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Kelp forests are known to be very productive ecosystems and constitute a central component of the marine carbon cycle in coastal areas. Nevertheless, crucial carbon‐related data are missing to be able to include them properly in carbon budgets. A thorough understanding of the kelp contribution to the carbon cycle is especially important in regions prone to experiencing strong seasonal fluctuations in environmental conditions, such as subarctic regions. This study aimed to quantify primary productivity through growth rates and oxygen fluxes of a dominant kelp species in subarctic regions, Saccharina latissima, and to link oxygen fluxes to environmental parameters. Our results showed that strong primary productivity oxygen fluxes coincided with high light levels in July and most of August, while growth rates stayed similar all summer. An overall decline in all primary productivity proxies happened from late August, suggesting a seasonal slowing down of S. latissima metabolism. The estimated quantity of carbon stored in tissue during growth represented from 6% to 28% of the gross primary productivity. Further research is needed to explore how and how much carbon transits through living kelp tissue in different seasons, to better understand the contribution of subarctic kelp to coastal carbon budgets. [ABSTRACT FROM AUTHOR]

Saccharina japonica, a significant brown macroalga in the Pacific Ocean, serves as a food source and industrial material. In aquaculture, collecting mature sporophytes for seedling production is essential but challenging due to environmental changes. In this study, transcriptomic analysis of vegetative and sorus tissues was done to identify differentially expressed genes (DEGs) and enhance our understanding of sorus formation regulation in S. japonica. KEGG pathway and Gene Otology (GO) analysis revealed that upregulated DEGs were involved in folate biosynthesis, riboflavin metabolism, and amino acid biosynthesis. In addition, the upregulation of genes associated with cell wall remodeling, such as mannuronan C-5-epimerases, vanadium-dependent haloperoxidases, and NADPH oxidase, was observed in sorus parts. Meanwhile, downregulated DEGs in sorus portions included genes related to chloroplast function. These findings will help us understand the regulatory mechanisms behind sorus formation in S. japonica and extracellular matrix remodeling in brown algae. [ABSTRACT FROM AUTHOR]

Brown algae are gaining traction as biorefinery feedstocks due to their advantages such as rapid growth and carbon dioxide sequestration. Saccharina japonica has high potential due to its high carbohydrate content, especially mannitol (26.7%). In this study, a biorefinery process for S. japonica was designed, with focusing on sugar conversion and bioconversion into lactic acid, a valuable platform chemical utilized in various industries. The existing sugar conversion process of S. japonica has been investigated by focusing on enzymatic or acid‐catalyzed hydrolysis, but not hot water extraction although mannitol can be easily recovered using water. The effect of temperature (60–120°C) on the mannitol yield from S. japonica was investigated, and a mannitol yield of 208 g/kg biomass was achieved at the optimal temperature of 100°C (about 78% of the theoretical maximum yield). This study emphasizes that this simple process has considerable potential for application as over 80% of the fermentable carbohydrates in S. japonica were mannitol. Then, S. japonica extract was applied to lactic acid production. First, lactic acid production of four bacterial strains was tested in a mannitol medium, and Lacticaseibacillus rhamnosus was selected as the superior producer, showing 1.93 to 2.92 times better lactic acid titer than others. Next, the optimal feeding concentration of mannitol was determined to be 20 g/L, which was all consumed by L. rhamnosus. Finally, S. japonica extract was applied to lactic acid production by L. rhamnosus, and the results showed similar fermentation profiles with the control medium: lactic acid production, 18.81 g/L (control: 18.97 g/L); lactic acid conversion, 95.1% (control: 95.9%); cell growth (OD600 nm), 8.9 (control: 7.4). The lactic acid yield in the designed biorefinery process was estimated to be 195.6 g/kg biomass, thus S. japonica has high potential as a biorefinery feedstock to produce valuable bioproducts, including lactic acid. [ABSTRACT FROM AUTHOR]

The brown macroalga Saccharina japonica (Laminariales, Phaeophyta) is the most productive cultured seaweed in the world. In order to improve the biosafety of transgenic kelp, it is necessary to develop endogenous constitutive promoters, replacing those of virus origin. In this study, the housekeeping actin gene from S. japonica (SjACT) was found to contain three exons and two introns, representing a unique actin gene structure pattern in brown algae. Additionally, the 5′ upstream region was obtained using genome walking, and fused to the reporter gene lacZ or EGFP to construct promoter-detective vectors. Using an established genetic transformation system, kelps in different life-cycle stages were transformed. The detection results showed that, in the diploid sporophyte stage, the transient expression from the lacZ gene could be observed in the frond, stipe, or holdfast of kelps, indicating a manner of being non-tissue-specific. And, in the haploid gametophyte stage of S. japonica, the fluorescence of the expressed EGFP were detected in vivo in gametophyte cells of both genders. These results indicate that the promoter of the SjACT gene (pSjACT) functions in a constitutive manner and is expected to be a key endogenous element in the genetic manipulation of kelps. [ABSTRACT FROM AUTHOR]

Brown algae are multicellular organisms that have evolved independently from plants and animals. Knowledge of the mechanisms involved in their embryogenesis is available only for the Fucus, Dictyota, and Ectocarpus, which are brown algae belonging to three different orders. Here, we address the control of cell growth and cell division orientation in the embryo of Saccharina latissima, a brown alga belonging to the order Laminariales, which grows as a stack of cells through transverse cell divisions until growth is initiated along the perpendicular axis. Using laser ablation, we show that apical and basal cells have different functions in the embryogenesis of this alga, with the apical cell being involved mainly in growth and basal cells controlling the orientation of cell division by inhibiting longitudinal cell division and thereby the widening of the embryo. These functions were observed in the very early development before the embryo reached the 8-cell stage. In addition, the growth of the apical and basal regions appears to be cell-autonomous, because there was no compensation for the loss of a significant part of the embryo upon laser ablation, resulting in smaller and less elongated embryos compared with intact embryos. In contrast, the orientation of cell division in the apical region of the embryo appears to be controlled by the basal cell only, which suggests a polarised, non-cell-autonomous mechanism. Altogether, our results shed light on the early mechanisms of growth rate and growth orientation at the onset of the embryogenesis of Saccharina, in which non-cell-specific cell-autonomous and cell-specific non-cell-autonomous processes are involved. This complex control differs from the mechanisms described in the other brown algal embryos, in which the establishment of embryo polarity depends on environmental cues. [ABSTRACT FROM AUTHOR]

