. Our findings are readily compatible with membrane free volume Vf changes due to osmotic forces under three different kinds of stress (shrinkage, swelling, and dehydration) applied on the lipid bilayers.
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Affiliation(s)
- J Y Lehtonen
- Department of Medical Chemistry, University of Helsinki, Finland
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Memon AR, Herrin DL, Thompson GA. Intracellular translocation of a 28 kDa GTP-binding protein during osmotic shock-induced cell volume regulation in Dunaliella salina. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1179:11-22. [PMID: 8399350 DOI: 10.1016/0167-4889(93)90070-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The primary aim of this study was to determine if small GTP-binding proteins play a role in the conspicuous and much-examined volume control process in Dunaliella salina. We confirmed the previous identification by Rodriguez et al. (Rodriguez Rosales, M.P., Herrin, D.L. and Thompson, G.A., Jr. (1992) Plant Physiol. 98, 446-451) of small GTP-binding proteins in the green alga Dunaliella salina and revealed the presence of at least five such proteins, having molecular masses of approx. 21, 28, 28.5, 29 and 30 kDa. These proteins were concentrated largely in the endoplasmic reticulum (ER) and in an intermediate density organelle fraction (GA) containing mainly Golgi vesicles, mitochondria and flagella. The chloroplast fraction and plasma membrane contained the 28-kDa GTP-binding protein exclusively, while the cytosol contained both the 28-kDa component and small amounts of a 21-kDa GTP-binding protein. Immunodetection analysis showed that the D. salina 28-kDa protein cross-reacted strongly with a polyclonal antibody raised against a Volvox carteri yptV1 type GTP-binding protein. This antibody was utilized for quantitative GTP-binding protein measurements as described below. Certain anti-GTP-binding protein antibodies derived from non-plant sources, namely, monoclonal antibodies raised against yeast and mouse ypt1 GTP-binding proteins, cross-reacted not only with the D. salina 28-kDa protein but also the 29-kDa component. The 30-kDa GTP-binding protein of D. salina did not bind the antibodies mentioned above but did cross-react with an anti-yeast ypt1 polyclonal antibody. None of the D. salina GTP-binding proteins reacted positively with polyclonal antibodies raised against SEC4, rab1 or rab6 proteins. When D. salina cells were subjected to hypoosmotic swelling by abruptly reducing the NaCl concentration of their medium from 1.7 M to 0.85 M, the increase in cell surface area was accompanied by a substantial translocation of the 28-kDa GTP-binding protein from the ER and GA fractions to the plasma membrane, chloroplast and cytosolic fractions, as determined by quantitative [32P]GTP binding and [125I]antibody binding on nitrocellulose blots. This translocation increased the content of the 28-kDa component in the plasma membrane, chloroplast and cytosol by 3-4-fold. No net movement of the 30-kDa GTP-binding protein from either the ER or GA fractions was observed following hypoosmotic shock.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- A R Memon
- Department of Botany, University of Texas, Austin 78713
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Yuasa T, Muto S. Ca(2+)-dependent protein kinase from the halotolerant green alga Dunaliella tertiolecta: partial purification and Ca(2+)-dependent association of the enzyme to the microsomes. Arch Biochem Biophys 1992; 296:175-82. [PMID: 1318689 DOI: 10.1016/0003-9861(92)90560-j] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ca(2+)-dependent protein kinase (CDPK) was purified 900-fold from the soluble fraction of Dunaliella tertiolecta cells by ammonium sulfate precipitation, DEAE-Toyopearl, phenyl-Sepharose, and hydroxylapatite column chromatography. The CDPK was activated by micromolar concentration of Ca2+ and required neither calmodulin nor phospholipids for its activation. The enzyme phosphorylated casein, myosin light chain, and histone type III-S (histone H-1), but did not phosphorylate protamine and phosvitin. The Km values for ATP and casein were 11 microM and 300 micrograms/ml, respectively. Phosphorylation of casein was inhibited by calmodulin antagonists, calmidazolium, trifluoperazine, and compound 48/80, but not affected by calmodulin. CDPK bound to phenyl-Sepharose in the presence of Ca2+ and was eluted by ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA). This suggests that hydrophobicity of the enzyme was increased by Ca2+. CDPK was also bound to the microsomes isolated from Dunaliella cells in the presence of micromolar concentration of Ca2+ and released in the presence of EGTA, suggesting the possibility of in vivo Ca(2+)-dependent association of the enzyme. The enzyme phosphorylated many proteins in the microsomes but few in the cytosol, if at all.
