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Jeffers TL, Purvine SO, Nicora CD, McCombs R, Upadhyaya S, Stroumza A, Whang K, Gallaher SD, Dohnalkova A, Merchant SS, Lipton M, Niyogi KK, Roth MS. Iron rescues glucose-mediated photosynthesis repression during lipid accumulation in the green alga Chromochloris zofingiensis. Nat Commun 2024; 15:6046. [PMID: 39025848 PMCID: PMC11258321 DOI: 10.1038/s41467-024-50170-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 07/02/2024] [Indexed: 07/20/2024] Open
Abstract
Energy status and nutrients regulate photosynthetic protein expression. The unicellular green alga Chromochloris zofingiensis switches off photosynthesis in the presence of exogenous glucose (+Glc) in a process that depends on hexokinase (HXK1). Here, we show that this response requires that cells lack sufficient iron (-Fe). Cells grown in -Fe+Glc accumulate triacylglycerol (TAG) while losing photosynthesis and thylakoid membranes. However, cells with an iron supplement (+Fe+Glc) maintain photosynthesis and thylakoids while still accumulating TAG. Proteomic analysis shows that known photosynthetic proteins are most depleted in heterotrophy, alongside hundreds of uncharacterized, conserved proteins. Photosynthesis repression is associated with enzyme and transporter regulation that redirects iron resources to (a) respiratory instead of photosynthetic complexes and (b) a ferredoxin-dependent desaturase pathway supporting TAG accumulation rather than thylakoid lipid synthesis. Combining insights from diverse organisms from green algae to vascular plants, we show how iron and trophic constraints on metabolism aid gene discovery for photosynthesis and biofuel production.
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Affiliation(s)
- Tim L Jeffers
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Samuel O Purvine
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Carrie D Nicora
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Ryan McCombs
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Shivani Upadhyaya
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Adrien Stroumza
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Ken Whang
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Sean D Gallaher
- UCLA DOE Institute for Genomics and Proteomics, University of California, Los Angeles, CA, 90095, USA
- Quantitative Biosciences Institute, University of California, Berkeley, CA, 94720, USA
| | - Alice Dohnalkova
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Sabeeha S Merchant
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
- Quantitative Biosciences Institute, University of California, Berkeley, CA, 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Mary Lipton
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - Krishna K Niyogi
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA.
- Howard Hughes Medical Institute, University of California, Berkeley, CA, 94720-3102, USA.
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Melissa S Roth
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA.
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Ding M, Zhou D, Ye Y, Wen S, Zhang X, Tian Q, Zhang X, Mou W, Dang C, Fang Y, Xue D. Genome-Wide Identification and Expression Analysis of the Stearoyl-Acyl Carrier Protein Δ9 Desaturase Gene Family under Abiotic Stress in Barley. Int J Mol Sci 2023; 25:113. [PMID: 38203283 PMCID: PMC10778905 DOI: 10.3390/ijms25010113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/11/2023] [Accepted: 12/18/2023] [Indexed: 01/12/2024] Open
Abstract
Stearoyl-acyl carrier protein (ACP) Δ9 desaturase (SAD) is a critical fatty acid dehydrogenase in plants, playing a prominent role in regulating the synthesis of unsaturated fatty acids (UFAs) and having a significant impact on plant growth and development. In this study, we conducted a comprehensive genomic analysis of the SAD family in barley (Hordeum vulgare L.), identifying 14 HvSADs with the FA_desaturase_2 domain, which were divided into four subgroups based on sequence composition and phylogenetic analysis, with members of the same subgroup possessing similar genes and motif structures. Gene replication analysis suggested that tandem and segmental duplication may be the major reasons for the expansion of the SAD family in barley. The promoters of HvSADs contained various cis-regulatory elements (CREs) related to light, abscisic acid (ABA), and methyl jasmonate (MeJA). In addition, expression analysis indicated that HvSADs exhibit multiple tissue expression patterns in barley as well as different response characteristics under three abiotic stresses: salt, drought, and cold. Briefly, this evolutionary and expression analysis of HvSADs provides insight into the biological functions of barley, supporting a comprehensive analysis of the regulatory mechanisms of oil biosynthesis and metabolism in plants under abiotic stress.
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Affiliation(s)
- Mingyu Ding
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
| | - Danni Zhou
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
| | - Yichen Ye
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
| | - Shuting Wen
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
| | - Xian Zhang
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
| | - Quanxiang Tian
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
| | - Xiaoqin Zhang
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
| | - Wangshu Mou
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
| | - Cong Dang
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
| | - Yunxia Fang
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
| | - Dawei Xue
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China; (M.D.); (D.Z.); (Y.Y.); (S.W.); (X.Z.); (Q.T.); (X.Z.); (W.M.); (C.D.); (Y.F.)
- Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China
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Senousy HH, El-Sheekh MM, Khairy HM, El-Sayed HS, Mahmoud GAE, Hamed AA. Biodiesel Production from the Marine Alga Nannochloropsis oceanica Grown on Yeast Wastewater and the Effect on Its Biochemical Composition and Gene Expression. PLANTS (BASEL, SWITZERLAND) 2023; 12:2898. [PMID: 37631110 PMCID: PMC10459201 DOI: 10.3390/plants12162898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 07/24/2023] [Accepted: 08/05/2023] [Indexed: 08/27/2023]
Abstract
Microalgae-based biodiesel synthesis is currently not commercially viable due to the high costs of culture realizations and low lipid yields. The main objective of the current study was to determine the possibility of growing Nannochloropsis oceanica on Saccharomyces cerevisiae yeast wastewater for biodiesel generation at an economical rate. N. oceanica was grown in Guillard F/2 synthetic medium and three dilutions of yeast wastewater (1, 1.25, and 1.5%). Biodiesel properties, in addition to carbohydrate, protein, lipid, dry weight, biomass, lipid productivity, amino acids, and fatty acid methyl ester (FAMEs) content, were analyzed and the quality of the produced biodiesel is assessed. The data revealed the response of N. oceanica to nitrogen-deficiency in the three dilutions of yeast wastewater. N. oceanica in Y2 (1.25%) yeast wastewater dilution exhibited the highest total carbohydrate and lipid percentages (21.19% and 41.97%, respectively), and the highest lipid productivity (52.46 mg L-1 day -1) under nitrogen deficiency in yeast wastewater. The fatty acids profile shows that N. oceanica cultivated in Y2 (1.25%) wastewater dilution provides a significant level of TSFA (47.42%) and can be used as a feedstock for biodiesel synthesis. In addition, N. oceanica responded to nitrogen shortage in wastewater dilutions by upregulating the gene encoding delta-9 fatty acid desaturase (Δ9FAD). As a result, the oleic and palmitoleic acid levels increased in the fatty acid profile of Y2 yeast wastewater dilution, highlighting the increased activity of Δ9FAD enzyme in transforming stearic acid and palmitic acid into oleic acid and palmitoleic acid. This study proved that the Y2 (1.25%) yeast wastewater dilution can be utilized as a growth medium for improving the quantity of specific fatty acids and lipid productivity in N. oceanica that affect biodiesel quality to satisfy global biodiesel requirements.
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Affiliation(s)
- Hoda H. Senousy
- Botany and Microbiology Department, Faculty of Science, Cairo University, Giza 12613, Egypt;
| | | | - Hanan M. Khairy
- National Institute of Oceanography and Fisheries (NIOF), Cairo 11516, Egypt; (H.M.K.); (H.S.E.-S.)
| | - Heba S. El-Sayed
- National Institute of Oceanography and Fisheries (NIOF), Cairo 11516, Egypt; (H.M.K.); (H.S.E.-S.)
| | | | - Amal A. Hamed
- Botany and Microbiology Department, Faculty of Science, Cairo University, Giza 12613, Egypt;
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Gao B, Hong J, Chen J, Zhang H, Hu R, Zhang C. The growth, lipid accumulation and adaptation mechanism in response to variation of temperature and nitrogen supply in psychrotrophic filamentous microalga Xanthonema hormidioides (Xanthophyceae). BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:12. [PMID: 36658609 PMCID: PMC9854199 DOI: 10.1186/s13068-022-02249-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND Microalgae are promising feedstocks for production of renewable biofuels and value-added bioproducts. Temperature and nitrogen supply are important environmental and nutritional factors affecting the growth and metabolism of microalgae, respectively. In this study, the growth and lipid accumulation of filamentous microalgae Xanthonema hormidioides under different temperatures (5, 7, 10, 15, 20, 25, 27 and 30 °C) and initial nitrogen concentrations (3, 9, 18 mM) were investigated, and its adaptive mechanisms of tolerance to low temperature and nitrogen stress were analysis by proteomics. RESULTS The optimum temperature range for the growth of X. hormidioides was between 15 and 20 °C, and the algal cells had slow growth rate at 5 °C and could not survive at 30 °C. The maximum biomass concentration was 11.73 g L-1 under the temperature of 20 °C, and the highest total lipid content was 56.63% of dry weight. Low temperature did not change the fatty acids profiles but promoted the accumulation of unsaturated fatty acids of X. hormidioides. The maximum contents of palmitoleic acid, eicosapentaenoic acid and total fatty acid were 23.64%, 2.49% and 41.14% of dry weight, respectively. Proteomics was performed under three temperature (7, 15, 25 °C), two nitrogen concentrations (3 and 18 mM) and two cultivation times (day 3 and 12). A total of 6503 proteins were identified. In the low temperature, photosynthesis-related proteins were down-regulated to protect the photosynthetic apparatus. The up-regulation of key enzymes DGAT and PDAT demonstrated the accumulation of TAGs under low nitrogen treatment. The proteins related to ribosome, phosphatidylinositol signaling system, antioxidant system and cold shock proteins (CSPs) in X. hormidioides were co-upregulated under the treatment of low temperature, which can alleviate the damages induced by temperature stress and maintain the normal growth and metabolism of algal cells. CONCLUSIONS X. hormidioides is a psychrotolerant microalga. It is an oleaginous filamentous microalga containing hyper palmitoleic acid and a certain amount of eicosapentaenoic acid with great potential for biofuel development, as well as for applications in nutritional health products and other industries.
