Mixotrophic culture enhances fucoxanthin production in the haptophyte Pavlova gyrans.

Fucoxanthin is a versatile substance in the food and pharmaceutical industries owing to its excellent antioxidant and anti-obesity properties. Several microalgae, including the haptophyte Pavlova spp., can produce fucoxanthin and are potential industrial fucoxanthin producers, as they lack rigid cell walls, which facilitates fucoxanthin extraction. However, the commercial application of Pavlova spp. is limited owing to insufficient biomass production. In this study, we aimed to develop a mixotrophic cultivation method to increase biomass and fucoxanthin production in Pavlova gyrans OPMS 30543X. The effects of culturing OPMS 30543X with different organic carbon sources, glycerol concentrations, mixed-nutrient conditions, and light intensities on the consumption of organic carbon sources, biomass production, and fucoxanthin accumulation were analyzed. Several organic carbon sources, such as glycerol, glucose, sucrose, and acetate, were examined, revealing that glycerol was well-consumed by the microalgae. Biomass and fucoxanthin production by OPMS 30543X increased in the presence of 10 mM glycerol compared to that observed without glycerol. Metabolomic analysis revealed higher levels of the metabolites related to the glycolytic, Calvin-Benson-Bassham, and tricarboxylic acid cycles under mixotrophic conditions than under autotrophic conditions. Cultures grown under mixotrophic conditions with a light intensity of 100 µmol photons m-2 s-1 produced more fucoxanthin than autotrophic cultures. Notably, the amount of fucoxanthin produced (18.9 mg/L) was the highest reported thus far for Pavlova species. In conclusion, the use of mixotrophic culture is a promising strategy for increasing fucoxanthin production in Pavlova species. KEY POINTS: • Glycerol enhances biomass and fucoxanthin production in Pavlova gyrans • Metabolite levels increase under mixotrophic conditions • Mixotrophic conditions and medium-light intensity are appropriate for P. gyrans.

Effects of micro- and nano-plastics on growth, antioxidant system, DMS, and DMSP production in Emiliania huxleyi.

Due to the potential impacts of microplastics (MPs) and nanoplastics (NPs) on algal growth and thereby affect the climate-relevant substances, dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS), we studied the polystyrene (PS) MPs and NPs of 1 µm and 80 nm impacts on the growth, chlorophyll content, reactive oxygen species (ROS), antioxidant enzyme activity, and DMS/DMSP production in Emiliania huxleyi. E. huxleyi is a prominent oceanic alga that plays a key role in DMS and DMSP production. The results revealed that high concentrations of MPs and NPs inhibited the growth, carotenoid (Car), and Chl a concentrations of E. huxleyi. However, short-time exposure to low concentrations of PS MPs and NPs stimulated the growth of E. huxleyi. Furthermore, high concentrations of MPs and NPs resulted in an increase in the superoxide anion radical (O2.-) production rate and a decrease in the malondialdehyde (MDA) content compared with the low concentrations. Exposure to MPs and NPs at 5 mg L-1 induced superoxide dismutase (SOD) activity as a response to scavenging ROS. High concentrations of MPs and NPs significantly inhibited the production of DMSP and DMS. The findings of this study support the potential ecotoxicological impacts of MPs and NPs on algal growth, antioxidant system, and dimethylated sulfur compounds production, which maybe potentially impact the global climate.

Enantioselective transformation of phytoplankton-derived dihydroxypropanesulfonate by marine bacteria.

