Publications by authors named "Yandu Lu"

21 Publications

  • Page 1 of 1

Manipulating fatty-acid profile at unit chain-length resolution in the model industrial oleaginous microalgae Nannochloropsis.

Metab Eng 2021 Apr 3;66:157-166. Epub 2021 Apr 3.

Single-Cell Center, CAS Key Laboratory of Biofuels, Shandong Laboratory of Energy Genetics and Shandong Energy Institute, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, China; Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory of Marine Science and Technology, Qingdao, Shandong, China; University of Chinese Academy of Sciences, Beijing, China. Electronic address:

The chain length (CL) of fatty acids (FAs) is pivotal to oil property, yet to what extent it can be customized in industrial oleaginous microalgae is unknown. In Nannochloropsis oceanica, to modulate long-chain FAs (LCFAs), we first discovered a fungi/bacteria-originated polyketide synthase (PKS) system which involves a cytoplasmic acyl-ACP thioesterase (NoTE1). NoTE1 hydrolyzes C16:0-, C16:1- and C18:1-ACP in vitro and thus intercepts the specific acyl-ACPs elongated by PKS for polyunsaturated FA biosynthesis, resulting in elevation of C16/C18 monounsaturated FAs when overproduced and increase of C20 when knocked out. For medium-chain FAs (MCFAs; C8-C14), C8:0 and C10:0 FAs are boosted by introducing a Cuphea palustris acyl-ACP TE (CpTE), whereas C12:0 elevated by rationally engineering CpTE enzyme's substrate-binding pocket to shift its CL preference towards C12:0. A mechanistic model exploiting both native and engineered PKS and type II FAS pathways was thus proposed for manipulation of carbon distribution among FAs of various CL. The ability to tailor FA profile at the unit CL resolution from C8 to C20 in Nannochloropsis spp. lays the foundation for scalable production of designer lipids via industrial oleaginous microalgae.
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http://dx.doi.org/10.1016/j.ymben.2021.03.015DOI Listing
April 2021

Sustainable development of microalgal biotechnology in coastal zone for aquaculture and food.

Sci Total Environ 2021 Mar 10;780:146369. Epub 2021 Mar 10.

State Key Laboratory of Marine Resource Utilization in South China Sea, College of Oceanology, Hainan University, Haikou, Hainan 570228, China. Electronic address:

Region-specific Research and Development (R&D) of microalga-derived product systems are crucial if "biotech's green gold" is to be explored in a rational and economically viable way. Coastal zones, particularly the locations around the equator, are typically considered to be optimum cultivation sites due to stable annual temperature, light, and ready availability of seawater. However, a 'cradle-to-grave' assessment of the development of microalgal biotechnology in these areas, not only under the laboratory conditions, but also in the fields has not yet been demonstrated. In this study, to evaluate the viability of microalga-derived multi-product technology, we showed the development of microalgal biotechnology in coastal zones for aquaculture and food. By creating and screening a (sub)tropical microalgal collection, a Chlorella strain MEM25 with a robust growth in a wide range of salinities, temperatures, and light intensities was identified. Evaluation of the economic viability and performance of different scale cultivation system designs (500 L and 5000 L closed photobioreactors and 60,000 L open race ponds, ORPs) at coastal zones under geographically specific conditions showed the stable and robust characteristics of MEM25 across different production system designs and various spatial and temporal scales. It produces high amounts of proteins and polyunsaturated fatty acids (PUFAs) in various conditions. Feeding experiments reveal the nutritional merits of MEM25 as food additives where PUFAs and essential amino acids are enriched and the algal diet improves consumers' growth. Economic evaluation highlights an appreciable profitability of MEM25 production as human or animal food using ORP systems. Therefore, despite the pros and cons, sound opportunities exist for the development of market-ready multiple-product systems by employing region-specific R&D strategies for microalgal biotechnology.
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http://dx.doi.org/10.1016/j.scitotenv.2021.146369DOI Listing
March 2021

Role of an ancient light-harvesting protein of PSI in light absorption and photoprotection.

Nat Commun 2021 01 29;12(1):679. Epub 2021 Jan 29.

Howard Hughes Medical Institute, Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA.

