101
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Proteomic analyses bring new insights into the effect of a dark stress on lipid biosynthesis in Phaeodactylum tricornutum. Sci Rep 2016; 6:25494. [PMID: 27147218 PMCID: PMC4857112 DOI: 10.1038/srep25494] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/19/2016] [Indexed: 01/24/2023] Open
Abstract
Microalgae biosynthesize high amount of lipids and show high potential for renewable biodiesel production. However, the production cost of microalgae-derived biodiesel hampers large-scale biodiesel commercialization and new strategies for increasing lipid production efficiency from algae are urgently needed. Here we submitted the marine algae Phaeodactylum tricornutum to a 4-day dark stress, a condition increasing by 2.3-fold the total lipid cell quotas, and studied the cellular mechanisms leading to lipid accumulation using a combination of physiological, proteomic (iTRAQ) and genomic (qRT-PCR) approaches. Our results show that the expression of proteins in the biochemical pathways of glycolysis and the synthesis of fatty acids were induced in the dark, potentially using excess carbon and nitrogen produced from protein breakdown. Treatment of algae in the dark, which increased algal lipid cell quotas at low cost, combined with optimal growth treatment could help optimizing biodiesel production.
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102
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Hung CH, Kanehara K, Nakamura Y. Isolation and characterization of a mutant defective in triacylglycerol accumulation in nitrogen-starved Chlamydomonas reinhardtii. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1282-1293. [PMID: 27060488 DOI: 10.1016/j.bbalip.2016.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 03/31/2016] [Accepted: 04/01/2016] [Indexed: 11/30/2022]
Abstract
Triacylglycerol (TAG), a major source of biodiesel production, accumulates in nitrogen-starved Chlamydomonas reinhardtii. However, the metabolic pathway of starch-to-TAG conversion remains elusive because an enzyme that affects the starch degradation is unknown. Here, we isolated a new class of mutant bgal1, which expressed an overaccumulation of starch granules and defective photosynthetic growth. The bgal1 was a null mutant of a previously uncharacterized β-galactosidase-like gene (Cre02.g119700), which decreased total β-galactosidase activity 40% of the wild type. Upon nitrogen starvation, the bgal1 mutant showed decreased TAG accumulation mainly due to the reduced flux of de novo TAG biosynthesis evidenced by increased unsaturation of fatty acid composition in TAG and reduced TAG accumulation by additional supplementation of acetate to the culture media. Metabolomic analysis of the bgal1 mutant showed significantly reduced levels of metabolites following the hydrolysis of starch and substrates for TAG accumulation, whereas metabolites in TCA cycle were unaffected. Upon nitrogen starvation, while levels of glucose 6-phosphate, fructose 6-phosphate and acetyl-CoA remained lower, most of the other metabolites in glycolysis were increased but those in the TCA cycle were decreased, supporting TAG accumulation. We suggest that BGAL1 may be involved in the degradation of starch, which affects TAG accumulation in nitrogen-starved C. reinhardtii. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.
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Affiliation(s)
- Chun-Hsien Hung
- Institute of Plant and Microbial Biology, Academia Sinica, 128 sec.2 Academia Rd. Nankang, Taipei 11529, Taiwan.
| | - Kazue Kanehara
- Institute of Plant and Microbial Biology, Academia Sinica, 128 sec.2 Academia Rd. Nankang, Taipei 11529, Taiwan.
| | - Yuki Nakamura
- Institute of Plant and Microbial Biology, Academia Sinica, 128 sec.2 Academia Rd. Nankang, Taipei 11529, Taiwan; PRESTO, Japan Science and Technology Agency, A-1-8 Honcho Kawaguchi, Saitama, Japan.
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103
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Saroussi SI, Wittkopp TM, Grossman AR. The Type II NADPH Dehydrogenase Facilitates Cyclic Electron Flow, Energy-Dependent Quenching, and Chlororespiratory Metabolism during Acclimation of Chlamydomonas reinhardtii to Nitrogen Deprivation. PLANT PHYSIOLOGY 2016; 170:1975-88. [PMID: 26858365 PMCID: PMC4825143 DOI: 10.1104/pp.15.02014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 02/05/2016] [Indexed: 05/18/2023]
Abstract
When photosynthetic organisms are deprived of nitrogen (N), the capacity to grow and assimilate carbon becomes limited, causing a decrease in the productive use of absorbed light energy and likely a rise in the cellular reduction state. Although there is a scarcity of N in many terrestrial and aquatic environments, a mechanistic understanding of how photosynthesis adjusts to low-N conditions and the enzymes/activities integral to these adjustments have not been described. In this work, we use biochemical and biophysical analyses of photoautotrophically grown wild-type and mutant strains of Chlamydomonas reinhardtii to determine the integration of electron transport pathways critical for maintaining active photosynthetic complexes even after exposure of cells to N deprivation for 3 d. Key to acclimation is the type II NADPH dehydrogenase, NDA2, which drives cyclic electron flow (CEF), chlororespiration, and the generation of an H(+) gradient across the thylakoid membranes. N deprivation elicited a doubling of the rate of NDA2-dependent CEF, with little contribution from PGR5/PGRL1-dependent CEF The H(+) gradient generated by CEF is essential to sustain nonphotochemical quenching, while an increase in the level of reduced plastoquinone would promote a state transition; both are necessary to down-regulate photosystem II activity. Moreover, stimulation of NDA2-dependent chlororespiration affords additional relief from the elevated reduction state associated with N deprivation through plastid terminal oxidase-dependent water synthesis. Overall, rerouting electrons through the NDA2 catalytic hub in response to photoautotrophic N deprivation sustains cell viability while promoting the dissipation of excess excitation energy through quenching and chlororespiratory processes.
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Affiliation(s)
- Shai I Saroussi
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305 (S.I.S., T.M.W., A.R.G.); andDepartment of Biology, Stanford University, Stanford, California 94305-5020 (T.M.W.)
| | - Tyler M Wittkopp
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305 (S.I.S., T.M.W., A.R.G.); andDepartment of Biology, Stanford University, Stanford, California 94305-5020 (T.M.W.)
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305 (S.I.S., T.M.W., A.R.G.); andDepartment of Biology, Stanford University, Stanford, California 94305-5020 (T.M.W.)
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104
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Légeret B, Schulz-Raffelt M, Nguyen HM, Auroy P, Beisson F, Peltier G, Blanc G, Li-Beisson Y. Lipidomic and transcriptomic analyses of Chlamydomonas reinhardtii under heat stress unveil a direct route for the conversion of membrane lipids into storage lipids. PLANT, CELL & ENVIRONMENT 2016; 39:834-47. [PMID: 26477535 DOI: 10.1111/pce.12656] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/01/2015] [Accepted: 10/06/2015] [Indexed: 05/18/2023]
Abstract
Studying how photosynthetic cells modify membrane lipids in response to heat stress is important to understand how plants and microalgae adapt to daily fluctuations in temperature and to investigate new lipid pathways. Here, we investigate changes occurring in lipid molecular species and lipid metabolism genes during early response to heat stress in the model photosynthetic microorganism Chlamydomonas reinhardtii. Lipid molecular species analyses revealed that, after 60 min at 42 °C, a strong decrease in specific polyunsaturated membrane lipids was observed together with an increase in polyunsaturated triacylglycerols (TAGs) and diacylglycerols (DAGs). The fact that decrease in the major chloroplastic monogalactosyldiacylglycerol sn1-18:3/sn2-16:4 was mirrored by an accumulation of DAG sn1-18:3/sn2-16:4 and TAG sn1-18:3/sn2-16:4/sn3-18:3 indicated that newly accumulated TAGs were formed via direct conversion of monogalactosyldiacylglycerols to DAGs then TAGs. Lipidomic analyses showed that the third fatty acid of a TAG likely originated from a phosphatidylethanolamine or a diacylglyceryl-O-4'-(N,N,N,-trimethyl)-homoserine betaine lipid species. Candidate genes for this TAG synthesis pathway were provided through comparative transcriptomic analysis and included a phospholipase A2 homolog and the DAG acyltransferase DGTT1. This study gives insights into the molecular events underlying changes in membrane lipids during heat stress and reveals an alternative route for TAG synthesis.
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Affiliation(s)
- B Légeret
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
| | - M Schulz-Raffelt
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
| | - H M Nguyen
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
| | - P Auroy
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
| | - F Beisson
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
| | - G Peltier
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
| | - G Blanc
- Laboratoire Information Génomique & Structurale, UMR7256 (IMM FR3479) CNRS Aix-Marseille Université, Marseille, France
| | - Y Li-Beisson
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique, UMR7265, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR7265, Marseille, France
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105
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Zhao X, Jarboe L, Wen Z. Utilization of pyrolytic substrate by microalga Chlamydomonas reinhardtii: cell membrane property change as a response of the substrate toxicity. Appl Microbiol Biotechnol 2016; 100:4241-51. [PMID: 26995605 DOI: 10.1007/s00253-016-7439-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/01/2016] [Accepted: 03/04/2016] [Indexed: 11/30/2022]
Abstract
Acetic acid derived from fast pyrolysis of lignocellulosic biomass is a promising substrate for microalgae fermentation for producing lipid-rich biomass. However, crude pyrolytic acetic acid solution contains various toxic compounds inhibiting algal growth. It was hypothesized that such an inhibition was mainly due to the cell membrane damage. In this work, the cell membrane property of algal cells was evaluated at various conditions to elucidate the mechanisms of inhibition caused by the pyrolytic substrate solution. It was found that acetic acid itself served a carbon source for boosting algal cell growth but also caused cell membrane leakage. The acetic acid concentration for highest cell density was 4 g/L. Over-liming treatment of crude pyrolytic acetic acid increased the algal growth with a concurrent reduction of cell membrane leakage. Directed evolution of algal strain enhanced cell membrane integrity and thus increased its tolerance to the toxicity of the crude substrate. Statistical analysis shows that there was a significant correlation between the cell growth performance and the cell membrane integrity (leakage) but not membrane fluidity. The addition of cyto-protectants such as Pluronic F68 and Pluronic F127 enhanced the cell membrane integrity and thus, resulted in enhanced cell growth. The transmission electron microscopy (TEM) of algal cells visually confirmed the cell membrane damage as the mechanism of the pyrolytic substrate inhibition. Collectively, this work indicates that the cell membrane is one major reason for the toxicity of pyrolytic acetic acid when being used for algal culture. To better use this pyrolytic substrate, cell membrane of the microorganism needs to be strengthened through either strain improvement or addition of membrane protectant reagents.