Chirality, a fundamental property of matter, is often overlooked in the studies of marine organic matter cycles. Dihydroxypropanesulfonate (DHPS), a globally abundant organosulfur compound, serves as an ecologically important currency for nutrient and energy transfer from phytoplankton to bacteria in the ocean. However, the chirality of DHPS in nature and its transformation remain unclear. Here, we developed a novel approach using chiral phosphorus-reagent labeling to separate DHPS enantiomers. Our findings demonstrated that at least one enantiomer of DHPS is present in marine diatoms and coccolithophores, and that both enantiomers are widespread in marine environments. A novel chiral-selective DHPS catabolic pathway was identified in marine Roseobacteraceae strains, where HpsO and HpsP dehydrogenases at the gateway to DHPS catabolism act specifically on R-DHPS and S-DHPS, respectively. R-DHPS is also a substrate for the dehydrogenase HpsN. All three dehydrogenases generate stable hydrogen bonds between the chirality-center hydroxyls of DHPS and highly conserved residues, and HpsP also form coordinate-covalent bonds between the chirality-center hydroxyls and Zn2+, which determines the mechanistic basis of strict stereoselectivity. We further illustrated the role of enzymatic promiscuity in the evolution of DHPS metabolism in Roseobacteraceae and SAR11. This study provides the first evidence of chirality's involvement in phytoplankton-bacteria metabolic currencies, opening a new avenue for understanding the ocean organosulfur cycle.

Structure and replication cycle of a virus infecting climate-modulating alga Emiliania huxleyi.

The globally distributed marine alga Emiliania huxleyi has cooling effect on the Earth's climate. The population density of E. huxleyi is restricted by Nucleocytoviricota viruses, including E. huxleyi virus 201 (EhV-201). Despite the impact of E. huxleyi viruses on the climate, there is limited information about their structure and replication. Here, we show that the dsDNA genome inside the EhV-201 virion is protected by an inner membrane, capsid, and outer membrane. EhV-201 virions infect E. huxleyi by using fivefold vertices to bind to and fuse the virus' inner membrane with the cell plasma membrane. Progeny virions assemble in the cytoplasm at the surface of endoplasmic reticulum-derived membrane segments. Genome packaging initiates synchronously with the capsid assembly and completes through an aperture in the forming capsid. The genome-filled capsids acquire an outer membrane by budding into intracellular vesicles. EhV-201 infection induces a loss of surface protective layers from E. huxleyi cells, which enables the continuous release of virions by exocytosis.

Metabolic trade-offs constrain the cell size ratio in a nitrogen-fixing symbiosis.

Biological dinitrogen (N2) fixation is a key metabolic process exclusively performed by prokaryotes, some of which are symbiotic with eukaryotes. Species of the marine haptophyte algae Braarudosphaera bigelowii harbor the N2-fixing endosymbiotic cyanobacteria UCYN-A, which might be evolving organelle-like characteristics. We found that the size ratio between UCYN-A and their hosts is strikingly conserved across sublineages/species, which is consistent with the size relationships of organelles in this symbiosis and other species. Metabolic modeling showed that this size relationship maximizes the coordinated growth rate based on trade-offs between resource acquisition and exchange. Our findings show that the size relationships of N2-fixing endosymbionts and organelles in unicellular eukaryotes are constrained by predictable metabolic underpinnings and that UCYN-A is, in many regards, functioning like a hypothetical N2-fixing organelle (or nitroplast).

Neuroprotection of Truncated Peptide IIAVE from Isochrysis zhanjiangensis: Quantum Chemical, Molecular Docking, and Bioactivity Studies.

Parkinson's disease (PD) is a progressive neurodegenerative disorder of the elderly for which there is no cure or disease-modifying therapy. Mitochondrial dysfunction and oxidative stress play a central role in dopaminergic neurodegeneration in PD. Therefore, antioxidants are considered a promising neuroprotective approach. In in vivo activity studies, 6-OHDA-induced oxidative stress in SH-SY5Y cells was established as a model of PD for cellular experiments. IIAVE (Ile-Ile-Ala-Val-Glu) was derived from Isochrysis zhanjiangensis octapeptide (IIAVEAGC), which has a small molecular weight. The structure and antioxidant activity of IIAVE were tested in a previous study and proved to have good antioxidant potential. In this study, the chemical properties of IIAVE were calculated using quantum chemical methods, including frontier molecular orbital (FMO), molecular electrostatic potential (MEP), natural population analysis (NPA), and global reactivity properties. The interaction of IIAVE with Bcl-2 and DJ-1 was investigated using the molecular docking method. The results showed that IIAVE promoted the activation of the Keap1/Nrf2 pathway and up-regulated the expression of the superoxide dismutase 1 (SOD-1) protein by inhibiting the level of reactive oxygen species (ROS) in cells. In addition, IIAVE inhibits ROS production and prevents 6-OHDA-induced oxidative damage by restoring mitochondrial membrane potential. Furthermore, IIAVE inhibited cell apoptosis by increasing the Bcl-2/Bax ratio and inhibiting the activation of Caspase-9 and Caspase-3. Thus, IIAVE may become a potential drug for the treatment and prevention of PD.