Diverse algae of the red lineage possess chlorophyll a-binding proteins termed LHCR, comprising the PSI light-harvesting system, which represent an ancient antenna form that evolved in red algae and was acquired through secondary endosymbiosis. However, the function and regulation of LHCR complexes remain obscure. Here we describe isolation of a Nannochloropsis oceanica LHCR mutant, named hlr1, which exhibits a greater tolerance to high-light (HL) stress compared to the wild type. We show that increased tolerance to HL of the mutant can be attributed to alterations in PSI, making it less prone to ROS production, thereby limiting oxidative damage and favoring growth in HL. HLR1 deficiency attenuates PSI light-harvesting capacity and growth of the mutant under light-limiting conditions. We conclude that HLR1, a member of a conserved and broadly distributed clade of LHCR proteins, plays a pivotal role in a dynamic balancing act between photoprotection and efficient light harvesting for photosynthesis.
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http://dx.doi.org/10.1038/s41467-021-20967-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7846763PMC
January 2021

Improving lipid productivity by engineering a control-knob gene in the oleaginous microalga .

Metab Eng Commun 2020 Dec 3;11:e00142. Epub 2020 Sep 3.

State Key Laboratory of Marine Resource Utilization in South China Sea, College of Oceanology, Hainan University, Haikou, 570228, Hainan Province, China.

spp. are promising industrial microalgae for scalable oil production and the lipid production can be boosted by nutrient starvation and high irradiance. However, these stimuli halt growth, thereby decreasing overall productivity. In this study, we created transgenic where gene encoding 1-deoxy-D-xylulose 5-phosphate synthase (DXS) derived from was overexpressed . Compared with the wild type (WT), engineered showed a higher CO absorption capacity and produced more biomass, lipids, and carbohydrates with more robust growth in either preferred conditions or various stressed conditions (low light, high light, nitrogen starvation, and trace element depletion). Specifically, relative to the WT, lipid production increased by ~68.6% in nitrogen depletion (~1.08 ​g ​L) and ~110.6% in high light (~1.15 ​g ​L) in the transgenic strains. As for neutral lipid (triacylglycerol, TAG), the engineered strains produced ~93.2% more in nitrogen depletion (~0.77 ​g ​L) and ~148.6% more in high light (~0.80 ​g ​L) than the WT. These values exceed available records in engineered industrial microalgae. Therefore, engineering control-knob genes could modify multiple biological processes simultaneously and enable efficient carbon partitioning to lipid biosynthesis with elevated biomass productivity. It could be further exploited for simultaneous enhancement of growth property and oil productivity in more industrial microalgae.
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http://dx.doi.org/10.1016/j.mec.2020.e00142DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7516279PMC
December 2020

Clade-Specific Sterol Metabolites in Dinoflagellate Endosymbionts Are Associated with Coral Bleaching in Response to Environmental Cues.

mSystems 2020 Sep 29;5(5). Epub 2020 Sep 29.

Shandong Rongchen Pharmaceuticals Inc., Qingdao, China

Cnidarians cannot synthesize sterols (which play essential roles in growth and development) but often use sterols acquired from endosymbiotic dinoflagellates. While sterol availability can impact the mutualistic interaction between coral host and algal symbiont, the biosynthetic pathways (in the dinoflagellate endosymbionts) and functional roles of sterols in these symbioses are poorly understood. In this study, we found that itraconazole, which perturbs sterol metabolism by inhibiting the sterol 14-demethylase CYP51 in dinoflagellates, induces bleaching of the anemone and that bleaching perturbs sterol metabolism of the dinoflagellate. While Symbiodiniaceae have clade-specific sterol metabolites, they share features of the common sterol biosynthetic pathway but with distinct architecture and substrate specificity features of participating enzymes. Tracking sterol profiles and transcripts of enzymes involved in sterol biosynthesis across time in response to different environmental cues revealed similarities and idiosyncratic features of sterol synthesis in the endosymbiont Exposure of algal cultures to high levels of light, heat, and acidification led to alterations in sterol synthesis, including blocks through downregulation of squalene synthase transcript levels accompanied by marked growth reductions. These results indicate that sterol metabolites in Symbiodiniaceae are clade specific, that their biosynthetic pathways share architectural and substrate specificity features with those of animals and plants, and that environmental stress-specific perturbation of sterol biosynthesis in dinoflagellates can impair a key mutualistic partnership for healthy reefs.
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http://dx.doi.org/10.1128/mSystems.00765-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7527140PMC
September 2020

Transcriptomic and proteomic responses to very low CO suggest multiple carbon concentrating mechanisms in .

