Optimizing Nitrate and Tryptone to Enhance Growth and Triacylglycerol Accumulation in .

, a unicellular diatom, is considered a potential feedstock for the production of biofuel and a promising producer for high-value products eicosapentaenoic acid and fucoxanthin. However, a high-efficient cultivating strategy to achieve commercial production of triacylglycerol (TAG) from the diatom is an urgent demand. In this study, we optimized the content and ratio of nitrate and tryptone in the medium to enhance biomass and TAG accumulation simultaneously.

Monogalactosyldiacylglycerol synthase isoforms play diverse roles inside and outside the diatom plastid.

Diatoms derive from a secondary endosymbiosis event, which occurred when a eukaryotic host cell engulfed a red alga. This led to the formation of a complex plastid enclosed by four membranes: two innermost membranes originating from the red alga chloroplast envelope, and two additional peri- and epiplastidial membranes (PPM, EpM). The EpM is linked to the endoplasmic reticulum (ER).

Turning the industrially relevant marine alga Nannochloropsis red: one move for multifaceted benefits.

Nannochloropsis oceanica is an industrially relevant marine microalga rich in eicosapentaenoic acid (EPA, a valuable ω-3 polyunsaturated fatty acid), yet the algal production potential remains to be unlocked. Here we engineered N. oceanica to synthesize the high-value carotenoid astaxanthin independent of high-light (HL) induction for achieving multifaceted benefits.

Delta-5 elongase knockout reduces docosahexaenoic acid and lipid synthesis and increases heat sensitivity in a diatom.

Recent global marine lipidomic analysis reveals a strong relationship between ocean temperature and phytoplanktonic abundance of omega-3 long-chain polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are essential for human nutrition and primarily sourced from phytoplankton in marine food webs. In phytoplanktonic organisms, EPA may play a major role in regulating the phase transition temperature of membranes, while the function of DHA remains unexplored. In the oleaginous diatom Phaeodactylum tricornutum, DHA is distributed mainly on extraplastidial phospholipids, which is very different from the EPA enriched in thylakoid lipids.

A key gene, violaxanthin de-epoxidase-like 1, enhances fucoxanthin accumulation in Phaeodactylum tricornutum.

Background: Fucoxanthin has been widely investigated owing to its beneficial biological properties, and the model diatom Phaeodactylum tricornutum, possessing fucoxanthin (Fux) chlorophyll proteins as light-harvesting systems, is considered to have the potential to become a commercial cell factory for the pigment production.

Results: Here, we compared the pigment contents in 10 different P. tricornutum strains from the globe, and found that strain CCMP631 (Pt6) exhibited the highest Fux content but with a low biomass.

Isolation of High-Quality Plastids from the Diatom Phaeodactylum tricornutum.

Phaeodactylum tricornutum, a model pennate diatom, carries a secondary plastid surrounded by four membranes. Its biological function remains mysterious, supposed to combine features of the primary chloroplast and the endomembrane system. Isolation of high-quality plastid from the diatom enables a more conclusive understanding of the special structure and metabolic pathways in the plastid.

Concomitant percutaneous coronary intervention and transcatheter aortic valve replacement for aortic stenosis complicated with acute STEMI: a case report and literature review.

Aortic stenosis (AS) complicated with acute ST-segment elevation myocardial infarction (STEMI) is a life-threatening emergency with high mortality. A 75-year-old male patient attended the emergency department of Wuhan Asia Heart Hospital in December 2021 with chest pain for 2 days and exacerbation for 1 h. The electrocardiogram (ECG) indicated atrial fibrillation with rapid ventricular response and ST-segment depression.

Two plastidial lysophosphatidic acid acyltransferases differentially mediate the biosynthesis of membrane lipids and triacylglycerols in Phaeodactylum tricornutum.

Lysophosphatidic acid acyltransferases (LPAATs) catalyze the formation of phosphatidic acid (PA), a central metabolite in both prokaryotic and eukaryotic organisms for glycerolipid biosynthesis. Phaeodactylum tricornutum contains at least two plastid-localized LPAATs (ptATS2a and ptATS2b), but their roles in lipid synthesis remain unknown. Both ptATS2a and ptATS2b could complement the high temperature sensitivity of the bacterial plsC mutant deficient in LPAAT.

Proteomes reveal the lipid metabolic network in the complex plastid of Phaeodactylum tricornutum.

Phaeodactylum tricornutum plastid is surrounded by four membranes, and its protein composition and function remain mysterious. In this study, the P. tricornutum plastid-enriched fraction was obtained and 2850 proteins were identified, including 92 plastid-encoded proteins, through label-free quantitative proteomic technology.

Zeaxanthin epoxidase is involved in the carotenoid biosynthesis and light-dependent growth of the marine alga Nannochloropsis oceanica.

Background: The marine alga Nannochloropsis oceanica, an emerging model belonging to Heterokont, is considered as a promising light-driven eukaryotic chassis for transforming carbon dioxide to various compounds including carotenoids. Nevertheless, the carotenogenic genes and their roles in the alga remain less understood and to be further explored.

Results: Here, two phylogenetically distant zeaxanthin epoxidase (ZEP) genes from N.

CRISPR/Cas9-Mediated Genome Editing via Homologous Recombination in a Centric Diatom .

, the most abundant genus of marine planktonic diatoms, can be used in mariculture. An effective genetic transformation system with a short transformation period was established in by electroporation in our previous study. In this study, a sequence-specific clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 vector applicable for was constructed, and the expressions of sgRNA, resistance gene, and gene were driven by the endogenous promoters , and , respectively, in the vector.