Ethanol extracts of Isochrysis zhanjiangensis alleviate acute alcoholic liver injury and modulate intestinal bacteria dysbiosis in mice.

BACKGROUND: Alcoholic liver disease (ALD) is responsible for 3.3 million deaths per annum. Efficacious therapeutic modalities or drug treatments for ALD have not yet been found, so it is urgent to seek new agents for preventing ALD and its related disease. Many experiments have indicated that modulating the gut microbiota and regulating the toll-like receptor 4 (TLR4)/nuclear transcription factor-κB (NF-κB) inflammatory pathway can provide a new target for prevention and treatment of ALD. Marine microalgae have their natural metabolic pathways to synthesize various of bioactive compounds as promising candidates for hepatoprotection. In this study, we investigated ethanol extracts from Isochrysis zhanjiangensis (EEIZ) to evaluate their ability to alleviate acute alcoholic liver injury, regulate TLR4/NF-κB inflammatory pathway and modulate intestinal bacteria dysbiosis in mice for ALD treatment. RESULTS: In the acute ALD mouse model, EEIZ reduced levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, triacylglyceride, total cholesterol and low-density lipoprotein, while increasing the level of high-density lipoprotein. Besides, TLR4, myeloid differentiation factor 88, NF-κB and tumor necrosis factor-α expression levels in liver tissue were effectively downregulated by EEIZ. Furthermore, treatment with EEIZ enhanced intestinal homeostasis and significantly alleviated the damage caused by alcohol. CONCLUSION: EEIZ showed effective hepatoprotective activity against alcohol-induced acute liver injury in mice as it could alleviate hepatocyte damage, suppress the TLR4/NF-κB inflammatory pathway and regulate the intestinal flora structure. EEIZ could be a good candidate for preventing acute alcoholic liver injury. © 2024 Society of Chemical Industry.

Cell-Penetrating Peptide Delivery of Nucleic Acid Cargo to Emiliania huxleyi, a Calcifying Marine Coccolithophore.

Coccolithophores are a group of unicellular marine phytoplankton that exhibit a prolific capacity for carbon conversion and are critical to ocean biogeochemistry. A fundamental understanding of coccolithophore biomineralization has been limited, in part, by the lack of genetic and molecular tools to investigate the organisms. In particular, it has proven to be difficult to deliver macromolecules across the coccosphere-membrane complex. To overcome this barrier, we employed cell-penetrating peptides (CPP) in the Emiliania huxleyi coccolithophores. We evaluated three established CPPs (TAT, R9, and KFF) and designed a CPP that incorporates a high proline content identified in the protein transduction domain of EhV060, an E. huxleyi virus lectin protein. To measure the delivery performance, we covalently linked CPPs to synthetic peptide nucleic acids (PNA) and attached a fluorescein marker. CPP-PNA-FITC complexes were efficiently delivered across the coccosphere-membrane complex to the cytoplasm of E. huxleyi cells. Characterization of E. huxleyi demonstrates that CPP-PNA are nontoxic and reveals specific effects of CPP-PNA on cell biology and calcification. Direct delivery and characterization of synthetic nucleic acids represent a step forward in synthetic biology to explore coccolithophore biomineralization.

Variability in Macro- and Micronutrients of 15 Rarely Researched Microalgae.