Biotechnol Biofuels 2019 28;12:168. Epub 2019 Jun 28.

1Single-Cell Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong China.

Background: In industrial oleaginous microalgae such as spp., the key components of the carbon concentration mechanism (CCM) machineries are poorly defined, and how they are mobilized to facilitate cellular utilization of inorganic carbon remains elusive.

Results: For , to unravel genes specifically induced by CO depletion which are thus potentially underpinning its CCMs, transcriptome, proteome and metabolome profiles were tracked over 0 h, 3 h, 6 h, 12 h and 24 h during cellular response from high CO level (HC; 50,000 ppm) to very low CO (VLC; 100 ppm). The activity of a biophysical CCM is evidenced based on induction of transcripts encoding a bicarbonate transporter and two carbonic anhydrases under VLC. Moreover, the presence of a potential biochemical CCM is supported by the upregulation of a number of key C4-like pathway enzymes in both protein abundance and enzymatic activity under VLC, consistent with a mitochondria-implicated C4-based CCM. Furthermore, a basal CCM underpinned by VLC-induced upregulation of photorespiration and downregulation of ornithine-citrulline shuttle and the ornithine urea cycles is likely present, which may be responsible for efficient recycling of mitochondrial CO for chloroplastic carbon fixation.

Conclusions: appears to mobilize a comprehensive set of CCMs in response to very low CO. Its genes induced by the stress are quite distinct from those of  and , suggesting tightly regulated yet rather unique CCMs. These findings can serve the first step toward rational engineering of the CCMs for enhanced carbon fixation and biomass productivity in industrial microalgae.
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http://dx.doi.org/10.1186/s13068-019-1506-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599299PMC
June 2019

Metabolite profiling of Breviolum minutum in response to acidification.

Aquat Toxicol 2019 Aug 30;213:105215. Epub 2019 May 30.

State Key Laboratory of Marine Resource Utilization in South China Sea, College of Oceanology, Hainan University, Haikou 570228, Hainan, China. Electronic address:

Coral reefs are in significant decline globally due to climate change and environmental pollution. The ocean is becoming more acidic due to rising atmospheric pCO, and ocean acidification is considered a major threat to coral reefs. However, little is known about the exact mechanism by which acidification impacts coral symbiosis. As an important component of the symbiotic association, to explore the responses of symbionts could greatly enhance our understanding of this issue. The present work aimed to identify metabolomic changes of Breviolum minutum in acidification (low pH) condition, and investigate the underlying mechanisms responsible. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was applied to determine metabolite profiles after exposure to ambient and acidic conditions. We analysed the resulting metabolite data, and acidification appeared to have little effect on photosynthetic parameters, but it inhibited growth. Marked alterations in metabolite pools were observed in response to acidification that may be important in acclimation to climate change. Acidification may affect the biosynthesis of amino acids and proteins, and thereby inhibit the growth of B. minutum. Metabolites identified using this approach provide targets for future analyses aimed at understanding the responses of Symbiodiniaceae to environmental disturbance.
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http://dx.doi.org/10.1016/j.aquatox.2019.05.017DOI Listing
August 2019

Artificial creation of Chlorella pyrenoidosa mutants for economic sustainable food production.

Bioresour Technol 2018 Nov 4;268:340-345. Epub 2018 Aug 4.

State Key Laboratory of Marine Resource Utilization in South China Sea, College of Oceanology, Hainan University, Haikou 570228, Hainan Province, China. Electronic address:

To improve the economic viability of Chlorella as feedstock for food commodities, a serial of concentrations of low-cost sweet sorghum juice (SSJ), alternative to glucose, were used for the fermentation of Chlorella pyrenoidosa. A high biomass and protein production (8.91 g L biomass and 4.52 g L protein) was revealed with 20% SSJ. To further increase productivity, heavy-ion irradiation-mediated mutagenesis was employed to create mutants where a strain K05, with desired phenotypes (increased biomass and protein production in pilot-scale fermentation), was screened. Compared with the parental strain, the production of biomass, proteins, and chlorophylls of mutant K05 increased by 11.6%, 31.8%, and 7.6%, respectively. Production capacities under industrial scale (two-ton) further pinpoint the stability and scalability of mutant K05. These results suggest that advances in cultivation techniques coupled with artificial strain improvement will further promote microalgae as an attractive platform of functional food.
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http://dx.doi.org/10.1016/j.biortech.2018.08.007DOI Listing
November 2018

Engineering the Chloroplast Genome of Oleaginous Marine Microalga .