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Affiliation(s)
- Xuefei Zhao
- Department of Agricultural and Biosystems Engineering, Iowa University, Ames, IA, 50011, USA
| | - Laura Jarboe
- Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - Zhiyou Wen
- Department of Food Science and Human Nutrition, Iowa State University, Ames, IA, 50011, USA.
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106
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Deep Learning in Label-free Cell Classification. Sci Rep 2016; 6:21471. [PMID: 26975219 PMCID: PMC4791545 DOI: 10.1038/srep21471] [Citation(s) in RCA: 214] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 01/25/2016] [Indexed: 01/11/2023] Open
Abstract
Label-free cell analysis is essential to personalized genomics, cancer diagnostics, and drug development as it avoids adverse effects of staining reagents on cellular viability and cell signaling. However, currently available label-free cell assays mostly rely only on a single feature and lack sufficient differentiation. Also, the sample size analyzed by these assays is limited due to their low throughput. Here, we integrate feature extraction and deep learning with high-throughput quantitative imaging enabled by photonic time stretch, achieving record high accuracy in label-free cell classification. Our system captures quantitative optical phase and intensity images and extracts multiple biophysical features of individual cells. These biophysical measurements form a hyperdimensional feature space in which supervised learning is performed for cell classification. We compare various learning algorithms including artificial neural network, support vector machine, logistic regression, and a novel deep learning pipeline, which adopts global optimization of receiver operating characteristics. As a validation of the enhanced sensitivity and specificity of our system, we show classification of white blood T-cells against colon cancer cells, as well as lipid accumulating algal strains for biofuel production. This system opens up a new path to data-driven phenotypic diagnosis and better understanding of the heterogeneous gene expressions in cells.
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107
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Bajhaiya AK, Dean AP, Zeef LAH, Webster RE, Pittman JK. PSR1 Is a Global Transcriptional Regulator of Phosphorus Deficiency Responses and Carbon Storage Metabolism in Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 2016; 170:1216-34. [PMID: 26704642 PMCID: PMC4775146 DOI: 10.1104/pp.15.01907] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 12/23/2015] [Indexed: 05/18/2023]
Abstract
Many eukaryotic microalgae modify their metabolism in response to nutrient stresses such as phosphorus (P) starvation, which substantially induces storage metabolite biosynthesis, but the genetic mechanisms regulating this response are poorly understood. Here, we show that P starvation-induced lipid and starch accumulation is inhibited in a Chlamydomonas reinhardtii mutant lacking the transcription factor Pi Starvation Response1 (PSR1). Transcriptomic analysis identified specific metabolism transcripts that are induced by P starvation but misregulated in the psr1 mutant. These include transcripts for starch and triacylglycerol synthesis but also transcripts for photosynthesis-, redox-, and stress signaling-related proteins. To further examine the role of PSR1 in regulating lipid and starch metabolism, PSR1 complementation lines in the psr1 strain and PSR1 overexpression lines in a cell wall-deficient strain were generated. PSR1 expression in the psr1 lines was shown to be functional due to rescue of the psr1 phenotype. PSR1 overexpression lines exhibited increased starch content and number of starch granules per cell, which correlated with a higher expression of specific starch metabolism genes but reduced neutral lipid content. Furthermore, this phenotype was consistent in the presence and absence of acetate. Together, these results identify a key transcriptional regulator in global metabolism and demonstrate transcriptional engineering in microalgae to modulate starch biosynthesis.
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Affiliation(s)
- Amit K Bajhaiya
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Andrew P Dean
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Leo A H Zeef
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Rachel E Webster
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Jon K Pittman
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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108
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Goncalves EC, Koh J, Zhu N, Yoo MJ, Chen S, Matsuo T, Johnson JV, Rathinasabapathi B. Nitrogen starvation-induced accumulation of triacylglycerol in the green algae: evidence for a role for ROC40, a transcription factor involved in circadian rhythm. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 85:743-57. [PMID: 26920093 DOI: 10.1111/tpj.13144] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 02/05/2016] [Accepted: 02/15/2016] [Indexed: 05/24/2023]
Abstract
Microalgal triacylglycerol (TAG), a promising source of biofuel, is induced upon nitrogen starvation (-N), but the proteins and genes involved in this process are poorly known. We performed isobaric tagging for relative and absolute quantification (iTRAQ)-based quantitative proteomics to identify Chlorella proteins with modulated expression under short-term -N. Out of 1736 soluble proteins and 2187 membrane-associated proteins identified, 288 and 56, respectively, were differentially expressed under -N. Gene expression analysis on select genes confirmed the same direction of mRNA modulation for most proteins. The MYB-related transcription factor ROC40 was the most induced protein, with a 9.6-fold increase upon -N. In a previously generated Chlamydomonas mutant, gravimetric measurements of crude total lipids revealed that roc40 was impaired in its ability to increase the accumulation of TAG upon -N, and this phenotype was complemented when wild-type Roc40 was expressed. Results from radiotracer experiments were consistent with the roc40 mutant being comparable to the wild type in recycling membrane lipids to TAG but being impaired in additional de novo synthesis of TAG during -N stress. In this study we provide evidence to support the hypothesis that transcription factor ROC40 has a role in -N-induced lipid accumulation, and uncover multiple previously unknown proteins modulated by short-term -N in green algae.
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Affiliation(s)
- Elton C Goncalves
- Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA
| | - Jin Koh
- Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, 32610, USA
| | - Ning Zhu
- Department of Biology, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, Gainesville, FL, 32611, USA
| | - Mi-Jeong Yoo
- Department of Biology, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, Gainesville, FL, 32611, USA
| | - Sixue Chen
- Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA
- Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, 32610, USA
- Department of Biology, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida, Gainesville, FL, 32611, USA
| | - Takuya Matsuo
- Center for Gene Research, Nagoya University, Furo, Chikusa, Nagoya, 464-8602, Japan
| | - Jodie V Johnson
- Chemistry Department, University of Florida, Gainesville, FL, 32611, USA
| | - Bala Rathinasabapathi
- Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611-0690, USA
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109
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Stress-induced neutral lipid biosynthesis in microalgae - Molecular, cellular and physiological insights. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1269-1281. [PMID: 26883557 DOI: 10.1016/j.bbalip.2016.02.008] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/04/2016] [Accepted: 02/07/2016] [Indexed: 01/01/2023]
Abstract
Photosynthetic microalgae have promise as biofuel feedstock. Under certain conditions, they produce substantial amounts of neutral lipids, mainly in the form of triacylglycerols (TAGs), which can be converted to fuels. Much of our current knowledge on the genetic and molecular basis of algal neutral lipid metabolism derives mainly from studies of plants, i.e. seed tissues, and to a lesser extent from direct studies of algal lipid metabolism. Thus, the knowledge of TAG synthesis and the cellular trafficking of TAG precursors in algal cells is to a large extent based on genome predictions, and most aspects of TAG metabolism have yet to be experimentally verified. The biofuel prospects of microalgae have raised the interest in mechanistic studies of algal TAG biosynthesis in recent years and resulted in an increasing number of publications on lipid metabolism in microalgae. In this review we summarize the current findings on genetic, molecular and physiological studies of TAG accumulation in microalgae. Special emphasis is on the functional analysis of key genes involved in TAG synthesis, molecular mechanisms of regulation of TAG biosynthesis, as well as on possible mechanisms of lipid droplet formation in microalgal cells. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.
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110
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Liberatore MW, Peterson BN, Nottoli T, McCulloch JM, Jinkerson RE, Boyle NR, Posewitz MC. Effectiveness of cationically modified cellulose polymers for dewatering algae. SEP SCI TECHNOL 2016. [DOI: 10.1080/01496395.2015.1121278] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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111
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Li X, Jonikas MC. High-Throughput Genetics Strategies for Identifying New Components of Lipid Metabolism in the Green Alga Chlamydomonas reinhardtii. Subcell Biochem 2016; 86:223-247. [PMID: 27023238 DOI: 10.1007/978-3-319-25979-6_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Microalgal lipid metabolism is of broad interest because microalgae accumulate large amounts of triacylglycerols (TAGs) that can be used for biodiesel production (Durrett et al Plant J 54(4):593-607, 2008; Hu et al Plant J 54(4):621-639, 2008). Additionally, green algae are close relatives of land plants and serve as models to understand conserved lipid metabolism pathways in the green lineage. The green alga Chlamydomonas reinhardtii (Chlamydomonas hereafter) is a powerful model organism for understanding algal lipid metabolism. Various methods have been used to screen Chlamydomonas mutants for lipid amount or composition, and for identification of the mutated loci in mutants of interest. In this chapter, we summarize the advantages and caveats for each of these methods with a focus on screens for mutants with perturbed TAG content. We also discuss technical opportunities and new tools that are becoming available for screens of mutants altered in TAG content or perturbed in other processes in Chlamydomonas.
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Affiliation(s)
- Xiaobo Li
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA.