Microalgae have enormous potential for human nutrition, yet the European Commission has authorized the consumption of only eleven species. Strains of fifteen rarely researched microalgae from two kingdoms were screened regarding their nutritional profile and value for human health in two cultivation phases. Contents of protein, fiber, lipids, fatty acids, minerals, trace elements and heavy metals were determined. In the growth phase, microalgae accumulated more arginine, histidine, ornithine, pure and crude protein, Mg, Mn, Fe and Zn and less Ni, Mo and I2 compared to the stationary phase. Higher contents of total fat, C14:0, C14:1n5, C16:1n7, C20:4n6, C20:5n3 and also As were observed in microalgae from the chromista kingdom in comparison to microalgae from the plantae kingdom (p < 0.05). Conversely, the latter had higher contents of C20:0, C20:1n9 and C18:3n3 as well as Ca and Pb (p < 0.05). More precisely, Chrysotila carterae appeared to have great potential for human nutrition because of its high nutrient contents such as fibers, carotenoids, C20:6n3, Mg, Ca, Mn, Fe, Se, Zn, Ni, Mo and I2. In summary, microalgae may contribute to a large variety of nutrients, yet the contents differ between kingdoms, cultivation phases and also species.

A joint proteomic and genomic investigation provides insights into the mechanism of calcification in coccolithophores.

Coccolithophores are globally abundant, calcifying microalgae that have profound effects on marine biogeochemical cycles, the climate, and life in the oceans. They are characterized by a cell wall of CaCO3 scales called coccoliths, which may contribute to their ecological success. The intricate morphologies of coccoliths are of interest for biomimetic materials synthesis. Despite the global impact of coccolithophore calcification, we know little about the molecular machinery underpinning coccolithophore biology. Working on the model Emiliania huxleyi, a globally distributed bloom-former, we deploy a range of proteomic strategies to identify coccolithogenesis-related proteins. These analyses are supported by a new genome, with gene models derived from long-read transcriptome sequencing, which revealed many novel proteins specific to the calcifying haptophytes. Our experiments provide insights into proteins involved in various aspects of coccolithogenesis. Our improved genome, complemented with transcriptomic and proteomic data, constitutes a new resource for investigating fundamental aspects of coccolithophore biology.

Enhancing the Thermotolerance of Isochrysis zhangjiangensis Through Co-culturing With Algoriphagus marincola.

Isochrysis zhangjiangensis is an important microalgal species used as bait in aquaculture. However, its optimal cultivation temperature is around 25 °C, limiting its use in summer when temperature is higher. To overcome this limitation, we aimed to develop a consortia of I. zhangjiangensis and bacteria that are more resistant to heat stress. Here, six thermotolerance-promoting bacterial strains were isolated from the culture of a heat-tolerant mutant strain of I. zhangjiangensis (IM), and identified as Algoriphagus marincola, Nocardioides sp., Pseudidiomarina sp., Labrenzia alba, Nitratireductor sp., and Staphylococcus haemolyticus. Further, co-culturing I. zhangjiangensis with A. marincola under high temperature conditions increased cell density, chlorophyll a, PSII maximum photochemical efficiency (Fv/Fm), and soluble protein content of microalgae. The presence of A. marincola positively influenced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and total antioxidant capacity (T-AOC) in I. zhangjiangensis cells, while concurrently reducing the levels of reactive oxygen species (ROS). Additionally, gene expression studies confirmed that co-culturing with A. marincola upregulated the expression of antioxidant-related genes (sod and pod) and stress tolerance genes (heat shock protein genes). Our findings indicate that A. marincola effectively helps I. zhangjiangensis withstand high temperature stress, leading to improved yield of microalgae during high temperature conditions. The thermotolerance-promoting bacteria can be exploited as potential inoculants for enhancing the productivity and sustainability of bait microalgae in aquaculture.

Lipid biomarkers for algal resistance to viral infection in the ocean.