Front Plant Sci 2018 11;9:439. Epub 2018 Apr 11.

State Key Laboratory of Marine Resource Utilization in South China Sea, College of Oceanology, Hainan University, Haikou, China.

Plastid engineering offers an important tool to fill the gap between the technical and the enormous potential of microalgal photosynthetic cell factory. However, to date, few reports on plastid engineering in industrial microalgae have been documented. This is largely due to the small cell sizes and complex cell-wall structures which make these species intractable to current plastid transformation methods (i.e., biolistic transformation and polyethylene glycol-mediated transformation). Here, employing the industrial oleaginous microalga as a model, an electroporation-mediated chloroplast transformation approach was established. Fluorescent microscopy and laser confocal scanning microscopy confirmed the expression of the green fluorescence protein, driven by the endogenous plastid promoter and terminator. Zeocin-resistance selection led to an acquisition of homoplasmic strains of which a stable and site-specific recombination within the chloroplast genome was revealed by sequencing and DNA gel blotting. This demonstration of electroporation-mediated chloroplast transformation opens many doors for plastid genome editing in industrial microalgae, particularly species of which the chloroplasts are recalcitrant to chemical and microparticle bombardment transformation.
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http://dx.doi.org/10.3389/fpls.2018.00439DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5904192PMC
April 2018

Characterization and engineering of a dual-function diacylglycerol acyltransferase in the oleaginous marine diatom .

Biotechnol Biofuels 2018 9;11:32. Epub 2018 Feb 9.

2State Key Laboratory of Marine Resource Utilization in South China Sea, College of Oceanology, Hainan University, Haikou, Hainan 570228 China.

Background: Photosynthetic oleaginous microalgae are promising feedstocks for biofuels. Acyl-CoA:diacylglycerol acyltransferases (DGATs) represent rich sources for engineering microalgal lipid production. The principal activity of DGATs has been defined as a single-function enzyme catalyzing the esterification of diacylglycerol with acyl-CoA.

Results: A dual-function PtWS/DGAT associated with diatom is discovered in the current study. Distinctive to documented microalgal DGAT types, PtWS/DGAT exhibits activities of both a wax ester synthase (WS) and a DGAT. WS/DGATs are broadly distributed in microalgae, with different topology and phylogeny from those of DGAT1s, DGAT2s, and DGAT3s. In vitro and in vivo assays revealed that PtWS/DGAT, functioning as either a WS or a DGAT, exhibited a preference on saturated FA substrate. Endogenous overexpression of PtWS/DGAT demonstrated that the DGAT activity was dominant, whereas the WS activity was condition dependent and relatively minor. Compared with the wild type (WT), overexpression of PtWS/DGAT in the diatom resulted in increased levels of total lipids (TL) and triacylglycerol (TAG) regardless of nitrogen availability. The stability and scalability of the introduced traits were further investigated at a 10-L photobioreactor, where the mutant growth resembled WT, with moderately increased productivity of TL and TAG. Furthermore, the production of wax esters increased considerably (from undetectable levels to 2.83%) under nitrogen-deplete conditions.

Conclusions: PtWS/DGAT is a bifunctional enzyme and may serve as a promising target for the engineering of microalga-based oils and waxes for future industrial use.
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http://dx.doi.org/10.1186/s13068-018-1029-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5806285PMC
February 2018

Culture-Free Detection of Crop Pathogens at the Single-Cell Level by Micro-Raman Spectroscopy.

Adv Sci (Weinh) 2017 11 10;4(11):1700127. Epub 2017 Jul 10.

State Key Laboratory of Marine Resource Utilization in South China Sea College of Oceanology Hainan University Haikou Hainan Province 570228 China.