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112
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Abstract
Plant and algal oils are some of the most energy-dense renewable compounds provided by nature. Triacylglycerols (TAGs) are the major constituent of plant oils, which can be converted into fatty acid methyl esters commonly known as biodiesel. As one of the most efficient producers of TAGs, photosynthetic microalgae have attracted substantial interest for renewable fuel production. Currently, the big challenge of microalgae based TAGs for biofuels is their high cost compared to fossil fuels. A conundrum is that microalgae accumulate large amounts of TAGs only during stress conditions such as nutrient deprivation and temperature stress, which inevitably will inhibit growth. Thus, a better understanding of why and how microalgae induce TAG biosynthesis under stress conditions would allow the development of engineered microalgae with increased TAG production during conditions optimal for growth. Land plants also synthesize TAGs during stresses and we will compare new findings on environmental stress-induced TAG accumulation in plants and microalgae especially in the well-characterized model alga Chlamydomonas reinhardtii and a biotechnologically relevant genus Nannochloropsis.
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Affiliation(s)
- Zhi-Yan Du
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
| | - Christoph Benning
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
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113
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Sakurai T, Aoki M, Ju X, Ueda T, Nakamura Y, Fujiwara S, Umemura T, Tsuzuki M, Minoda A. Profiling of lipid and glycogen accumulations under different growth conditions in the sulfothermophilic red alga Galdieria sulphuraria. BIORESOURCE TECHNOLOGY 2016; 200:861-866. [PMID: 26595665 DOI: 10.1016/j.biortech.2015.11.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 11/04/2015] [Accepted: 11/05/2015] [Indexed: 06/05/2023]
Abstract
The unicellular red alga Galdieria sulphuraria grows efficiently and produces a large amount of biomass in acidic conditions at high temperatures. It has great potential to produce biofuels and other beneficial compounds without becoming contaminated with other organisms. In G. sulphuraria, biomass measurements and glycogen and lipid analyses demonstrated that the amounts and compositions of glycogen and lipids differed when cells were grown under autotrophic, mixotrophic, and heterotrophic conditions. Maximum biomass production was obtained in the mixotrophic culture. High amounts of glycogen were obtained in the mixotrophic cultures, while the amounts of neutral lipids were similar between mixotrophic and heterotrophic cultures. The amounts of neutral lipids were highest in red algae, including thermophiles. Glycogen structure and fatty acids compositions largely depended on the growth conditions.
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Affiliation(s)
- Toshihiro Sakurai
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Motohide Aoki
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Xiaohui Ju
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaragi 305-8572, Japan
| | - Tatsuya Ueda
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Yasunori Nakamura
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita 010-0195, Japan
| | - Shoko Fujiwara
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Tomonari Umemura
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Mikio Tsuzuki
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan; Japan Science and Technology Agency, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan
| | - Ayumi Minoda
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaragi 305-8572, Japan.
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114
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Abstract
In response to demands for sustainable domestic fuel sources, research into biofuels has become increasingly important. Many challenges face biofuels in their effort to replace petroleum fuels, but rational strain engineering of algae and photosynthetic organisms offers a great deal of promise. For decades, mutations and stress responses in photosynthetic microbiota were seen to result in production of exciting high-energy fuel molecules, giving hope but minor capability for design. However, '-omics' techniques for visualizing entire cell processing has clarified biosynthesis and regulatory networks. Investigation into the promising production behaviors of the model organism C. reinhardtii and its mutants with these powerful techniques has improved predictability and understanding of the diverse, complex interactions within photosynthetic organisms. This new equipment has created an exciting new frontier for high-throughput, predictable engineering of photosynthetically produced carbon-neutral biofuels.
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Affiliation(s)
- Hanna R Aucoin
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, 80401, USA
| | - Joseph Gardner
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, 80401, USA
| | - Nanette R Boyle
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, 80401, USA.
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115
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Zhu S, Wang Y, Xu J, Shang C, Wang Z, Xu J, Yuan Z. Luxury uptake of phosphorus changes the accumulation of starch and lipid in Chlorella sp. under nitrogen depletion. BIORESOURCE TECHNOLOGY 2015; 198:165-71. [PMID: 26386419 DOI: 10.1016/j.biortech.2015.08.142] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 08/24/2015] [Accepted: 08/27/2015] [Indexed: 05/15/2023]
Abstract
The aim of this research was to study the effect of phosphorus supply on starch and lipid production under nitrogen starvation using Chlorella sp. as a model. High phosphate level had marginal effect on cell density but increased biomass growth. Massive phosphorus was assimilated quickly and mainly stored in the form of polyphosphate. The algal cells ceased phosphorus uptake when intracellular phosphorus reached a certain level. 5mM phosphate in the culture rendered a 16.7% decrease of starch synthesis and a 22.4% increase of lipid synthesis relative to low phosphate (0.17 mM). It is plausible that phosphate can regulate carbon partitioning between starch and lipid synthesis pathway by influencing ADP-glucose pyrophosphorylase activity. Moreover, high phosphate concentration enhanced the abundance of oleic acid, improving oil quality for biodiesel production. It is a promising cultivation strategy by integration of phosphorus removal from wastewater with biodiesel production for this alga.
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Affiliation(s)
- Shunni Zhu
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Yajie Wang
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Jin Xu
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Changhua Shang
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Zhongming Wang
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Jingliang Xu
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Zhenhong Yuan
- Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China.
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Cody RB, McAlpin CR, Cox CR, Jensen KR, Voorhees KJ. Identification of bacteria by fatty acid profiling with direct analysis in real time mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:2007-2012. [PMID: 26443400 DOI: 10.1002/rcm.7309] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2015] [Revised: 08/06/2015] [Accepted: 08/07/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE Bacterial fatty acid profiling is a well-established technique for bacterial identification. Current methods involving esterification and gas chromatography/mass spectrometry (GC/MS) or matrix-assisted laser desorption/ionization (MALDI) analysis are effective, but there are potential benefits to be gained by investigating ambient ionization methods that can provide rapid analysis without derivatization or additional sample handling. METHODS Lipid extracts from colonies of five Gram-positive and five Gram-negative pathogenic bacteria were analyzed by Direct Analysis in Real Time (DART) ionization coupled with a time-of-flight mass spectrometer. Fatty acid profiles were obtained from the negative-ion DART mass spectra without additional derivatization or sample preparation. RESULTS Fatty acid profiles obtained from the deprotonated molecules [M - H](-) were found to be highly species-specific and reproducible. Leave-one-out cross validation (LOOCV) for principal component analysis (PCA) showed 100% correct classification accuracy. CONCLUSIONS The results of this preliminary feasibility study show good precision and accuracy, and the fatty acid patterns are clearly distinctive for each of the ten species examined. The speed and ease of analysis and the high classification accuracy for this initial study indicate that DART is an effective method for bacterial fatty acid profiling.
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Affiliation(s)
- Robert B Cody
- JEOL USA, Inc., 11 Dearborn Rd., Peabody, MA, 01960, USA
| | - Casey R McAlpin
- Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA
| | | | - Kirk R Jensen
- Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA
| | - Kent J Voorhees
- Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA
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Abstract
When green algae are exposed to physiological stresses such as nutrient deprivation, growth is arrested and the cells channel fixed carbon instead into storage compounds, accumulating first starch granules and then lipid bodies containing triacylglycerides. In recent years there has been significant interest in the commercial exploitation of algal lipids as a sustainable source of biodiesel. Since starch and lipid biosynthesis involves the same C3 precursor pool, it has been proposed that mutations blocking starch accumulation should result in increased lipid yields, and indeed several studies have supported this. The fast-growing, thermotolerant alga Chlorella sorokiniana represents an attractive strain for industrial cultivation. We have therefore generated and characterized starch-deficient mutants of C. sorokiniana and determined whether lipid levels are increased in these strains under stress conditions. One mutant (ST68) is shown to lack isoamylase, whilst two others (ST3 and ST12) are defective in starch phosphorylase. However, we find no significant change in the accumulation or profile of fatty acids in these mutants compared to the wild-type, suggesting that a failure to accumulate starch per se is not sufficient for the hyper-accumulation of lipid, and that more subtle regulatory steps underlie the partitioning of carbon to the two storage products. We have isolated a collection of starch deficient mutants of Chlorella sorokiniana. We have characterized mutants defective in isoamylase and starch phosphorylase. Mutants show no increase in storage lipids as seen for other algal starch mutants.
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118
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Manandhar-Shrestha K, Hildebrand M. Characterization and manipulation of a DGAT2 from the diatom Thalassiosira pseudonana: Improved TAG accumulation without detriment to growth, and implications for chloroplast TAG accumulation. ALGAL RES 2015. [DOI: 10.1016/j.algal.2015.09.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Hlavova M, Turoczy Z, Bisova K. Improving microalgae for biotechnology — From genetics to synthetic biology. Biotechnol Adv 2015; 33:1194-203. [DOI: 10.1016/j.biotechadv.2015.01.009] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 01/11/2015] [Accepted: 01/17/2015] [Indexed: 01/01/2023]
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120
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Vitova M, Bisova K, Kawano S, Zachleder V. Accumulation of energy reserves in algae: From cell cycles to biotechnological applications. Biotechnol Adv 2015; 33:1204-18. [DOI: 10.1016/j.biotechadv.2015.04.012] [Citation(s) in RCA: 131] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 04/27/2015] [Accepted: 04/28/2015] [Indexed: 01/28/2023]
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121
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Sumiya N, Kawase Y, Hayakawa J, Matsuda M, Nakamura M, Era A, Tanaka K, Kondo A, Hasunuma T, Imamura S, Miyagishima SY. Expression of Cyanobacterial Acyl-ACP Reductase Elevates the Triacylglycerol Level in the Red Alga Cyanidioschyzon merolae. PLANT & CELL PHYSIOLOGY 2015; 56:1962-80. [PMID: 26272551 DOI: 10.1093/pcp/pcv120] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 08/07/2015] [Indexed: 05/21/2023]
Abstract
Nitrogen starvation is known to induce the accumulation of triacylglycerol (TAG) in many microalgae, and potential use of microalgae as a source of biofuel has been explored. However, nitrogen starvation also stops cellular growth. The expression of cyanobacterial acyl-acyl carrier protein (ACP) reductase in the unicellular red alga Cyanidioschyzon merolae chloroplasts resulted in an accumulation of TAG, which led to an increase in the number and size of lipid droplets while maintaining cellular growth. Transcriptome and metabolome analyses showed that the expression of acyl-ACP reductase altered the activities of several metabolic pathways. The activities of enzymes involved in fatty acid synthesis in chloroplasts, such as acetyl-CoA carboxylase and pyruvate dehydrogenase, were up-regulated, while pyruvate decarboxylation in mitochondria and the subsequent consumption of acetyl-CoA by the tricarboxylic acid (TCA) cycle were down-regulated. Aldehyde dehydrogenase, which oxidizes fatty aldehydes to fatty acids, was also up-regulated in the acyl-ACP reductase expresser. This activation was required for the lipid droplet accumulation and metabolic changes observed in the acyl-ACP reductase expresser. Nitrogen starvation also resulted in lipid droplet accumulation in C. merolae, while cell growth ceased as in the case of other algal species. The metabolic changes that occur upon the expression of acyl-ACP reductase are quite different from those caused by nitrogen starvation. Therefore, there should be a method for further increasing the storage lipid level while still maintaining cell growth that is different from the metabolic response to nitrogen starvation.