Phaeoviruses (Phycodnaviridae) are large icosahedral viruses in the phylum Nucleocytoviricota with dsDNA genomes ranging from 160 to 560 kb, infecting multicellular brown algae (Phaeophyceae). The phaeoviral host range is broader than expected, not only infecting algae from the Ectocarpales but also from the Laminariales order. However, despite phaeoviral infections being reported globally, Norwegian kelp species have not been screened. A molecular analysis of cultured and wild samples of two economically important kelp species in Norway (Saccharina latissima and Laminaria hyperborea) revealed that phaeoviruses are recurrently present along the Norwegian coast. We found the viral prevalence in S. latissima to be significantly higher at the present time compared to four years ago. We also observed regional differences within older samples, in which infections were significantly lower in northern areas than in the south or the fjords. Moreover, up to three different viral sequences were found in the same algal individual, one of which does not belong to the Phaeovirus genus and has never been reported before. This master variant therefore represents a putative new member of an unclassified phycodnavirus genus. [ABSTRACT FROM AUTHOR]

The phenology of the alga-dwelling amphipod Ceinina japonica Stephensen, 1933 (Amphipoda: Eophliantidae) was studied at Rishiri Island, Hokkaido, Japan, from May 2016 to March 2017. Seasonal shifting between the host algal species was confirmed through observations at a coastal field site and a nearby aquaculture facility for kelp. Amphipods mainly occurred in the farmed biennial kelp Saccharina japonica var. ochotensis and wild algae Undaria pinnatifida, with Agarum clathratum, Costaria costata, Saccharina cichorioides, and Sargassum boreale as new host algal records. Amphipods occurred in sporophytes of U. pinnatifida at the field site from February to March and from May to July, but they were found in the kelp of S. j. var. ochotensis during the rest of the year, from August to the following January. Individuals of C. japonica infected sporophytes of the large brown alga Undaria pinnatifida from February to July, and C. japonica reproduced from July to September, a period during which the amphipods switch to a different host in July, the sporophytes of the saccharinan kelp S. j. var. ochotensis, where they stay until January. The amphipods then switched back to U. pinnatifida in January or February. Experimental evidence from a kelp-culturing facility also confirmed the timing of this host shift. The removal of U. pinnatifida from algal culture ropes in such facilities is suggested as a method to prevent amphipod damage, which is important for commercially farmed S. j. var. ochotensis. [ABSTRACT FROM AUTHOR]

Alginates are heteropolysaccharides comprising β-D-mannuronate (M) and α-L-guluronate (G) units. Natural sources of alginate include brown algae and certain bacteria. Brown algal alginates possess a greater degree of sequence diversity than do those produced by bacteria, and this may be due to the presence of multiple mannuronan C5-epimerase (MC5E) isozymes in brown algae, although only three have been enzymatically studied to date. In this study, a novel MC5E candidate protein, CoC5-1, from the brown alga Cladosiphon okamuranus, for which no enzymatic function has been previously determined, was expressed as a glycosylated protein in insect cells. The action of recombinant CoC5-1 on polymannuronate (polyM) increased the amount of gel formed in the presence of Ca2+, indicating that CoC5-1 possesses MC5E activity. The optimum temperature, pH, and NaCl concentration were 40 °C, pH 8.0, and 100 mM, respectively. The thermal stability of CoC5-1 was higher than that of the Saccharina japonica MC5E SjC5-VI. CoC5-1 remained active after incubation at 50 °C for 1 h, whereas SjC5-VI was completely inactivated. 1H-nuclear magnetic resonance (NMR) analysis revealed that the M:G ratio of the polyM substrate was altered from 9.0 to 2.1 by CoC5-1. This is the first report of MC5E enzymatic activity in brown algae of the family Chordariaceae. [ABSTRACT FROM AUTHOR]

Iodide is accumulated by the brown alga Saccharina japonica at a high concentration and has been proven to be an inorganic antioxidant that plays an important role in oxidative metabolism. Vanadium-dependent bromoperoxidases (vBPOs) and iodoperoxidases (vIPOs), which catalyze the oxidation of iodide, are essential for iodine accumulation and metabolism. Heavy metal pollutant cadmium (Cd) from anthropogenic activities can cause damage to algae mainly by producing oxidative stress. Here, the effects of iodine pretreatment on the stress of S. japonica caused by cadmium were analyzed. The growth experiment showed that iodine pretreatment could reduce the damage of low concentration cadmium on S. japonica young thalli. At the transcriptomic level, gene ontology (GO) enrichment analysis confirmed that cadmium stress could cause a peroxidation reaction in S. japonica. However, the most significant GO term was "photosystem I" in the series with iodine pretreatment. Weighted gene co-expression network analysis (WGCNA) indicated that iodine pretreatment alleviated cadmium stress responses of S. japonica by affecting the photosynthesis process. Analysis of the differentially expressed genes (DEGs) showed that five enzymes from the vBPO family and 13 enzymes from the vIPO family might play crucial roles in this process. [ABSTRACT FROM AUTHOR]

Brown seaweeds (Laminariaceae) vary considerably in the content of toxic and essential elements; these variations depend on the taxonomic group and geographical factors. Seaweeds are extensively used in the food industry and widely applied in medicine for both humans and animals. Therefore, it is relevant to examine the correlation between the elemental composition and the geographical origin of kelp thalli obtained from different sources.The aim of the study was to collect, collate, and analyse primary and secondary data on the accumulation of essential, toxic and potentially carcinogenic elements, including iodine, in the thalli of brown seaweeds (Laminariaceae).Materials and methods. This study investigated the concentrations of 17 elements in Laminaria spp. (Al, As, Cd, Cr, Co, Cu, Fe, Hg, Mn, Mo, Ni, Se, Pb, Sr, V, Zn, and I). Experiments were conducted on an Agilent 7900 inductively coupled plasma mass spectrometer. The authors studied publications on the elemental composition of brown seaweeds (Laminariaceae) using literature search and data analysis methods.Results. This article reflects the updated classification of brown seaweeds (Laminariaceae) and summarises information about the mechanisms by which iodine and other elements accumulate in the thallus. The authors established species-specific variations in the order of element uptake and in the accumulation of elemental toxicants. The mutual influence of elements on their accumulation in brown seaweeds (Laminariaceae) was evaluated using Spearman’s rank correlation coefficients.Conclusions. The study results can inform the implementation of a risk-based quality control strategy for herbal medicinal products aimed at reducing human exposure to toxic elements. The authors suggest that the upper limit of iodine content in kelp-based food products should be standardised.