The rapid and sensitive identification of invasive plant pathogens has important applications in biotechnology, plant quarantine, and food security. Current methods are far too time-consuming and need a pre-enrichment period ranging from hours to days. Here, a micro-Raman spectroscopy-based bioassay for culture-free pathogen quarantine inspection at the single cell level within 40 min is presented. The application of this approach can readily and specifically detect plant pathogens pv. and that are closely related pathogenically. Furthermore, the single-bacterium detection was able to discriminate them from a reference Raman spectral library including multiple quarantine-relevant pathogens with broad host ranges and an array of pathogenic variants. To show the usefulness of this assay, pv. and are detected at single-bacterium level in plant tissue lesions without pre-enrichment. The results are confirmed by the plate-counting method and a genetic molecular approach, which display comparable recognition ratios to the Raman spectroscopy-based bioassay. The results represent a critical step toward the use of micro-Raman spectroscopy in rapid and culture-free discrimination of quarantine relevant plant pathogens.
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http://dx.doi.org/10.1002/advs.201700127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5700641PMC
November 2017

Producing Designer Oils in Industrial Microalgae by Rational Modulation of Co-evolving Type-2 Diacylglycerol Acyltransferases.

Mol Plant 2017 12 26;10(12):1523-1539. Epub 2017 Oct 26.

Single-Cell Center, CAS Key Laboratory of Biofuels and Shandong Laboratory of Energy Genetics, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address:

Microalgal oils, depending on their degree of unsaturation, can be utilized as either nutritional supplements or fuels; thus, a feedstock with genetically designed and tunable degree of unsaturation is desirable to maximize process efficiency and product versatility. Systematic profiling of ex vivo (in yeast), in vitro, and in vivo activities of type-2 diacylglycerol acyltransferases in Nannochloropsis oceanica (NoDGAT2s or NoDGTTs), via reverse genetics, revealed that NoDGAT2A prefers saturated fatty acids (SFAs), NoDGAT2D prefers monounsaturated fatty acids (MUFAs), and NoDGAT2C exhibits the strongest activity toward polyunsaturated fatty acids (PUFAs). As NoDGAT2A, 2C, and 2D originated from the green alga, red alga, and eukaryotic host ancestral participants of secondary endosymbiosis, respectively, a mechanistic model of oleaginousness was unveiled, in which the indigenous and adopted NoDGAT2s formulated functional complementarity and specific transcript abundance ratio that underlie a rigid SFA:MUFA:PUFA hierarchy in triacylglycerol (TAG). By rationally modulating the ratio of NoDGAT2A:2C:2D transcripts, a bank of N. oceanica strains optimized for nutritional supplement or fuel production with a wide range of degree of unsaturation were created, in which proportion of SFAs, MUFAs, and PUFAs in TAG varied by 1.3-, 3.7-, and 11.2-fold, respectively. This established a novel strategy to simultaneously improve productivity and quality of oils from industrial microalgae.
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http://dx.doi.org/10.1016/j.molp.2017.10.011DOI Listing
December 2017

Genome editing of model oleaginous microalgae Nannochloropsis spp. by CRISPR/Cas9.

Plant J 2016 12 18;88(6):1071-1081. Epub 2016 Oct 18.

Single-Cell Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, 266101, China.

Microalgae are promising feedstock for biofuels yet mechanistic probing of their cellular network and industrial strain development have been hindered by lack of genome-editing tools. Nannochloropsis spp. are emerging model microalgae for scalable oil production and carbon sequestration. Here we established a CRISPR/Cas9-based precise genome-editing approach for the industrial oleaginous microalga Nannochloropsis oceanica, using nitrate reductase (NR; g7988) as example. A new screening procedure that compares between restriction enzyme-digested nested PCR (nPCR) products derived from enzyme-digested and not-digested genomic DNA of transformant pools was developed to quickly, yet reliably, detect genome-engineered mutants. Deep sequencing of nPCR products directly amplified from pooled genomic DNA revealed over an 1% proportion of 5-bp deletion mutants and a lower frequency of 12-bp deletion mutants, with both types of editing precisely located at the targeted site. The isolated mutants, in which precise deletion of five bases caused a frameshift in NR translation, grow normally under NH Cl but fail to grow under NaNO , and thus represent a valuable chassis strain for transgenic-strain development. This demonstration of CRISPR/Cas9-based genome editing in industrial microalgae opens many doors for microalgae-based biotechnological applications.
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http://dx.doi.org/10.1111/tpj.13307DOI Listing
December 2016

Phytohormones in microalgae: a new opportunity for microalgal biotechnology?

