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Vijayan J, Wase N, Liu K, Morse W, Zhang C, Riekhof WR. ROS-mediated thylakoid membrane remodeling and triacylglycerol biosynthesis under nitrogen starvation in the alga Chlorella sorokiniana. FRONTIERS IN PLANT SCIENCE 2024; 15:1418049. [PMID: 39040507 PMCID: PMC11261311 DOI: 10.3389/fpls.2024.1418049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 06/11/2024] [Indexed: 07/24/2024]
Abstract
Many microbes accumulate energy storage molecules such as triglycerides (TAG) and starch during nutrient limitation. In eukaryotic green algae grown under nitrogen-limiting conditions, triglyceride accumulation is coupled with chlorosis and growth arrest. In this study, we show that reactive oxygen species (ROS) actively accumulate during nitrogen limitation in the microalga Chlorella sorokiniana. Accumulation of ROS is mediated by the downregulation of genes encoding ROS-quenching enzymes, such as superoxide dismutases, catalase, peroxiredoxin, and glutathione peroxidase-like, and by the upregulation of enzymes involved in generating ROS, such as NADPH oxidase, xanthine oxidase, and amine oxidases. The expression of genes involved in ascorbate and glutathione metabolism is also affected under this condition. ROS accumulation contributes to the degradation of monogalactosyl diacylglycerol (MGDG) and thylakoid membrane remodeling, leading to chlorosis. Quenching ROS under nitrogen limitation reduces the degradation of MGDG and the accumulation of TAG. This work shows that ROS accumulation, membrane remodeling, and TAG accumulation under nitrogen limitation are intricately linked in the microalga C. sorokiniana.
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Affiliation(s)
- Jithesh Vijayan
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, United States
- Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Nishikant Wase
- PPD, part of ThermoFisher Scientific, Henrico, VA, United States
| | - Kan Liu
- Mayo Clinic, Rochester, MN, United States
| | - Wyatt Morse
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Chi Zhang
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
- Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Wayne R. Riekhof
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
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2
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Kong F, Blot C, Liu K, Kim M, Li-Beisson Y. Advances in algal lipid metabolism and their use to improve oil content. Curr Opin Biotechnol 2024; 87:103130. [PMID: 38579630 DOI: 10.1016/j.copbio.2024.103130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 03/24/2024] [Accepted: 03/25/2024] [Indexed: 04/07/2024]
Abstract
Microalgae are eukaryotic photosynthetic micro-organisms that convert CO2 into carbohydrates, lipids, and other valuable metabolites. They are considered promising chassis for the production of various bioproducts, including fatty acid-derived biofuels. However, algae-based biofuels are not yet commercially available, mainly because of their low yields and high production cost. Optimizing strains to improve lipid productivity using the principles of synthetic biology should help move forward. This necessitates developments in the following areas: (1) identification of molecular bricks (enzymes, transcription factors, regulatory proteins etc.); (2) development of genetic tools; and (3) availability of high-throughput phenotyping methods. Here, we highlight the most recent developments in some of these areas and provide examples of the use of genome editing tools to improve oil content.
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Affiliation(s)
- Fantao Kong
- MOE Key Laboratory of Bio-Intelligent Manufacturing, School of Bioengineering, Dalian University of Technology, Dalian 116024, Liaoning, China.