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Affiliation(s)
- T Yuasa
- Institute of Applied Microbiology, University of Tokyo, Japan
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Rodríguez-Rosales MP, Herrin DL, Thompson GA. Identification of Low Molecular Mass GTP-Binding Proteins in Membranes of the Halotolerant Alga Dunaliella salina. PLANT PHYSIOLOGY 1992; 98:446-51. [PMID: 16668660 PMCID: PMC1080209 DOI: 10.1104/pp.98.2.446] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A family of specific guanine nucleotide-binding proteins in Dunaliella salina was studied. Polypeptides of different subcellular fractions were separated by electrophoresis and transferred to nitrocellulose or Immobilon membranes. Incubation of the transfer blots with [(35)S]GTPgammaS or [alpha-(32)P]GTP showed no evidence for GTP-binding proteins in the chloroplast and cytosol fractions. However, two GTP-binding proteins with molecular masses of 28 and 30 kilodaltons were present in the plasma membrane and microsomal fractions. An additional 29 kilodalton GTP-binding protein was detected in the plasma membrane. The mitochondrial fraction contained significant amounts of only the 28 kilodalton GTP-binding protein. Binding of [(32)P]GTP to the protein blots was completely prevented by 10 micromolar GTP or guanosine 5'-O-(2-thiodiphosphate) (added in 3 x 10(4)-fold excess), whereas ATP or CTP had no effect on the binding. The 28 kilodalton GTP-binding protein was recognized by polyclonal antibodies to the ras-related YPT1 protein of yeast but not by the anti-ras Y13-259 monoclonal antibody. GTP-binding proteins present in the microsomal fraction could not be solubilized by incubation of microsomes with 1 molar NaCl or 0.2 molar Na(2)CO(3), but some GTP-binding activity was solubilized when microsomes were treated with 6 molar urea. These results indicate that D. salina GTP-binding proteins are tightly associated with the membranes. The covalent attachment of fatty acids to these proteins was also investigated. Electrophoresis followed by fluorography of delipidated microsomal proteins extracted from [(3)H]myristic acid-labeled cells showed an intense labeling of a 28 kilodalton protein. We conclude that D. salina contains proteins resembling the ras-related proteins found in animal cells and higher plants.
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Ha KS, Thompson GA. Biphasic changes in the level and composition of Dunaliella salina plasma membrane diacylglycerols following hypoosmotic shock. Biochemistry 1992; 31:596-603. [PMID: 1731914 DOI: 10.1021/bi00117a042] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hypoosmotic shock has been shown to trigger an immediate and selective increase of plasma membrane diacylglycerols (DAG) in the green alga Dunaliella salina, coinciding with an approximately equivalent loss of phosphatidylinositol 4,5-bisphosphate from this membrane [Ha, K.S., & Thompson, G.A., Jr. (1991) Plant Physiol. 97, 921-927]. Following a slight decline in amount, DAG levels of the plasma membrane resumed their rise by 2 min after the shock and by 40 min had achieved a maximum concentration equivalent to 230% of DAG levels in unstressed cells. This second, more sustained increase of plasma membrane DAG was matched by a DAG increase in the microsome-enriched cytoplasmic membrane fraction, commencing at 2 min and peaking at 140% of control values. The changing pattern of DAG molecular species produced in the plasma membrane during the early phases of hypoosmotic stress was compatible with their derivation from phospholipase C hydrolysis of inositol phospholipids and phosphatidylcholine. From 8 min following hypoosmotic shock, as relatively larger scale DAG accumulations developed in the cytoplasmic membranes, the molecular species composition changed to reflect a marked increase in de novo synthesis of sn-1-oleoyl, sn-2-palmitoylglycerol, and dioleoylglycerol. The former molecular species appears to be synthesized in the chloroplast while the latter is produced in the endoplasmic reticulum. The radioisotope labeling data with Na2(14)CO3 confirmed that the biphasic formation of DAG triggered by hypoosmotic shock culminates in a large-scale de novo synthesis of DAG. This is the first clear evidence for de novo synthesis as a source of DAG following PIP2-mediated signaling.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- K S Ha
- Department of Botany, University of Texas, Austin 78713