Authors:
Yandu Lu Jian Xu

Trends Plant Sci 2015 May 17;20(5):273-282. Epub 2015 Feb 17.

Single-Cell Center, Chinese Academy of Sciences Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101, China. Electronic address:

Phytohormones, including auxin, abscisic acid (ABA), cytokinin (CK), ethylene (ET), and gibberellins (GAs), have been found in a broad spectrum of microalgal lineages. Although the functional role of microalgal endogenous phytohormones remains elusive, molecular evidence from the oleaginous microalga Nannochloropsis oceanica suggests that endogenous ABA and CK are functional and that their physiological effects are similar to those in higher plants. In this Opinion article, proceeding from genome-based metabolic reconstruction, we suggest that modern higher plant phytohormone biosynthesis pathways originate from ancient microalgae even though some of the microalgal phytohormone signaling pathways remain unknown. Dissection and manipulation of microalgal phytohormone systems could offer a new view of phytohormone evolution in plants and present new opportunities in developing microalgal feedstock for biofuels.
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http://dx.doi.org/10.1016/j.tplants.2015.01.006DOI Listing
May 2015

Antagonistic roles of abscisic acid and cytokinin during response to nitrogen depletion in oleaginous microalga Nannochloropsis oceanica expand the evolutionary breadth of phytohormone function.

Plant J 2014 Oct 28;80(1):52-68. Epub 2014 Aug 28.

Single Cell Center, Chinese Academy of Sciences Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, 266101, China.

The origin of phytohormones is poorly understood, and their physiological roles in microalgae remain elusive. Genome comparison of photosynthetic autotrophic eukaryotes has revealed that the biosynthetic pathways of abscisic acid (ABA) and cytokinins (CKs) emerged in unicellular algae. While ABA and CK degradation mechanisms emerged broadly in algal lineages, complete vascular plant-type conjugation pathways emerged prior to the rise of Streptophyta. In microalgae, a complete set of proteins from the canonical ABA and CK sensing and signaling pathways is not essential, but individual components are present, suggesting stepwise recruitment of phytohormone signaling components. In the oleaginous eustigmatophyte Nannochloropsis oceanica IMET1, UHPLC-MS/MS detected a wide array of plant hormones, despite a phytohormone profile that is very distinct from that of flowering plants. Time-series transcriptional analysis during nitrogen depletion revealed activation of the ABA biosynthetic pathway and antagonistic transcription of CK biosynthetic genes. Correspondingly, the ABA level increases while the dominant bioactive CK forms decrease. Moreover, exogenous CKs stimulate cell-cycle progression while exogenous ABA acts as both an algal growth repressor and a positive regulator in response to stresses. The presence of such functional flowering plant-like phytohormone signaling systems in Nannochloropsis sp. suggests a much earlier origin of phytohormone biosynthesis and degradation than previously believed, and supports the presence in microalgae of as yet unknown conjugation and sensing/signaling systems that may be exploited for microalgal feedstock development.
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http://dx.doi.org/10.1111/tpj.12615DOI Listing
October 2014

Regulation of the cholesterol biosynthetic pathway and its integration with fatty acid biosynthesis in the oleaginous microalga Nannochloropsis oceanica.

Biotechnol Biofuels 2014 30;7:81. Epub 2014 May 30.

Single-Cell Center, CAS Key Laboratory of Biofuels and Shandong Key Laboratory of Energy Genetics, Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101, China.

Background: Sterols are vital structural and regulatory components in eukaryotic cells; however, their biosynthetic pathways and functional roles in microalgae remain poorly understood.

