Undaria Pinnatifida Research Articles

Perception and acceptance of high seaweed content novel foods (Ulva spp. and Undaria pinnatifida) across New Zealand and Singaporean consumers

Edible seaweeds are gaining global popularity as nutritious and sustainable food sources, extending beyond Asian into Western diets. To investigate consumer perception and acceptance of high seaweed content foods, two novel products, seaweed dumplings and pasta, were developed using the mixture of Ulva spp. and Undaria pinnatifida as a primary ingredient. Consumer evaluations were conducted in New Zealand (NZ, n = 157) and Singapore (SG, n = 176). Results showed low overall liking and willingness to purchase for both products in each country, though NZ consumers rated them more positively in terms of liking, healthiness and sustainability than SG consumers. Willingness to purchase was positively correlated with ratings of liking, healthiness, and sustainability. Emotional responses differed by country and product, with more NZ participants reporting positive emotions (e.g., pleased, happy, hopeful and loving) and dumplings evoking more activate emotions (e.g., energetic, shocked and amazed). Umami taste enhanced overall liking in both countries, while slimy texture (NZ) and fish-like flavour (SG) decreased overall liking. These results underscore the current challenges in consumer acceptance of high seaweed content novel foods, but also highlight cross-cultural differences that can guide the development of seaweed-based foods in global markets.

Bioactive Compounds of Sea Mustard (Undaria pinnatifida) Waste Affected by Drying Methods

Sea mustard (Undaria pinnatifida) is a brown macroalga extensively cultivated and consumed in South Korea. However, the high volume of seaweed production in the country results in substantial waste generation. To mitigate this issue, the bioactive compounds of sea mustard waste parts (sporophyll, root, and stem) were assessed under different drying conditions (freeze, oven, and microwave drying) to evaluate their potential as functional ingredients. The sporophyll contained the highest levels of total chlorophyll (540.38 μg/g), fucoxanthin (165.87 μg/g), flavonoids (5.47 μg QE/g), phytomenadione (332.59 μg/100 g), and cobalamin (5.92 μg/100 g). In contrast, the root exhibited the highest antioxidant activities (DPPH: 1582.37 μg GAE/g; ABTS: 0.93 mg AA/g), total polyphenol (2718.81 μg GAE/g) and phlorotannin (4298.22 μg PGE/g) contents. Freeze drying achieved the best retention rates for most bioactive compounds, except for fucoxanthin, which was highest in microwave-dried samples. These results demonstrate the potential of sea mustard waste as a valuable source of bioactive compounds, with the retention of these compounds being influenced by drying methods, depending on the specific part of the seaweed.

Assessment of climate change impacts on large brown seaweed (Undaria pinnatifida) growth in the Sanriku coastal area, Japan

Assessment of climate change impacts on large brown seaweed (Undaria pinnatifida) growth in the Sanriku coastal area, Japan

Fucoidan from Undaria pinnatifida Enhances Exercise Performance and Increases the Abundance of Beneficial Gut Bacteria in Mice.

Fucoidans, known for their diverse biological properties such as anti-inflammatory, antiviral, antitumor, and immune stimulatory effects, have recently gained attention for their potential benefits in exercise endurance, muscle mass, and anti-fatigue. However, the mechanisms by which fucoidans enhance exercise performance are still unclear. To investigate these effects, we administered 400 mg/kg/day of fucoidan extract derived from Undaria pinnatifida to 64 C57BL/6J mice over 10 weeks. We evaluated changes in running activity, mitochondrial-related gene expression in skeletal muscle, and alterations in the intestinal microbiome. Our results showed that fucoidan supplementation significantly increased daily running distance and muscle mass by 25.5% and 10.4%, respectively, in mice on a standard chow diet, and with more modest effects observed in those on a high-fat diet (HFD). Additionally, fucoidan supplementation led to a significant increase in beneficial gut bacteria, including Bacteroides/Prevotella, Akkermansia muciniphila, and Lactobacillus, along with a notable reduction in the Firmicutes/Bacteroidetes ratio, indicating improved gut microbiome health. Mechanistically, fucoidan supplementation upregulated the mRNA expression of key genes related to mitochondrial biogenesis and oxidative capacity, such as COX4, MYH1, PGC-1α, PPAR-γ, and IGF1, in both standard chow and HFD-fed mice. Our findings suggest that fucoidan supplementation enhances exercise performance, improves muscle function, and positively modulates the gut microbiome in mice, regardless of diet. These effects may be attributed to fucoidans' potential prebiotic role, promoting the abundance of beneficial gut bacteria and contributing to enhanced exercise performance, increased muscle strength, and improved recovery.