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Affiliation(s)
- Baoyan Gao
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Jian Hong
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Jiamin Chen
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Hu Zhang
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China
| | - Ren Hu
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China.
| | - Chengwu Zhang
- Department of Ecology, Research Center for Hydrobiology, Jinan University, Guangzhou, 510632, People's Republic of China.
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Ding W, Liu J. Rutin Stimulates the Green Alga Chromochloris zofingiensis for Improved Biomass and Astaxanthin Production. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:13626-13636. [PMID: 36219673 DOI: 10.1021/acs.jafc.2c04928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Chromochloris zofingiensis represents a potential algal producer of the value-added ketocarotenoid astaxanthin. Here, rutin, a low-cost flavonoid compound, was evaluated regarding its roles in C. zofingiensis production under astaxanthin-inducing conditions via physiological, biochemical, and transcriptomics analyses. The rutin treatment allowed C. zofingiensis to achieve 81.2% more biomass and 20.5% greater astaxanthin content under nitrogen deprivation, leading to more than doubled astaxanthin production. The rutin-treated C. zofingiensis had higher levels of chlorophylls, proteins, and lipids and lower carbohydrate level than the control. Rutin promoted the intracellular abscisic acid (ABA) level, which could be restored by the ABA biosynthesis inhibitor, accompanied by the restoration of biomass concentration and astaxanthin content. The application of exogenous ABA to C. zofingiensis also furthered biomass concentration and astaxanthin accumulation. Together with the comparative transcriptomics analysis, our study provides implications into the involvement of ABA in rutin-mediated stimulation of C. zofingiensis growth and astaxanthin accumulation and highlights a feasible strategy of combining stress and chemical induction for improved microalgal production.
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Affiliation(s)
- Wei Ding
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing 100871, China
| | - Jin Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing 100871, China
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6
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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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Shi M, Yu L, Shi J, Liu J. A conserved MYB transcription factor is involved in regulating lipid metabolic pathways for oil biosynthesis in green algae. THE NEW PHYTOLOGIST 2022; 235:576-594. [PMID: 35342951 DOI: 10.1111/nph.18119] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/21/2022] [Indexed: 06/14/2023]
Abstract
Green algae can accumulate high levels of triacylglycerol (TAG), yet knowledge remains fragmented on the regulation of lipid metabolic pathways by transcription factors (TFs). Here, via bioinformatics and in vitro and in vivo analyses, we revealed the roles of a myeloblastosis (MYB) TF in regulating TAG accumulation in green algae. CzMYB1, an R2R3-MYB from Chromochloris zofingiensis, was transcriptionally upregulated upon TAG-inducing conditions and correlated well with many genes involved in the de novo fatty acid synthesis, fatty acid activation and desaturation, membrane lipid turnover, and TAG assembly. Most promoters of these genes were transactivated by CzMYB1 in the yeast one-hybrid assay and contained the binding elements CNGTTA that were recognized by CzMYB1 through the electrophoretic mobility shift assay. CrMYB1, a close homologue of CzMYB1 from Chlamydomonas reinhardtii that recognized similar elements for binding, also transcriptionally correlated with many lipid metabolic genes. Insertional disruption of CrMYB1 severely suppressed the transcriptional expression of CrMYB1, as well as of key lipogenic genes, and impaired TAG level considerably under stress conditions. Our results reveal that this MYB, conserved in green algae, is involved in regulating global lipid metabolic pathways for TAG biosynthesis and accumulation.
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Affiliation(s)
- Meicheng Shi
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Lihua Yu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Jianan Shi
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Jin Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
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Huang K, Su Z, He M, Wu Y, Wang M. Simultaneous accumulation of astaxanthin and β-carotene in Chlamydomonas reinhardtii by the introduction of foreign β-carotene hydroxylase gene in response to high light stress. Biotechnol Lett 2022; 44:321-331. [PMID: 35119571 DOI: 10.1007/s10529-022-03230-5] [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: 10/13/2021] [Accepted: 01/26/2022] [Indexed: 11/02/2022]
Abstract
Carotenoids are important photosynthetic pigments with many physiological functions, nutritional properties and high commercial value. β-carotene hydroxylase is one of the key enzymes in the carotenoid synthesis pathway of Chlamydomonas reinhardtii for the conversion of β-carotene to astaxanthin. The vector p64DZ containing the β-carotene hydroxylase gene crtZ from Haematococcus pluvialis was transformed into C. reinhardtii CC-503. The transformants were selected by alternate culture in solid-liquid medium containing spectinomycin (100 µg mL-1). PCR results indicated that the gene crtZ and aadA were integrated into the genome of C. reinhardtii. RT-PCR analysis showed that the gene crtZ was transcribed in Chlamydomonas transformants. HPLC analysis showed that the content of astaxanthin and β-carotene in cells of C. reinhardtii were simultaneously increased. Under medium light intensity cultivation (60 µmol m-2 s-1), transgenic C. reinhardtii had an 85.8% increase in β-carotene content compared with the wild type. The content of astaxanthin and β-carotene reached 1.97 ± 0.13 mg g-1 fresh cell weight (FCW) and 105.94 ± 5.84 µg g-1 FCW, which were increased 18% and 42.4% than the wild type after 6 h of high light treatment (200 µmol m-2 s-1), respectively. Our results indicate the regulatory effect on pigments in C. reinhardtii by β-carotene hydroxylase gene of H. pluvialis, and demonstrate the positive effect of high light stress on pigment accumulation in transgenic C. reinhardtii.
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Affiliation(s)
- Kunmei Huang
- College of Chemical Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China
| | - Zhongliang Su
- College of Chemical Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China.
| | - Mingyan He
- College of Chemical Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China
| | - Yaoyao Wu
- College of Chemical Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China
| | - Meiqi Wang
- College of Chemical Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China
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Metabolic engineering of the oleaginous alga Nannochloropsis for enriching eicosapentaenoic acid in triacylglycerol by combined pulling and pushing strategies. Metab Eng 2021; 69:163-174. [PMID: 34864212 DOI: 10.1016/j.ymben.2021.11.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 11/20/2021] [Accepted: 11/30/2021] [Indexed: 11/23/2022]
Abstract
The marine alga Nannochloropsis oceanica has been considered as a promising photosynthetic cell factory for synthesizing eicosapentaenoic acid (EPA), yet the accumulation of EPA in triacylglycerol (TAG) is restricted to an extreme low level. Poor channeling of EPA to TAG was observed in N. oceanica under TAG induction conditions, likely due to the weak activity of endogenous diacylglycerol acyltransferases (DGATs) on EPA-CoA. Screening over thirty algal DGATs revealed potent enzymes acting on EPA-CoA. Whilst overexpressing endogenous DGATs had no or slight effect on EPA abundance in TAG, introducing selected DGATs with strong activity on EPA-CoA, particularly the Chlamydomonas-derived CrDGTT1, which resided at the outermost membrane of the chloroplast and provided a strong pulling power to divert EPA to TAG for storage and protection, led to drastic increases in EPA abundance in TAG and TAG-derived EPA level in N. oceanica. They were further promoted by additional overexpression of an elongase gene involved in EPA biosynthesis, reaching 5.9- and 12.3-fold greater than the control strain, respectively. Our results together demonstrate the concept of applying combined pulling and pushing strategies to enrich EPA in algal TAG and provide clues for the enrichment of other desired fatty acids in TAG as well.