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Affiliation(s)
- Nobuko Sumiya
- Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Yasuko Kawase
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
| | - Jumpei Hayakawa
- Department of Biological Sciences, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan
| | - Mami Matsuda
- Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075, Japan
| | - Mami Nakamura
- Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), 1111 Yata, Mishima, Shizuoka, 411-8540, Japan
| | - Atsuko Era
- Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Kan Tanaka
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
| | - Akihiko Kondo
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan Biomass Engineering Program, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Tomohisa Hasunuma
- Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075, Japan
| | - Sousuke Imamura
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
| | - Shin-ya Miyagishima
- Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), 1111 Yata, Mishima, Shizuoka, 411-8540, Japan
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Gonzalez-Ballester D, Jurado-Oller JL, Fernandez E. Relevance of nutrient media composition for hydrogen production in Chlamydomonas. PHOTOSYNTHESIS RESEARCH 2015; 125:395-406. [PMID: 25952745 DOI: 10.1007/s11120-015-0152-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 04/29/2015] [Indexed: 05/23/2023]
Abstract
Microalgae are capable of biological H2 photoproduction from water, solar energy, and a variety of organic substrates. Acclimation responses to different nutrient regimes finely control photosynthetic activity and can influence H2 production. Hence, nutrient stresses are an interesting scenario to study H2 production in photosynthetic organisms. In this review, we mainly focus on the H2-production mechanisms in Chlamydomonas reinhardtii and the physiological relevance of the nutrient media composition when producing H2.
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Affiliation(s)
- David Gonzalez-Ballester
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Córdoba, Campus de Rabanales, Edif. Severo Ochoa, 14071, Córdoba, Spain,
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123
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Wase N, Tu B, Black PN, DiRusso CC. Phenotypic screening identifies Brefeldin A/Ascotoxin as an inducer of lipid storage in the algae Chlamydomonas reinhardtii. ALGAL RES 2015. [DOI: 10.1016/j.algal.2015.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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124
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Stopka SA, Shrestha B, Maréchal É, Falconet D, Vertes A. Metabolic transformation of microalgae due to light acclimation and genetic modifications followed by laser ablation electrospray ionization mass spectrometry with ion mobility separation. Analyst 2015; 139:5945-53. [PMID: 25254963 DOI: 10.1039/c4an01368a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Metabolic profiling of various microalga species and their genetic variants, grown under varied environmental conditions, has become critical to accelerate the exploration of phytoplankton biodiversity and biology. The accumulation of valuable metabolites, such as glycerolipids, is also sought in microalgae for biotechnological applications ranging from food, feed, medicine, cosmetics to bioenergy and green chemistry. In this report we describe the direct analysis of metabolites and lipids in small cell populations of the green alga Chlamydomonas reinhardtii, using laser ablation electrospray ionization (LAESI) mass spectrometry (MS) coupled with ion mobility separation (IMS). These microorganisms are capable of redirecting energy storage pathways from starch to neutral lipids depending on environmental conditions and nutrient availability. Metabolite and lipid productions were monitored in wild type (WT), and genetically modified C. reinhardtii strains with an impaired starch pathway. Lipids, such as triacylglycerols (TAG) and diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), were monitored over time under altered light conditions. More than 200 ions related to metabolites, e.g., arginine, cysteine, serine, palmitate, chlorophyll a, chlorophyll b, etc., were detected. The lipid profiles at different light intensities for strains with impaired starch pathway (Sta1 and Sta6) contained 26 glycerolipids, such as DGTS, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), as well as 33 TAG species. Results were obtained over a 72 hour time period under high and low light conditions for the WT species and the two mutants. Our results indicate that LAESI-IMS-MS can be utilized for the rapid analysis of increased TAG production at elevated light intensities. Compared to WT, the Sta6 strain showed 2.5 times higher lipid production at 72 hours under high light conditions. The results demonstrate our ability to rapidly observe numerous changes in metabolite and lipid levels in microalgal population. These capabilities are expected to facilitate the exploration of genetically altered microalgal strains for biofuel production.
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Affiliation(s)
- Sylwia A Stopka
- Department of Chemistry, W. M. Keck Institute for Proteomics Technology and Applications, The George Washington University, Washington, DC 20052, USA.
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125
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Chien LJ, Hsu TP, Huang CC, Teng K, Hsieh HJ. Novel Codon-optimization Genes Encoded in Chlorella for Triacylglycerol Accumulation. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.egypro.2015.07.136] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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126
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Dynamics of Photosynthesis in a Glycogen-Deficient glgC Mutant of Synechococcus sp. Strain PCC 7002. Appl Environ Microbiol 2015; 81:6210-22. [PMID: 26150450 DOI: 10.1128/aem.01751-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 06/25/2015] [Indexed: 11/20/2022] Open
Abstract
Cyanobacterial glycogen-deficient mutants display impaired degradation of light-harvesting phycobilisomes under nitrogen-limiting growth conditions and secrete a suite of organic acids as a putative reductant-spilling mechanism. This genetic background, therefore, represents an important platform to better understand the complex relationships between light harvesting, photosynthetic electron transport, carbon fixation, and carbon/nitrogen metabolisms. In this study, we conducted a comprehensive analysis of the dynamics of photosynthesis as a function of reductant sink manipulation in a glycogen-deficient glgC mutant of Synechococcus sp. strain PCC 7002. The glgC mutant showed increased susceptibility to photoinhibition during the initial phase of nitrogen deprivation. However, after extended periods of nitrogen deprivation, glgC mutant cells maintained higher levels of photosynthetic activity than the wild type, supporting continuous organic acid secretion in the absence of biomass accumulation. In contrast to the wild type, the glgC mutant maintained efficient energy transfer from phycobilisomes to photosystem II (PSII) reaction centers, had an elevated PSII/PSI ratio as a result of reduced PSII degradation, and retained a nitrogen-replete-type ultrastructure, including an extensive thylakoid membrane network, after prolonged nitrogen deprivation. Together, these results suggest that multiple global signals for nitrogen deprivation are not activated in the glgC mutant, allowing the maintenance of active photosynthetic complexes under conditions where photosynthesis would normally be abolished.
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127
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Avidan O, Brandis A, Rogachev I, Pick U. Enhanced acetyl-CoA production is associated with increased triglyceride accumulation in the green alga Chlorella desiccata. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:3725-35. [PMID: 25922486 PMCID: PMC4473976 DOI: 10.1093/jxb/erv166] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Triglycerides (TAGs) from microalgae can be utilized as food supplements and for biodiesel production, but little is known about the regulation of their biosynthesis. This work aimed to test the relationship between acetyl-CoA (Ac-CoA) levels and TAG biosynthesis in green algae under nitrogen deprivation. A novel, highly sensitive liquid chromatography mass spectrometry (LC-MS/MS) technique enabled us to determine the levels of Ac-CoA, malonyl-CoA, and unacetylated (free) CoA in green microalgae. A comparative study of three algal species that differ in TAG accumulation levels shows that during N starvation, Ac-CoA levels rapidly rise, preceding TAG accumulation in all tested species. The levels of Ac-CoA in the high TAG accumulator Chlorella desiccata exceed the levels in the moderate TAG accumulators Dunaliella tertiolecta and Chlamydomonas reinhardtii. Similarly, malonyl-CoA and free CoA levels also increase, but to lower extents. Calculated cellular concentrations of Ac-CoA are far lower than reported K mAc-CoA values of plastidic Ac-CoA carboxylase (ptACCase) in plants. Transcript level analysis of plastidic pyruvate dehydrogenase (ptPDH), the major chloroplastic Ac-CoA producer, revealed rapid induction in parallel with Ac-CoA accumulation in C. desiccata, but not in D. tertiolecta or C. reinhardtii. It is proposed that the capacity to accumulate high TAG levels in green algae critically depends on their ability to divert carbon flow towards Ac-CoA. This requires elevation of the chloroplastic CoA pool level and enhancement of Ac-CoA biosynthesis. These conclusions may have important implications for future genetic manipulation to enhance TAG biosynthesis in green algae.
