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Sun K, Meesapyodsuk D, Qiu X. Biosynthetic mechanisms of omega-3 polyunsaturated fatty acids in microalgae. J Biol Chem 2024:107699. [PMID: 39173949 DOI: 10.1016/j.jbc.2024.107699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2024] [Revised: 08/08/2024] [Accepted: 08/12/2024] [Indexed: 08/24/2024] Open
Abstract
Marine microalgae are the primary producers of ω3 polyunsaturated fatty acids (PUFAs), such as octadecapentaenoic acid (OPA, 18:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) for food chains. However, the biosynthetic mechanisms of these PUFAs in the algae remain elusive. To study how these fatty acids are synthesized in microalgae, a series of radiolabeled precursors were used to trace the biosynthetic process of PUFAs in Emiliania huxleyi. Feeding the alga with 14C-labeled acetic acid in a time course showed that OPA was solely found in glycoglycerolipids such as monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) synthesized plastidically by sequential desaturations while DHA was exclusively found in phospholipids synthesized extraplastidically. Feeding the alga with 14C-labeled α-linolenic acid (ALA), linoleic acid (LA) and oleic acid (OA) showed that DHA was synthesized extraplastidically from fed ALA and LA, but not from OA, implying that the aerobic pathway of DHA biosynthesis is incomplete with missing a Δ12 desaturation step. The in vitro enzymatic assays with 14C-labeled malonyl-CoA showed that DHA was synthesized from acetic acid by a PUFA synthase. These results provide the first and conclusive biochemistry evidence that OPA is synthesized by a plastidic aerobic pathway through sequential desaturations with the last step of Δ3 desaturation, while DHA is synthesized by an extraplastidic anaerobic pathway catalyzed by a PUFA synthase in the microalga.
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Affiliation(s)
- Kaiwen Sun
- Department of Food & Bioproduct Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A8, Canada
| | | | - Xiao Qiu
- Department of Food & Bioproduct Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A8, Canada.
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Sun K, Meesapyodsuk D, Qiu X. Molecular cloning and functional analysis of a plastidial ω3 desaturase from Emiliania huxleyi. Front Microbiol 2024; 15:1381097. [PMID: 39056009 PMCID: PMC11269151 DOI: 10.3389/fmicb.2024.1381097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 06/26/2024] [Indexed: 07/28/2024] Open
Abstract
Emiliania huxleyi is a marine microalga playing a significant ecological and biogeochemical role in oceans. It can produce several polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA, 22:6-4,7,10,13,16,19) and octadecapentaenoic acid (OPA, 18:5-3,6,9,12,15), providing a primary source for nutritionally important ω3 PUFAs in the marine food chain. However, the biosynthesis of these PUFAs in this organism is not well understood. In this study, a full length plastidial ω3 desaturase cDNA (EhN3) was cloned from this alga. Heterologous expression of EhN3 with and without the chloroplast targeting peptide (cTP) in cyanobacterium Synechococcus elongatus showed that it possessed high desaturation activity toward C18-ω6 PUFAs, linoleic acid (LA, 18:2-9,12), γ-linolenic acid (GLA, 18:3-6,9,12), and C20-ω6 PUFAs, dihomo-γ-linolenic acid (DGLA, 20:3-8,11,14) and arachidonic acid (ARA, 20:4-5,8,11,14) that were exogenously supplied. Desaturation efficiency could reach almost 100% in a time course. On the other hand, when expressed in Saccharomyces cerevisiae, EhN3 with and without cTP did not exhibit any activity. Lipid analysis of Synechococcus transformants expressing EhN3 showed that it utilized galactolipids as substrates. Transcriptional expression analysis revealed that the expression of the gene increased while the growth temperature decreased, which was correlated with the increased production of ω3-PUFAs, particularly OPA. This is the first report of a plastidial ω3 desaturase from microalgae that can effectively introduce an ω3 double bond into both C18-ω6 and C20-ω6 PUFAs. EhN3 might also be one of the key enzymes involved in the biosynthesis of OPA in E. huxleyi through the plastidial aerobic pathway.