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Wu T, Yu L, Zhang Y, Liu J. Characterization of fatty acid desaturases reveals stress-induced synthesis of C18 unsaturated fatty acids enriched in triacylglycerol in the oleaginous alga Chromochloris zofingiensis. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:184. [PMID: 34535156 PMCID: PMC8447527 DOI: 10.1186/s13068-021-02037-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 09/07/2021] [Indexed: 05/16/2023]
Abstract
BACKGROUND The green microalga Chromochloris zofingiensis is capable of producing high levels of triacylglycerol rich in C18 unsaturated fatty acids (UFAs). FA desaturation degree is regulated by FA desaturases (FADs). Nevertheless, it remains largely unknown regarding what FADs are involved in FA desaturations and how these FADs collaborate to contribute to the high abundance of C18 UFAs in triacylglycerol in C. zofingiensis. RESULTS To address these issues, we firstly determined the transcription start sites of 11 putative membrane-bound FAD-coding genes (CzFADs) and updated their gene models. Functional validation of these CzFADs in yeast and cyanobacterial cells revealed that seven are bona fide FAD enzymes with distinct substrates. Combining the validated functions and predicted subcellular compartments of CzFADs and the FA profiles of C. zofingiensis, the FA desaturation pathways in this alga were reconstructed. Furthermore, a multifaceted lipidomic analysis by systematically integrating thin-layer chromatography, gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry techniques was conducted, unraveling profiles of polar membrane lipids in C. zofingiensis and major desaturation steps occurring in these lipids. By correlating transcriptional patterns of CzFAD genes and changes of lipids upon abiotic stress conditions, our results highlighted collaboration of CzFADs for C18 UFA synthesis and supported that both de novo FA synthesis and membrane lipid remodeling contributed C18 UFAs to triacylglycerol for storage. CONCLUSIONS Taken together, our study for the first time elucidated the pathways of C18 FA desaturations and comprehensive profiles of polar membrane lipids in C. zofingiensis and shed light on collaboration of CzFADs for the synthesis and enrichment of C18 UFAs in triacylglycerol.
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Affiliation(s)
- Tao Wu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
| | - Lihua Yu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
| | - Yu Zhang
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
| | - Jin Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
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11
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Shi Y, Liu M, Pan Y, Hu H, Liu J. Δ6 Fatty Acid Elongase is Involved in Eicosapentaenoic Acid Biosynthesis Via the ω6 Pathway in the Marine Alga Nannochloropsis oceanica. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:9837-9848. [PMID: 34414763 DOI: 10.1021/acs.jafc.1c04192] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Nannochloropsis oceanica represents a promising sunlight-driven alga for producing eicosapentaenoic acid (EPA, 20:5Δ5,8,11,14,17), a value-added very long-chain polyunsaturated fatty acid (VLC-PUFA). Here, we unraveled the function and roles of a Δ6 fatty acid elongase (NoΔ6-FAE) in N. oceanica. Heterologous expression of NoΔ6-FAE in yeast confirmed its function in elongating C18 Δ6-PUFAs rather than others. Subcellular localization experiments suggested that NoΔ6-FAE resides in the chloroplast endoplasmic reticulum. NoΔ6-FAE knockdown attenuated C20:3Δ8,11,14, C20:4Δ5,8,11,14, and EPA yet enhanced C18:3Δ6,9,12, leading to overall decreases in total fatty acids, triacylglycerol, diacylglycerol, free fatty acids, and polar membrane lipids. In contrast, NoΔ6-FAE overexpression in N. oceanica caused nearly opposite phenotypes. Moreover, N. oceanica lacked detectable C18:3Δ9,12,15, C18:4Δ6,9,12,15, and C20:4Δ8,11,14,17 even under NoΔ6-FAE knockdown or overexpression. Our results reveal the involvement of NoΔ6-FAE in EPA biosynthesis via the ω6 pathway in N. oceanica and highlight the potential of manipulating NoΔ6-FAE for improved lipid production.
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Affiliation(s)
- Ying Shi
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing 100871, China
| | - Meijing Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing 100871, China
| | - Yufang Pan
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Hanhua Hu
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Jin Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing 100871, China
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12
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Xiang Q, Wei X, Yang Z, Xie T, Zhang Y, Li D, Pan X, Liu X, Zhang X, Yao C. Acclimation to a broad range of nitrate strength on a euryhaline marine microalga Tetraselmis subcordiformis for photosynthetic nitrate removal and high-quality biomass production. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 781:146687. [PMID: 33812104 DOI: 10.1016/j.scitotenv.2021.146687] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 03/19/2021] [Accepted: 03/19/2021] [Indexed: 06/12/2023]
Abstract
Industrial wastewaters usually possess a wide range of nitrate strength. Microalgae-based nitrate-rich wastewater treatment could realize nitrate recovery along with CO2 sequestration for sustainable biomass production, but the low tolerance of the microalgal strains to high-strength nitrate restricted the treatment process. The present study comprehensively evaluated a euryhaline marine microalga Tetraselmis subcordiformis for photosynthetic nitrate removal and biomass production in synthetic wastewater with a broad range of nitrate strength (0.24-7.0 g NO3--N/L). This alga could acclimate to high nitrate strength up to 3.5 g NO3--N/L (HN) without compromising biomass production. Nitrate could be completely removed within four days when low nitrate (0.24 g NO3--N/L, LN) was loaded. The maximum nitrate removal rate of 331 mg N/L/day and specific nitrate removal rate of 360 mg N/day/g cell was obtained under medium nitrate condition (1.8 g NO3--N/L, MN). High-nitrate stress under 7.0 g NO3--N/L (SHN) caused an increased light energy dissipation while decreased the density of photosystem II active reaction center, which partially protect the cells from photodamage and contributed to their acclimation to SHN. The algae also enhanced amino acid/fatty acid proportions essential for maintaining intracellular redox states to cope with the stress caused by LN or SHN. HN and SHN was in favor of protein accumulation and maintenance with enhanced proportion of essential amino acids, which entitled the algal biomass to be of high quality for animal feed applied in livestock graziery and aquaculture. LN facilitated productive starch and lipid accumulation with good quality for biofuels production. The nitrate removal rate and biomass productivity exceeded most of the microalgae reported in literature under similar conditions, which highlighted Tetraselmis subcordiformis as a potent strain for flexible nitrate-rich wastewater remediation coupled with fast CO2 bio-mitigation and high-quality biomass production for sustainable algal biorefinery.
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Affiliation(s)
- Qi Xiang
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Xiaolong Wei
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Zezhou Yang
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Tonghui Xie
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Yongkui Zhang
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Defu Li
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Xuerong Pan
- Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu, Sichuan 610213, China
| | - Xiaolong Liu
- Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu, Sichuan 610213, China
| | - Xiang Zhang
- Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu, Sichuan 610213, China
| | - Changhong Yao
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China.
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13
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Lovio-Fragoso JP, de Jesús-Campos D, López-Elías JA, Medina-Juárez LÁ, Fimbres-Olivarría D, Hayano-Kanashiro C. Biochemical and Molecular Aspects of Phosphorus Limitation in Diatoms and Their Relationship with Biomolecule Accumulation. BIOLOGY 2021; 10:biology10070565. [PMID: 34206287 PMCID: PMC8301168 DOI: 10.3390/biology10070565] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/31/2021] [Accepted: 06/09/2021] [Indexed: 11/24/2022]
Abstract
Simple Summary Phosphorus (P) is a key nutrient involved in the transfer of energy and the synthesis of several cellular components. It has been reported that P limitation in diatoms induces the synthesis of biomolecules and the accumulation of storage compounds, such as pigments, carbohydrates and lipids, with diverse biological activities, which can be used in diverse biotechnological applications. However, the molecular and biochemical mechanisms related to how diatoms cope with P deficiency are not clear, and research into this has been limited to a few species. The integration of results obtained from omics sciences could provide a broad understanding of the response of diatoms to P limitation, and the information obtained could help to solve challenges such as biomass production, by-products yield and genetic improvement of strains. Abstract Diatoms are the most abundant group of phytoplankton, and their success lies in their significant adaptation ability to stress conditions, such as nutrient limitation. Phosphorus (P) is a key nutrient involved in the transfer of energy and the synthesis of several cellular components. Molecular and biochemical mechanisms related to how diatoms cope with P deficiency are not clear, and research into this has been limited to a few species. Among the molecular responses that have been reported in diatoms cultured under P deficient conditions is the upregulation of genes encoding enzymes related to the transport, assimilation, remobilization and recycling of this nutrient. Regarding biochemical responses, due to the reduction of the requirements for carbon structures for the synthesis of proteins and phospholipids, more CO2 is fixed than is consumed by the Calvin cycle. To deal with this excess, diatoms redirect the carbon flow toward the synthesis of storage compounds such as triacylglycerides and carbohydrates, which are excreted as extracellular polymeric substances. This review aimed to gather all current knowledge regarding the biochemical and molecular mechanisms of diatoms related to managing P deficiency in order to provide a wider insight into and understanding of their responses, as well as the metabolic pathways affected by the limitation of this nutrient.