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Affiliation(s)
- Omri Avidan
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Alexander Brandis
- Biological Services Unit, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ilana Rogachev
- Department of Plant and Environmental Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Uri Pick
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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129
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Biochemical Modulation of Lipid Pathway in Microalgae Dunaliella sp. for Biodiesel Production. BIOMED RESEARCH INTERNATIONAL 2015; 2015:597198. [PMID: 26146623 PMCID: PMC4469783 DOI: 10.1155/2015/597198] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 01/07/2015] [Accepted: 01/08/2015] [Indexed: 12/31/2022]
Abstract
Exploitation of renewable sources of energy such as algal biodiesel could turn energy supplies problem around. Studies on a locally isolated strain of Dunaliella sp. showed that the mean lipid content in cultures enriched by 200 mg L(-1) myoinositol was raised by around 33% (1.5 times higher than the control). Similarly, higher lipid productivity values were achieved in cultures treated by 100 and 200 mg L(-1) myoinositol. Fluorometry analyses (microplate fluorescence and flow cytometry) revealed increased oil accumulation in the Nile red-stained algal samples. Moreover, it was predicted that biodiesel produced from myoinositol-treated cells possessed improved oxidative stability, cetane number, and cloud point values. From the genomic point of view, real-time analyses revealed that myoinositol negatively influenced transcript abundance of AccD gene (one of the key genes involved in lipid production pathway) due to feedback inhibition and that its positive effect must have been exerted through other genes. The findings of the current research are not to interprete that myoinositol supplementation could answer all the challenges faced in microalgal biodiesel production but instead to show that "there is a there there" for biochemical modulation strategies, which we achieved, increased algal oil quantity and enhanced resultant biodiesel quality.
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130
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Kajikawa M, Sawaragi Y, Shinkawa H, Yamano T, Ando A, Kato M, Hirono M, Sato N, Fukuzawa H. Algal dual-specificity tyrosine phosphorylation-regulated kinase, triacylglycerol accumulation regulator1, regulates accumulation of triacylglycerol in nitrogen or sulfur deficiency. PLANT PHYSIOLOGY 2015; 168:752-64. [PMID: 25922058 PMCID: PMC4453788 DOI: 10.1104/pp.15.00319] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Accepted: 04/24/2015] [Indexed: 05/17/2023]
Abstract
Although microalgae accumulate triacylglycerol (TAG) and starch in response to nutrient-deficient conditions, the regulatory mechanisms are poorly understood. We report here the identification and characterization of a kinase, triacylglycerol accumulation regulator1 (TAR1), that is a member of the yeast (Saccharomyces cerevisiae) Yet another kinase1 (Yak1) subfamily in the dual-specificity tyrosine phosphorylation-regulated kinase family in a green alga (Chlamydomonas reinhardtii). The kinase domain of TAR1 showed auto- and transphosphorylation activities. A TAR1-defective mutant, tar1-1, accumulated TAG to levels 0.5- and 0.1-fold of those of a wild-type strain in sulfur (S)- and nitrogen (N)-deficient conditions, respectively. In N-deficient conditions, tar1-1 showed more pronounced arrest of cell division than the wild type, had increased cell size and cell dry weight, and maintained chlorophyll and photosynthetic activity, which were not observed in S-deficient conditions. In N-deficient conditions, global changes in expression levels of N deficiency-responsive genes in N assimilation and tetrapyrrole metabolism were noted between tar1-1 and wild-type cells. These results indicated that TAR1 is a regulator of TAG accumulation in S- and N-deficient conditions, and it functions in cell growth and repression of photosynthesis in conditions of N deficiency.
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Affiliation(s)
- Masataka Kajikawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Yuri Sawaragi
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Haruka Shinkawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Takashi Yamano
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Akira Ando
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Misako Kato
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Masafumi Hirono
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Naoki Sato
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
| | - Hideya Fukuzawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan (Ma.K., Y.S., H.S., T.Y., H.F.);Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan (A.A., Mi.K.);Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan (M.H.); andGraduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan (N.S.)
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131
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Jinkerson RE, Jonikas MC. Molecular techniques to interrogate and edit the Chlamydomonas nuclear genome. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:393-412. [PMID: 25704665 DOI: 10.1111/tpj.12801] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/13/2015] [Accepted: 02/16/2015] [Indexed: 05/23/2023]
Abstract
The success of the green alga Chlamydomonas reinhardtii as a model organism is to a large extent due to the wide range of molecular techniques that are available for its characterization. Here, we review some of the techniques currently used to modify and interrogate the C. reinhardtii nuclear genome and explore several technologies under development. Nuclear mutants can be generated with ultraviolet (UV) light and chemical mutagens, or by insertional mutagenesis. Nuclear transformation methods include biolistic delivery, agitation with glass beads, and electroporation. Transforming DNA integrates into the genome at random sites, and multiple strategies exist for mapping insertion sites. A limited number of studies have demonstrated targeted modification of the nuclear genome by approaches such as zinc-finger nucleases and homologous recombination. RNA interference is widely used to knock down expression levels of nuclear genes. A wide assortment of transgenes has been successfully expressed in the Chlamydomonas nuclear genome, including transformation markers, fluorescent proteins, reporter genes, epitope tagged proteins, and even therapeutic proteins. Optimized expression constructs and strains help transgene expression. Emerging technologies such as the CRISPR/Cas9 system, high-throughput mutant identification, and a whole-genome knockout library are being developed for this organism. We discuss how these advances will propel future investigations.
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Affiliation(s)
- Robert E Jinkerson
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA, 94305, USA
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA, 94305, USA
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132
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Li-Beisson Y, Beisson F, Riekhof W. Metabolism of acyl-lipids in Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:504-522. [PMID: 25660108 DOI: 10.1111/tpj.12787] [Citation(s) in RCA: 156] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Revised: 01/24/2015] [Accepted: 02/02/2015] [Indexed: 05/03/2023]
Abstract
Microalgae are emerging platforms for production of a suite of compounds targeting several markets, including food, nutraceuticals, green chemicals, and biofuels. Many of these products, such as biodiesel or polyunsaturated fatty acids (PUFAs), derive from lipid metabolism. A general picture of lipid metabolism in microalgae has been deduced from well characterized pathways of fungi and land plants, but recent advances in molecular and genetic analyses of microalgae have uncovered unique features, pointing out the necessity to study lipid metabolism in microalgae themselves. In the past 10 years, in addition to its traditional role as a model for photosynthetic and flagellar motility processes, Chlamydomonas reinhardtii has emerged as a model organism to study lipid metabolism in green microalgae. Here, after summarizing data on total fatty acid composition, distribution of acyl-lipid classes, and major acyl-lipid molecular species found in C. reinhardtii, we review the current knowledge on the known or putative steps for fatty acid synthesis, glycerolipid desaturation and assembly, membrane lipid turnover, and oil remobilization. A list of characterized or putative enzymes for the major steps of acyl-lipid metabolism in C. reinhardtii is included, and subcellular localizations and phenotypes of associated mutants are discussed. Biogenesis and composition of Chlamydomonas lipid droplets and the potential importance of lipolytic processes in increasing cellular oil content are also highlighted.
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Affiliation(s)
- Yonghua Li-Beisson
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, 13108, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique (CNRS), 13108, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR 7265, 13284, Marseille, France
| | - Fred Beisson
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Institut de Biologie Environnementale et Biotechnologie, CEA Cadarache, 13108, Saint-Paul-lez-Durance, France
- Centre National de la Recherche Scientifique (CNRS), 13108, Saint-Paul-lez-Durance, France
- Aix-Marseille Université, UMR 7265, 13284, Marseille, France
| | - Wayne Riekhof
- School of Biological Sciences and Center for Biological Chemistry, University of Nebraska - Lincoln, Lincoln, NE, 68588, USA
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133
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Transgressive, reiterative selection by continuous buoyant density gradient centrifugation of Dunaliella salina results in enhanced lipid and starch content. ALGAL RES 2015. [DOI: 10.1016/j.algal.2015.03.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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134
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Scranton MA, Ostrand JT, Fields FJ, Mayfield SP. Chlamydomonas as a model for biofuels and bio-products production. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:523-531. [PMID: 25641390 PMCID: PMC5531182 DOI: 10.1111/tpj.12780] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/08/2015] [Accepted: 01/12/2015] [Indexed: 05/18/2023]
Abstract
Developing renewable energy sources is critical to maintaining the economic growth of the planet while protecting the environment. First generation biofuels focused on food crops like corn and sugarcane for ethanol production, and soybean and palm for biodiesel production. Second generation biofuels based on cellulosic ethanol produced from terrestrial plants, has received extensive funding and recently pilot facilities have been commissioned, but to date output of fuels from these sources has fallen well short of what is needed. Recent research and pilot demonstrations have highlighted the potential of algae as one of the most promising sources of sustainable liquid transportation fuels. Algae have also been established as unique biofactories for industrial, therapeutic, and nutraceutical co-products. Chlamydomonas reinhardtii's long established role in the field of basic research in green algae has paved the way for understanding algal metabolism and developing genetic engineering protocols. These tools are now being utilized in C. reinhardtii and in other algal species for the development of strains to maximize biofuels and bio-products yields from the lab to the field.
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135
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Gu H, Nagle N, Pienkos PT, Posewitz MC. Nitrogen recycling from fuel-extracted algal biomass: residuals as the sole nitrogen source for culturing Scenedesmus acutus. BIORESOURCE TECHNOLOGY 2015; 184:153-160. [PMID: 25539998 DOI: 10.1016/j.biortech.2014.11.095] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 11/21/2014] [Accepted: 11/24/2014] [Indexed: 05/18/2023]
Abstract
In this study, the reuse of nitrogen from fuel-extracted algal residues was investigated. The alga Scenedesmus acutus was found to be able to assimilate nitrogen contained in amino acids, yeast extracts, and proteinaceous alga residuals. Moreover, these alternative nitrogen resources could replace nitrate in culturing media. The ability of S. acutus to utilize the nitrogen remaining in processed algal biomass was unique among the promising biofuel strains tested. This alga was leveraged in a recycling approach where nitrogen is recovered from algal biomass residuals that remain after lipids are extracted and carbohydrates are fermented to ethanol. The protein-rich residuals not only provided an effective nitrogen resource, but also contributed to a carbon "heterotrophic boost" in subsequent culturing, improving overall biomass and lipid yields relative to the control medium with only nitrate. Prior treatment of the algal residues with Diaion HP20 resin was required to remove compounds inhibitory to algal growth.