Antioxidant effect and inhibitory effect on nitric oxide production of sea mustard fractions from Busan, Korea

We investigated the chemical characteristics and nitric oxide (NO) production and antioxidant effects of sea mustard (Undaria pinnatifida) fractions obtained from Taejongdae in Busan, Korea. Dried sea mustard was extracted using different solvents, and antioxidant effects was evaluated based on the radical scavenging and DNA oxidation assays and the effect on reactive oxygen species (ROS) production. Total phenolic content was significantly higher in the 85% aq. MeOH fraction than that in the other factions. The 85% aq. MeOH fraction was more effective in scavenging free radicals than other fractions, as assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2.2'-azino-bis (3-ethylbenothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS) assays (P<0.05). All sea mustard fractions decreased H2O2-induced cellular ROS production compared to the control (P<0.05), however, the 85% aq. MeOH fraction exhibited the greatest inhibitory effect on ROS production among all fractions. Moreover, the 85% aq. MeOH fraction significantly inhibited genomic DNA oxidation. In addition, we measured NO levels to determine the potential anti-inflammatory effects of fractions from sea mustard and observed the highest level of activity in case of the 85% aq. MeOH fraction. These results indicated that the antioxidant effects of sea mustard are associated with its higher phenol content. This study proposes that processed food products supplemented with sea mustard can be developed into functional foods to promote the health of the local populations.

Physicochemical characterization of bioactive polysaccharides from three seaweed and application of functional fruit packaging films

Seaweed polysaccharides show tremendous research and application value because of their significant and unique biological activities. However, reports on seaweed polysaccharides usually focus on in-depth studies of a specific biological activity, which severely limits their further development. Herein, three seaweed polysaccharides were isolated from Undaria pinnatifida (UPPS), Sargassum pallidum (SPPS), and Ulva lactuca (ULPS), respectively. The physicochemical properties, structure, rheological properties, antioxidant activities, antibacterial activities, and anti-glycation activities of UPPS, ULPS, and SPPS were comprehensively studied. It was first demonstrated that SPPS and UPPS had triple prominent biological activities. SPPS exhibited the best biological activities in antioxidation (IC50 in the ABTS test: 0.4616 ± 0.0134 mg/mL), antibacterial effect, and anti-glycation activity (inhibitory rate: 84.74 ± 0.07 %). Additionally, UPPS films (UPPSF) demonstrated superior ultraviolet shielding performance, lower water vapor permeability (1.78 ± 0.01 g/m·s·Pa × 10−11), higher hydrophobicity (water contact angle: 96.91 ± 2.52°), and higher antioxidant activity compared to ULPS films (ULPSF). UPPSF and ULPSF effectively prolonged the shelf life of strawberries to six days, and UPPSF showed better preservation properties. This work provides novel theoretical insights into the use of polysaccharides as medicinal nutraceuticals, bioactive agents, and food packaging films.