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14
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Zhang Y, Ye Y, Bai F, Liu J. The oleaginous astaxanthin-producing alga Chromochloris zofingiensis: potential from production to an emerging model for studying lipid metabolism and carotenogenesis. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:119. [PMID: 33992124 PMCID: PMC8126118 DOI: 10.1186/s13068-021-01969-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 05/07/2021] [Indexed: 05/05/2023]
Abstract
The algal lipids-based biodiesel, albeit having advantages over plant oils, still remains high in the production cost. Co-production of value-added products with lipids has the potential to add benefits and is thus believed to be a promising strategy to improve the production economics of algal biodiesel. Chromochloris zofingiensis, a unicellular green alga, has been considered as a promising feedstock for biodiesel production because of its robust growth and ability of accumulating high levels of triacylglycerol under multiple trophic conditions. This alga is also able to synthesize high-value keto-carotenoids and has been cited as a candidate producer of astaxanthin, the strongest antioxidant found in nature. The concurrent accumulation of triacylglycerol and astaxanthin enables C. zofingiensis an ideal cell factory for integrated production of the two compounds and has potential to improve algae-based production economics. Furthermore, with the advent of chromosome-level whole genome sequence and genetic tools, C. zofingiensis becomes an emerging model for studying lipid metabolism and carotenogenesis. In this review, we summarize recent progress on the production of triacylglycerol and astaxanthin by C. zofingiensis. We also update our understanding in the distinctive molecular mechanisms underlying lipid metabolism and carotenogenesis, with an emphasis on triacylglycerol and astaxanthin biosynthesis and crosstalk between the two pathways. Furthermore, strategies for trait improvements are discussed regarding triacylglycerol and astaxanthin synthesis in C. zofingiensis.
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Affiliation(s)
- Yu Zhang
- Laboratory for Algae Biotechnology and Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Ying Ye
- Laboratory for Algae Biotechnology and Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Fan Bai
- Laboratory for Algae Biotechnology and Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Jin Liu
- Laboratory for Algae Biotechnology and Innovation, College of Engineering, Peking University, Beijing, 100871, China.
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15
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Kou Y, Liu M, Sun P, Dong Z, Liu J. High light boosts salinity stress-induced biosynthesis of astaxanthin and lipids in the green alga Chromochloris zofingiensis. ALGAL RES 2020. [DOI: 10.1016/j.algal.2020.101976] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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16
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Anne-Marie K, Yee W, Loh SH, Aziz A, Cha TS. Influence of nitrogen availability on biomass, lipid production, fatty acid profile, and the expression of fatty acid desaturase genes in Messastrum gracile SE-MC4. World J Microbiol Biotechnol 2020; 36:17. [PMID: 31912247 DOI: 10.1007/s11274-019-2790-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 12/20/2019] [Indexed: 10/25/2022]
Abstract
In this study, the effects of limited and excess nitrate on biomass, lipid production, and fatty acid profile in Messastrum gracile SE-MC4 were determined. The expression of fatty acid desaturase genes, namely stearoyl-ACP desaturase (SAD), omega-6 fatty acid desaturase (ω-6 FAD), omega-3 fatty acid desaturase isoform 1 (ω-3 FADi1), and omega-3 fatty acid desaturase isoform 2 (ω-3 FADi2) was also assessed. It was found that nitrate limitation generally increased the total oil, α-linolenic acid (C18:3n3) and total polyunsaturated fatty acid (PUFA) contents in M. gracile. The reduction of nitrate concentration from 1.76 to 0.11 mM increased the total oil content significantly from 32.5 to 41.85% (dry weight). Palmitic (C16:0) and oleic (C18:1) acids as the predominant fatty acids in this microalgae constituted between 82 and 87% of the total oil content and were relatively consistent throughout all nitrate concentrations tested. The expression of SAD, ω-6 FAD, and ω-3 FADi2 genes increased under nitrate limitation, especially at 0.11 mM nitrate. The ω-3 FADi1 demonstrated a binary up-regulation pattern of expression under both nitrate-deficient (0.11 mM) and -excess (3.55 mM) conditions. Thus, findings from this study suggested that limited or excess nitrate could be used as part of a cultivation strategy to increase oil and PUFA content following media optimisation and more efficient culture methodology. Data obtained from the expression of desaturase genes would provide valuable insights into their roles under excess and limited nitrate conditions in M. gracile, potentially paving the way for future genetic modifications.
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Affiliation(s)
- Kaben Anne-Marie
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia.,Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Willy Yee
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Saw Hong Loh
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Ahmad Aziz
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Thye San Cha
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia. .,Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia.
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17
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Mao X, Zhang Y, Wang X, Liu J. Novel insights into salinity-induced lipogenesis and carotenogenesis in the oleaginous astaxanthin-producing alga Chromochloris zofingiensis: a multi-omics study. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:73. [PMID: 32322303 PMCID: PMC7161124 DOI: 10.1186/s13068-020-01714-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 04/09/2020] [Indexed: 05/03/2023]
Abstract
BACKGROUND Chromochloris zofingiensis, a freshwater alga capable of synthesizing both triacylglycerol (TAG) and astaxanthin, has been receiving increasing attention as a leading candidate producer. While the mechanism of oleaginousness and/or carotenogenesis has been studied under such induction conditions as nitrogen deprivation, high light and glucose feeding, it remains to be elucidated in response to salt stress, a condition critical for reducing freshwater footprint during algal production processes. RESULTS Firstly, the effect of salt concentrations on growth, lipids and carotenoids was examined for C. zofingiensis, and 0.2 M NaCl demonstrated to be the optimal salt concentration for maximizing both TAG and astaxanthin production. Then, the time-resolved lipid and carotenoid profiles and comparative transcriptomes and metabolomes were generated in response to the optimized salt concentration for congruent analysis. A global response was triggered in C. zofingiensis allowing acclimation to salt stress, including photosynthesis impairment, ROS build-up, protein turnover, starch degradation, and TAG and astaxanthin accumulation. The lipid metabolism involved a set of stimulated biological pathways that contributed to carbon precursors, energy and reductant molecules, pushing and pulling power, and storage sink for TAG accumulation. On the other hand, salt stress suppressed lutein biosynthesis, stimulated astaxanthin biosynthesis (mainly via ketolation), yet had little effect on total carotenoid flux, leading to astaxanthin accumulation at the expense of lutein. Astaxanthin was predominantly esterified and accumulated in a well-coordinated manner with TAG, pointing to the presence of common regulators and potential communication for the two compounds. Furthermore, the comparison between salt stress and nitrogen deprivation conditions revealed distinctions in TAG and astaxanthin biosynthesis as well as critical genes with engineering potential. CONCLUSIONS Our multi-omics data and integrated analysis shed light on the salt acclimation of C. zofingiensis and underlying mechanisms of TAG and astaxanthin biosynthesis, provide engineering implications into future trait improvements, and will benefit the development of this alga for production uses under saline environment, thus reducing the footprint of freshwater.
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Affiliation(s)
- Xuemei Mao
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
| | - Yu Zhang
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
| | - Xiaofei Wang
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
| | - Jin Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871 China
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18
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Anne-Marie K, Yee W, Loh SH, Aziz A, Cha TS. Effects of Excess and Limited Phosphate on Biomass, Lipid and Fatty Acid Contents and the Expression of Four Fatty Acid Desaturase Genes in the Tropical Selenastraceaen Messastrum gracile SE-MC4. Appl Biochem Biotechnol 2019; 190:1438-1456. [PMID: 31782088 DOI: 10.1007/s12010-019-03182-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 11/11/2019] [Indexed: 01/31/2023]
Abstract
In this study, the effects of limited and excess phosphate on biomass content, oil content, fatty acid profile and the expression of three fatty acid desaturases in Messastrum gracile SE-MC4 were determined. It was found that total biomass (0.67-0.83 g L-1), oil content (30.99-38.08%) and the duration for cells to reach stationary phase (25-27 days) were not considerably affected by phosphate limitation. However, excess phosphate slightly reduced total biomass and oil content to 0.50 g L-1 and 25.36% respectively. The dominant fatty acids in M. gracile, pamitic acid (C16:0) and oleic acid (C18:1) which constitute more than 81% of the total fatty acids remained relatively high and constant across all phosphate concentrations. Reduction of phosphate concentration to 25% and below significantly increased total MUFA, whereas increasing phosphate concentration to ≥ 50% and ≥ 100% significantly increased total SFA and PUFA content respectively. The expression of omega-3 fatty acid desaturase (ω-3 FADi1, ω-3 FADi2) and omega-6 fatty acid desaturase (ω-6 FAD) was increased under phosphate limitation, especially at ≤ 12.5% phosphate, whereas levels of streoyl-ACP desaturase (SAD) transcripts were relatively unchanged across all phosphate concentrations. The first isoform of ω-3 FAD (ω-3 FADi) displayed a binary upregulation under limited (≤ 12.5%) and excess (200%) phosphate. The expression of ω-6 FAD, ω-3 FAD and SAD were inconsistent with the accumulation of oleic acid (C18:1), linoleic acid (C18:2) and alpha-linolenic acid (C18:3), suggesting that these genes may be regulated indirectly by phosphate availability via post-transcriptional or post-translational mechanisms.