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Affiliation(s)
- Kaiwen Sun
- Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK, Canada
| | | | - Xiao Qiu
- Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK, Canada
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Ishikawa T, Domergue F, Amato A, Corellou F. Characterization of Unique Eukaryotic Sphingolipids with Temperature-Dependent Δ8-Unsaturation from the Picoalga Ostreococcus tauri. PLANT & CELL PHYSIOLOGY 2024; 65:1029-1046. [PMID: 38252418 DOI: 10.1093/pcp/pcae007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 11/28/2023] [Accepted: 01/18/2024] [Indexed: 01/23/2024]
Abstract
Sphingolipids (SLs) are ubiquitous components of eukaryotic cell membranes and are found in some prokaryotic organisms and viruses. They are composed of a sphingoid backbone that may be acylated and glycosylated. Assembly of various sphingoid base, fatty acyl and glycosyl moieties results in highly diverse structures. The functional significance of variations in SL chemical diversity and abundance is still in the early stages of investigation. Among SL modifications, Δ8-desaturation of the sphingoid base occurs only in plants and fungi. In plants, SL Δ8-unsaturation is involved in cold hardiness. Our knowledge of the structure and functions of SLs in microalgae lags far behind that of animals, plants and fungi. Original SL structures have been reported from microalgae. However, functional studies are still missing. Ostreococcus tauri is a minimal microalga at the base of the green lineage and is therefore a key organism for understanding lipid evolution. In the present work, we achieved the detailed characterization of O. tauri SLs and unveiled unique glycosylceramides as sole complex SLs. The head groups are reminiscent of bacterial SLs, as they contain hexuronic acid residues and can be polyglycosylated. Ceramide backbones show a limited variety, and SL modification is restricted to Δ8-unsaturation. The Δ8-SL desaturase from O. tauri only produced E isomers. Expression of both Δ8-SL desaturase and Δ8-unsaturation of sphingolipids varied with temperature, with lower levels at 24°C than at 14°C. Overexpression of the Δ8-SL desaturase dramatically increases the level of Δ8 unsaturation at 24°C and is paralleled by a failure to increase cell size. Our work provides the first characterization of O. tauri SLs and functional evidence for the involvement of SL Δ8-unsaturation for temperature acclimation in microalgae, suggesting that this function is an ancestral feature in the green lineage.
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Affiliation(s)
- Toshiki Ishikawa
- Graduate School of Science and Engineering, Saitama University, 225 Shimo-Okubo, Sakura-ku, Saitama-city, Saitama, 338-8570 Japan
| | - Frédéric Domergue
- Laboratoire de Biogenèse Membranaire, University of Bordeaux, CNRSUMR 5200, Av. Edouard Bourlaux, Villenave d'Ornon 33140, France
| | - Alberto Amato
- Laboratoire de Physiologie Végétale et Cellulaire, Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement, Centre National de la Recherche Scientifique UMR 5168, Université Grenoble Alpes, CEA, IRIG, 17 Av. Des Martyrs, Grenoble 38000, France
| | - Florence Corellou
- Laboratoire de Physiologie Végétale et Cellulaire, Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement, Centre National de la Recherche Scientifique UMR 5168, Université Grenoble Alpes, CEA, IRIG, 17 Av. Des Martyrs, Grenoble 38000, France
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Xin Y, Wu S, Miao C, Xu T, Lu Y. Towards Lipid from Microalgae: Products, Biosynthesis, and Genetic Engineering. Life (Basel) 2024; 14:447. [PMID: 38672718 PMCID: PMC11051065 DOI: 10.3390/life14040447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 03/27/2024] [Accepted: 03/27/2024] [Indexed: 04/28/2024] Open
Abstract
Microalgae can convert carbon dioxide into organic matter through photosynthesis. Thus, they are considered as an environment-friendly and efficient cell chassis for biologically active metabolites. Microalgal lipids are a class of organic compounds that can be used as raw materials for food, feed, cosmetics, healthcare products, bioenergy, etc., with tremendous potential for commercialization. In this review, we summarized the commercial lipid products from eukaryotic microalgae, and updated the mechanisms of lipid synthesis in microalgae. Moreover, we reviewed the enhancement of lipids, triglycerides, polyunsaturated fatty acids, pigments, and terpenes in microalgae via environmental induction and/or metabolic engineering in the past five years. Collectively, we provided a comprehensive overview of the products, biosynthesis, induced strategies and genetic engineering in microalgal lipids. Meanwhile, the outlook has been presented for the development of microalgal lipids industries, emphasizing the significance of the accurate analysis of lipid bioactivity, as well as the high-throughput screening of microalgae with specific lipids.