Marine viruses play a key role in regulating phytoplankton populations, greatly affecting the biogeochemical cycling of major nutrients in the ocean. Resistance to viral infection has been reported for various phytoplankton species under laboratory conditions. Nevertheless, the occurrence of resistant cells in natural populations is underexplored due to the lack of sensitive tools to detect these rare phenotypes. Consequently, our current understanding of the ecological importance of resistance and its underlying mechanisms is limited. Here, we sought to identify lipid biomarkers for the resistance of the bloom-forming alga Emiliania huxleyi to its specific virus, E. huxleyi virus (EhV). By applying an untargeted lipidomics approach, we identified a group of glycosphingolipid (GSL) biomarkers that characterize resistant E. huxleyi strains and were thus termed resistance-specific GSLs (resGSLs). Further, we detected these lipid biomarkers in E. huxleyi isolates collected from induced E. huxleyi blooms and in samples collected during an open-ocean E. huxleyi bloom, indicating that resistant cells predominantly occur during the demise phase of the bloom. Last, we show that the GSL composition of E. huxleyi cultures that recover following infection and gain resistance to the virus resembles that of resistant strains. These findings highlight the metabolic plasticity and coevolution of the GSL biosynthetic pathway and underscore its central part in this host-virus arms race.

Cell cycle of microalga Isochrysis galbana arrested by neurotoxin ß-N-methylamino-l-alanine and corresponding molecular mechanisms.

The phycotoxin ß-N-methylamino-l-alanine (BMAA) has attracted attention due to its risks to marine organisms and human health. In this study, approximately 85 % of synchronized cells of the marine microalga Isochrysis galbana were arrested at the cell cycle G1 phase by BMAA at 6.5 µM for a 24-h exposure. The concentration of chlorophyll a (Chl a) gradually decreased, while the maximum quantum yield of PSII (Fv/Fm), the maximum relative electron transport rate (rETRmax), light utilization efficiency (α) and half-saturated light irradiance (Ik) reduced early and recovered gradually in I. galbana exposed to BMAA in 96-h batch cultures. Transcriptional expression of I. galbana analyzed at 10, 12, and 16 h disclosed multiple mechanisms of BMAA to suppress the microalgal growth. Production of ammonia and glutamate was limited by the down-regulation of nitrate transporters, glutamate synthase, glutamine synthetase, cyanate hydrolase, and formamidase. Diverse extrinsic proteins related to PSII, PSI, cytochrome b6f complex, and ATPase were influenced by BMAA at transcriptional level. Suppression of the DNA replication and mismatch repair pathways increased the accumulation of misfolded proteins, which was reflected by the up-regulated expression of proteasome to accelerate proteolysis. This study improves our understanding of the chemical ecology impacts of BMAA in marine ecosystems.

Response mechanism of harmful algae Phaeocystis globosa to ocean warming and acidification.

Simultaneous ocean warming and acidification will alter marine ecosystem structure and directly affect marine organisms. The alga Phaeocystis globosa commonly causes harmful algal blooms in coastal areas of eastern China. P. globosa often outcompetes other species due to its heterotypic life cycle, primarily including colonies and various types of solitary cells. However, little is known about the adaptive response of P. globosa to ocean warming and acidification. This study aimed to reveal the global molecular regulatory networks implicated in the response of P. globosa to simultaneous warming and acidification. After exposure to warming and acidification, the phosphatidylinositol (PI) and mitogen-activated protein kinase (MAPK) signaling pathways of P. globosa were activated to regulate other molecular pathways in the cell, while the light harvesting complex (LHC) genes were downregulated to decrease photosynthesis. Exposure to warming and acidification also altered the intracellular energy flow, with more energy allocated to the TCA cycle rather than to the biosynthesis of fatty acids and hemolytic substances. The upregulation of genes associated with glycosaminoglycan (GAG) degradation prevented the accumulation of polysaccharides, which led to a reduction in colony formation. Finally, the upregulation of the Mre11 and Rad50 genes in response to warming and acidification implied an increase in meiosis, which may be used by P. globosa to increase the number of solitary cells. The increase in genetic diversity through sexual reproduction may be a strategy of P. globosa that supports rapid response to complex environments. Thus, the life cycle of P. globosa underwent a transition from colonies to solitary cells in response to warming and acidification, suggesting that this species may be able to rapidly adapt to future climate changes through life cycle transitions.