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Affiliation(s)
- Kaben Anne-Marie
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia.,Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Willy Yee
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Saw Hong Loh
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Ahmad Aziz
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia
| | - Thye San Cha
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia. .,Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia.
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19
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Liu J, Sun Z, Mao X, Gerken H, Wang X, Yang W. Multiomics analysis reveals a distinct mechanism of oleaginousness in the emerging model alga Chromochloris zofingiensis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 98:1060-1077. [PMID: 30828893 DOI: 10.1111/tpj.14302] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/15/2019] [Accepted: 02/19/2019] [Indexed: 06/09/2023]
Abstract
Chromochloris zofingiensis, featured due to its capability to simultaneously synthesize triacylglycerol (TAG) and astaxanthin, is emerging as a leading candidate alga for production uses. To better understand the oleaginous mechanism of this alga, we conducted a multiomics analysis by systematically integrating time-resolved transcriptomes, lipidomes and metabolomes in response to nitrogen deprivation. The data analysis unraveled the distinct mechanism of TAG accumulation, which involved coordinated stimulation of multiple biological processes including supply of energy and reductants, carbon reallocation from protein and starch, and 'pushing' and 'pulling' carbon to TAG synthesis. Unlike the model alga Chlamydomonas, de novo fatty acid synthesis in C. zofingiensis was promoted, together with enhanced turnover of both glycolipids and phospholipids, supporting the drastic need of acyls for TAG assembly. Moreover, genomewide analysis identified many key functional enzymes and transcription factors that had engineering potential for TAG modulation. Two genes encoding glycerol-3-phosphate acyltransferase (GPAT), the first committed enzyme for TAG assembly, were found in the C. zofingiensis genome; in vivo functional characterization revealed that extrachloroplastic GPAT instead of chloroplastic GPAT played a central role in TAG synthesis. These findings illuminate distinct oleaginousness mechanisms in C. zofingiensis and pave the way towards rational manipulation of this alga to becone an emerging model for trait improvements.
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Affiliation(s)
- Jin Liu
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Zheng Sun
- International Research Center for Marine Biosciences, Ministry of Science and Technology, Shanghai Ocean University, Shanghai, 201306, China
| | - Xuemei Mao
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Henri Gerken
- School of Sustainable Engineering and the Built Environment, Arizona State University Polytechnic campus, Mesa, AZ, 85212, USA
| | - Xiaofei Wang
- Laboratory for Algae Biotechnology & Innovation, College of Engineering, Peking University, Beijing, 100871, China
| | - Wenqiang Yang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
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Li-Beisson Y, Thelen JJ, Fedosejevs E, Harwood JL. The lipid biochemistry of eukaryotic algae. Prog Lipid Res 2019; 74:31-68. [PMID: 30703388 DOI: 10.1016/j.plipres.2019.01.003] [Citation(s) in RCA: 175] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 01/22/2019] [Accepted: 01/23/2019] [Indexed: 02/06/2023]
Abstract
Algal lipid metabolism fascinates both scientists and entrepreneurs due to the large diversity of fatty acyl structures that algae produce. Algae have therefore long been studied as sources of genes for novel fatty acids; and, due to their superior biomass productivity, algae are also considered a potential feedstock for biofuels. However, a major issue in a commercially viable "algal oil-to-biofuel" industry is the high production cost, because most algal species only produce large amounts of oils after being exposed to stress conditions. Recent studies have therefore focused on the identification of factors involved in TAG metabolism, on the subcellular organization of lipid pathways, and on interactions between organelles. This has been accompanied by the development of genetic/genomic and synthetic biological tools not only for the reference green alga Chlamydomonas reinhardtii but also for Nannochloropsis spp. and Phaeodactylum tricornutum. Advances in our understanding of enzymes and regulatory proteins of acyl lipid biosynthesis and turnover are described herein with a focus on carbon and energetic aspects. We also summarize how changes in environmental factors can impact lipid metabolism and describe present and potential industrial uses of algal lipids.
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Affiliation(s)
- Yonghua Li-Beisson
- Aix-Marseille Univ, CEA, CNRS, BIAM, UMR7265, CEA Cadarache, Saint-Paul-lez Durance F-13108, France.
| | - Jay J Thelen
- Department of Biochemistry, University of Missouri, Christopher S. Bond Life Sciences Center, Columbia, MO 65211, United States.
| | - Eric Fedosejevs
- Department of Biochemistry, University of Missouri, Christopher S. Bond Life Sciences Center, Columbia, MO 65211, United States.
| | - John L Harwood
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
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21
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Peng D, Zhou B, Jiang Y, Tan X, Yuan D, Zhang L. Enhancing freezing tolerance of Brassica napus L. by overexpression of a stearoyl-acyl carrier protein desaturase gene (SAD) from Sapium sebiferum (L.) Roxb. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2018; 272:32-41. [PMID: 29807604 DOI: 10.1016/j.plantsci.2018.03.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 03/25/2018] [Accepted: 03/28/2018] [Indexed: 05/06/2023]
Abstract
Sapium sebiferum (L.) Roxb. is an important woody oil tree and traditional herbal medicine in China. Stearoyl-acyl carrier protein desaturase (SAD) is a dehydrogenase enzyme that plays a key role in the transformation of saturated fatty acids into unsaturated fatty acids in oil; these fatty acids greatly influence the freezing tolerance of plants. However, it remains unclear whether freezing tolerance can be regulated by the expression level of SsSAD in S. sebiferum L. Our research indicated that SsSAD expression in S. sebiferum L. increased under freezing stress. To further confirm this result, we constructed a pEGAD-SsSAD vector and transformed it into B. napus L. W10 by Agrobacterium tumefaciens-mediated transformation. Transgenic plants that overexpressed the SsSAD gene exhibited significantly higher linoleic (18:2) and linolenic acid (18:3) content and advanced freezing tolerance. These results suggest that SsSAD overexpression in B. napus L. can increase the content of polyunsaturated fatty acids (PUFAs) such as linoleic (18:2) and linolenic acid (18:3), which are likely pivotal in improving freezing tolerance in B. napus L. plants. Thus, SsSAD overexpression could be useful in the production of freeze-tolerant varieties of B. napus L.
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Affiliation(s)
- Dan Peng
- College of Bioscience and Biotechnology of Central South University of Forestry and Technology, 410018, Changsha, China; Forestry Biotechnology Hunan Key Laboratories, Hunan Changsha, 410018, China
| | - Bo Zhou
- College of Bioscience and Biotechnology of Central South University of Forestry and Technology, 410018, Changsha, China; Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, 410018, Changsha, China; Collaborative Innovation Central of Cultivation and Utilization for Non-Wood Forest Tree Central South University of Forestry and Technology, 410018, Changsha, China; Forestry Biotechnology Hunan Key Laboratories, Hunan Changsha, 410018, China.
| | - Yueqiao Jiang
- College of Bioscience and Biotechnology of Central South University of Forestry and Technology, 410018, Changsha, China
| | - XiaoFeng Tan
- Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, 410018, Changsha, China; Collaborative Innovation Central of Cultivation and Utilization for Non-Wood Forest Tree Central South University of Forestry and Technology, 410018, Changsha, China
| | - DeYi Yuan
- Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, 410018, Changsha, China; Collaborative Innovation Central of Cultivation and Utilization for Non-Wood Forest Tree Central South University of Forestry and Technology, 410018, Changsha, China
| | - Lin Zhang
- Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, 410018, Changsha, China; Collaborative Innovation Central of Cultivation and Utilization for Non-Wood Forest Tree Central South University of Forestry and Technology, 410018, Changsha, China
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Che R, Huang L, Xu JW, Zhao P, Li T, Ma H, Yu X. Effect of fulvic acid induction on the physiology, metabolism, and lipid biosynthesis-related gene transcription of Monoraphidium sp. FXY-10. BIORESOURCE TECHNOLOGY 2017; 227:324-334. [PMID: 28042988 DOI: 10.1016/j.biortech.2016.12.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 12/02/2016] [Accepted: 12/03/2016] [Indexed: 05/03/2023]
Abstract
Fulvic acid (FA) triggers lipid accumulation in Monoraphidium sp. FXY-10, which can produce biofuels. Therefore, the metabolism shift and gene expression changes influenced by fulvic acid should be investigated. In this study, lipid and protein contents increased rapidly from 44.6% to 54.3% and from 31.4% to 39.7% under FA treatment, respectively. By contrast, carbohydrate content sharply declined from 49.5% to 32.5%. The correlation between lipid content and gene expression was also analyzed. Results revealed that accD, ME, and GPAT genes were significantly correlated with lipid accumulation. These genes could likely influence lipid accumulation and could be selected as modification candidates. These results demonstrated that FA significantly increased microalgal lipid accumulation by changing the intracellular reactive oxygen species, gene expression, and enzyme activities of acetyl-CoA carboxylase, malic enzyme, and phosphoenolpyruvate carboxylase.