Exploration of an efficient and universal extraction strategy for fucoidan with glycolipid-lowering activity from typical brown algae: The importance of ball milling combined with acid treatment

Fucoidan possesses a variety of biological activities beneficial for human wellness. It is a good candidate for ameliorating obesity and diabetes. However, high-purity fucoidan products are limited due to the co-extraction of impurities i.e. alginate, protein and small molecular substances. In this study, the optimal preparation strategy for high-purity fucoidan from a template brown alga (Saccharina japonica) was screened out by the exploration of key and auxiliary steps. The key step was confirmed as moderate-temperature acid extraction and the auxiliary steps were fixed on ethanol refluxing and ball milling pretreatment. The fucose content of S. japonica fucoidan increased by 7.15 times and the sulfate group content increased by 4.87 times compared with those of fucoidans prepared by classic high-temperature acid extraction. Ball milling-assisted moderate-temperature acid extraction performed great effectiveness and universality in the extraction of high-purity fucoidans derived from four brown algae including S. japonica, Undaria pinnatifida, Sargassum fusiforme, and Fucus vesiculosus. Glycolipid-lowering activities of four fucoidans were confirmed by their interactions with intestinal bile acid, cholesterol micellar, glucose and probiotics including butyrate-producing bacteria, Bacteroides, Bifidobacterium, and Lactobacillus. Our study provided an efficient and universal extraction process for high-purity fucoidan with glycolipid-lowering activity from typical brown algae.

Характеристика антиоксидантной активности СО2- экстрактов бурых водорослей и стабилизации липидов

Vegetable oils are susceptible to oxidation during storage, which is a serious problem for shelf-life and food safety. The article describes the antioxidant properties of supercritical extracts from brown algae (Undaria pinnatifida and Costaria costata), Russian Far East. It also explains their prospects as stabilizers that preserve the quality and safety of vegetable oils by affecting the kinetics of oxidation and hydrolysis. The study featured supercritical extracts of marine brown algae Undaria pinnatifida and Costaria costata from Russian Far East. The methods involved spectrophotometry and high-performance liquid chromatography. Supercritical extracts of marine brown algae proved to be reliable sources of bioactive substances, e.g., phenolic compounds, carotenoids, and mannitol. They also possessed antioxidant properties in terms of antiradical activity, hydroxyl ion binding, superoxide radical absorption, and Fe+2 chelating. The experiments revealed nine phenolic compounds responsible for antioxidant properties. The supercritical extract of Costaria costata demonstrated a greater antioxidant effect on lipid oxidation in vegetable oils than Undaria pinnatifida. Both algae proved effective in stabilizing hydrolysis and were able to increase the shelf-life of soy and sunflower oils by three months. Supercritical extracts of Undaria pinnatifida and Costaria costata served as antioxidants to stabilize lipid oxidation in refined and unrefined soy and sunflower oils. The research revealed high approximation coefficients for regression equations describing the patterns of changes in the peroxide and acid numbers of vegetable oils stabilized with supercritical extracts of these marine brown algae.

Degradation of Natural Undaria pinnatifida into Unsaturated Guluronic Acid Oligosaccharides by a Single Alginate Lyase.

Here, we report on a bifunctional alginate lyase (Vnalg7) expressed in Pichia pastoris, which can degrade natural Undaria pinnatifida into unsaturated guluronic acid di- and trisaccharide without pretreatment. The enzyme activity of Vnalg7 (3620.00 U/mL-culture) was 15.81-fold higher than that of the original alg (228.90 U/mL-culture), following engineering modification. The degradation rate reached 52.75%, and reducing sugar reached 30.30 mg/mL after combining Vnalg7 (200.00 U/mL-culture) and 14% (w/v) U. pinnatifida for 6 h. Analysis of the action mode indicated that Vnalg7 could degrade many substrates to produce a variety of unsaturated alginate oligosaccharides (AOSs), and the minimal substrate was tetrasaccharide. Site-directed mutagenesis showed that Glu238, Glu241, Glu312, Arg236, His307, Lys414, and Tyr418 are essential catalytic sites, while Glu334, Glu344, and Asp311 play auxiliary roles. Mechanism analysis revealed the enzymatic degradation pattern of Vnalg7, which mainly recognizes and attacks the third glycosidic linkage from the reducing end of oligosaccharide substrate. Our findings provide a novel alginate lyase tool and a sustainable and commercial production strategy for value-added biomolecules using seaweeds.