Background: Glutathione S-transferase (GST) is a crucial enzyme for metabolism, detoxification, and stress resistance in organisms. Many GSTs have been identified in seaweeds, but the isolation and functional analysis of GSTs in Saccharina japonica have not been completed. Result: In this study, a total of 32 SjGST genes, localized on 10 scaffolds and 6 contigs, were identified and categorized into three groups. Most of these SjGSTs were presumed to be distributed in the cytoplasm. Tandem duplication had a significant influence on the expansion of the SjGST gene family. Functional analysis of cis-acting elements in the promoter regions demonstrated that SjGSTs enhance the stress resistance of the kelp. Quantitative real-time PCR tests confirmed that SjGSTs positively influence S. japonica sporophytes under stress from low salinity, drought, and high temperature. Recombinant yeast tests further affirmed the role of SjGSTs in stress resistance; SjGSTs improved the growth rate of recombinant yeast under 1.5 M NaCl or 8 mM H2O2. Analysis of biochemical parameters indicated that the optimum temperatures for SjGST20 and SjGST22 were 20 °C, and the optimum pH values were 7.0 and 8.0 for SjGST20 and SjGST22, respectively. The Km values for the substrate 1-chloro-2,4-dinitrobenzene (CDNB) were 2.706 mM and 0.674 mM and were 6.146 mM and 3.559 mM for the substrate glutathione (GSH) for SjGST20 and SjGST22, respectively. Conclusion: SjGSTs are important stress resistant genes in S. japonica. This research results will enhance our understanding the function of GSTs in brown seaweeds, and explained its functional roles in stress resistance in marine environments. [ABSTRACT FROM AUTHOR]

Melanoma is the most aggressive and treatment-resistant form of skin cancer. It is phenotypically characterized by aerobic glycolysis that provides higher proliferative rates and resistance to cell death. The glycolysis regulation in melanoma cells by means of effective metabolic modifiers represents a promising therapeutic opportunity. This work aimed to assess the metabolically oriented effect and mechanism of action of fucoidan from the brown alga Saccharina cichorioides (ScF) and its carboxymethylated derivative (ScFCM) in combination with 2-deoxy-D-glucose (2-DG) on the proliferation and colony formation of human melanoma cell lines SK-MEL-28, SK-MEL-5, and RPMI-7951. The metabolic profile of melanoma cells was determined by the glucose uptake and Lactate-GloTM assays. The effect of 2-DG, ScF, ScFCM, and their combination on the proliferation, colony formation, and activity of glycolytic enzymes was assessed by the MTS, soft agar, and Western blot methods, respectively. When applied separately, 2-DG (IC50 at 72 h = 8.7 mM), ScF (IC50 at 72 h > 800 µg/mL), and ScFCM (IC50 at 72 h = 573.9 μg/mL) inhibited the proliferation and colony formation of SK-MEL-28 cells to varying degrees. ScF or ScFCM enhanced the inhibiting effect of 2-DG at low, non-toxic concentrations via the downregulation of Glut 1, Hexokinase II, PKM2, LDHA, and pyruvate dehydrogenase activities. The obtained results emphasize the potential of the use of 2-DG in combination with algal fucoidan or its derivative as metabolic modifiers for inhibition of melanoma SK-MEL-28 cell proliferation. [ABSTRACT FROM AUTHOR]

Background: Macroalgal epiphytic microbial communities constitute a rich resource for novel enzymes and compounds, but studies so far largely focused on tag-based microbial diversity analyses or limited metagenome sequencing of single macroalgal species. Results: We sampled epiphytic bacteria from specimens of Ulva sp. (green algae), Saccharina sp. (brown algae), Grateloupia sp. and Gelidium sp. (both red algae) together with seawater and sediment controls from a coastal reef in Weihai, China, during all seasons. Using 16S rRNA amplicon sequencing, we identified 14 core genera (consistently present on all macroalgae), and 14 dominant genera (consistently present on three of the macroalgae). Core genera represented ~ 0.7% of all genera, yet accounted for on average 51.1% of the bacterial abundances. Plate cultivation from all samples yielded 5,527 strains (macroalgae: 4,426) representing 1,235 species (685 potentially novel). Sequencing of selected strains yielded 820 non-redundant draft genomes (506 potentially novel), and sequencing of 23 sampled metagenomes yielded 1,619 metagenome-assembled genomes (MAGs), representing further 1,183 non-redundant genomes. 230 isolates and 153 genomes were obtained from the 28 core/dominant genera. We analyzed the genomic potential of phycosphere bacteria to degrade algal polysaccharides and to produce bioactive secondary metabolites. We predicted 4,451 polysaccharide utilization loci (PULs) and 8,810 biosynthetic gene clusters (BGCs). These were particularly prevalent in core/dominant genera. Conclusions: Our metabolic annotations and analyses of MAGs and genomes provide new insights into novel species of phycosphere bacteria and their ecological niches for an improved understanding of the macroalgal phycosphere microbiome. DnRc39z963CYrL7RdN5UNd Video Abstract [ABSTRACT FROM AUTHOR]

Introduction: Saccharina latissima is a canopy-forming species of brown algae and, as such, is considered an ecosystem engineer. Several populations of this alga are exploited worldwide, and a decrease in the abundance of S. latissima at its southern distributional range limits has been observed. Despite its economic and ecological interest, only a few data are available on the composition of microbiota associated with S. latissima and its role in algal physiologyn. Methods: We studied the whole bacterial community composition associated with S. latissima samples from three locations (Brittany, Helgoland, and Skagerrak) by 16S metabarcoding analyses at different scales: algal blade part, regions, season (at one site), and algal physiologic state. Results and Discussion: We have shown that the difference in bacterial composition is driven by factors of decreasing importance: (i) the algal tissues (apex/meristem), (ii) the geographical area, (iii) the seasons (at the Roscoff site), and (iv) the algal host's condition (healthy vs. symptoms). Overall, Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia dominated the general bacterial communities. Almost all individuals hosted bacteria of the genus Granulosicoccus, accounting for 12% of the total sequences, and eight additional core genera were identified. Our results also highlight a microbial signature characteristic for algae in poor health independent of the disease symptoms. Thus, our study provides a comprehensive overview of the S. latissima microbiome, forming a basis for understanding holobiont functioning. [ABSTRACT FROM AUTHOR]

Calmodulins (CaMs) and Calmodulin-like proteins (CMLs) are vital in plant growth, development, and stress responses. However, CaMs and CMLs have not been fully identified and characterized in brown algae, which has been evolving independently of the well-studied green plant lineage. In this study, whole-genome searches revealed one SjCaM and eight SjCMLs in Saccharina japonica, and one EsCaM and eleven EsCMLs in Ectocarpus sp. SjCaM and EsCaM encoded identical protein products and shared 88.59–89.93% amino acid identities with Arabidopsis thaliana AtCaMs, thereby indicating that brown algae CaMs retained a similar Ca2+ sensors function as in plants. The phylogenetic and gene structure analysis results showed that there was significant divergence in the gene sequences among brown algae CMLs. Furthermore, evolutionary analysis indicated that the function of brown alga CMLs was relatively conserved, which may be related to the fact that brown algae do not need to face complex environments like terrestrial plants. Regulatory elements prediction and the expression analysis revealed the probable functioning of SjCaM/CML genes in gametophyte development and the stress response in S. japonica. In addition, the SjCaM/SjCMLs interacting proteins and chemicals were preliminarily predicted, suggesting that SjCaM/SjCMLs might play putative roles in Ca2+/CaM-mediated growth and development processes and stimulus responses. Therefore, these results will facilitate our understanding of the evolution of brown algae CaMs/CMLs and the functional identification of SjCaM/SjCMLs. [ABSTRACT FROM AUTHOR]