| | - Carla Blot
- Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, Saint Paul-Lez-Durance 13108, France
| | - Keqing Liu
- MOE Key Laboratory of Bio-Intelligent Manufacturing, School of Bioengineering, Dalian University of Technology, Dalian 116024, Liaoning, China
| | - Minjae Kim
- Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, Saint Paul-Lez-Durance 13108, France
| | - Yonghua Li-Beisson
- Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, Saint Paul-Lez-Durance 13108, France
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3
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Wang R, Li J, Zhang F, Miao X. Non-Tandem CCCH-Type Zinc-Finger Protein CpZF_CCCH1 Improves Fatty Acid Desaturation and Stress Tolerance in Chlamydomonas reinhardtii. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023. [PMID: 37910392 DOI: 10.1021/acs.jafc.3c05511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
The properties and nutritional value of microalgal bioproducts depend significantly on fatty acid desaturation, which is generally modulated by manipulating the culture conditions or associated gene expressions. Here, we investigated the role of CpZF_CCCH1, a non-tandem CCCH-type zinc-finger (non-TZF) protein, in elevating polyunsaturated fatty acid (PUFA) content (11.00-16.36%) in Chlamydomonas reinhardtii. Through lipidomic and flow cytometry analyses, we observed reduced triacylglycerol accumulation (7.01-21.15%) and elevated levels of membrane lipids containing PUFAs (7.81-46.18%) in C. reinhardtii overexpressing CpZF_CCCH1. Additionally, overexpression of nucleus-located CpZF_CCCH1 downregulated genes associated with triacylglycerol assembly and lipid turnover from 2.00- to 2.90-fold, likely by binding to GCN4 motif and promoter of 3-phosphate-glycerol acyltransferase. Furthermore, overexpression of CpZF_CCCH1 alleviated reactive oxygen species levels by 59.28-73.26% and enhanced stress tolerance under adverse conditions. These findings expanded the roles of non-TZF proteins in lipid metabolism, opening new avenues for metabolic engineering to enhance the nutritional value and stress tolerance of microalgae and agricultural crops.
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Affiliation(s)
- Rui Wang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
- Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Junhao Li
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
- Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Feng Zhang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
- Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiaoling Miao
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
- Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai 200240, China
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4
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Li X, Dong Y, Chen K, Perumal AB, Zhan Z, Gouda M, He Y. 13C-metabolic flux analysis of lipid accumulation in the green microalgae Tetradesmus obliquus under nitrogen deficiency stress. BIORESOURCE TECHNOLOGY 2023; 388:129740. [PMID: 37717702 DOI: 10.1016/j.biortech.2023.129740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/23/2023] [Accepted: 09/06/2023] [Indexed: 09/19/2023]
Abstract
Metabolic fluxes (MF) serve as the functional phenotypes of biochemical processes and are crucial to describe the distribution of precursors within metabolic networks. There is a lack of experimental observations for carbon flux towards lipids, which is important for biodiesel generation. Here, the accumulation of lipid, and MF in Tetradesmus obliquus under nitrogen deficiency stress (NF) using a 13C isotope tracer at different time intervals was investigated. The 13C based MF showed enhanced de novo synthesis of G3P and PEP, indicating increased carbon flux from CO2 into lipid synthesis. An increase in palmitic acid (3500 μmol/mg), linoleic acid (2100 μmol/mg), and oleic acid (2000 μmol/mg) was observed. The accumulation of C16:0 under NF was mainly related to de novo synthesis while C18:3 was accumulated through a non de novo pathway. Under NF stress, T. obliquus had higher flux in PPP and glycolysis pathway, together, it might provide more NADPH and substrate acetyl-CoA for fatty acid synthesis.
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Affiliation(s)
- Xiaoli Li
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Yulun Dong
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Kai Chen
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Anand Babu Perumal
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
| | - Zhihao Zhan
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Mostafa Gouda
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China; Department of Nutrition & Food Science, National Research Centre, Dokki, Giza 12622, Egypt
| | - Yong He
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
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Shitanaka T, Higa L, Bryson AE, Bertucci C, Vande Pol N, Lucker B, Khanal SK, Bonito G, Du ZY. Flocculation of oleaginous green algae with Mortierella alpina fungi. BIORESOURCE TECHNOLOGY 2023; 385:129391. [PMID: 37364649 DOI: 10.1016/j.biortech.2023.129391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 06/28/2023]
Abstract
Microalgae are promising sources of valuable bioproducts such as biofuels, food, and nutraceuticals. However, harvesting microalgae is challenging due to their small size and low biomass concentrations. To address this challenge, bio-flocculation of starchless mutants of Chlamydomonas reinhardtii (sta6/sta7) was investigated with Mortierella alpina, an oleaginous fungus with high concentrations of arachidonic acid (ARA). Triacylglycerides (TAG) reached 85 % of total lipids in sta6 and sta7 through a nitrogen regime. Scanning electron microscopy determined cell-wall attachment and extra polymeric substances (EPS) to be responsible for flocculation. An algal-fungal biomass ratio around 1:1 (three membranes) was optimal for bio-flocculation (80-85 % flocculation efficiency in 24 h). Nitrogen-deprived sta6/sta7 were flocculated with strains of M. alpina (NVP17b, NVP47, and NVP153) with aggregates exhibiting fatty acid profiles similar to C. reinhardtii, with ARA (3-10 % of total fatty acids). This study showcases M. alpina as a strong bio-flocculation candidate for microalgae and advances a mechanistic understanding of algal-fungal interaction.