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Affiliation(s)
- Raoqiong Che
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Li Huang
- Institute of Chemical Industry, Kunming Metallurgy College, Kunming, China
| | - Jun-Wei Xu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Peng Zhao
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Tao Li
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Huixian Ma
- School of Foreign Languages, Kunming University, Kunming 650200, China
| | - Xuya Yu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China.
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Wei H, Shi Y, Ma X, Pan Y, Hu H, Li Y, Luo M, Gerken H, Liu J. A type-I diacylglycerol acyltransferase modulates triacylglycerol biosynthesis and fatty acid composition in the oleaginous microalga, Nannochloropsis oceanica. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:174. [PMID: 28694845 PMCID: PMC5499063 DOI: 10.1186/s13068-017-0858-1] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 06/27/2017] [Indexed: 05/03/2023]
Abstract
BACKGROUND Photosynthetic oleaginous microalgae are considered promising feedstocks for biofuels. The marine microalga, Nannochloropsis oceanica, has been attracting ever-increasing interest because of its fast growth, high triacylglycerol (TAG) content, and available genome sequence and genetic tools. Diacylglycerol acyltransferase (DGAT) catalyzes the last and committed step of TAG biosynthesis in the acyl-CoA-dependent pathway. Previous studies have identified 13 putative DGAT-encoding genes in the genome of N. oceanica, but the functional role of DGAT genes, especially type-I DGAT (DGAT1), remains ambiguous. RESULTS Nannochloropsis oceanica IMET1 possesses two DGAT1 genes: NoDGAT1A and NoDGAT1B. Functional complementation demonstrated the capability of NoDGAT1A rather than NoDGAT1B to restore TAG synthesis in a TAG-deficient yeast strain. In vitro DGAT assays revealed that NoDGAT1A preferred saturated/monounsaturated acyl-CoAs and eukaryotic diacylglycerols (DAGs) for TAG synthesis, while NoDGAT1B had no detectable enzymatic activity. Assisted with green fluorescence protein (GFP) fusion, fluorescence microscopy analysis indicated the localization of NoDGAT1A in the chloroplast endoplasmic reticulum (cER) of N. oceanica. NoDGAT1A knockdown caused ~25% decline in TAG content upon nitrogen depletion, accompanied by the reduced C16:0, C18:0, and C18:1 in TAG sn-1/sn-3 positions and C18:1 in the TAG sn-2 position. NoDGAT1A overexpression, on the other hand, led to ~39% increase in TAG content upon nitrogen depletion, accompanied by the enhanced C16:0 and C18:1 in the TAG sn-1/sn-3 positions and C18:1 in the TAG sn-2 position. Interestingly, NoDGAT1A overexpression also promoted TAG accumulation (by ~2.4-fold) under nitrogen-replete conditions without compromising cell growth, and TAG yield of the overexpression line reached 0.49 g L-1 at the end of a 10-day batch culture, 47% greater than that of the control line. CONCLUSIONS Taken together, our work demonstrates the functional role of NoDGAT1A and sheds light on the underlying mechanism for the biosynthesis of various TAG species in N. oceanica. NoDGAT1A resides likely in cER and prefers to transfer C16 and C18 saturated/monounsaturated fatty acids to eukaryotic DAGs for TAG assembly. This work also provides insights into the rational genetic engineering of microalgae by manipulating rate-limiting enzymes such as DGAT to modulate TAG biosynthesis and fatty acid composition for biofuel production.
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Affiliation(s)
- Hehong Wei
- Institute for Food and Bioresource Engineering, Department of Energy and Resources Engineering and BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
| | - Ying Shi
- Institute for Food and Bioresource Engineering, Department of Energy and Resources Engineering and BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
| | - Xiaonian Ma
- Institute for Food and Bioresource Engineering, Department of Energy and Resources Engineering and BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
| | - Yufang Pan
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 China
| | - Hanhua Hu
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 China
| | - Yantao Li
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science and University of Maryland Baltimore County, Baltimore, MA 21202 USA
| | - Ming Luo
- Guangdong Provincial Key Laboratory of Applied Botany, Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650 China
| | - Henri Gerken
- School of Sustainable Engineering and the Built Environment, Arizona State University Polytechnic campus, Mesa, AZ 85212 USA
| | - Jin Liu
- Institute for Food and Bioresource Engineering, Department of Energy and Resources Engineering and BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
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Liu J, Mao X, Zhou W, Guarnieri MT. Simultaneous production of triacylglycerol and high-value carotenoids by the astaxanthin-producing oleaginous green microalga Chlorella zofingiensis. BIORESOURCE TECHNOLOGY 2016; 214:319-327. [PMID: 27152772 DOI: 10.1016/j.biortech.2016.04.112] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 04/21/2016] [Accepted: 04/22/2016] [Indexed: 05/03/2023]
Abstract
The production of lipids and astaxanthin, a high-value carotenoid, by Chlorella zofingiensis was investigated under different culture conditions. Comparative analysis revealed a good correlation between triacylglycerol (TAG) and astaxanthin accumulation in C. zofingiensis. Stress conditions promoted cell size and weight and induced the accumulation of neutral lipids, especially TAG and astaxanthin, with a concomitant decrease in membrane lipids. The highest contents of TAG and astaxanthin achieved were 387 and 4.89mgg(-1) dry weight, respectively. A semi-continuous culture strategy was developed to optimize the TAG and astaxanthin productivities, which reached 297 and 3.3mgL(-1)day(-1), respectively. Additionally, astaxanthin accumulation was enhanced by inhibiting de novo fatty acid biosynthesis. In summary, our study represents a pioneering work of utilizing Chlorella for the integrated production of lipids and high-value products and C. zofingiensis has great potential to be a promising production strain and serve as an emerging oleaginous model alga.
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Affiliation(s)
- Jin Liu
- Institute for Food and Bioresource Engineering and Department of Energy and Resources Engineering, College of Engineering, Peking University, Beijing 100871, China.
| | - Xuemei Mao
- Institute for Food and Bioresource Engineering and Department of Energy and Resources Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Wenguang Zhou
- School of Resources, Environmental & Chemical Engineering and MOE Biomass Engineering Research Center, Nanchang University, Nanchang, China; Center for Biorefining, Bioproducts and Biosystems Engineering Department, University of Minnesota, Saint Paul, MN 55108, USA
| | - Michael T Guarnieri
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
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Liu J, Han D, Yoon K, Hu Q, Li Y. Characterization of type 2 diacylglycerol acyltransferases in Chlamydomonas reinhardtii reveals their distinct substrate specificities and functions in triacylglycerol biosynthesis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 86:3-19. [PMID: 26919811 DOI: 10.1111/tpj.13143] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 02/04/2016] [Accepted: 02/08/2016] [Indexed: 05/03/2023]
Abstract
Diacylglycerol acyltransferases (DGATs) catalyze a rate-limiting step of triacylglycerol (TAG) biosynthesis in higher plants and yeast. The genome of the green alga Chlamydomonas reinhardtii has multiple genes encoding type 2 DGATs (DGTTs). Here we present detailed functional and biochemical analyses of Chlamydomonas DGTTs. In vitro enzyme analysis using a radiolabel-free assay revealed distinct substrate specificities of three DGTTs: CrDGTT1 preferred polyunsaturated acyl CoAs, CrDGTT2 preferred monounsaturated acyl CoAs, and CrDGTT3 preferred C16 CoAs. When diacylglycerol was used as the substrate, CrDGTT1 preferred C16 over C18 in the sn-2 position of the glycerol backbone, but CrDGTT2 and CrDGTT3 preferred C18 over C16. In vivo knockdown of CrDGTT1, CrDGTT2 or CrDGTT3 resulted in 20-35% decreases in TAG content and a reduction of specific TAG fatty acids, in agreement with the findings of the in vitro assay and fatty acid feeding test. These results demonstrate that CrDGTT1, CrDGTT2 and CrDGTT3 possess distinct specificities toward acyl CoAs and diacylglycerols, and may work in concert spatially and temporally to synthesize diverse TAG species in C. reinhardtii. CrDGTT1 was shown to prefer prokaryotic lipid substrates and probably resides in both the endoplasmic reticulum and chloroplast envelope, indicating its role in prokaryotic and eukaryotic TAG biosynthesis. Based on these findings, we propose a working model for the role of CrDGTT1 in TAG biosynthesis. This work provides insight into TAG biosynthesis in C. reinhardtii, and paves the way for engineering microalgae for production of biofuels and high-value bioproducts.