Fucoidans from brown algae are described as anti-inflammatory, antioxidative, and antiangiogenic. We tested two Saccharina latissima fucoidans (SL-FRO and SL-NOR) regarding their potential biological effects against age-related macular degeneration (AMD). Primary porcine retinal pigment epithelium (RPE), human RPE cell line ARPE-19, and human uveal melanoma cell line OMM-1 were used. Cell survival was assessed in tetrazolium assay (MTT). Oxidative stress assays were induced with erastin or H2O2. Supernatants were harvested to assess secreted vascular endothelial growth factor A (VEGF-A) in ELISA. Barrier function was assessed by measurement of trans-epithelial electrical resistance (TEER). Protectin (CD59) and retinal pigment epithelium-specific 65 kDa protein (RPE65) were evaluated in western blot. Polymorphonuclear elastase and complement inhibition assays were performed. Phagocytosis of photoreceptor outer segments was tested in a fluorescence assay. Secretion and expression of proinflammatory cytokines were assessed with ELISA and real-time PCR. Fucoidans were chemically analyzed. Neither toxic nor antioxidative effects were detected in ARPE-19 or OMM-1. Interleukin 8 gene expression was slightly reduced by SL-NOR but induced by SL-FRO in RPE. VEGF secretion was reduced in ARPE-19 by SL-FRO and in RPE by both fucoidans. Polyinosinic:polycytidylic acid induced interleukin 6 and interleukin 8 secretion was reduced by both fucoidans in RPE. CD59 expression was positively influenced by fucoidans, and they exhibited a complement and elastase inhibitory effect in cell-free assay. RPE65 expression was reduced by SL-NOR in RPE. Barrier function of RPE was transiently reduced. Phagocytosis ability was slightly reduced by both fucoidans in primary RPE but not in ARPE-19. Fucoidans from Saccharina latissima, especially SL-FRO, are promising agents against AMD, as they reduce angiogenic cytokines and show anti-inflammatory and complement inhibiting properties; however, potential effects on gene expression and RPE functions need to be considered for further research. [ABSTRACT FROM AUTHOR]

Cancer is one of the main causes of human mortality worldwide. Despite the advances in the diagnostics, surgery, radiotherapy, and chemotherapy, the search for more effective treatment regimens and drug combinations are relevant. This work aimed to assess the radiomodifying effect and molecular mechanism of action of fucoidan from the brown alga Saccharina cichorioides (ScF) and product of its autohydrolysis (ScF_AH) in combination with pacificusoside D from the starfish Solaster pacificus (SpD) on the model of viability and invasion of three-dimension (3D) human melanoma cells SK-MEL-2. The cytotoxicity of ScF (IC50 JB6 Cl41 > 800 µg/mL; IC50 SK-MEL-2 = 685.7 µg/mL), ScF_AH (IC50 JB6 Cl41/SK-MEL-2 > 800 µg/mL), SpD (IC50 JB6 Cl41 = 22 µM; IC50 SK-MEL-2 = 5.5 µM), and X-ray (ID50 JB6 Cl41 = 11.7 Gy; ID50 SK-MEL-2 = 6.7 Gy) was determined using MTS assay. The efficiency of two-component treatment of 3D SK-MEL-2 cells was revealed for ScF in combination with SpD or X-ray but not for the combination of fucoidan derivative ScF_AH with SpD or X-ray. The pre-treatment of spheroids with ScF, followed by cell irradiation with X-ray and treatment with SpD (three-component treatment) at low non-toxic concentrations, led to significant inhibition of the spheroids' viability and invasion and appeared to be the most effective therapeutic scheme for SK-MEL-2 cells. The molecular mechanism of radiomodifying effect of ScF with SpD was associated with the activation of the initiator and effector caspases, which in turn caused the DNA degradation in SK-MEL-2 cells as determined by the Western blotting and DNA comet assays. Thus, the combination of fucoidan from brown algae and triterpene glycoside from starfish with radiotherapy might contribute to the development of highly effective method for melanoma therapy. [ABSTRACT FROM AUTHOR]

Macroalgae (seaweeds) are key primary producers in marine coastal habitats and largely contribute to global ocean carbon fluxes. They also represent attractive renewable feedstock for the production of biofuels, food, feed, and bioactive. Brown algae are seaweeds that produce alginates and fucose containing sulfated polysaccharides in their cell wall and laminarin and mannitol for carbon storage. The availability of genomes of the kelp Saccharina japonica and of the filamentous Ectocarpus sp. paved the way for the biochemical characterization of recombinant enzymes involved in their polysaccharide and carbohydrates synthesis, including, notably, mannitol. Brown algal mannitol biosynthesis starts with the conversion of fructose-6-phospate into mannitol-1-phosphate (mannitol-1P), and this intermediate is hydrolysed by a haloacid dehalogenase phosphatase (M1Pase) to produce mannitol. We report here the biochemical characterization of a second M1Pase in Ectocarpus sp. (EsM1Pase1). Both Ectocarpus M1Pases were redox-sensitive enzymes, with EsM1Pase1 active only in presence of the reducing agent. Such catalytic properties have not been observed for any M1Pases yet. EsM1Pases were specific to mannitol-1-P, in contrast to S. japonica M1Pases that could act on other phosphorylated sugars. Finally, brown algal M1Pases formed two well-supported clades, with possible distinct subcellular localization and physiological role(s) under diverse environmental conditions and/or life cycle stages. [ABSTRACT FROM AUTHOR]