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Affiliation(s)
- Ty Shitanaka
- Department of Molecular Biosciences & Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI 96822, United States
| | - Lauren Higa
- Department of Molecular Biosciences & Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI 96822, United States
| | - Abigail E Bryson
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, United States
| | - Conor Bertucci
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, United States
| | - Natalie Vande Pol
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, United States
| | - Ben Lucker
- Trait Biosciences, Los Alamos, NM 87544, United States
| | - Samir Kumar Khanal
- Department of Molecular Biosciences & Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI 96822, United States; Department of Civil and Environmental Engineering, University of Hawai'i at Mānoa, Honolulu, HI 96822, United States
| | - Gregory Bonito
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, United States.
| | - Zhi-Yan Du
- Department of Molecular Biosciences & Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI 96822, United States.
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6
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Hoffmann DY, Shachar-Hill Y. Do betaine lipids replace phosphatidylcholine as fatty acid editing hubs in microalgae? FRONTIERS IN PLANT SCIENCE 2023; 14:1077347. [PMID: 36743481 PMCID: PMC9892843 DOI: 10.3389/fpls.2023.1077347] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 01/04/2023] [Indexed: 06/18/2023]
Abstract
Acyl editing refers to a deacylation and reacylation cycle on a lipid, which allows for fatty acid desaturation and modification prior to being removed and incorporated into other pools. Acyl editing is an important determinant of glycerolipid synthesis and has been well-characterized in land plants, thus this review begins with an overview of acyl editing in plants. Much less is known about acyl editing in algae, including the extent to which acyl editing impacts lipid synthesis and on which lipid substrate(s) it occurs. This review compares what is known about acyl editing on its major hub phosphatidylcholine (PC) in land plants with the evidence for acyl editing of betaine lipids such as diacylglyceryltrimethylhomoserine (DGTS), the structural analog that replaces PC in several species of microalgae. In land plants, PC is also known to be a major source of fatty acids and diacylglycerol (DAG) for synthesis of the neutral lipid triacylglycerol (TAG). We review the evidence that DGTS contributes substantially to TAG accumulation in algae as a source of fatty acids, but not as a precursor to DAG. We conclude with evidence of acyl editing on other membrane lipid substrates in plants and algae apart from PC or DGTS, and discuss future analyses to elucidate the role of DGTS and other betaine lipids in acyl editing in microalgae.