Extraction, phytochemicals characterization, in vivo and in vitro anti-diabetic ability of non-extractable polyphenols from Undaria pinnatifida

Undaria pinnatifida (Up) is an edible seaweed known for its abundant nutrients and active compounds. In this research, six different methods, including acid hydrolysis extraction (AHE), alkaline hydrolysis extraction (LHE), enzymatic hydrolysis extraction (EHE), as well as their combinations with ultrasonic assisted extraction (AHE-U, LHE-U, EHE-U), were applied to extract non-extractable polyphenols from Up (UNEPPs). Results revealed that LHE-U was the most effective way to extract UNEPPs, it gave the highest yield (1.26 %) and total phenolics content (29.88 μg GAE/mg E), as well as considerable antioxidant and in vitro hypoglycemic effects. HPLC-Q-TOF-MS/MS analysis revealed the identification of 36 compounds from ULNEPPs, ferulic acid, p-coumaric acid and ferulic acid 4-O-glucuronide were the major compounds. In vivo study found that ULNEPPs could reduce fasting blood glucose (FBG) level, ameliorate abnormal glucose metabolism and dyslipidemia, repair insulin resistance and pancreas islet damage in type 2 diabetes (T2D) mice. Additionally, RT-qPCR analysis revealed that ULNEPPs improved glucose metabolism through the up-regulation of gene expression levels of Pi3k, Glut4, Akt, Ampk and the down-regulation of gene expression levels of Foxo1, Pgc-1α, Gsk-3β, Glut4, and G6pc. These results evidence that has the potential as dietary ingredients for preventing and treating T2D.

Glutamic-Alanine Rich Glycoprotein from Undaria pinnatifida: A Promising Natural Anti-Inflammatory Agent.

This study aimed to assess the anti-inflammatory properties of a bioactive glutamic-alanine rich glycoprotein (GP) derived from Undaria pinnatifida on both LPS-stimulated RAW264.7 cells, peritoneal macrophages, and mouse models of carrageenan- and xylene-induced inflammation, investigating the underlying molecular mechanisms. In both in-vitro and in-vivo settings, GP was found to reduce the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) while also inhibiting the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in response to lipopolysaccharide (LPS) stimulation. GP treatment significantly impeded the nuclear translocation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway by blocking the phosphorylation of IKKα and IκBα, leading to a reduction in proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Additionally, GP effectively inhibited the activation of mitogen-activated protein kinases (MAPKs), with specific inhibitors of p38 and extra-cellular signal regulated kinase (ERK) enhancing GP's anti-inflammatory efficacy. Notably, GP administration at 10 mg/kg/day (p.o.) markedly reduced carrageenan-induced paw inflammation and xylene-induced ear edema by preventing the infiltration of inflammatory cells into targeted tissues. GP treatment also downregulated key inflammatory markers, including iNOS, COX-2, IκBα, and NF-κB, by suppressing the phosphorylation of p38 and ERK, thereby improving the inflammatory index in both carrageenan- and xylene-induced mouse models. These findings suggest that marine resources, particularly seaweeds like U. pinnatifida, could serve as valuable sources of natural anti-inflammatory proteins for the effective treatment of inflammation and related conditions.