Saccharina japonica (Laminariales, Phaeophyta) is a brown alga and the major component of algae beds on the northwest coast of the Pacific Ocean. Rubisco, the key enzyme of CO 2 fixation in photosynthesis, is inhibited by nonproductive binding of its substrate RuBP and other sugar phosphates. The inhibited Rubisco in eukaryotic phytoplankton of the red plastid lineage was reactivated by CbbXs, the red-type Rubisco activases, through the process of ATP-hydrolysis-powered remodeling. As well documented, CbbXs had two types of subunits encoded by the plastid or nuclear genome respectively. In this study, both proteins of S. japonica (SjCbbX-n and SjCbbX-p) were localized in the chloroplast illustrated by immuno-electron microscopy technique. GST pull-down detection verified SjCbbX-n could interact with SjCbbX-p. Two-dimensional electrophoresis-based Western blot analysis illustrated that the endogenous SjCbbXs could form heterohexamer in the ratio of 1:1. Activase activity assays showed that although both the recombinant proteins of SjCbbXs were functional, SjCbbX-n illustrated the significantly higher activase activity than SjCbbX-p. Notably, when the two proteins were mixed, the highest specific efficiencies of Rubisco were obtained. These results implied SjCbbX-n may be essential for Rubisco activation. Molecular evolutionary analysis of cbbx genes revealed that cbbx -n originated from the duplication of cbbx -p and then evolved independently under the positive selection pressure. This is the first report about the functional relationship between the two types of CbbXs in macroalge with the red-type Rubisco and provides useful information for revealing the mechanism of high photosynthetic efficiency of this important kelp. • Two subunits of Rubisco activase (SjCbbX-n and SjCbbX-p) were identified in Saccharina japonica. • Both SjCbbX-n and SjCbbX-p were localized in the chloroplast of S. japonica. • SjCbbX-n interacted with SjCbbX-p and formed heterohexamer in the chloroplast of S. japonica. • SjCbbX-n exhibited higher activase activity than SjCbbX-p. • Cbbx -n gene originated from the duplication of cbbx -p and then evolved independently. [ABSTRACT FROM AUTHOR]

Saccharina japonica (known as Laminaria japonica or Phaeophyta japonica), one of the largest macroalgae, has been recognized as food and medicine for a long time in some Asian countries, such as China, South Korea, Japan, etc. In recent years, S. japonica has also been considered the most promising third-generation biofuel feedstock to replace fossil fuels, contributing to solving the challenges people face regarding energy and the environment. In particular, S. japonica-derived biohydrogen (H2) is expected to be a major fuel source in the future because of its clean, high-yield, and sustainable properties. Therefore, this review focuses on recent advances in bio-H2 production from S. japonica. The cutting-edge biological technologies with suitable operating parameters to enhance S. japonica's bio-H2 production efficiency are reviewed based on the Scopus database. In addition, guidelines for future developments in this field are discussed. [ABSTRACT FROM AUTHOR]

Background: Brown macroalgae dominate temperate coastal ecosystems, and their productivity is typically limited by nitrate availability. As an economically important kelp, Saccharina japonica is the most productive farmed seaweed and needs to be supplemented with sufficient nitrate throughout the cultivation process. However, molecular characterization of genes involved in nitrogen assimilation has not been conducted in brown macroalgae. Results: Here, we described the identification of the nitrate reductase (NR) gene from S. japonica (SjNR). Using two different cloning methods for SjNR, i.e. rapid amplification of cDNA ends (RACE) and cDNA cloning alone, a single fragment was obtained respectively. According to results of sequence analysis between these two fragments, the tentative coding sequence in two clones, SjNR-L and SjNR-S, were suggested to represent two transcripts of the single copy SjNR, and the ATG of SjNR-S was located inside the third exon of SjNR-L. In the 5′ upstream sequence of each transcript, promoter core elements, response elements, especially multiple N response elements which occurred in microalgal NR, were all predicted. Further sequence analysis revealed that both transcripts encoded all five domains conserved in eukaryotic plant NRs. RT-qPCR results showed that the transcription level of SjNR in juvenile sporophytes could be significantly induced by nitrate and inhibited by ammonium, which was in line with plant NRs. The recombinant SjNR-L and SjNR-S were all proved to have NR activity, suggesting that the single-copy gene SjNR might be regulated on transcription level based on alternative promoters and multiple transcriptional start sites. Moreover, both NADH and NADPH were found to be able to act as electron donors for SjNR alone, which is the first confirmation that brown algal NR has a NAD(P)H-bispecific form. Conclusion: These results will provide a scientific basis for understanding the N demand of kelp in various stages of cultivation and evaluating the environmental remediation potential of kelp in eutrophic sea areas. [ABSTRACT FROM AUTHOR]

Polysaccharides' derivatives are promising biologically active compounds for biotechnology, nutrition, industries, and are becoming increasingly important in medicine and pharmacy. Laminaran from brown alga Saccharina cichorioides (ScL) was chemically modified to obtain the carboxymethylated derivative (ScLCM) with improved structure and bioactivity. ScLCM was identified as (1 → 3)-β-D-glucan with –CH 2 -COOH groups at some positions 2, 4, and 6 of glucose residues. The anticancer activity of ScLCM was studied on the models of viability and invasion of 3D human melanoma SK-MEL-28, breast cancer T-47D, and colorectal carcinoma DLD-1 cells in comparison with native laminaran or its sulfated or aminated derivatives. ScLCM had the highest anticancer and anti-invasive effects among investigated polysaccharides. ScLCM significantly suppressed the viability and invasion of 3D SK-MEL-28 cells via the regulation of the activity of matrix metalloproteinase 9 (MMP 9) and protein kinases of ERK/MAPK signaling pathway. These findings may contribute to the reported anticancer effects of algal polysaccharides' derivatives. • Carboxymethylated derivative ScLCM was obtained by algal laminaran modification. • Carboxymethyl groups substituted all free hydroxyls at C2, C4, and C6 of glucose. • ScLCM effectively inhibited the viability and invasion of 3D human cancer cells. • ScLCM had the highest anticancer effect on 3D cancer cells than ScL, ScLs, ScLNH 2. • ScLCM regulated the activity of MMP 9 and protein kinases of ERK/MAPK pathway. [ABSTRACT FROM AUTHOR]

Brown algae are a group of multicellular, heterokont algae that have convergently evolved developmental complexity that rivals that of embryophytes, animals or fungi. Early in development, brown algal zygotes establish a basal and an apical pole, which will become respectively the basal system (holdfast) and the apical system (thallus) of the adult alga. Brown algae are interesting models for understanding the establishment of cell polarity in a broad evolutionary context, because they exhibit a large diversity of life cycles, reproductive strategies and, importantly, their zygotes are produced in large quantities free of parental tissue, with symmetry breaking and asymmetric division taking place in a highly synchronous manner. This review describes the current knowledge about the establishment of the apical-basal axis in the model brown seaweeds Ectocarpus , Dictyota , Fucus and Saccharina , highlighting the advantages and specific interests of each system. Ectocarpus is a genetic model system that allows access to the molecular basis of early development and life-cycle control over apical-basal polarity. The oogamous brown alga Fucus , together with emerging comparative models Dictyota and Saccharina, emphasize the diversity of strategies of symmetry breaking in determining a cell polarity vector in brown algae. A comparison with symmetry-breaking mechanisms in land plants, animals and fungi, reveals that the one-step zygote polarisation of Fucus compares well to Saccharomyces budding and Arabidopsis stomata development, while the two-phased symmetry breaking in the Dictyota zygote compares to Schizosaccharomyces fission, the Caenorhabditis anterior-posterior zygote polarisation and Arabidopsis prolate pollen polarisation. The apical-basal patterning in Saccharina zygotes on the other hand, may be seen as analogous to that of land plants. Overall, brown algae have the potential to bring exciting new information on how a single cell gives rise to an entire complex body plan. [ABSTRACT FROM AUTHOR]