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7
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Wang R, Miao X. Lipid turnover and SQUAMOSA promoter-binding proteins mediate variation in fatty acid desaturation under early nitrogen deprivation revealed by lipidomic and transcriptomic analyses in Chlorella pyrenoidosa. FRONTIERS IN PLANT SCIENCE 2022; 13:987354. [PMID: 36247620 PMCID: PMC9558234 DOI: 10.3389/fpls.2022.987354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 09/06/2022] [Indexed: 06/16/2023]
Abstract
Nitrogen deprivation induces variations in fatty acid desaturation in microalgae, which determines the performance of biodiesel and the nutritional value of bioproducts. However, the detailed scenario and the underlying regulatory mechanism remain unclear. In this study, we attempt to outline these scenario and mechanisms by performing biochemical, lipidomic, and transcriptomic analyses in Chlorella pyrenoidosa and functional characterization of transcription factors in Yarrowia lipolytica. We found that early nitrogen deprivation dramatically reduced fatty acid desaturation without increasing lipid content. The contents of palmitic acid (16:0) and oleic acid (18:1) dramatically increased to 2.14 and 2.87 times that of nitrogen repletion on the second day, respectively. Lipidomic analysis showed the transfer of polyunsaturated fatty acids from phospholipids and glycolipids to triacylglycerols, and an increase in lipid species with 16:0 or 18:1 under nitrogen deprivation conditions. Upregulated stearoyl-ACP desaturase and oleyl-ACP thioesterase promoted the synthesis of 18:1, but restricted acetyl-CoA supply revealed that it was the intensive lipid turnover instead of an attenuated Kennedy pathway that played an important role in the variation in fatty acid composition under early nitrogen deprivation. Finally, two differentially expressed SQUAMOSA promoter-binding proteins (SBPs) were heterologously expressed in Y. lipolytica, demonstrating their role in promoting the accumulation of total fatty acid and the reduction in fatty acid desaturation. These results revealed the crucial role of lipid turnover and SBPs in determining fatty acid desaturation under early nitrogen deprivation, opening new avenues for the metabolic engineering of fatty acid desaturation in microalgae.
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Affiliation(s)
- Rui Wang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai, China
- Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoling Miao
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
- Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai, China
- Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai, China
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8
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Kato N, McCuiston C, Szuska KA, Lauersen KJ, Nelson G, Strain A. Chlamydomonas reinhardtii Alternates Peroxisomal Contents in Response to Trophic Conditions. Cells 2022; 11:cells11172724. [PMID: 36078132 PMCID: PMC9454557 DOI: 10.3390/cells11172724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 08/23/2022] [Accepted: 08/29/2022] [Indexed: 11/16/2022] Open
Abstract
Chlamydomonas reinhardtii is a model green microalga capable of heterotrophic growth on acetic acid but not fatty acids, despite containing a full complement of genes for β-oxidation. Recent reports indicate that the alga preferentially sequesters, rather than breaks down, lipid acyl chains as a means to rebuild its membranes rapidly. Here, we assemble a list of potential Chlamydomonas peroxins (PEXs) required for peroxisomal biogenesis to suggest that C. reinhardtii has a complete set of peroxisome biogenesis factors. To determine involvements of the peroxisomes in the metabolism of exogenously added fatty acids, we examined transgenic C. reinhardtii expressing fluorescent proteins fused to N- or C-terminal peptide of peroxisomal proteins, concomitantly with fluorescently labeled palmitic acid under different trophic conditions. We used confocal microscopy to track the populations of the peroxisomes in illuminated and dark conditions, with and without acetic acid as a carbon source. In the cells, four major populations of compartments were identified, containing: (1) a glyoxylate cycle enzyme marker and a protein containing peroxisomal targeting signal 1 (PTS1) tripeptide but lacking the fatty acid marker, (2) the fatty acid marker alone, (3) the glyoxylate cycle enzyme marker alone, and (4) the PTS1 marker alone. Less than 5% of the compartments contained both fatty acid and peroxisomal markers. Statistical analysis on optically sectioned images found that C. reinhardtii simultaneously carries diverse populations of the peroxisomes in the cell and modulates peroxisomal contents based on light conditions. On the other hand, the ratio of the compartment containing both fatty acid and peroxisomal markers did not change significantly regardless of the culture conditions. The result indicates that β-oxidation may be only a minor occurrence in the peroxisomal population in C. reinhardtii, which supports the idea that lipid biosynthesis and not β-oxidation is the primary metabolic preference of fatty acids in the alga.