Results: In the oleaginous microalga Nannochloropsis oceanica, the sterol biosynthetic pathway produces phytosterols as minor products and cholesterol as the major product. The evidence together with their deduced biosynthetic pathways suggests that N. oceanica exhibits features of both higher plants and mammals. Temporal tracking of sterol profiles and sterol-biosynthetic transcripts in response to changes in light intensity and nitrogen supply reveal that sterols play roles in cell proliferation, chloroplast differentiation, and photosynthesis. Furthermore, the dynamics of fatty acid (FA) and FA-biosynthetic transcripts upon chemical inhibitor-induced sterol depletion reveal possible co-regulation of sterol production and FA synthesis, in that the squalene epoxidase inhibitor terbinafine reduces sterol content yet significantly elevates free FA production. Thus, a feedback regulation of sterol and FA homeostasis is proposed, with the 1-deoxy-D-xylulose 5-phosphate synthase (DXS, the committed enzyme in isoprenoid and sterol biosynthesis) gene potentially subject to feedback regulation by sterols.

Conclusion: These findings reveal features of sterol function and biosynthesis in microalgae and suggest new genetic engineering or chemical biology approaches for enhanced oil production in microalgae.
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http://dx.doi.org/10.1186/1754-6834-7-81DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4052811PMC
June 2014

Establishing oleaginous microalgae research models for consolidated bioprocessing of solar energy.

Adv Biochem Eng Biotechnol 2012 ;128:69-84

CAS Key Laboratory of Biofuels, Shandong Key Laboratory of Energy Genetics, BioEnergy Genome Center, Qingdao, 266101, Shandong, China.

Algal feedstock is the foundation of the emerging algal biofuel industry. However, few algae found in nature have demonstrated the combination of high biomass accumulation rate, robust oil yield and tolerance to environmental stresses, all complex traits that a large-scale, economically competitive production scheme demands. Therefore, untangling the intricate sub-cellular networks underlying these complex traits, in one or a series of carefully selected algal research models, has become an urgent research mission, which can take advantage of the emerging model oleaginous microalgae that have already demonstrated small, simple and tackleable genomes and the potential for large-scale open-pond cultivation. The revolutions in whole-genome-based technologies, coupled with systems biology, metabolic engineering and synthetic biology approaches, would enable the rational design and engineering of algal feedstock and help to fill the gaps between the technical and economical reality and the enormous potential of algal biofuels.
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http://dx.doi.org/10.1007/10_2011_122DOI Listing
May 2014

Biosynthesis of fluorescent cyanobacterial allophycocyanin trimer in Escherichia coli.

Photosynth Res 2010 Aug 6;105(2):135-42. Epub 2010 Jul 6.

Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, People's Republic of China.

Allophycocyanin (APC), a cyanobacterial photosynthetic phycobiliprotein, functions in energy transfer as a light-harvesting protein. One of the prominent spectroscopic characteristics of APC is a strong red-shift in the absorption and emission maxima when monomers are assembled into a trimer. Previously, holo-APC alpha and beta subunits (holo-ApcA and ApcB) were successfully synthesized in Escherichia coli. In this study, both holo-subunits from Synechocystis sp. PCC 6803 were co-expressed in E. coli, and found to self-assemble into trimers. The recombinant APC trimer was purified by metal affinity and size-exclusion chromatography, and had a native structure identical to native APC, as determined by characteristic spectroscopic measurements, fluorescence quantum yield, tryptic digestion analysis, and molecular weight measurements. Combined with results from a study in which only the monomer was formed, our results indicate that bilin synthesis and the subsequent attachment to apo-subunits are important for the successful assembly of APC trimers. This is the first study to report on the assembly of recombinant ApcA and ApcB into a trimer with native structure. Our study provides a promising method for producing better fluorescent tags, as well as a method to facilitate the genetic analysis of APC trimer assembly and biological function.
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http://dx.doi.org/10.1007/s11120-010-9574-4DOI Listing
August 2010

Methyl jasmonate- or gibberellins A3-induced astaxanthin accumulation is associated with up-regulation of transcription of beta-carotene ketolase genes (bkts) in microalga Haematococcus pluvialis.

Bioresour Technol 2010 Aug 18;101(16):6468-74. Epub 2010 Apr 18.

YanTai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.