Biomethane production modelling from third-generation biomass

Third-generation biomass constitutes a renewable energy source that could substitute fossil fuels. This study evaluated the biomethane potential (BMP) of Ulva sp., Codium sp. and Undaria pinnatifida through anaerobic digestion. The daily production of biomethane was evaluated using different models, including Modified Gompertz, Chen and Hashimoto, First-order, Transfer and Cone models, as well as an Artificial Neural Network (ANN) model. The experimental BMP was 0.17, 0.26, and 0.32 Nm³/kg VS for Ulva sp., Codium sp., and U pinnatifida, respectively. Among the non-linear regression models, the Transfer model (R2 > 0.9915) and the First-order model (R2 > 0.9889) are the ones that best fit the experimental data. However, the ANN shows a better fit (R2 > 0.999 and RMSE<4.537) to the data compared to the non-linear regression models. Furthermore, ANN can capture the complexity of biological systems, allowing for more accurate and detailed modelling of the processes involved. The identification and optimization of the biomethane potential of macroalgae contribute to developing sustainable energy alternatives, offering a renewable energy source that could mitigate the environmental stress associated with traditional fossil fuels.

Phosphoryl oligosaccharide alleviates food allergy by suppressing IgE class switch recombination through LCN2 pathway

Specific algal polysaccharides exhibit significant anti-allergic activity. B cell class switch recombination (CSR) is a crucial step in food allergies, however, the role of polysaccharides in regulating CSR remains unclear. To investigate the regulation of B cell CSR by algal polysaccharides, an in vitro IgE-type CSR cell model was used to screen for active algal polysaccharides, and four active polysaccharides were identified. In a food allergy mouse model, Undaria pinnatifida polysaccharides (UPP) and phosphoryl oligosaccharides (POS) suppressed allergic responses and reduced the proliferation of IgE+ B cells. Transcriptome sequencing of B cells identified LCN2 as a potential target of POS, and inhibition of LCN2 blocked the activity of POS on CSR. These findings demonstrated the efficacy of POS in regulating B cell CSR and alleviating allergic responses and revealed the underlying mechanisms. This work provided data and theoretical support for the development of polysaccharide-based functional foods for individuals with allergies.

Whole-genome resequencing highlights the phycosphere microbial network in global populations of the edible kelp Undaria pinnatifida

The interplay between the host and microbiome has emerged as a central issue in biological science. This concept considers both host and microbiome sides to investigate their physiological and metabolic mechanisms, often referred to as a holobiont. Macroalgae, which can provide tremendous habitats to associated microorganisms in coastlines by constituting the marine forest, are promising targets to explore the interaction. Undaria pinnatifida is one of the edible brown macroalgae that is intensively cultured in Northeast Asia. Despite its ecological and economical importance, the microbiome of its phycosphere is largely unknown. In this study, we explored the microbial communities from 41 whole-genome resequencing data collected from South Korea (KR), New Zealand (NZ), and France (FR). We investigated the microbiome profiles and microbial ecological network to identify ecological and functional central taxa. We demonstrated that the microbiome profiles of KR cultivars are more similar to those of overseas introduced populations (i.e., NZ, and FR) than to those of the KR natural populations. We also identified two groups of central genera of the algal species' microbiome, the algal polysaccharide depolymerizing group (e.g., Lacinutrix and Winogradskiella) and the algal growth-promoting group (e.g., Sulfitobacter). This study supports the idea that the microbiome can be secured from unmapped reads of the host sequencing data. Furthermore, our data provide the first study on the U. pinnatifida microbiome, which probably will be used to develop new aquaculture strategies for this important seaweed.

Evaluation of Antioxidant Activity of Residue from Bioethanol Production Using Seaweed Biomass.

This study explores the potential of producing bioethanol from seaweed biomass and reusing the residues as antioxidant compounds. Various types of seaweed, including red (Gelidium amansii, Gloiopeltis furcata, Pyropia tenera), brown (Saccharina japonica, Undaria pinnatifida, Ascophyllum nodosum), and green species (Ulva intestinalis, Ulva prolifera, Codium fragile), were pretreated with dilute acid and enzymes and subsequently processed to produce bioethanol with Saccharomyces cerevisiae BY4741. Ethanol production followed the utilization of sugars, resulting in the highest yields from red algae > brown algae > green algae due to their high carbohydrate content. The residual biomass was extracted with water, ethanol, or methanol to evaluate its antioxidant activity. Among the nine seaweeds, the A. nodosum bioethanol residue extract (BRE) showed the highest antioxidant activity regarding the 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity, ferric reducing antioxidant power (FRAP), and reactive oxygen species (ROS) inhibition of H2O2-treated RAW 264.7 cells. These by-products can be valorized, contributing to a more sustainable and economically viable biorefinery process. This dual approach not only enhances the utilization of marine resources but also supports the development of high-value bioproducts.