Conservation units are still unclear for the commercially important kelp Saccharina japonica. Previous analyses of population genetic structure have yielded inconsistent results regarding the number of clusters, especially in Japan. Thus, the genetic structure of S. japonica in Japan was studied using the mitochondrial nad3-16S rDNA region. We detected 88 haplotypes in 483 individuals collected from 46 localities. Unique haplotypes and one or a few shared haplotypes at a local scale were found in most localities. The observed genetic structure revealed cryptic invasions of S. japonica within Japan and the value of the nad3-16S rDNA region for identifying the geographic origin of kelp. Bayesian Analysis of Population Structure analysis and FST revealed the genetic divergence of populations in southwestern Hokkaido. The haplotype network showed a more detailed starburst pattern compared with the results of previous studies based on mitochondrial COI and trnW-trnI. Accordingly, S. japonica in Japan may represent one genetic group that experienced a recent expansion. Unique or locally shared haplotypes and similarity in haplotype diversity on different coasts of Hokkaido could be explained by refugia during the Last Glacial Maximum on various coasts. Furthermore, the present study demonstrated inconsistencies between the genetic structure and distribution of S. japonica varieties. Therefore, further investigations focused on the taxonomic validation of varieties are needed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Protein extraction from macroalgae using deep eutectic solvents was investigated. • Betaine:2Urea:Water gave the highest protein recovery yield (11 %). • Temperature of 30 °C and 47 % of added water improved protein recovery. • The size of extracted proteins was in the range of 5–10 kDa. • Betaine:2Urea:Water was more selective than bead milling, providing similar yields. Interest in seaweed as a sustainable source of protein is growing, and deep eutectic solvents (DESs) are a promising green alternative with proven efficacy in protein extraction. This work studies the selective extraction of protein towards carbohydrates from the brown algae Saccharina latissima using DESs. Eleven DESs based on choline chloride (ChCl) and betaine were tested for freeze-dried biomass. The four DESs with the best performance (ChCl:Oxalic acid, ChCl:2Urea, ChCl:2Levulinic acid and Betaine:2Urea:Water) were subsequently used to investigate the effect of temperature (20, 30 and 40 °C) and the addition of water (0 and 47 %) on the extraction process. Betaine:2Urea:Water at 1 h, 40 °C, and 47 % added water provided the highest protein recovery yield (10.6 %) while minimizing carbohydrate extraction (1.3 %). These results demonstrated similar protein recovery yields to a benchmark process using bead milling, but with better selectivity. Thus, this work provides a sustainable extraction method for the recovery of proteins from seaweed and open new alternatives combining both approaches. [ABSTRACT FROM AUTHOR]

Suboptimal iodine status is a prominent public health issue in several European coun-tries. Brown algae have a high iodine content that, upon intake, may exceed the recommended dietary intake level, but iodine bioavailability has been reported to be lower than from potassium iodide (KI) and highly depends on algae species. Further, potential negative effects from other components in algae, such as cadmium (Cd) and arsenic (As), have also been addressed. In this study, we observed a lower bioavailability of iodine from farmed sugar kelp (Saccharina latissima) than from KI in female Wistar IGS rats. Urinary iodine excretion was 94–95% in rats fed KI and 73–81% in rats fed sugar kelp, followed by increased faecal iodine levels in rats fed sugar kelp. No effects on body weight, feed efficiency, or plasma markers for liver or kidney damage were detected. The highest dose of iodine reduced plasma free thyroxine (fT4) and total T4 levels, but no significant effects on circulating levels of thyroid-stimulating hormone (TSH) and free triiodo-thyronine (fT3) were detected. Faeces and urine measurements indicate that 60–80% of total As and 93% of Cd ingested were excreted in rats fed 0.5 and 5% kelp. Liver metabolomic profiling demonstrates that a high inclusion of sugar kelp in the diet for 13 weeks of feeding modulates metabolites with potential antioxidant activity and phytosterols. [ABSTRACT FROM AUTHOR]

The combined effect of elevated pCO2 (Partial Pressure of Carbon Dioxide) and decreased salinity, which is mainly caused by freshwater input, on the growth and physiological traits of algae has been poorly assessed. In order to investigate their individual and interactive effects on the development of commercially farmed algae, the juvenile sporophytes of Saccharina japonica were cultivated under different levels of salinity (30, 25 and 20 psu) and pCO2 (400 and 1000 µatm). Individually, decreased salinity significantly reduced the growth rate and pigments of S. japonica, indicating that the alga was low-salinity stressed. The maximum quantum yield, Fv/Fm, declined at low salinities independent of pCO2, suggesting that the hyposalinity showed the main effect. Unexpectedly, the higher pCO2 enhanced the maximum relative electron transport rate (rETRmax) but decreased the growth rate, pigments and soluble carbohydrates contents. This implies a decoupling between the photosynthesis and growth of this alga, which may be linked to an energetic reallocation among the different metabolic processes. Interactively and previously untested, the decreased salinity offset the improvement of rETRmax and aggravated the declines of growth rate and pigment content caused by the elevated pCO2. These behaviors could be associated with the additionally decreased pH that was induced by the low salinity. Our data, therefore, unveils that the decreased salinity may increase the risks of future CO2-induced ocean acidification on the production of S. japonica. [ABSTRACT FROM AUTHOR]

Due to their specific physicochemical, capillary, and porous properties, the cellulosic sorbents from macrophytes have a high number of possible uses. The number of studies of alternative sources of cellulose is nowadays increasing. One of the most interesting cellulose-containing components of brown algae biomass is protein-cellulose complexes (PCC). The capillary and porous structure of protein-cellulose complexes of brown algae Laminaria digitata and Saccharina latissima was studied. The mesoporous structure of PCC was revealed using the nitrogen adsorption method. The surface area of protein-cellulose complexes is 5.31 m2/g and 2.94 m2/g for PCC S. latissima and PCC L. digitata, respectively. The adsorption of cationic methylene blue was more effective (maximum uptake capacity 24 mg/g) than anionic methyl orange (maximum uptake capacity 11 mg/g), which could be explained by the surface properties of protein-cellulose complexes and their charge, as well as the acid–base features of the dyes. The obtained results highlight the potential of the studied materials for the adsorption of organic toxicants. [ABSTRACT FROM AUTHOR]