Characterization of the molecular mechanisms of silicon uptake in coccolithophores.

Coccolithophores are an important group of calcifying marine phytoplankton. Although coccolithophores are not silicified, some species exhibit a requirement for Si in the calcification process. These species also possess a novel protein (SITL) that resembles the SIT family of Si transporters found in diatoms. However, the nature of Si transport in coccolithophores is not yet known, making it difficult to determine the wider role of Si in coccolithophore biology. Here, we show that coccolithophore SITLs act as Na+ -coupled Si transporters when expressed in heterologous systems and exhibit similar characteristics to diatom SITs. We find that CbSITL from Coccolithus braarudii is transcriptionally regulated by Si availability and is expressed in environmental coccolithophore populations. However, the Si requirement of C. braarudii and other coccolithophores is very low, with transport rates of exogenous Si below the level of detection in sensitive assays of Si transport. As coccoliths contain only low levels of Si, we propose that Si acts to support the calcification process, rather than forming a structural component of the coccolith itself. Si is therefore acting as a micronutrient in coccolithophores and natural populations are only likely to experience Si limitation in circumstances where dissolved silicon (DSi) is depleted to extreme levels.

Effects of nutrient limitation on cell growth, exopolysaccharide secretion and TEP production of Phaeocystis globosa.

Phaeocystis globosa (P. globosa) often colonizes and produces mucus, which may cause massive blooms in coastal areas. To understand mechanism of the growth and the impact factors for better control of the bloom, we conducted a laboratory experiment on the effect of nitrogen (N) or phosphorus (P) limitation on the cell growth, production of exopolysaccharide (EPS), and transparent exopolymeric particles (TEP) of P. globosa. Results show no obvious differences in the N- and/or P-limitation in TEP production, polysaccharide secretion, and colony growth of P. globosa. Particularly in the death phase of the algae growth, the TEP production level in the experiment differed significantly, and was higher in the P-limitation group than that in the N-limitation group; additionally, the P-limitation group produced a relatively higher amount of EPS than N-limitation group, with greater cellular chlorophyll-a content, and in greater photosynthetic reaction rate of P. globosa cells, than those of the N-limitation group. However, under N-limited conditions, the algae colony survived longer. Under P-limited condition, P. globosa cells spend the photosynthesis-produced substances and energy for the secretion of extracellular substances but for cell reproduction, which was indicated by P. globosa cell growth and carbon content ratio between TEP and biomass.

Quantitative Proteomic Analysis Reveals the Key Molecular Events Driving Phaeocystis globosa Bloom and Dissipation.

Phaeocystis globosa is a marine-bloom-forming haptophyte with a polymorphic life cycle alternating between free-living cells and a colonial morphotype, that produces high biomass and impacts ecological structure and function. The mechanisms of P. globosa bloom formation have been extensively studied, and various environmental factors are believed to trigger these events. However, little is known about the intrinsic biological processes that drive the bloom process, and the mechanisms underlying P. globosa bloom formation remain enigmatic. Here, we investigated a P. globosa bloom occurring along the Chinese coast and compared the proteomes of in situ P. globosa colonies from bloom and dissipation phases using a tandem mass tag (TMT)-based quantitative proteomic approach. Among the 5540 proteins identified, 191 and 109 proteins displayed higher abundances in the bloom and dissipation phases, respectively. The levels of proteins involved in photosynthesis, pigment metabolism, nitrogen metabolism, and matrix substrate biosynthesis were distinctly different between these two phases. Ambient nitrate is a key trigger of P. globosa bloom formation, while the enhanced light harvest and multiple inorganic carbon-concentrating mechanisms support the prosperousness of colonies in the bloom phase. Additionally, colonies in the bloom phase have greater carbon fixation potential, with more carbon and energy being fixed and flowing toward the colonial matrix biosynthesis. Our study revealed the key biological processes underlying P. globosa blooms and provides new insights into the mechanisms behind bloom formation.