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Affiliation(s)
- Naohiro Kato
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
- Correspondence:
| | - Clayton McCuiston
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Kimberly A. Szuska
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Kyle J. Lauersen
- Bioengineering Program, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Gabela Nelson
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Alexis Strain
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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9
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Peter J, Huleux M, Spaniol B, Sommer F, Neunzig J, Schroda M, Li-Beisson Y, Philippar K. Fatty acid export (FAX) proteins contribute to oil production in the green microalga Chlamydomonas reinhardtii. Front Mol Biosci 2022; 9:939834. [PMID: 36120551 PMCID: PMC9470853 DOI: 10.3389/fmolb.2022.939834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 07/11/2022] [Indexed: 11/24/2022] Open
Abstract
In algae and land plants, transport of fatty acids (FAs) from their site of synthesis in the plastid stroma to the endoplasmic reticulum (ER) for assembly into acyl lipids is crucial for cellular lipid homeostasis, including the biosynthesis of triacylglycerol (TAG) for energy storage. In the unicellular green alga Chlamydomonas reinhardtii, understanding and engineering of these processes is of particular interest for microalga-based biofuel and biomaterial production. Whereas in the model plant Arabidopsis thaliana, FAX (fatty acid export) proteins have been associated with a function in plastid FA-export and hence TAG synthesis in the ER, the knowledge on the function and subcellular localization of this protein family in Chlamydomonas is still scarce. Among the four FAX proteins encoded in the Chlamydomonas genome, we found Cr-FAX1 and Cr-FAX5 to be involved in TAG production by functioning in chloroplast and ER membranes, respectively. By in situ immunolocalization, we show that Cr-FAX1 inserts into the chloroplast envelope, while Cr-FAX5 is located in ER membranes. Severe reduction of Cr-FAX1 or Cr-FAX5 proteins by an artificial microRNA approach results in a strong decrease of the TAG content in the mutant strains. Further, overexpression of chloroplast Cr-FAX1, but not of ER-intrinsic Cr-FAX5, doubled the content of TAG in Chlamydomonas cells. We therefore propose that Cr-FAX1 in chloroplast envelopes and Cr-FAX5 in ER membranes represent a basic set of FAX proteins to ensure shuttling of FAs from chloroplasts to the ER and are crucial for oil production in Chlamydomonas.
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Affiliation(s)
- Janick Peter
- Plant Biology, Center for Human- and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
| | - Marie Huleux
- Aix Marseille Univ, CEA, CNRS, Institute of Bioscience and Biotechnology of Aix Marseille, BIAM, Saint Paul-Lez-Durance, France
| | - Benjamin Spaniol
- Molecular Biotechnology and Systems Biology, TU Kaiserslautern, Kaiserslautern, Germany
| | - Frederik Sommer
- Molecular Biotechnology and Systems Biology, TU Kaiserslautern, Kaiserslautern, Germany
| | - Jens Neunzig
- Plant Biology, Center for Human- and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
| | - Michael Schroda
- Molecular Biotechnology and Systems Biology, TU Kaiserslautern, Kaiserslautern, Germany
| | - Yonghua Li-Beisson
- Aix Marseille Univ, CEA, CNRS, Institute of Bioscience and Biotechnology of Aix Marseille, BIAM, Saint Paul-Lez-Durance, France
| | - Katrin Philippar
- Plant Biology, Center for Human- and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
- *Correspondence: Katrin Philippar,
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10
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Bender ML, Zhu XG, Falkowski P, Ma F, Griffin K. On the rate of phytoplankton respiration in the light. PLANT PHYSIOLOGY 2022; 190:267-279. [PMID: 35652738 PMCID: PMC9434318 DOI: 10.1093/plphys/kiac254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
The rate of algal and cyanobacterial respiration in the light is an important ecophysiological term that remains to be completely characterized and quantified. To address this issue, we exploited process-specific decarboxylation rates from flux balance analysis and isotopically nonstationary metabolic flux analysis. Our study, based on published data, suggested that decarboxylation is about 22% of net CO2 assimilation when the tricarboxylic acid cycle is completely open (characterized by the commitment of alpha ketoglutarate to amino acid synthesis and very low rates of succinate formation). This estimate was supported by calculating the decarboxylation rates required to synthesize the major components of biomass (proteins, lipids, and carbohydrates) at their typical abundance. Of the 22 CO2 molecules produced by decarboxylation (normalized to net assimilation = 100), approximately 13 were from pyruvate and 3 were from isocitrate. The remaining six units of decarboxylation were in the amino acid synthesis pathways outside the tricarboxylic acid cycle. A small additional flux came from photorespiration, decarboxylations of six phosphogluconate in the oxidative pentose phosphate pathway, and decarboxylations in the syntheses of lower-abundance compounds, including pigments and ribonucleic acids. This general approach accounted for the high decarboxylation rates in algae and cyanobacteria compared to terrestrial plants. It prompts a simple speculation for the origin of the Kok effect and helps constrain the photoautotrophic respiration rate, in the light, in the euphotic zone of the ocean and lakes.