SUMMARY: In this study, we applied a chemostat culture method, for the first time, to measure the nutrient uptake rate of macroalgae. We examined two methods of measuring the nutrient uptake rate of two macroalgae, Saccharina japonica var. religiosa and Ulva australis, by comparing nutrient uptake kinetics between the chemostat culture and batch culture. In the chemostat culture, the nutrient concentration was kept constant by monitoring the change in nutrient concentration using an Auto Analyzer in real time and adding nutrients to compensate for the macroalgae's nutrient consumption. The nutrient uptake in the chemostat culture could be best fitted to the Michaelis–Menten saturation kinetics. In the batch culture, the nutrient concentration decreased with time, either constantly or exponentially due to a rapid uptake of nutrients by the macroalgae. The nutrient uptake rate in the batch culture generally showed a scattered relationship with nutrient concentration, with a weak fitting to the Michaelis–Menten saturation kinetics. This discrepancy seemed to be partly because the change in nutrient concentration was large between the sampling intervals in the batch culture. Determining an appropriate sampling interval for detectable concentration change is difficult unless the nutrient concentration is measured in real time. Therefore, the application of the chemostat culture method to the measurement of the uptake rate by macroalgae could greatly improve our understanding of nutrient uptake kinetics. [ABSTRACT FROM AUTHOR]

The fucoidan SdeF was isolated from brown alga Saccharina dentigera. The structure of the obtained polysaccharide was studied by chemical methods, NMR spectroscopy of the fully and partially desulfated derivatives, and mass spectrometry of the fucoidan fragments, labeled with 18O. The SdeF was shown to be sulfated (40%) 1,3-linked α-L-fucan, with branches at C2. The sulfate groups were found at positions C2 and C4. Derivatives SdeFDS and SdeFPL were obtained by solvolytic desulfation and autohydrolysis of SdeF , respectively. According to 13C NMR data, SdeFDS is 1,3-linked α-L-fucan, while SdeFPL is 4-sulfated 1,3-linked α-L-fucan. Native fucoidan SdeF was shown to be a non-toxic anticancer substance in the model of human malignant melanoma RPMI-7951, colorectal adenocarcinoma HCT-116, and small intestine adenocarcinoma HuTu 80 cells. The partial desulfation of SdeF at C2 and/or the reduction of its Mw, from 229 to 28 kDa, decreased the anticancer activity; complete removal of the sulfated groups and/or Mw reduction to 4.7 kDa further reduced the effect of this polysaccharide. [ABSTRACT FROM AUTHOR]

SUMMARY: We determined the response of photochemical efficiency to desiccation and salinity in an edible brown alga, Saccharina japonica (var. japonica), using a pulse amplitude modulation chlorophyll fluorometer. Natural populations of this species in Muroran, Hokkaido, Japan are most of the time immersed in the subtidal zone; however, those at the uppermost part of the sublittoral are sometimes emersed during low tide. In the laboratory experiment, the alga under aerial exposure up to 8 h under dim light at 20°C and 50% humidity showed that the effective quantum yields (ΔF/Fm′) of Photosystem II quickly declined after more than 45 min of emersion; ΔF/Fm′ also failed to recover to the initial level even after 1 day of rehydration in seawater. Under emersion, the ΔF/Fm′ values were relatively stable and above 0.5 when the absolute water content (AWC, %) was greater than 50%; however, it declined as the AWC decreased. Once the algae were dehydrated to an AWC of less than 50%, their ΔF/Fm′ did not return to the initial level despite subsequent reimmersion in seawater, suggesting the low ability of photosynthetic recovery from dehydration. Results of in situ measurements in Muroran showed that the ΔF/Fm′ of S. japonica declined during the tidal exposure; however, it recovered after they were again immersed in seawater due to the rising tide. Furthermore, S. japonica showed a stenohaline photosynthetic response between 20 and 40 psu, as their ΔF/Fm′ values were found to be unchanged in these salinities after 5 days of laboratory culture; this suggests the seaweed's photosynthetic tolerance and/or acclimation within such a relatively narrow range, which might be one of the traits that preclude its occurrence in the intertidal and brackish waters. Indeed, desiccation risk and fluctuating salinity are important limiting factors that influence the stability of kelp beds for sustainable utilization in the regional fishery including mariculture of this species. [ABSTRACT FROM AUTHOR]

Enriching foods with long‐chain n‐3 polyunsaturated fatty acids requires a delivery emulsion system, which is both thermodynamically and oxidatively stable. The antioxidant and stabilizing properties of three types of polysaccharide extracts from brown algae Saccharina latissima with a mixed composition of polysaccharides (SA: 98% sodium alginate, SF: 90% alginate and 9% fucoidan, SL: 14.5% fucoidan, 9.5% laminarin, and co‐extracted nonpolysaccharides) were evaluated. SA, SF, SL, and REF (added commercial sodium alginate) showed in vitro ferrous ion chelating ability in the order: SA (99%) > SL (78%) > REF (31%) > SF (16%). The difference in antioxidant activity between SA, REF, and SF appeared related to structural differences of alginate (M/G ratio). A storage trial was conducted using 70% (w/w) fish oil‐in‐water delivery emulsions added sodium caseinate (NaCas) (0.23 wt%) as emulsifier in combination with SA, SF, SL, or commercial NaAlg (REF) in different concentrations (C1 = 0.1, C2 = 0.2, C3 = 0.3, and C4 = 0.4 wt%). A control with only NaCas was included (CON). The physical (e.g., creaming and droplet‐size distribution) and oxidative (peroxide value and volatiles) stability of the emulsions, were evaluated (12 days, dark at 20˚C). Acceptable physical stability (creaming index) was found for REF (all concentrations), SF = 0.2 wt% (C2), SL and SA = 0.3 wt% (C3) and 0.4 wt% (C4). In general, the oxidative stability decreased by adding REF, SA, and SF (except for REF at C1), as prooxidant activity was observed. However, SA showed antioxidant activity against the formation of 2‐ethylfuran. SL showed antioxidant activity in decreasing the formation of volatile compounds in emulsions when added in concentrations above 0.2 wt%. [ABSTRACT FROM AUTHOR]