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Affiliation(s)
- Huiya Gu
- Department of Chemistry and Geochemistry, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, USA
| | - Nick Nagle
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
| | - Philip T Pienkos
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
| | - Matthew C Posewitz
- Department of Chemistry and Geochemistry, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, USA.
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136
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Sarkar D, Shimizu K. An overview on biofuel and biochemical production by photosynthetic microorganisms with understanding of the metabolism and by metabolic engineering together with efficient cultivation and downstream processing. BIORESOUR BIOPROCESS 2015. [DOI: 10.1186/s40643-015-0045-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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137
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Hu G, Ji S, Yu Y, Wang S, Zhou G, Li F. Organisms for biofuel production: natural bioresources and methodologies for improving their biosynthetic potentials. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2015; 147:185-224. [PMID: 24085385 DOI: 10.1007/10_2013_245] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
In order to relieve the pressure of energy supply and environment contamination that humans are facing, there are now intensive worldwide efforts to explore natural bioresources for production of energy storage compounds, such as lipids, alcohols, hydrocarbons, and polysaccharides. Around the world, many plants have been evaluated and developed as feedstock for bioenergy production, among which several crops have successfully achieved industrialization. Microalgae are another group of photosynthetic autotroph of interest due to their superior growth rates, relatively high photosynthetic conversion efficiencies, and vast metabolic capabilities. Heterotrophic microorganisms, such as yeast and bacteria, can utilize carbohydrates from lignocellulosic biomass directly or after pretreatment and enzymatic hydrolysis to produce liquid biofuels such as ethanol and butanol. Although finding a suitable organism for biofuel production is not easy, many naturally occurring organisms with good traits have recently been obtained. This review mainly focuses on the new organism resources discovered in the last 5 years for production of transport fuels (biodiesel, gasoline, jet fuel, and alkanes) and hydrogen, and available methods to improve natural organisms as platforms for the production of biofuels.
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Affiliation(s)
- Guangrong Hu
- Shandong Provincial Key Laboratory of Energy Genetics, Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
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138
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Krishnan A, Kumaraswamy GK, Vinyard DJ, Gu H, Ananyev G, Posewitz MC, Dismukes GC. Metabolic and photosynthetic consequences of blocking starch biosynthesis in the green alga Chlamydomonas reinhardtii sta6 mutant. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 81:947-60. [PMID: 25645872 DOI: 10.1111/tpj.12783] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 05/20/2023]
Abstract
Upon nutrient deprivation, microalgae partition photosynthate into starch and lipids at the expense of protein synthesis and growth. We investigated the role of starch biosynthesis with respect to photosynthetic growth and carbon partitioning in the Chlamydomonas reinhardtii starchless mutant, sta6, which lacks ADP-glucose pyrophosphorylase. This mutant is unable to convert glucose-1-phosphate to ADP-glucose, the precursor of starch biosynthesis. During nutrient-replete culturing, sta6 does not re-direct metabolism to make more proteins or lipids, and accumulates 20% less biomass. The underlying molecular basis for the decreased biomass phenotype was identified using LC-MS metabolomics studies and flux methods. Above a threshold light intensity, photosynthetic electron transport rates (water → CO2) decrease in sta6 due to attenuated rates of NADPH re-oxidation, without affecting photosystems I or II (no change in isolated photosynthetic electron transport). We observed large accumulations of carbon metabolites that are precursors for the biosynthesis of lipids, amino acids and sugars/starch, indicating system-wide consequences of slower NADPH re-oxidation. Attenuated carbon fixation resulted in imbalances in both redox and adenylate energy. The pool sizes of both pyridine and adenylate nucleotides in sta6 increased substantially to compensate for the slower rate of turnover. Mitochondrial respiration partially relieved the reductant stress; however, prolonged high-light exposure caused accelerated photoinhibition. Thus, starch biosynthesis in Chlamydomonas plays a critical role as a principal carbon sink influencing cellular energy balance however, disrupting starch biosynthesis does not redirect resources to other bioproducts (lipids or proteins) during nutrient-replete culturing, resulting in cells that are susceptible to photochemical damage caused by redox stress.
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Affiliation(s)
- Anagha Krishnan
- Waksman Institute of Microbiology, Rutgers: The State University of New Jersey, Piscataway, NJ, 08854, USA
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139
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Li T, Gargouri M, Feng J, Park JJ, Gao D, Miao C, Dong T, Gang DR, Chen S. Regulation of starch and lipid accumulation in a microalga Chlorella sorokiniana. BIORESOURCE TECHNOLOGY 2015; 180:250-7. [PMID: 25616239 DOI: 10.1016/j.biortech.2015.01.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 12/29/2014] [Accepted: 01/03/2015] [Indexed: 05/06/2023]
Abstract
Microalgae have attracted growing attention due to their potential in biofuel feedstock production. However, current understanding of the regulatory mechanisms for lipid biosynthesis and storage in microalgae is still limited. This study revealed that the microalga Chlorella sorokiniana showed sequential accumulation of starch and lipids. When nitrogen was replete and/or depleted over a short period, starch was the predominant carbon storage form with basal levels of lipid accumulation. After prolonged nitrogen depletion, lipid accumulation increased considerably, which was partially due to starch degradation, as well as the turnover of primary metabolites. Lipid accumulation is also strongly dependent on the linear electron flow of photosynthesis, peaking at lower light intensities. Collectively, this study reveals a relatively clear regulation pattern of starch and lipid accumulation that is basically controlled by nitrogen levels. The mixotrophic growth of C. sorokiniana shows promise for biofuel production in terms of lipid accumulation in the final biomass.
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Affiliation(s)
- Tingting Li
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
| | - Mahmoud Gargouri
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6120, USA
| | - Jie Feng
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Jeong-Jin Park
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6120, USA
| | - Difeng Gao
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
| | - Chao Miao
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
| | - Tao Dong
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
| | - David R Gang
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6120, USA
| | - Shulin Chen
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA.
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140
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Juergens MT, Deshpande RR, Lucker BF, Park JJ, Wang H, Gargouri M, Holguin FO, Disbrow B, Schaub T, Skepper JN, Kramer DM, Gang DR, Hicks LM, Shachar-Hill Y. The regulation of photosynthetic structure and function during nitrogen deprivation in Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 2015; 167:558-73. [PMID: 25489023 PMCID: PMC4326741 DOI: 10.1104/pp.114.250530] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 12/01/2014] [Indexed: 05/19/2023]
Abstract
The accumulation of carbon storage compounds by many unicellular algae after nutrient deprivation occurs despite declines in their photosynthetic apparatus. To understand the regulation and roles of photosynthesis during this potentially bioenergetically valuable process, we analyzed photosynthetic structure and function after nitrogen deprivation in the model alga Chlamydomonas reinhardtii. Transcriptomic, proteomic, metabolite, and lipid profiling and microscopic time course data were combined with multiple measures of photosynthetic function. Levels of transcripts and proteins of photosystems I and II and most antenna genes fell with differing trajectories; thylakoid membrane lipid levels decreased, while their proportions remained similar and thylakoid membrane organization appeared to be preserved. Cellular chlorophyll (Chl) content decreased more than 2-fold within 24 h, and we conclude from transcript protein and (13)C labeling rates that Chl synthesis was down-regulated both pre- and posttranslationally and that Chl levels fell because of a rapid cessation in synthesis and dilution by cellular growth rather than because of degradation. Photosynthetically driven oxygen production and the efficiency of photosystem II as well as P700(+) reduction and electrochromic shift kinetics all decreased over the time course, without evidence of substantial energy overflow. The results also indicate that linear electron flow fell approximately 15% more than cyclic flow over the first 24 h. Comparing Calvin-Benson cycle transcript and enzyme levels with changes in photosynthetic (13)CO2 incorporation rates also pointed to a coordinated multilevel down-regulation of photosynthetic fluxes during starch synthesis before the induction of high triacylglycerol accumulation rates.
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Affiliation(s)
- Matthew T Juergens
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Rahul R Deshpande
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Ben F Lucker
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Jeong-Jin Park
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Hongxia Wang
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Mahmoud Gargouri
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - F Omar Holguin
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Bradley Disbrow
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Tanner Schaub
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Jeremy N Skepper
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - David M Kramer
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - David R Gang
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Leslie M Hicks
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
| | - Yair Shachar-Hill
- Department of Plant Biology (M.T.J., R.R.D., B.D., Y.S.-H.) and Plant Research Laboratory (M.T.J., B.F.L., D.M.K.), Michigan State University, East Lansing, Michigan 48824;Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 (J.-J.P., M.G., D.R.G.);Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (H.W., L.M.H.);National Center of Biomedical Analysis, Beijing 100850, China (H.W.);College of Agricultural, Consumer, and Environmental Sciences, New Mexico State University, Las Cruces, New Mexico 88003 (F.O.H., T.S.);Department of Physiology, Cambridge Advanced Imaging Centre, Cambridge CB2 3DY, United Kingdom (J.N.S.); andDepartment of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599 (L.M.H.)