Multi-omics Analyses Provide Insight into the Biosynthesis Pathways of Fucoxanthin in Isochrysis galbana.

Isochrysis galbana is considered an ideal bait for functional foods and nutraceuticals of humans because of its high fucoxanthin (Fx) content. However, multi-omics analysis of the regulatory networks for Fx biosynthesis in I. galbana has not been reported. In this study, we report a high-quality genome assembly of I. galbana LG007, which has a genome size of 92.73 Mb, with a contig N50 of 6.99 Mb and 14,900 protein-coding genes. Phylogenetic analysis confirmed the monophyly of Haptophyta, with I. galbana sister to Emiliania huxleyi and Chrysochromulina tobinii. Evolutionary analysis revealed an estimated divergence time between I. galbana and E. huxleyi of âˆ¼ 133 million years ago. Gene family analysis indicated that lipid metabolism-related genes exhibited significant expansion, including IgPLMT, IgOAR1, and IgDEGS1. Metabolome analysis showed that the content of carotenoids in I. galbana cultured under green light for 7 days was higher than that under white light, and ß-carotene was the main carotenoid, accounting for 79.09% of the total carotenoids. Comprehensive multi-omics analysis revealed that the content of ß-carotene, antheraxanthin, zeaxanthin, and Fx was increased by green light induction, which was significantly correlated with the expression of IgMYB98, IgZDS, IgPDS, IgLHCX2, IgZEP, IgLCYb, and IgNSY. These findings contribute to the understanding of Fx biosynthesis and its regulation, providing a valuable reference for food and pharmaceutical applications.

Mechanism analysis of octapeptide from microalgae, Isochrysis zhanjiangensis for suppressing vascular injury and angiogenesis in human umbilical vein endothelial cell.

Incorporating microalgae active peptides into functional foods is one of the hottest topics in algae research. Ile-Ile-Ala-Val-Glu-Ala-Gly-Cys (IEC) is a novel octapeptide isolated from the microalgae, Isochrysis Zhanjiangensis that inhibits the vascular injury, angiogenesis and has a protective effect on cardiovascular diseases. In this study, IEC can suppress ROS production and inhibit pro-inflammatory factors through the Nrf2/SOD/HO-1 and NF-κB signaling pathways. Additionally, IEC inhibits angiogenesis by reducing the expression of MMP2 and MMP9 via the PI3K/AKT, NF-κB, and MAPK pathways. Molecular docking also demonstrated that IEC possesses an excellent docking effect with SOD, Bcl-2 and VEGFR-2. In conclusion, this study not only provides a new idea for the prevention of cardiovascular diseases, but also proves the possibility of octapeptide (IEC) in functional food and drugs, and further improves the use value of microalgae (Isochrysis Zhanjiangensis).

Evolution of a chimeric mitochondrial carbonic anhydrase through gene fusion in a haptophyte alga.

Carbonic anhydrases (CAs) are a universal enzyme family that catalyses the interconversion of carbon dioxide and bicarbonate, and they are localized in most compartments including mitochondria and plastids. Thus far, eight classes of CAs (α-, ß-, γ-, δ-, ζ-, η-, θ- and ι-CA) have been characterized. This study reports an interesting gene encoding a fusion protein of ß-CA and ι-CA found in the haptophyte Isochrysis galbana. Recombinant protein assays demonstrated that the C-terminal ι-CA region catalyses CO2 hydration, whereas the N-terminal ß-CA region no longer exhibits enzymatic activity. Considering that haptophytes generally have mitochondrion-localized ß-CAs and plastid-localized ι-CAs, the fusion CA would show an intermediate stage in which mitochondrial ß-CA is replaced by ι-CA in a haptophyte species.