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Pick U, Zeelon O, Weiss M. Amine Accumulation in Acidic Vacuoles Protects the Halotolerant Alga Dunaliella salina Against Alkaline Stress. PLANT PHYSIOLOGY 1991; 97:1226-33. [PMID: 16668513 PMCID: PMC1081146 DOI: 10.1104/pp.97.3.1226] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Amines at alkaline pH induce in cells of the halotolerant alga Dunaliella a transient stress that is manifested by a drop in ATP and an increase of cytoplasmic pH. As much as 300 millimolar NH(4) (+) are taken up by the cells at pH 9. The uptake is not associated with gross changes in volume and is accompanied by K(+) efflux. Most of the amine is not metabolized, and can be released by external acidification. Recovery of the cells from the amine-induced stress occurs within 30 to 60 minutes and is accompanied by massive swelling of vacuoles and by release of the fluorescent dye atebrin from these vacuoles, suggesting that amines are compartmentalized into acidic vacuoles. The time course of ammonia uptake into Dunaliella cells is biphasic-a rapid influx, associated with cytoplasmic alkalinization, followed by a temperature-dependent slow uptake phase, which is correlated with recovery of cellular ATP and cytoplasmic pH. The dependence of amine uptake on external pH indicates that it diffuses into the cells in the free amine form. Studies with lysed cell preparations, in which vacuoles become exposed but retain their capacity to accumulate amines, indicate that the permeability of the vacuolar membrane to amines is much higher than that of the plasma membrane. The results can be retionalized by assuming that the initial amine accumulation, which leads to rapid vacuolar alkalinization, activates metabolic reactions that further increase the capacity of the vacuoles to sequester most of the amine from the cytoplasm. The results indicate that acidic vacuoles in Dunaliella serve as a high-capacity buffering system for amines, and as a safeguard against cytoplasmic alkalinization and uncoupling of photosynthesis.
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Affiliation(s)
- U Pick
- Department of Biochemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Weiss M, Pick U. Uptake of the fluorescent indicator atebrin into acidic vacuoles in the halotolerant alga Dunaliella satina. PLANTA 1991; 185:494-501. [PMID: 24186526 DOI: 10.1007/bf00202958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/1991] [Accepted: 06/25/1991] [Indexed: 06/02/2023]
Abstract
The fluorescent indicator atebrin (3-chloro-9-(4-diethylamino-1-methylbutyl)-7-methyoxy-acridine) is taken up by Dunaliella salina cells at alkaline external pH and accumulates in acidic vacuoles. The uptake is unaffected by light, by photosynthetic inhibitors, by protonophores or by ionophores; however, the dye can be released by amines, indicating that it is specifically accumulating in acidic vacuoles. Amines induce a biphasic enhancement of atebrin fluorescence - a fast phase, accompanied by redistribution within the cell, consistent with release of the dye from the vacuoles to the cytoplasm, and a slow phase, correlated with release of atebrin from the cells. These results are interpreted to indicate a slow equilibration of atebrin across the plasma membrane and a fast equilibration across the vacuolar membrane. Part of the dye cannot be released by the amines, and appears to be internally bound. Atebrin uptake is inhibited by cholesteryl hemisuccinate and is stimulated by lysophosphatidylcholine, indicating that modification of the lipid composition of the plasma membrane affects the permeability to atebrin. Analysis of the pH dependence of atebrin uptake indicates that the dye enters the cells by fluid-phase permeation. Different stresses enhance the rate of atebrin uptake and release, indicating that they modify plasma-membrane structure or composition. Atebrin may serve as a specific marker for acidic vacuoles, as an indicator for amine uptake, and as a probe for subtle changes in the permeability of the plasma membrane.
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Affiliation(s)
- M Weiss
- Department of Biochemistry, Weizmann Institute of Science, P.O. B. 26, 76100, Rehovot, Israel
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Weiss M, Bental M, Pick U. Hydrolysis of polyphosphates and permeability changes in response to osmotic shocks in cells of the halotolerant alga dunaliella. PLANT PHYSIOLOGY 1991; 97:1241-8. [PMID: 16668515 PMCID: PMC1081148 DOI: 10.1104/pp.97.3.1241] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The effects of osmotic shocks on polyphosphates and on the vacuolar fluorescent indicator atebrin have been investigated to test whether acidic vacuoles in the halotolerant alga Dunaliella salina have a role in osmoregulation. Upshocks and downshocks induce different patterns of polyphosphate hydrolysis. Upshocks induce rapid formation of new components, tentatively identified as 5 or 6 linear polyphosphates, formed only after upshocks with NaCl and not with glycerol, indicative of compartmentation of Na(+) into the vacuoles. Conversely, downshocks induce a slower transient accumulation of tripolyphosphates, indicating activation of a different hydrolytic process within the vacuoles. Osmotic shocks do not lead to release of atebrin from acidic vacuoles, indicating that they do not induce a major intravacuolar alkalinization. However, osmotic shocks induce transient permeability changes measured by amine-induced atebrin release from vacuoles. Hypoosmotic shocks transiently increase the permeability (up to 20-fold), whereas hyperosmotic shocks induce a rapid drop in permeability. Electron micrographs of osmotically shocked cells also reveal transient changes in the surface and internal organelles of D. salina cells. It is suggested that hyperosmotic and hypoosmotic shocks induce different changes within acidic vacuoles and in the organization and/or composition of the plasma membrane in Dunaliella.