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Affiliation(s)
- Jin Liu
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science and University of Maryland Baltimore County, Baltimore, MD, 21202, USA
- Department of Energy and Resources Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Danxiang Han
- Center for Microalgal Biotechnology and Biofuels, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Kangsup Yoon
- Center for Microalgal Biotechnology and Biofuels, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Qiang Hu
- Center for Microalgal Biotechnology and Biofuels, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Yantao Li
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science and University of Maryland Baltimore County, Baltimore, MD, 21202, USA
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Shen PL, Wang HT, Pan YF, Meng YY, Wu PC, Xue S. Identification of Characteristic Fatty Acids to Quantify Triacylglycerols in Microalgae. FRONTIERS IN PLANT SCIENCE 2016; 7:162. [PMID: 26941747 PMCID: PMC4761805 DOI: 10.3389/fpls.2016.00162] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 01/30/2016] [Indexed: 05/08/2023]
Abstract
The fatty acid profiles of lipids from microalgae are unique. Polyunsaturated fatty acids are generally enriched in polar lipids, whereas saturated and monounsaturated fatty acids constitute the majority of fatty acids in triacylglycerols (TAG). Each species has characteristic fatty acids, and their content is positively or negatively correlated with TAGs. The marine oleaginous diatom Phaeodactylum tricornutum was used as the paradigm to determine the quantitative relationship between TAG and characteristic fatty acid content. Fatty acid profiles and TAG content of Phaeodactylum tricornutum were determined in a time course. C16:0/C16:1 and eicosapentaenoic acid (EPA, C20:5n3) were identified as characteristic fatty acids in TAGs and polar lipids, respectively. The percentage of those characteristic fatty acids in total fatty acids had a significant linear relationship with TAG content, and thus, the correlation coefficient presenting r (2) were 0.96, 0.94, and 0.97, respectively. The fatty acid-based method for TAG quantification could also be applied to other microalgae such as Nannochloropsis oceanica in which the r (2) of C16:0 and EPA were 0.94 and 0.97, respectively, and in Chlorella pyrenoidosa r (2)-values for C18:1 and C18:3 with TAG content were 0.91 and 0.99, repectively. This characteristic fatty acid-based method provided a distinct way to quantify TAGs in microalgae, by which TAGs could be measured precisely by immediate transesterification from wet biomass rather than using conventional methods. This procedure simplified the operation and required smaller samples than conventional methods.
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Affiliation(s)
- Pei-Li Shen
- Marine Bioengineering Group, Department of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of SciencesDalian, China
- University of Chinese Academy of SciencesBeijing, China
| | - Hai-Tao Wang
- Marine Bioengineering Group, Department of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of SciencesDalian, China
- University of Chinese Academy of SciencesBeijing, China
| | - Yan-Fei Pan
- Department of Environmental Science and Engineering, College of Environment and Chemical Engineering, Dalian UniversityDalian, China
| | - Ying-Ying Meng
- School of Life Science and Biotechnology, Dalian University of TechnologyDalian, China
| | - Pei-Chun Wu
- Marine Bioengineering Group, Department of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of SciencesDalian, China
| | - Song Xue
- Marine Bioengineering Group, Department of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of SciencesDalian, China
- *Correspondence: Song Xue
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Yao L, Tan TW, Ng YK, Ban KHK, Shen H, Lin H, Lee YK. RNA-Seq transcriptomic analysis with Bag2D software identifies key pathways enhancing lipid yield in a high lipid-producing mutant of the non-model green alga Dunaliella tertiolecta. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:191. [PMID: 26613001 PMCID: PMC4660794 DOI: 10.1186/s13068-015-0382-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 11/13/2015] [Indexed: 05/09/2023]
Abstract
BACKGROUND For many years, increasing demands for fossil fuels have met with limited supply. As a potential substitute and renewable source of biofuel feedstock, microalgae have received significant attention. However, few of the current algal species produce high lipid yields to be commercially viable. To discover more high yielding strains, next-generation sequencing technology is used to elucidate lipid synthetic pathways and energy metabolism involved in lipid yield. When subjected to manipulation by genetic and metabolic engineering, enhancement of such pathways may further enhance lipid yield. RESULTS In this study, transcriptome profiling of a random insertional mutant with enhanced lipid production generated from a non-model marine microalga Dunaliella tertiolecta is presented. D9 mutant has a lipid yield that is 2- to 4-fold higher than that of wild type. Using novel Bag2D-workflow scripts developed and reported here, the non-redundant transcripts from de novo assembly were annotated based on the best hits in five model microalgae, namely Chlamydomonas reinhardtii, Coccomyxa subellipsoidea C-169, Ostreococcus lucimarinus, Volvox carteri, Chlorella variabilis NC64A and a high plant species Arabidopsis thaliana. The assembled contigs (~181 Mb) includes 481,381 contigs, covering 10,185 genes. Pathway analysis showed that a pathway from inositol phosphate metabolism to fatty acid biosynthesis is the most significantly correlated with higher lipid yield in this mutant. CONCLUSIONS Herein, we described a pipeline to analyze RNA-Seq data without pre-existing transcriptomic information. The draft transcriptome of D. tertiolecta was constructed and annotated, which offered useful information for characterizing high lipid-producing mutants. D. tertiolecta mutant was generated with an enhanced photosynthetic efficiency and lipid production. RNA-Seq data of the mutant and wild type were compared, providing biological insights into the expression patterns of contigs associated with energy metabolism and carbon flow pathways. Comparison of D. tertiolecta genes with homologs of five other green algae and a model high plant species can facilitate the annotation of D. tertiolecta and lead to a more complete annotation of its sequence database, thus laying the groundwork for optimization of lipid production pathways based on genetic manipulation.
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Affiliation(s)
- Lina Yao
- />Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Tin Wee Tan
- />Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Yi-Kai Ng
- />Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Kenneth Hon Kim Ban
- />Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- />Institute of Molecular and Cell Biology, A*STAR, Singapore, Singapore
| | - Hui Shen
- />Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Huixin Lin
- />Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Yuan Kun Lee
- />Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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28
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Sharma T, Gour RS, Kant A, Chauhan RS. Lipid content in Scenedesmus species correlates with multiple genes of fatty acid and triacylglycerol biosynthetic pathways. ALGAL RES 2015. [DOI: 10.1016/j.algal.2015.09.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Light attenuates lipid accumulation while enhancing cell proliferation and starch synthesis in the glucose-fed oleaginous microalga Chlorella zofingiensis. Sci Rep 2015; 5:14936. [PMID: 26442783 PMCID: PMC4595723 DOI: 10.1038/srep14936] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/14/2015] [Indexed: 01/08/2023] Open
Abstract
The objective of this study was to investigate the effect of light on lipid and starch accumulation in the oleaginous green algae Chlorella zofingiensis supplemented with glucose. C. zofingiensis, when fed with 30 g/L glucose, synthesized lipids up to 0.531 g/g dry weight; while in the presence of light, the lipid content dropped down to 0.352 g/g dry weight. Lipid yield on glucose was 0.184 g/g glucose, 14% higher than that cultured with light. The light-mediated lipid reduction was accompanied by the down-regulation of fatty acid biosynthetic genes at the transcriptional level. Furthermore, light promoted cell proliferation, starch accumulation, and the starch yield based on glucose. Taken together, light may attenuate lipid accumulation, possibly through the inhibition of lipid biosynthetic pathway, leading to more carbon flux from glucose to starch. This study reveals the dual effects of light on the sugar-fed C. zofingiensis and provides valuable insights into the possible optimization of algal biomass and lipid production by manipulation of culture conditions.
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30
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Liu B, Liu J, Sun P, Ma X, Jiang Y, Chen F. Sesamol Enhances Cell Growth and the Biosynthesis and Accumulation of Docosahexaenoic Acid in the Microalga Crypthecodinium cohnii. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:5640-5. [PMID: 26017014 DOI: 10.1021/acs.jafc.5b01441] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Sesamol is a strong antioxidant phenolic compound found in sesame seed. It possesses the ability to scavenge intracellular reactive oxygen species (ROS) and to inhibit malic enzyme activity and NADPH supply, resulting possibly in cell proliferation and alteration in the fatty acid composition. In the present study, the effect of sesamol on the growth and accumulation of docosahexaenoic acid (DHA) was investigated in the marine microalga Crypthecodinium cohnii, a prolific producer of DHA. C. cohnii showed a great decrease in the intracellular ROS level with the addition of sesamol. In contrast, the biomass concentration, DHA content (% of total fatty acids), and DHA productivity were significantly increased by 44.20, 11.25, and 20.00%, respectively (P < 0.01). Taken together, this work represents the first report of employing sesamol for enhanced production of DHA by C. cohnii, providing valuable insights into this alga for future biotechnological applications.