The microalga Haematococcus pluvialis accumulates astaxanthin in response to abiotic stresses. Since methyl jasmonate (MJ) and gibberellins A(3) (GA(3)) are involved in the stress responses of plants, the impact of these compounds on astaxanthin metabolism was studied. Alga cells treated separately with MJ and GA(3) accumulated more astaxanthin than the controls. MJ and GA(3) treatment increased the transcription of three beta-carotene ketolase genes (bkts). MJ- and GA(3)-responsive cis-acting elements were identified in the 5'-flanking regions of bkt genes. These results suggest that MJ and GA(3) constitute molecular signals in the network of astaxanthin accumulation. Induction of astaxanthin accumulation by MJ or GA(3) without any other stimuli presents an attractive application potential.
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http://dx.doi.org/10.1016/j.biortech.2010.03.072DOI Listing
August 2010

Isolation and characterization of a stress-dependent plastidial delta12 fatty acid desaturase from the Antarctic microalga Chlorella vulgaris NJ-7.

Lipids 2010 Feb 20;45(2):179-87. Epub 2010 Jan 20.

YanTai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, People's Republic of China.

An acclimation to the changing physicochemical conditions and high amount of Delta(12)-unsaturated fatty acids of the Antarctic Chlorella vulgaris NJ-7 prompted us to speculate about the involvement of Delta(12)-fatty acid desaturases (FAD) in its adaptation to the extremely unfavorable ambience. A full-length cDNA sequence, designated CvFAD6, was isolated from C. vulgaris NJ-7 via RT-PCR and RACE methods. Sequence alignment showed that the gene was homologous to corresponding Delta(12)-FAD from other eukaryotes. Phylogenetic analysis showed that it was grouped with plastidial Delta(12)-FAD with conserved histidine boxes. Yeast cells transformed with a plasmid construct containing CvFAD6 coding region accumulated a considerable amount of linoleic acid (18:2Delta(9,12)), normally not present in wild-type yeast cells, suggesting that the isolated gene encodes a functional Delta(12) enzyme. The correlation between the accumulation of CvFAD6 and temperature has been examined by real time PCR. The analysis showed a constant expression of CvFAD6 from 25 to 15 degrees C whereas a fourfold increased from 25 to 4 degrees C. Moreover, CvFAD6 transcription was more sensitive to saline stress since a 20-fold increase at 6% NaCl was detected. Our data demonstrate that CvFAD6 is the enzyme responsible for the Delta(12) fatty acids desaturation involved in low temperature and high salinity acclimation for Antarctic C. vulgaris NJ-7.
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http://dx.doi.org/10.1007/s11745-009-3381-8DOI Listing
February 2010

Molecular cloning and stress-dependent expression of a gene encoding Delta(12)-fatty acid desaturase in the Antarctic microalga Chlorella vulgaris NJ-7.

Extremophiles 2009 Nov 1;13(6):875-84. Epub 2009 Sep 1.

Yantai Institute of Coastal Zone Research for Sustainable Development, Chinese Academy of Sciences, Yantai, People's Republic of China.

The psychrotrophic Antarctic alga, Chlorella vulgaris NJ-7, grows under an extreme environment of low temperature and high salinity. In an effort to better understand the correlation between fatty acid metabolism and acclimation to Antarctic environment, we analyzed its fatty acid compositions. An extremely high amount of Delta(12) unsaturated fatty acids was identified which prompted us to speculate about the involvement of Delta(12) fatty acid desaturase in the process of acclimation. A full-length cDNA sequence, designated CvFAD2, was isolated from C. vulgaris NJ-7 via reverse transcription polymerase chain reaction (RT-PCR) and RACE methods. Sequence alignment and phylogenetic analysis showed that the gene was homologous to known microsomal Delta(12)-FADs with the conserved histidine motifs. Heterologous expression in yeast was used to confirm the regioselectivity and the function of CvFAD2. Linoleic acid (18:2), normally not present in wild-type yeast cells, was detected in transformants of CvFAD2. The induction of CvFAD2 at an mRNA level under cold stress and high salinity is detected by real-time PCR. The results showed that both temperature and salinity motivated the upregulation of CvFAD2 expression. The accumulation of CvFAD2 increased 2.2-fold at 15 degrees C and 3.9-fold at 4 degrees C compared to the alga at 25 degrees C. Meanwhile a 1.7- and 8.5-fold increase at 3 and 6% NaCl was detected. These data suggest that CvFAD2 is the enzyme responsible for the Delta(12) fatty acids desaturation involved in the adaption to cold and high salinity for Antarctic C. vugaris NJ-7.
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http://dx.doi.org/10.1007/s00792-009-0275-xDOI Listing
November 2009