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Affiliation(s)
- M Weiss
- Department of Biochemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Gilkey JC, Staehelin LA. A new organelle related to osmoregulation in ultrarapidly frozenPelvetia embryos. PLANTA 1989; 178:425-435. [PMID: 24213038 DOI: 10.1007/bf00963811] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/1988] [Accepted: 10/28/1988] [Indexed: 06/02/2023]
Abstract
Freeze-fracture electron microscopy of the cortical cytoplasm of unfixed, uncryoprotected, ultrarapidly frozen embryos of the marine brown algaPelvetia fastigiata has demonstrated the presence of numerous 0.5-μm diameter, disc-shaped vesicles lying adjacent and nearly parallel to the plasma membrane. Some vesicles are fused with the plasma membrane through a narrow connection; this however appears to be a reversible attachment rather than an intermediate stage in the incorporation of the vesicle into the plasma membrane. The distribution of these connections in the plane of the membrane is not uniform; they tend to occur in patches. The fraction of vesicles that is fused with the plasma membrane at any one time appears to be related to a cell's perception of a stressful hypotonic imbalance between the internal and external concentrations of osmotically active compounds. Thus, a sudden 5% decrease in osmolarity of the artificial seawater medium just before freezing leads to a 38% increase in connections per unit membrane area, while a 20% decrease in osmolarity leads to a 75% increase in connections per unit area. Based on these findings and the corresponding ion-transport studies of R. Nuccitelli and L.F. Jaffe (1976, Planta131, 315-320), we postulate that the disc-shaped vesicles mediate short-term osmoregulation inPelvetia embryos by reversibly inserting chloride channels into the plasma membrane.
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Affiliation(s)
- J C Gilkey
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 80309-0347, Boulder, CO, USA
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Chitlaru E, Pick U. Selection and Characterization of Dunaliella salina Mutants Defective in Haloadaptation. PLANT PHYSIOLOGY 1989; 91:788-94. [PMID: 16667101 PMCID: PMC1062072 DOI: 10.1104/pp.91.2.788] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A technique for selection of Dunaliella mutants defective in their capacity to recover from osmotic shocks has been developed. The selection is based on physical separation of mutants on density gradients. This technique takes advantage of the fact that Dunaliella cells, when exposed to osmotic shocks, initially change volume and density due to water gain or loss and subsequently recover their volume and density by readjusting their intracellular glycerol. Eight mutants that do not recover their original density following hyperosmotic shocks have been isolated. The mutants grow similar to wild type cells in 1 molar NaCl, and recover like the wild type from hypotonic shocks but are defective in recovering from hypertonic shocks. A partial characterization of one of the mutants is described.
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Affiliation(s)
- E Chitlaru
- Department of Biochemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Einspahr KJ, Maeda M, Thompson GA. Concurrent changes in Dunaliella salina ultrastructure and membrane phospholipid metabolism after hyperosmotic shock. J Biophys Biochem Cytol 1988; 107:529-38. [PMID: 3417760 PMCID: PMC2115205 DOI: 10.1083/jcb.107.2.529] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Hyperosmotic shock, induced by raising the NaCl concentration of Dunaliella salina medium from 1.71 to 3.42 M, elicited a rapid decrease of nearly one-third in whole cell volume and in the volume of intracellular organelles. The decrease in cell volume was accompanied by plasmalemma infolding without overall loss of surface area. This contrasts with the dramatic increase in plasmalemma surface area after hypoosmotic shock (Maeda, M., and G. A. Thompson. 1986. J. Cell Biol. 102:289-297). Although plasmalemma surface area remained constant after hyperosmotic shock, the nucleus, chloroplast, and mitochondria lost membrane surface area, apparently through membrane fusion with the endoplasmic reticulum. Thus the endoplasmic reticulum serves as a reservoir for excess membrane during hyperosmotic stress, reversing its role as membrane donor to the same organelles during hypoosmotically induced cell expansion. Hyperosmotic shock also induced rapid changes in phospholipid metabolism. The mass of phosphatidic acid dropped to 56% of control and that of phosphatidylinositol 4,5-bisphosphate rose to 130% of control within 4 min. Further analysis demonstrated that within 10 min after hyperosmotic shock, there was 2.5-fold increase in phosphatidylcholine turnover, a twofold increase in lysophosphatidylcholine mass, a four-fold increase in lysophosphatidate mass, and an elevation in free fatty acids to 124% of control, all observations suggesting activation of phospholipase A. The observed biophysical and biochemical phenomena are likely to be causally interrelated in providing mechanisms for successful accommodation to such severe osmotic extremes.