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Affiliation(s)
- Bin Liu
- †School of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510641, China
- §Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Jin Liu
- §Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing 100871, China
- #Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland 21202, United States
| | - Peipei Sun
- †School of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510641, China
| | - Xiaonian Ma
- §Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Yue Jiang
- ⊥School of Food Science, Jiangnan University, Wuxi 214122, China
| | - Feng Chen
- §Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing 100871, China
- ΔSingapore-Peking University Research Centre for a Sustainable Low-Carbon Future, CREATE Tower, Singapore 138602
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Zhou B, Peng D, Tan X, Yuan D, Liu X, Zhang L. WITHDRAWN: Expression of Sapium sebiferum (L.) Roxb stearoyl-acyl carrier protein desaturase in Escherichia coli. Protein Expr Purif 2015; 109:127. [DOI: 10.1016/j.pep.2014.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 05/18/2014] [Accepted: 05/19/2014] [Indexed: 11/30/2022]
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32
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Jusoh M, Loh SH, Chuah TS, Aziz A, Cha TS. Elucidating the role of jasmonic acid in oil accumulation, fatty acid composition and gene expression in Chlorella vulgaris (Trebouxiophyceae) during early stationary growth phase. ALGAL RES 2015. [DOI: 10.1016/j.algal.2015.02.020] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Sun Z, Zhou ZG, Gerken H, Chen F, Liu J. Screening and characterization of oleaginous Chlorella strains and exploration of photoautotrophic Chlorella protothecoides for oil production. BIORESOURCE TECHNOLOGY 2015; 184:53-62. [PMID: 25266686 DOI: 10.1016/j.biortech.2014.09.054] [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: 08/02/2014] [Revised: 09/09/2014] [Accepted: 09/11/2014] [Indexed: 05/04/2023]
Abstract
The growth and oil production of nine Chlorella strains were comparatively assessed and Chlorellaprotothecoides CS-41 demonstrated the greatest lipid production potential. The effects of different nitrogen forms and concentrations, phosphorus concentrations and light intensities on growth and oil production were studied in laboratory columns. C. protothecoides CS-41 accumulated lipids up to 55% of dry weight, with triacylglycerol and oleic acid being 71% of total lipids and 59% of total fatty acids, respectively. High biomass and lipid productivities were achieved in outdoor panel PBRs, up to 1.25 and 0.59 g L(-1) day(-1), or 44. 1 and 16.1 g m(-2) day(-1), respectively. A two-stage cultivation strategy was proposed to enhance the algal biomass and lipid production. This is the first comprehensive investigation of both indoor and outdoor photoautotrophic C. protothecoides cultures for oil production, and C. protothecoides CS-41 represents a promising biofuel feedstock worthy of further exploration.
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Affiliation(s)
- Zheng Sun
- College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, PR China
| | - Zhi-Gang Zhou
- College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, PR China
| | - Henri Gerken
- Department of Applied Sciences and Mathematics, Arizona State University Polytechnic Campus, Mesa, AZ 85212, USA
| | - Feng Chen
- Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing 100871, PR China
| | - Jin Liu
- Institute for Food and Bioresource Engineering, College of Engineering, Peking University, Beijing 100871, PR China; Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, MD 21202, USA.
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Wang HT, Meng YY, Cao XP, Ai JN, Zhou JN, Xue S, Wang WL. Coordinated response of photosynthesis, carbon assimilation, and triacylglycerol accumulation to nitrogen starvation in the marine microalgae Isochrysis zhangjiangensis (Haptophyta). BIORESOURCE TECHNOLOGY 2015; 177:282-8. [PMID: 25496949 DOI: 10.1016/j.biortech.2014.11.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 11/07/2014] [Accepted: 11/09/2014] [Indexed: 05/26/2023]
Abstract
The photosynthetic performance, carbon assimilation, and triacylglycerol accumulation of Isochrysis zhangjiangensis under nitrogen-deplete conditions were studied to understand the intrinsic correlations between them. The nitrogen-deplete period was divided into two stages based on the photosynthetic parameters. During the first stage, carbon assimilation was not reduced compared with that under favorable conditions. The marked increase in triacylglycerols and the variation in the fatty acid profile suggested that triacylglycerols were mainly derived from de novo synthesized acyl groups. In the second stage, the triacylglycerol content continued increasing while the carbohydrate content decreased from 44.0% to 26.3%. These results indicated that the intracellular conversion of carbohydrates to triacylglycerols occurred. Thus, we propose that sustainable carbon assimilation and incremental triacylglycerol production can be achieved by supplying appropriate amounts of nitrogen in medium to protect the photosynthetic process from severe damage using the photosynthetic parameters as indicators.
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Affiliation(s)
- Hai-Tao Wang
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ying-Ying Meng
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China; School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, China
| | - Xu-Peng Cao
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Jiang-Ning Ai
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Jian-Nan Zhou
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Song Xue
- Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
| | - Wei-liang Wang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
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Rosenberg JN, Kobayashi N, Barnes A, Noel EA, Betenbaugh MJ, Oyler GA. Comparative analyses of three Chlorella species in response to light and sugar reveal distinctive lipid accumulation patterns in the Microalga C. sorokiniana. PLoS One 2014; 9:e92460. [PMID: 24699196 PMCID: PMC3974682 DOI: 10.1371/journal.pone.0092460] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 02/21/2014] [Indexed: 02/02/2023] Open
Abstract
While photosynthetic microalgae, such as Chlorella, serve as feedstocks for nutritional oils and biofuels, heterotrophic cultivation can augment growth rates, support high cell densities, and increase triacylglycerol (TAG) lipid content. However, these species differ significantly in their photoautotrophic and heterotrophic characteristics. In this study, the phylogeny of thirty Chlorella strains was determined in order to inform bioprospecting efforts and detailed physiological assessment of three species. The growth kinetics and lipid biochemistry of C. protothecoides UTEX 411, C. vulgaris UTEX 265, and C. sorokiniana UTEX 1230 were quantified during photoautotrophy in Bold's basal medium (BBM) and heterotrophy in BBM supplemented with glucose (10 g L−1). Heterotrophic growth rates of UTEX 411, 265, and 1230 were found to be 1.5-, 3.7-, and 5-fold higher than their respective autotrophic rates. With a rapid nine-hour heterotrophic doubling time, Chlorella sorokiniana UTEX 1230 maximally accumulated 39% total lipids by dry weight during heterotrophy compared to 18% autotrophically. Furthermore, the discrete fatty acid composition of each strain was examined in order to elucidate lipid accumulation patterns under the two trophic conditions. In both modes of growth, UTEX 411 and 265 produced 18∶1 as the principal fatty acid while UTEX 1230 exhibited a 2.5-fold enrichment in 18∶2 relative to 18∶1. Although the total lipid content was highest in UTEX 411 during heterotrophy, UTEX 1230 demonstrated a two-fold increase in its heterotrophic TAG fraction at a rate of 28.9 mg L−1 d−1 to reach 22% of the biomass, corresponding to as much as 90% of its total lipids. Interestingly, UTEX 1230 growth was restricted during mixotrophy and its TAG production rate was suppressed to 18.2 mg L−1 d−1. This constraint on carbon flow raises intriguing questions about the impact of sugar and light on the metabolic regulation of microalgal lipid biosynthesis.
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Affiliation(s)
- Julian N Rosenberg
- Department of Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America; Synaptic Research LLC, Baltimore, Maryland, United States of America
| | - Naoko Kobayashi
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Austin Barnes
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Eric A Noel
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Michael J Betenbaugh
- Department of Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - George A Oyler
- Department of Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America; Synaptic Research LLC, Baltimore, Maryland, United States of America; Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
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36
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Genetic engineering of the green alga Chlorella zofingiensis: a modified norflurazon-resistant phytoene desaturase gene as a dominant selectable marker. Appl Microbiol Biotechnol 2014; 98:5069-79. [PMID: 24584513 DOI: 10.1007/s00253-014-5593-y] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/13/2014] [Accepted: 02/04/2014] [Indexed: 12/19/2022]
Abstract
The unicellular green alga Chlorella zofingiensis has been proposed as a promising producer of natural astaxanthin, a commercially important ketocarotenoid. But the genetic toolbox for this alga is not available. In the present study, an efficient transformation system was established for C. zofingiensis. The transformation system utilized a modified norflurazon-resistant phytoene desaturase (PDS-L516F, with an leucine-phenylalanine change at position 516) as the selectable marker. Three promoters from endogenous PDS, nitrate reductase (NIT), and ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (RBCS) genes were tested, with the RBCS promoter demonstrating the highest transformation efficiency. Inclusion of the first intron of the PDS gene further enhanced the efficiency by 91 %. Both particle bombardment and electroporation methods were examined, and the latter gave a fourfold higher transformation efficiency. The introduction of PDS-L516F, which exhibited a 33 % higher desaturation activity than the unaltered enzyme, enabled C. zofingiensis to produce 32.1 % more total carotenoids (TCs) and 54.1 % more astaxanthin. The enhanced accumulation of astaxanthin in transformants was revealed to be related to the increase in the transcripts of PDS, β-carotenoid ketolase (BKT), and hydroxylase (CHYb) genes. Our study clearly shows that the modified PDS gene is a dominant selectable marker for the transformation of C. zofingiensis and possibly for the genetic engineering of the carotenoid biosynthetic pathway. In addition, the engineered C. zofingiensis might serve as an improved source of natural astaxanthin.
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