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141
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Park JJ, Wang H, Gargouri M, Deshpande RR, Skepper JN, Holguin FO, Juergens MT, Shachar-Hill Y, Hicks LM, Gang DR. The response of Chlamydomonas reinhardtii to nitrogen deprivation: a systems biology analysis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 81:611-24. [PMID: 25515814 DOI: 10.1111/tpj.12747] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 12/04/2014] [Accepted: 12/09/2014] [Indexed: 05/18/2023]
Abstract
Drastic alteration in macronutrients causes large changes in gene expression in the photosynthetic unicellular alga Chlamydomonas reinhardtii. Preliminary data suggested that cells follow a biphasic response to this change hinging on the initiation of lipid accumulation, and we hypothesized that drastic repatterning of metabolism also followed this biphasic modality. To test this hypothesis, transcriptomic, proteomic, and metabolite changes that occur under nitrogen (N) deprivation were analyzed. Eight sampling times were selected covering the progressive slowing of growth and induction of oil synthesis between 4 and 6 h after N deprivation. Results of the combined, systems-level investigation indicated that C. reinhardtii cells sense and respond on a large scale within 30 min to a switch to N-deprived conditions turning on a largely gluconeogenic metabolic state, which then transitions to a glycolytic stage between 4 and 6 h after N depletion. This nitrogen-sensing system is transduced to carbon- and nitrogen-responsive pathways, leading to down-regulation of carbon assimilation and chlorophyll biosynthesis, and an increase in nitrogen metabolism and lipid biosynthesis. For example, the expression of nearly all the enzymes for assimilating nitrogen from ammonium, nitrate, nitrite, urea, formamide/acetamide, purines, pyrimidines, polyamines, amino acids and proteins increased significantly. Although arginine biosynthesis enzymes were also rapidly up-regulated, arginine pool size changes and isotopic labeling results indicated no increased flux through this pathway.
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Affiliation(s)
- Jeong-Jin Park
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
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142
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Jia J, Han D, Gerken HG, Li Y, Sommerfeld M, Hu Q, Xu J. Molecular mechanisms for photosynthetic carbon partitioning into storage neutral lipids in Nannochloropsis oceanica under nitrogen-depletion conditions. ALGAL RES 2015. [DOI: 10.1016/j.algal.2014.11.005] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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143
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Terashima M, Freeman ES, Jinkerson RE, Jonikas MC. A fluorescence-activated cell sorting-based strategy for rapid isolation of high-lipid Chlamydomonas mutants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 81:147-59. [PMID: 25267488 PMCID: PMC4280329 DOI: 10.1111/tpj.12682] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 08/22/2014] [Accepted: 09/19/2014] [Indexed: 05/22/2023]
Abstract
There is significant interest in farming algae for the direct production of biofuels and valuable lipids. Chlamydomonas reinhardtii is the leading model system for studying lipid metabolism in green algae, but current methods for isolating mutants of this organism with a perturbed lipid content are slow and tedious. Here, we present the Chlamydomonas high-lipid sorting (CHiLiS) strategy, which enables enrichment of high-lipid mutants by fluorescence-activated cell sorting (FACS) of pooled mutants stained with the lipid-sensitive dye Nile Red. This method only takes 5 weeks from mutagenesis to mutant isolation. We developed a staining protocol that allows quantification of lipid content while preserving cell viability. We improved separation of high-lipid mutants from the wild type by using each cell's chlorophyll fluorescence as an internal control. We initially demonstrated 20-fold enrichment of the known high-lipid mutant sta1 from a mixture of sta1 and wild-type cells. We then applied CHiLiS to sort thousands of high-lipid cells from a pool of about 60,000 mutants. Flow cytometry analysis of 24 individual mutants isolated by this approach revealed that about 50% showed a reproducible high-lipid phenotype. We further characterized nine of the mutants with the highest lipid content by flame ionization detection and mass spectrometry lipidomics. All mutants analyzed had a higher triacylglycerol content and perturbed whole-cell fatty acid composition. One arbitrarily chosen mutant was evaluated by microscopy, revealing larger lipid droplets than the wild type. The unprecedented throughput of CHiLiS opens the door to a systems-level understanding of green algal lipid biology by enabling genome-saturating isolation of mutants in key genes.
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Affiliation(s)
- Mia Terashima
- Department of Plant Biology, Carnegie Institution for Science260 Panama Street, Stanford, CA, 94305, USA
| | - Elizabeth S Freeman
- Department of Plant Biology, Carnegie Institution for Science260 Panama Street, Stanford, CA, 94305, USA
- Department of Biology, Stanford UniversityStanford, CA, 94305, USA
| | - Robert E Jinkerson
- Department of Plant Biology, Carnegie Institution for Science260 Panama Street, Stanford, CA, 94305, USA
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science260 Panama Street, Stanford, CA, 94305, USA
- *For correspondence (e-mail )
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144
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Hadady H, Wong JJ, Hiibel SR, Redelman D, Geiger EJ. High frequency dielectrophoretic response of microalgae over time. Electrophoresis 2014; 35:3533-40. [PMID: 25229637 PMCID: PMC4526272 DOI: 10.1002/elps.201400306] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 08/28/2014] [Accepted: 09/03/2014] [Indexed: 11/09/2022]
Abstract
The high frequency dielectrophoresis (>20 MHz) response of microalgae cells with different lipid content was monitored over time. Chlamydomonas reinhardtii was cultured in regular medium and under nitrogen-depleted conditions in order to produce populations of cells with low and high lipid content, respectively. The electrical conductivity of the culture media was also monitored over the same time. The upper crossover frequency decreased for high-lipid cells over time. The single-shell model predicts that the upper crossover frequency is dictated primarily by the dielectric properties of the cytoplasm. The high frequency DEP response of the high-lipid cells' cytoplasm was changed by lipid accumulation. DEP response of the low-lipid cells also varied with the conductivity of the culture media due to nutrient consumption. Relative lipid content was estimated with BODIPY 505/515 dye by calculating the area-weighted intensity average of fluorescent images. Finally, microalgae cells were successfully separated based on lipid content at 41 MHz and DEP media conductivity 106 ± 1 μS/cm.
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Affiliation(s)
- Hanieh Hadady
- Mechanical Eng. Department, University of Nevada, Reno, USA
| | | | - Sage R. Hiibel
- Civil and Environmental Eng. Department, University of Nevada, Reno, USA
| | - Doug Redelman
- Physiology & Cell Biology Molecular Bioscience, University of Nevada, School of Medicine Reno, USA
| | - Emil J. Geiger
- Mechanical Eng. Department, University of Nevada, Reno, USA
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145
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Shtaida N, Khozin-Goldberg I, Solovchenko A, Chekanov K, Didi-Cohen S, Leu S, Cohen Z, Boussiba S. Downregulation of a putative plastid PDC E1α subunit impairs photosynthetic activity and triacylglycerol accumulation in nitrogen-starved photoautotrophic Chlamydomonas reinhardtii. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:6563-76. [PMID: 25210079 PMCID: PMC4246187 DOI: 10.1093/jxb/eru374] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The chloroplast pyruvate dehydrogenase complex (cpPDC) catalyses the oxidative decarboxylation of pyruvate forming acetyl-CoA, an immediate primer for the initial reactions of de novo fatty acid (FA) synthesis. Little is known about the source of acetyl-CoA in the chloroplasts of photosynthetic microalgae, which are capable of producing high amounts of the storage lipid triacylglycerol (TAG) under conditions of nutrient stresses. We generated Chlamydomonas reinhardtii CC-1618 mutants with decreased expression of the PDC2_E1α gene, encoding the putative chloroplast pyruvate dehydrogenase subunit E1α, using artificial microRNA. A comparative study on the effects of PDC2_E1α silencing on FAs and TAG production in C. reinhardtii, grown photoautotrophically and mixotrophically, with and without a nitrogen source in the nutrient medium, was carried out. Reduced expression of PDC2 _E1α led to a severely hampered photoautotrophic growth phenotype with drastic impairment in TAG accumulation under nitrogen deprivation. In the presence of acetate, downregulation of PDC2_E1α exerted little to no effect on TAG production and photosynthetic activity. In contrast, under photoautotrophic conditions, especially in the absence of a nitrogen source, a dramatic decline in photosynthetic oxygen evolution and photosystem II quantum yield against a background of the apparent over-reduction of the photosynthetic electron chain was recorded. Our results suggest an essential role of cpPDC in the supply of carbon precursors for de novo FA synthesis in microalgae under conditions of photoautotrophy. A shortage of this supply is detrimental to the nitrogen-starvation-induced synthesis of storage TAG, an important carbon and energy sink in stressed Chlamydomonas cells, thereby impairing the acclimation ability of the microalga.