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Affiliation(s)
| | - Xin-Guang Zhu
- State Key Laboratory of Plant Molecular Genetics, Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Paul Falkowski
- Environmental Biophysics and Molecular Ecology Program, Department of Marine and Coastal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA
| | - Fangfang Ma
- State Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018, China
| | - Kevin Griffin
- Department of Earth and Environmental Sciences, Columbia University, Palisades, New York 10964, USA
- Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, New York 10027, USA
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA
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11
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Choi BY, Shim D, Kong F, Auroy P, Lee Y, Li-Beisson Y, Lee Y, Yamaoka Y. The Chlamydomonas transcription factor MYB1 mediates lipid accumulation under nitrogen depletion. THE NEW PHYTOLOGIST 2022; 235:595-610. [PMID: 35383411 DOI: 10.1111/nph.18141] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/29/2022] [Indexed: 06/14/2023]
Abstract
Microalgae accumulate high levels of oil under stress, but the underlying biosynthetic pathways are not fully understood. We sought to identify key regulators of lipid metabolism under stress conditions. We found that the Chlamydomonas reinhardtii gene encoding the MYB-type transcription factor MYB1 is highly induced under stress conditions. Two myb1 mutants accumulated less total fatty acids and storage lipids than their parental strain upon nitrogen (N) depletion. Transcriptome analysis revealed that genes involved in lipid metabolism are highly enriched in the wild-type but not in the myb1-1 mutant after 4 h of N depletion. Among these genes were several involved in the transport of fatty acids from the chloroplast to the endoplasmic reticulum (ER): acyl-ACP thioesterase (FAT1), Fatty Acid EXporters (FAX1, FAX2), and long-chain acyl-CoA synthetase1 (LACS1). Furthermore, overexpression of FAT1 in the chloroplast increased lipid production. These results suggest that, upon N depletion, MYB1 promotes lipid accumulation by facilitating fatty acid transport from the chloroplast to the ER. This study identifies MYB1 as an important positive regulator of lipid accumulation in C. reinhardtii upon N depletion, adding another player to the established regulators of this process, including NITROGEN RESPONSE REGULATOR 1 (NRR1) and TRIACYLGLYCEROL ACCUMULATION REGULATOR 1 (TAR1).