A statistical optimization for almost-complete methylene blue biosorption by Gracilariabursa-pastoris

In this study, the dried biomass of four marine algae, namely Porphyra sp., Gracilaria bursa-pastoris, Undaria pinnatifida and Laminaria sp., were screened for their ability to remove methylene blue (MB) dye from aqueous solutions. Statistical approaches of the Plackett-Burman Design (PBD) and Box-Behnken Design (BBD) were applied to optimize different environmental conditions in order to achieve the maximum MB removal percentage by Gracilaria bursa-pastoris. The biosorbent was characterized before and after adsorption process using FTIR, XRD and SEM analysis. Additionally, isotherms, kinetics and thermodynamics studies were conducted to investigate the adsorption behavior of the adsorbent. The results showed that Gracilaria bursa-pastoris achieved the highest dye removal efficiency (98.5 %) compared to 96.5 %, 93.5 % and 93.9 % for Undaria pinnatifida, Porphyra sp. and Laminaria sp., respectively. PBD analysis revealed that the agitation speed, pH, and biomass dose were found to be the significant parameters affecting MB removal onto Gracilaria dried biomass. According to the BBD results, the maximum dye removal percentage (99.68 %) was obtained at agitation speed of 132 rpm, pH 7 and biomass dose of 7.5 g/L. FTIR, XRD and SEM analysis demonstrated the participation of several functional groups in the adsorption process and changes in the cell surface morphology of the adsorbent following the dye adsorption. The adsorption isotherms showed better fit to Freundlich model (R2 = 0.9891) than the Langmuir, Temkin, and Dubinin-Radushkevich models. The adsorption kinetics were best described by the pseudo-second-order model (R2 = 0.9999), suggesting the chemical interactions between dye ions and the algal biomass. The thermodynamic parameters indicated that the adsorption of MB onto Gracilaria dried biomass was spontaneous, feasible, endothermic and random. These results indicate that dried biomass of Gracilaria bursa-pastoris is an attractive, environmentally friendly, cheap and effective agent for MB dye removal from environmental discharges.

A Comparative Analysis of the Anti-Tumor Activity of Sixteen Polysaccharide Fractions from Three Large Brown Seaweed, Sargassum horneri, Scytosiphon lomentaria, and Undaria pinnatifida.

Searching for natural products with anti-tumor activity is an important aspect of cancer research. Seaweed polysaccharides from brown seaweed have shown promising anti-tumor activity; however, their structure, composition, and biological activity vary considerably, depending on many factors. In this study, 16 polysaccharide fractions were extracted and purified from three large brown seaweed species (Sargassum horneri, Scytosiphon lomentaria, and Undaria pinnatifida). The chemical composition analysis revealed that the polysaccharide fractions have varying molecular weights ranging from 8.889 to 729.67 kDa, and sulfate contents ranging from 0.50% to 10.77%. Additionally, they exhibit different monosaccharide compositions and secondary structures. Subsequently, their anti-tumor activity was compared against five tumor cell lines (A549, B16, HeLa, HepG2, and SH-SY5Y). The results showed that different fractions exhibited distinct anti-tumor properties against tumor cells. Flow cytometry and cytoplasmic fluorescence staining (Hoechst/AO staining) further confirmed that these effective fractions significantly induce tumor cell apoptosis without cytotoxicity. qRT-RCR results demonstrated that the polysaccharide fractions up-regulated the expression of Caspase-3, Caspase-8, Caspase-9, and Bax while down-regulating the expression of Bcl-2 and CDK-2. This study comprehensively compared the anti-tumor activity of polysaccharide fractions from large brown seaweed, providing valuable insights into the potent combinations of brown seaweed polysaccharides as anti-tumor agents.