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Affiliation(s)
- Nastassia Shtaida
- Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
| | - Inna Khozin-Goldberg
- Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
| | - Alexei Solovchenko
- Department of Bioengineering, Faculty of Biology, Moscow State University, 119234, GSP-1 Moscow, Russia
| | - Konstantin Chekanov
- Department of Bioengineering, Faculty of Biology, Moscow State University, 119234, GSP-1 Moscow, Russia
| | - Shoshana Didi-Cohen
- Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
| | - Stefan Leu
- Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
| | - Zvi Cohen
- Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
| | - Sammy Boussiba
- Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
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146
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Bellou S, Baeshen MN, Elazzazy AM, Aggeli D, Sayegh F, Aggelis G. Microalgal lipids biochemistry and biotechnological perspectives. Biotechnol Adv 2014; 32:1476-93. [PMID: 25449285 DOI: 10.1016/j.biotechadv.2014.10.003] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Revised: 10/02/2014] [Accepted: 10/06/2014] [Indexed: 01/05/2023]
Abstract
In the last few years, there has been an intense interest in using microalgal lipids in food, chemical and pharmaceutical industries and cosmetology, while a noteworthy research has been performed focusing on all aspects of microalgal lipid production. This includes basic research on the pathways of solar energy conversion and on lipid biosynthesis and catabolism, and applied research dealing with the various biological and technical bottlenecks of the lipid production process. In here, we review the current knowledge in microalgal lipids with respect to their metabolism and various biotechnological applications, and we discuss potential future perspectives. The committing step in fatty acid biosynthesis is the carboxylation of acetyl-CoA to form malonyl-CoA that is then introduced in the fatty acid synthesis cycle leading to the formation of palmitic and stearic acids. Oleic acid may also be synthesized after stearic acid desaturation while further conversions of the fatty acids (i.e. desaturations, elongations) occur after their esterification with structural lipids of both plastids and the endoplasmic reticulum. The aliphatic chains are also used as building blocks for structuring storage acylglycerols via the Kennedy pathway. Current research, aiming to enhance lipogenesis in the microalgal cell, is focusing on over-expressing key-enzymes involved in the earlier steps of the pathway of fatty acid synthesis. A complementary plan would be the repression of lipid catabolism by down-regulating acylglycerol hydrolysis and/or β-oxidation. The tendency of oleaginous microalgae to synthesize, apart from lipids, significant amounts of other energy-rich compounds such as sugars, in processes competitive to lipogenesis, deserves attention since the lipid yield may be considerably increased by blocking competitive metabolic pathways. The majority of microalgal production occurs in outdoor cultivation and for this reason biotechnological applications face some difficulties. Therefore, algal production systems need to be improved and harvesting systems need to be more effective in order for their industrial applications to become more competitive and economically viable. Besides, a reduction of the production cost of microalgal lipids can be achieved by combining lipid production with other commercial applications. The combined production of bioactive products and lipids, when possible, can support the commercial viability of both processes. Hydrophobic compounds can be extracted simultaneously with lipids and then purified, while hydrophilic compounds such as proteins and sugars may be extracted from the defatted biomass. The microalgae also have applications in environmental biotechnology since they can be used for bioremediation of wastewater and to monitor environmental toxicants. Algal biomass produced during wastewater treatment may be further valorized in the biofuel manufacture. It is anticipated that the high microalgal lipid potential will force research towards finding effective ways to manipulate biochemical pathways involved in lipid biosynthesis and towards cost effective algal cultivation and harvesting systems, as well.
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Affiliation(s)
- Stamatia Bellou
- Division of Genetics, Cell & Development Biology, Department of Biology, University of Patras, Patras 26504, Greece
| | - Mohammed N Baeshen
- Department of Biological Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Ahmed M Elazzazy
- Department of Biological Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Department of Chemistry of Natural and Microbial Products, National Research Centre, Dokki 12622, Giza, Egypt
| | - Dimitra Aggeli
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Fotoon Sayegh
- Department of Biological Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - George Aggelis
- Division of Genetics, Cell & Development Biology, Department of Biology, University of Patras, Patras 26504, Greece; Department of Biological Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
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147
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Whan A, Dielen AS, Mieog J, Bowerman AF, Robinson HM, Byrne K, Colgrave M, Larkin PJ, Howitt CA, Morell MK, Ral JP. Engineering α-amylase levels in wheat grain suggests a highly sophisticated level of carbohydrate regulation during development. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:5443-57. [PMID: 25053646 PMCID: PMC4157717 DOI: 10.1093/jxb/eru299] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 06/12/2014] [Accepted: 06/15/2014] [Indexed: 05/20/2023]
Abstract
Wheat starch degradation requires the synergistic action of different amylolytic enzymes. Our spatio-temporal study of wheat α-amylases throughout grain development shows that AMY3 is the most abundant isoform compared with the other known α-amylases. Endosperm-specific over-expression of AMY3 resulted in an increase of total α-amylase activity in harvested grains. Unexpectedly, increased activity did not have a significant impact on starch content or composition but led to an increase of soluble carbohydrate (mainly sucrose) in dry grain. In AMY3 overexpression lines (A3OE), germination was slightly delayed and triacylglycerol (TAG) content was increased in the endosperm of mature grain. Despite increased AMY3 transcript and protein content throughout grain development, alterations of α-amylase activity and starch granule degradation were not detected until grain maturation, suggesting a post-translational inhibition of α-amylase activity in the endosperm during the starch filling period. These findings show unexpected effects of a high level of α-amylase on grain development and composition, notably in carbon partitioning and TAG accumulation, and suggest the presence of a hitherto unknown regulatory pathway during grain filling.
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Affiliation(s)
- Alex Whan
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia
| | - Anne-Sophie Dielen
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia. Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Jos Mieog
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia
| | - Andrew F Bowerman
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia. Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Hannah M Robinson
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia. Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Keren Byrne
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia. CSIRO Animal, Food and Health Sciences, St Lucia, Queensland, Australia
| | - Michelle Colgrave
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia. CSIRO Animal, Food and Health Sciences, St Lucia, Queensland, Australia
| | - Philip J Larkin
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia. CSIRO Plant Industry, GPO Box 1600, Canberra ACT 2601 Australia
| | - Crispin A Howitt
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia
| | - Matthew K Morell
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia
| | - Jean-Philippe Ral
- CSIRO Food Futures National Research Flagship, GPO Box 1600, Canberra ACT 2601 Australia.
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148
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Acetate and bicarbonate assimilation and metabolite formation in Chlamydomonas reinhardtii: a 13C-NMR study. PLoS One 2014; 9:e106457. [PMID: 25207648 PMCID: PMC4160175 DOI: 10.1371/journal.pone.0106457] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 07/30/2014] [Indexed: 12/28/2022] Open
Abstract
Cellular metabolite analyses by 13C-NMR showed that C. reinhardtii cells assimilate acetate at a faster rate in heterotrophy than in mixotrophy. While heterotrophic cells produced bicarbonate and CO2aq, mixotrophy cells produced bicarbonate alone as predominant metabolite. Experiments with singly 13C-labelled acetate (13CH3-COOH or CH3-13COOH) supported that both the 13C nuclei give rise to bicarbonate and CO2aq. The observed metabolite(s) upon further incubation led to the production of starch and triacylglycerol (TAG) in mixotrophy, whereas in heterotrophy the TAG production was minimal with substantial accumulation of glycerol and starch. Prolonged incubation up to eight days, without the addition of fresh acetate, led to an increased TAG production at the expense of bicarbonate, akin to that of nitrogen-starvation. However, such TAG production was substantially high in mixotrophy as compared to that in heterotrophy. Addition of mitochondrial un-coupler blocked the formation of bicarbonate and CO2aq in heterotrophic cells, even though acetate uptake ensued. Addition of PSII-inhibitor to mixotrophic cells resulted in partial conversion of bicarbonate into CO2aq, which were found to be in equilibrium. In an independent experiment, we have monitored assimilation of bicarbonate via photoautotrophy and found that the cells indeed produce starch and TAG at a much faster rate as compared to that in mixotrophy and heterotrophy. Further, we noticed that the accumulation of starch is relatively more as compared to TAG. Based on these observations, we suggest that acetate assimilation in C. reinhardtii does not directly lead to TAG formation but via bicarbonate/CO2aq pathways. Photoautotrophic mode is found to be the best growth condition for the production of starch and TAG and starch in C. reinhardtii.
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149
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Xie B, Stessman D, Hart JH, Dong H, Wang Y, Wright DA, Nikolau BJ, Spalding MH, Halverson LJ. High-throughput fluorescence-activated cell sorting for lipid hyperaccumulating Chlamydomonas reinhardtii mutants. PLANT BIOTECHNOLOGY JOURNAL 2014; 12:872-82. [PMID: 24702864 DOI: 10.1111/pbi.12190] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 01/03/2014] [Accepted: 02/26/2014] [Indexed: 05/16/2023]
Abstract
The genetically tractable microalga Chlamydomonas reinhardtii has many advantages as a model for renewable bioproducts and/or biofuels production. However, one limitation of C. reinhardtii is its relatively low-lipid content compared with some other algal species. To overcome this limitation, we combined ethane methyl sulfonate mutagenesis with fluorescence-activated cell sorting (FACS) of cells stained with the lipophilic stain Nile Red to isolate lipid hyperaccumulating mutants of C. reinhardtii. By manipulating the FACS gates, we sorted mutagenized cells with extremely high Nile Red fluorescence signals that were rarely detected in nonmutagenized populations. This strategy successfully isolated several putative lipid hyperaccumulating mutants exhibiting 23% to 58% (dry weight basis) higher fatty acid contents than their progenitor strains. Significantly, for most mutants, nitrogen starvation was not required to attain high-lipid content nor was there a requirement for a deficiency in starch accumulation. Microscopy of Nile Red stained cells revealed that some mutants exhibit an increase in the number of lipid bodies, which correlated with TLC analysis of triacyglycerol content. Increased lipid content could also arise through increased biomass production. Collectively, our findings highlight the ability to enhance intracellular lipid accumulation in algae using random mutagenesis in conjunction with a robust FACS and lipid yield verification regime. Our lipid hyperaccumulating mutants could serve as a genetic resource for stacking additional desirable traits to further increase lipid production and for identifying genes contributing to lipid hyperaccumulation, without lengthy lipid-induction periods.
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Affiliation(s)
- Bo Xie
- Department of Plant Pathology & Microbiology, Iowa State University, Ames, IA, USA
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150
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Lim HS, Kim JYH, Kwak HS, Sim SJ. Integrated Microfluidic Platform for Multiple Processes from Microalgal Culture to Lipid Extraction. Anal Chem 2014; 86:8585-92. [DOI: 10.1021/ac502324c] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Hyun Seok Lim
- Department
of Chemical and
Biological Engineering, Korea University, Seoul, 136-713, Republic of Korea
| | - Jaoon Y. H. Kim
- Department
of Chemical and
Biological Engineering, Korea University, Seoul, 136-713, Republic of Korea
| | - Ho Seok Kwak
- Department
of Chemical and
Biological Engineering, Korea University, Seoul, 136-713, Republic of Korea
| | - Sang Jun Sim
- Department
of Chemical and
Biological Engineering, Korea University, Seoul, 136-713, Republic of Korea
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