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Affiliation(s)
- K J Einspahr
- Department of Botany, University of Texas, Austin 78713
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Rapid changes in polyphosphoinositide metabolism associated with the response of Dunaliella salina to hypoosmotic shock. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)60633-7] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Vigh L, Horváth I, Thompson GA. Recovery of Dunaliella salina cells following hydrogenation of lipids in specific membranes by a homogeneous palladium catalyst. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 937:42-50. [PMID: 3334846 DOI: 10.1016/0005-2736(88)90225-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Unsaturated fatty acyl chains of Dunaliella salina membrane lipids can be catalytically reduced by the homogeneous hydrogenation catalyst palladium di(sodium alizarine monosulphonate), Pd(QS)2, under conditions permitting full recovery of the cells within 24 h. The hydrogenation is accomplished by incubation of cells with the hydride form of Pd(QS)2 under 1 atmosphere of H2 and for 2 min or less. Following this protocol, hydrogenation reduces only those fatty acids located in the plasma membrane and other membranes located near the cell surface. The limited reactivity in vivo is due to the fact the Pd(QS)2 permeates into the living cells more slowly than it does into liposomes prepared from extracted Dunaliella membrane lipids. While Dunaliella is completely unaffected by exposure to the oxygenated, inactive catalyst, hydrogenated cells cease growth for approximately 12 h, during which time the hydrogenated acyl chains are being enzymatically retroconverted to their original unsaturated form. When the lipid composition approaches its prehydrogenation values, growth resumes, presumably due to the restoration of normal membrane functions. The system shows promise for studying the metabolic regulation of membrane microviscosity.
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Affiliation(s)
- L Vigh
- Department of Botany, University of Texas, Austin 78713
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Ahmad I, Hellebust JA. The Role of Glycerol and Inorganic Ions in Osmoregulatory Responses of the Euryhaline Flagellate Chlamydomonas pulsatilla Wollenweber. PLANT PHYSIOLOGY 1986; 82:406-10. [PMID: 16665042 PMCID: PMC1056131 DOI: 10.1104/pp.82.2.406] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The green euryhaline flagellate Chlamydomonas pulsatilla Wollenweber, isolated from a coastal marine environment, was grown exponentially over the salinity range of 10 to 200% artificial seawater (ASW). The cellular volume and aqueous space of the alga, measured by [(14)C] mannitol and (3)H(2)O tracer analyses of centrifuged cell pellets, ranged between 2.3 and 3.1 picoliters and between 1.5 and 2.1 picoliters, respectively. The nonaqueous space determined in those analyses (28-35%) was consistent with the cell composition of the alga. The glycerol content of the alga increased almost linearly with increasing salinity; its contribution to intracellular osmolality at 200% ASW was about 57%. The contribution of amino acids and soluble carbohydrates to the cell osmotic balance was small. Intracellular ion concentrations determined by analyzing centrifuged cell pellets of known [(14)C]mannitol space by atomic absorption spectrophotometry, and by neutron activation analyses of washed cells were similar. At 10% ASW, potassium and magnesium were the major cations, and chloride and phosphate were the major anions. The sodium and chloride content of the alga increased with increasing salinity; at 200% ASW the intracellular concentration of both sodium and chloride was about 400 millimolar. The intracellular osmolality (pi(int)) matched closely the external osmolality (pi(ext)) over the entire salinity range except at 10% ASW where pi(int) exceeded pi(ext) by 120 to 270 milliosmoles per kilogram H(2)O.
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Affiliation(s)
- I Ahmad
- Department of Botany, University of Toronto, Toronto, Ontario M5S 1A1 Canada
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