CGI-58 Protein Acts as a Positive Regulator of Triacylglycerol Accumulation in .

Comparative gene identification-58 (CGI-58) is an activating protein of triacylglycerol (TAG) lipase. It has a variety of catalytic activities whereby it may play different roles in diverse organisms. In this study, a homolog of CGI-58 in (PtCGI-58) was identified.

PDAT regulates PE as transient carbon sink alternative to triacylglycerol in Nannochloropsis.

Triacylglycerols (TAGs) are the main storage lipids in photosynthetic organisms under stress. In the oleaginous alga Nannochloropsis oceanica, while multiple acyl CoA:diacylglycerol (DAG) acyltransferases (NoDGATs) are involved in TAG production, the role of the unique phospholipid:DAG acyltransferase (NoPDAT) remains unknown. Here, we performed a functional complementation assay in TAG-deficient yeast (Saccharomyces cerevisiae) and an in vitro assay to probe the acyltransferase activity of NoPDAT.

The Transition Toward Nitrogen Deprivation in Diatoms Requires Chloroplast Stand-By and Deep Metabolic Reshuffling.

Microalgae have adapted to face abiotic stresses by accumulating energy storage molecules such as lipids, which are also of interest to industries. Unfortunately, the impairment in cell division during the accumulation of these molecules constitutes a major bottleneck for the development of efficient microalgae-based biotechnology processes. To address the bottleneck, a multidisciplinary approach was used to study the mechanisms involved in the transition from nitrogen repletion to nitrogen starvation conditions in the marine diatom that was cultured in a turbidostat.

Impaired photoprotection in Phaeodactylum tricornutum KEA3 mutants reveals the proton regulatory circuit of diatoms light acclimation.

Diatoms are successful phytoplankton clades able to acclimate to changing environmental conditions, including e.g. variable light intensity.

Multiplexed CRISPR/Cas9 editing of the long-chain acyl-CoA synthetase family in the diatom Phaeodactylum tricornutum reveals that mitochondrial ptACSL3 is involved in the synthesis of storage lipids.

Long-chain acyl-CoA synthetases (LACS) play diverse and fundamentally important roles in lipid metabolism. While their functions have been well established in bacteria, yeast and plants, the mechanisms by which LACS isozymes regulate lipid metabolism in unicellular oil-producing microalgae, including the diatom Phaeodactylum tricornutum, remain largely unknown. In P.

Metabolic engineering of the oleaginous alga Nannochloropsis for enriching eicosapentaenoic acid in triacylglycerol by combined pulling and pushing strategies.

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.

Δ6 Fatty Acid Elongase is Involved in Eicosapentaenoic Acid Biosynthesis Via the ω6 Pathway in the Marine Alga .

represents a promising sunlight-driven alga for producing eicosapentaenoic acid (EPA, 20:5Δ,8,), 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 . Heterologous expression of NoΔ6-FAE in yeast confirmed its function in elongating C18 Δ6-PUFAs rather than others.

Amino Acid Catabolism During Nitrogen Limitation in .

Diatoms can accumulate high levels of triacylglycerols (TAGs) under nitrogen depletion and have attracted increasing attention as a potential system for biofuel production. In , a model diatom, about 40% of lipid is synthesized from the breakdown of cellular components under nitrogen starvation. Our previous studies indicated that carbon skeletons from enhanced branched-chain amino acid (BCAA) degradation under nitrogen deficiency contribute to TAG biosynthesis in .

Screening High CO-Tolerant Oleaginous Microalgae from Genera Desmodesmus and Scenedesmus.

Microalgae from genus Scenedesmus sensu lato (including Desmodesmus and Scenedesmus) were reported to be particularly suitable candidates for CO biomitigation. In this study, 16 strains from Scenedesmus sensu lato were obtained from different climate zones of China and their phylogenetic positions were determined. Seven strains out of the 16 showed high CO tolerance and grew much faster under 20% CO than air condition.

Screening of High Temperature-Tolerant Oleaginous Diatoms.

Screening suitable strains with high temperature adaptability is of great importance for reducing the cost of temperature control in microalgae cultivation, especially in summer. To obtain high temperature-tolerant diatoms, water samples were collected in summer from 7 different regions of China across the Northeast, North and East. A total of 731 water samples was collected and from them 131 diatom strains were isolated and identified based on the 18S rRNA sequences.

A genomics approach reveals the global genetic polymorphism, structure, and functional diversity of ten accessions of the marine model diatom Phaeodactylum tricornutum.

Diatoms emerged in the Mesozoic period and presently constitute one of the main primary producers in the world's ocean and are of a major economic importance. In the current study, using whole genome sequencing of ten accessions of the model diatom Phaeodactylum tricornutum, sampled at broad geospatial and temporal scales, we draw a comprehensive landscape of the genomic diversity within the species. We describe strong genetic subdivisions of the accessions into four genetic clades (A-D) with constituent populations of each clade possessing a conserved genetic and functional makeup, likely a consequence of the limited dispersal of P.

Electroporation Transformation Protocol for Phaeodactylum tricornutum.

Genetic transformation system is very important for both basic biological research and commercial exploitation of diatoms. Here we describe a high-efficiency nuclear transformation method for the model diatom Phaeodactylum tricornutum using an electroporation system, and the maximum transformation frequency obtained is about 3 × 10 cells. The described protocol also provides some clue for developing electroporation transformation system in other eukaryotic microalgae.