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Affiliation(s)
- Bae Young Choi
- Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea
| | - Donghwan Shim
- Department of Biological Sciences, Chungnam National University, Daejeon, 34134, Korea
| | - Fantao Kong
- Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China
| | - Pascaline Auroy
- CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, Aix Marseille Université, CEA Cadarache, Saint Paul-Lez-Durance, 13108, France
| | - Yuree Lee
- School of Biological Sciences, Seoul National University, Seoul, 08826, Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, 08826, Korea
- Plant Genomics and Breeding Institute, Seoul National University, Seoul, 08826, Korea
| | - Yonghua Li-Beisson
- CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, Aix Marseille Université, CEA Cadarache, Saint Paul-Lez-Durance, 13108, France
| | - Youngsook Lee
- Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Korea
| | - Yasuyo Yamaoka
- Division of Biotechnology, The Catholic University of Korea, Bucheon, 420-743, Korea
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Young DY, Pang N, Shachar-Hill Y. 13C-labeling reveals how membrane lipid components contribute to triacylglycerol accumulation in Chlamydomonas. PLANT PHYSIOLOGY 2022; 189:1326-1344. [PMID: 35377446 PMCID: PMC9237737 DOI: 10.1093/plphys/kiac154] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/09/2022] [Indexed: 06/14/2023]
Abstract
Lipid metabolism in microalgae has attracted much interest due to potential utilization of lipids as feedstocks for biofuels, nutraceuticals, and other high-value compounds. Chlamydomonas reinhardtii is a model organism for characterizing the synthesis of the neutral lipid triacylglycerol (TAG), from which biodiesel is made. While much of TAG accumulation under N-deprivation is the result of de novo fatty acid (FA) synthesis, recent work has revealed that approximately one-third of FAs, especially polyunsaturated FAs (PUFAs), come from preexisting membrane lipids. Here, we used 13C-isotopic labeling and mass spectrometry to analyze the turnover of glycerol backbones, headgroups, FAs, whole molecules, and molecular fragments of individual lipids. About one-third of the glyceryl backbones in TAG are derived from preexisting membrane lipids, as are approximately one-third of FAs. The different moieties of the major galactolipids turn over synchronously, while the FAs of diacylglyceryltrimethylhomoserine (DGTS), the most abundant extraplastidial lipid, turn over independently of the rest of the molecule. The major plastidic lipid monogalactosyldiacylglycerol (MGDG), whose predominant species is 18:3α/16:4, was previously shown to be a major source of PUFAs for TAG synthesis. This study reveals that MGDG turns over as whole molecules, the 18:3α/16:4 species is present in both DAG and TAG, and the positional distribution of these PUFAs is identical in MGDG, DAG, and TAG. We conclude that headgroup removal with subsequent acylation is the mechanism by which the major MGDG species is converted to TAG during N-deprivation. This has noteworthy implications for engineering the composition of microalgal TAG for food, fuel, and other applications.
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Affiliation(s)
- Danielle Yvonne Young
- Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA
| | - Na Pang
- Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA
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Subcellular Localizations of Catalase and Exogenously Added Fatty Acid in Chlamydomonas reinhardtii. Cells 2021; 10:cells10081940. [PMID: 34440712 PMCID: PMC8391285 DOI: 10.3390/cells10081940] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 07/22/2021] [Accepted: 07/26/2021] [Indexed: 02/01/2023] Open
Abstract
Fatty acids are important biological components, yet the metabolism of fatty acids in microalgae is not clearly understood. Previous studies found that Chlamydomonas reinhardtii, the model microalga, incorporates exogenously added fatty acids but metabolizes them differently from animals and yeast. Furthermore, a recent metabolic flux analysis found that the majority of lipid turnover in C. reinhardtii is the recycling of acyl chains from and to membranes, rather than β -oxidation. This indicates that for the alga, the maintenance of existing acyl chains may be more valuable than their breakdown for energy. To gain cell-biological knowledge of fatty acid metabolism in C. reinhardtii, we conducted microscopy analysis with fluorescent probes. First, we found that CAT1 (catalase isoform 1) is in the peroxisomes while CAT2 (catalase isoform 2) is localized in the endoplasmic reticulum, indicating the alga is capable of detoxifying hydrogen peroxide that would be produced during β-oxidation in the peroxisomes. Second, we compared the localization of exogenously added FL-C16 (fluorescently labelled palmitic acid) with fluorescently marked endosomes, mitochondria, peroxisomes, lysosomes, and lipid droplets. We found that exogenously added FL-C16 are incorporated and compartmentalized via a non-endocytic route within 10 min. However, the fluorescence signals from FL-C16 did not colocalize with any marked organelles, including peroxisomes. During triacylglycerol accumulation, the fluorescence signals from FL-C16 were localized in lipid droplets. These results support the idea that membrane turnover is favored over β-oxidation in C. reinhardtii. The knowledge gained in these analyses would aid further studies of the fatty acid metabolism.
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