A novel fucoxanthin enriched seaweed gummy: Physicochemical qualities and protective effect on UVB-induced retinal müller cells

Retinal disease has become the major cause of visual impairment and vision loss worldwide. Carotenoids, which have the potential antioxidant and eye-care activities, have been widely used in functional foods. Our previous study showed that fucoxanthin could exert photoprotective activity in UVB-induced retinal müller cells (RMCs). To extend the application of fucoxanthin in food industry, fucoxanthin, Undaria pinnatifida pulp (UPP), carrageenan, and other ingredients were mixed to prepare seaweed-flavoured photoprotective gummies in this study. The structural and functional properties of the gummies were then evaluated by physicochemical test and cell experiments. As a result, fucoxanthin enriched gummies presented favourable structural properties and flavour. The hydroxyl groups in fucoxanthin and κ-carrageenan are bonded through hydrogen bonds, forming the spatial network structure inside the gummies, enhancing its elasticity. The gummies showed significant antioxidant effect and alleviated the UVB oxidation damage in RMCs. Moreover, the main ingredients carrageenan and UPP improved the stability of fucoxanthin during in vitro digestion. The results enhance the application of fucoxanthin in functional food with photoprotective activity.

Cell wall-mediated maternal control of apical-basal patterning of the kelp Undaria pinnatifida.

The role of maternal tissue in embryogenesis remains enigmatic in many complex organisms. Here, we investigate the contribution of maternal tissue to apical-basal patterning in the kelp embryo. Focussing on Undaria pinnatifida, we studied the effects of detachment from the maternal tissue using microsurgery, staining of cell wall modifications, morphometric measurements, flow cytometry, genotyping and a modified kelp fertilisation protocol synchronising kelp embryogenesis. Detached embryos are rounder and often show aberrant morphologies. When a part of the oogonial cell wall remains attached to the zygote, the apical-basal patterning is rescued. Furthermore, the absence of contact with maternal tissue increases parthenogenesis, highlighting the critical role of maternal signals in the initial stages of development. These results show a key role for the connection to the maternal oogonial cell wall in apical-basal patterning in kelps. This observation is reminiscent of another brown alga, Fucus, where the cell wall directs the cell fate. Our findings suggest a conserved mechanism across phylogenetically distant oogamous lineages, where localised secretion of sulphated F2 fucans mediates the establishment of the apical-basal polarity. In this model, the maternal oogonial cell wall mediates basal cell fate determination by providing an extrinsic patterning cue to the future kelp embryo.

Evaluation of cryptic invasion in Japanese Undaria populations based on mitochondrial haplotypic analysis

Abstract To improve the quality and quantity of seaweed mariculture harvests, seedlings are frequently introduced from regions geographically apart from cultivation sites. The effects of such introduction have been insufficiently studied, despite increasing demands on seaweed cultivation as a measure against global warming. We here evaluated the degree of cryptic invasion occurring through mariculture using a brown algal species, Undaria pinnatifida. Cultivated materials used in the Seto Inland Sea, Japan, were introduced from northern Japan in the 1970s. Based on the clear genetic structure among Japanese Undaria populations, we compared mitochondrial haplotypes between wild populations and cultivated materials in the Seto Inland Sea. All cultivated materials analyzed had haplogroups native to northern Japan. Multiple haplogroups were observed in the wild populations, especially those in the eastern Seto Inland Sea, which is exceptional considering the reported genetic structure. Some northern Japan haplotypes were observed both in cultivated materials and wild individuals. A northern Japan haplogroup was predominant at several sites near Undaria-cultivation sites. These results strongly suggested that cryptic invasion through Undaria mariculture occurred here, although its ecological impact remains unclear. There is a clear risk of invasion by mariculture seedlings from other regions, even when native conspecific populations are present.