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Affiliation(s)
- Yi Xin
- State Key Laboratory of Marine Resource Utilization in South China Sea, School of Marine Life and Aquaculture, Hainan University, Haikou 570228, China; (S.W.); (C.M.); (T.X.)
- Haikou Technology Innovation Center for Research and Utilization of Algal Bioresources, Hainan University, Haikou 570228, China
| | - Shan Wu
- State Key Laboratory of Marine Resource Utilization in South China Sea, School of Marine Life and Aquaculture, Hainan University, Haikou 570228, China; (S.W.); (C.M.); (T.X.)
| | - Congcong Miao
- State Key Laboratory of Marine Resource Utilization in South China Sea, School of Marine Life and Aquaculture, Hainan University, Haikou 570228, China; (S.W.); (C.M.); (T.X.)
| | - Tao Xu
- State Key Laboratory of Marine Resource Utilization in South China Sea, School of Marine Life and Aquaculture, Hainan University, Haikou 570228, China; (S.W.); (C.M.); (T.X.)
| | - Yandu Lu
- State Key Laboratory of Marine Resource Utilization in South China Sea, School of Marine Life and Aquaculture, Hainan University, Haikou 570228, China; (S.W.); (C.M.); (T.X.)
- Haikou Technology Innovation Center for Research and Utilization of Algal Bioresources, Hainan University, Haikou 570228, China
- Hainan Provincial Key Laboratory of Tropical Hydrobiotechnology, Hainan University, Haikou 570228, China
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Degraeve-Guilbault C, Pankasem N, Gueirrero M, Lemoigne C, Domergue F, Kotajima T, Suzuki I, Joubès J, Corellou F. Temperature Acclimation of the Picoalga Ostreococcus tauri Triggers Early Fatty-Acid Variations and Involves a Plastidial ω3-Desaturase. FRONTIERS IN PLANT SCIENCE 2021; 12:639330. [PMID: 33815446 PMCID: PMC8018280 DOI: 10.3389/fpls.2021.639330] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 02/19/2021] [Indexed: 05/07/2023]
Abstract
Alteration of fatty-acid unsaturation is a universal response to temperature changes. Marine microalgae display the largest diversity of polyunsaturated fatty-acid (PUFA) whose content notably varies according to temperature. The physiological relevance and the molecular mechanisms underlying these changes are however, still poorly understood. The ancestral green picoalga Ostreococcus tauri displays original lipidic features that combines PUFAs from two distinctive microalgal lineages (Chlorophyceae, Chromista kingdom). In this study, optimized conditions were implemented to unveil early fatty-acid and desaturase transcriptional variations upon chilling and warming. We further functionally characterized the O. tauri ω3-desaturase which is closely related to ω3-desaturases from Chromista species. Our results show that the overall omega-3 to omega-6 ratio is swiftly and reversibly regulated by temperature variations. The proportion of the peculiar 18:5 fatty-acid and temperature are highly and inversely correlated pinpointing the importance of 18:5 temperature-dependent variations across kingdoms. Chilling rapidly and sustainably up-regulated most desaturase genes. Desaturases involved in the regulation of the C18-PUFA pool as well as the Δ5-desaturase appear to be major transcriptional targets. The only ω3-desaturase candidate, related to ω3-desaturases from Chromista species, is localized at chloroplasts in Nicotiana benthamiana and efficiently performs ω3-desaturation of C18-PUFAs in Synechocystis sp. PCC6803. Overexpression in the native host further unveils a broad impact on plastidial and non-plastidial glycerolipids illustrated by the alteration of omega-3/omega-6 ratio in C16-PUFA and VLC-PUFA pools. Global glycerolipid features of the overexpressor recall those of chilling acclimated cells.
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Affiliation(s)
| | - Nattiwong Pankasem
- School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Maurean Gueirrero
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse membranaire, UMR 5200, Villenave d’Ornon, France
| | - Cécile Lemoigne
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse membranaire, UMR 5200, Villenave d’Ornon, France
| | - Frédéric Domergue
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse membranaire, UMR 5200, Villenave d’Ornon, France
| | - Tomonori Kotajima
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Iwane Suzuki
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Jérôme Joubès
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse membranaire, UMR 5200, Villenave d’Ornon, France
| | - Florence Corellou
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse membranaire, UMR 5200, Villenave d’Ornon, France
- *Correspondence: Florence Corellou,
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