Saccharina sculpera is highly valued for human consumption and value-added products. However, natural resources of this kelp have decreased sharply and it is in danger of extinction. Resources recovery through cultivation is being trialed to enable the sustainable use of this species. In this study, the temperature range for survival and optimal growth of juvenile S. sculpera was identified and applied to field cultivation. This study investigated the survival and growth of juvenile S. sculpera under six temperatures (i.e., 5, 10, 15, 16, 18, and 20°C) and two light intensities (i.e., 20 and 40 µmol photons m-2 s-1) in an indoor culture experiment. In these experiments, the blade length decreased at 16°C under the both light intensities. The thalli died at 20°C and 20 µmol photons m-2 s-1, and at 18--20°C and 40 µmol photons m-2 s-1. During the field cultivation, early growth of S. sculpera was highest at the 5 m depth and growth decreased as the water depth increased. When the initial rearing depth was maintained without adjustment throughout the cultivation period (from December to October), all the cultivated S. sculpera plants died during August and September. However, S. sculpera plants lowered from 5 to 15 m and grew to 90.8 ± 13.1 cm in July. The seawater temperature at 15 m depth was similar to the upper level of thermal tolerance demonstrated by juvenile S. sculpera in the indoor culture experiments (16°C or lower). The plants were subsequently lowered to 25 m depth in August, which eventually led to their maturation in October. The present study confirmed that improved growth rates and a delay in biomass loss can be achieved by adjusting the depth at which the seaweeds are grown during the cultivation period. These results will contribute to the establishment of sustainable cultivation systems for S. sculpera. [ABSTRACT FROM AUTHOR]

Brown algae represent a valuable source of various biologically active compounds. Their accumulation is influenced by many environmental factors. The purpose of this study was a comparison of the total chemical composition of brown algae from the White and Yellow Seas to substantiate the possibility of their use for production of new pharmaceutical substances. Using a scheme, which involves consecutive supercritical fluid, acid, alkaline and water extractions, various components of brown algae have been isolated including a protein-polysaccharide complex, which, in the case of Laminaria digitata and L. saccharina, consisted of cellulose and proteins for more than 80%. FTIR spectroscopy has confirmed the qualitative composition of the complex and indicated its purity. Significant differences in the elemental and component composition affected by growing conditions of macrophytes have been revealed. Chemical compounds obtained from brown algae biomass, especially the protein–polysaccharide complex, have a high potential as a basis for new pharmacological preparations for health protection purposes. Based on the earlier obtained data, one can suppose this complex has both enterosorption and immunomodulatory activity. [ABSTRACT FROM AUTHOR]

The brown alga Saccharina japonica is widely consumed in Asian countries, and post-harvest drying methods such as sun drying and oven drying are commonly used to extend the shelf life of S. japonica. Thus, the present study analyzed the ethanol extract and organic solvent fractions of S. japonica to examine the effects of UVA and heating on certain bioactive compounds (fucoxanthin, phlorotannin compounds, and total antioxidants) during the drying process. The fucoxanthin contents in the ethanol extract and different solvent fractions significantly decreased in response to UVA. However, fucoxanthin in the ethanol extract and other fractions showed resistance to thermal treatment. It is noteworthy that the total phlorotannin content (TPC) in the ethanol extract and all fractions showed an approximately 2.5-fold increase upon UVA radiation. The TPC also increased in all samples exposed to high temperatures, except for those in the chloroform fraction. The total antioxidant capacity (TAC) also exhibited significant increases in a pattern similar to the TPC. The findings demonstrate that UVA exposure and heating stimulated the degradation of fucoxanthin while it increased the TPC and TAC in the extract and fractions of S. japonica. [ABSTRACT FROM AUTHOR]

Background: In brown algae, dioicy is the prevalent sexual system, and phenotypic differences between male and female gametophytes have been found in many dioicous species. Saccharina japonica show remarkable sexual dimorphism in gametophytes before gametogenesis. A higher level of phenotypic differentiation was also found in female and male gametes after gametogenesis. However, the patterns of differential gene expression throughout gametophyte development and how these changes might relate to sex-specific fitness at the gamete stage in S. japonica are not well known. Results: In this study, differences in gene expression between male and female gametophytes in different developmental stages were investigated using comparative transcriptome analysis. Among the 20,151 genes expressed in the haploid gametophyte generation, 37.53% were sex-biased. The abundance of sex-biased genes in mature gametophytes was much higher than that in immature gametophytes, and more male-biased than female-biased genes were observed in the mature stage. The predicted functions of most sex-biased genes were closely related to the sex-specific characteristics of gametes, including cell wall biosynthesis, sperm motility, and sperm and egg recognition. In addition, 51 genes were specifically expressed in males in both stages, showing great potential as candidate male sex-determining region (SDR) genes. Conclusions: This study describes a thorough investigation into differential gene expression between male and female gametophytes in the dioicous kelp S. japonica. A large number of sex-biased genes in mature gametophytes may be associated with the divergence of phenotypic traits and physiological functions between female gametes (eggs) and male gametes (sperm) during sexual differentiation. These genes may mainly come from new sex-biased genes that have recently evolved in the S. japonica lineage. The duplication of sex-biased genes was detected, which may increase the number of sex-biased genes after gametogenesis in S. japonica to some extent. The excess of male-biased genes over female-biased genes in the mature stage may reflect the different levels of sexual selection across sexes. This study deepens our understanding of the regulation of sex development and differentiation in the dioicous kelp S. japonica. [ABSTRACT FROM AUTHOR]

Chitosan films enriched with aqueous extract of Sugar kelp Saccharina latissima (SLE) were developed and characterized by measuring the equilibrium moisture, moisture content, water vapor permeability, mechanical properties, antioxidant properties, optical properties, surface morphology and thermostability. The developed films were tested as separators with antioxidant properties for sliced Havarti cheese. The addition of SLE showed a decrease in mechanical properties such as tensile strength from 48.99 to 36.16 MPa and Young's Modulus from 929.49 to 743.71 MPa compared with pure chitosan films. The resulting chitosan-SLE films showed a high free-radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+). Moreover, the presence of SLE in the chitosan matrix significantly improved the UV-barrier of the samples. When the chitosan-SLE films were employed as separators for cheese, a significant reduction of 52.8% in cheese lipid oxidation was observed after 45 days of refrigerated storage compared to the control group using chitosan films. Hence, an environmentally sustainable alternative to synthetic and non-biodegradable slice separators has been successfully developed using chitosan, a by-product of the fishing industry, fortified with an extract from sugar kelp, a commonly found brown algae. [Display omitted] • Chitosan- Sugar kelp Saccharina latissima (SLE) films were developed. • Chitosan-SLE films were applied as sustainable sliced-cheese separators. • Chitosan-SLE films boost UV-barrier, protecting cheese quality. • Antioxidant chitosan-SLE films: High DPPH and ABTS + activity. • Chitosan-SLE films reduced cheese lipid oxidation by 52.8%. [ABSTRACT FROM AUTHOR]

We previously reported the alginate lyase, SjAly, from a brown alga, Saccharina japonica , providing the first experimental evidence for a functional alginate-degradation enzyme in brown algae. 4-deoxy-L- erythro -5-hexoseulose uronate (DEHU), derived from an unsaturated monosaccharide, was identified as the minimum degradation product produced by SjAly-mediated lysis of alginate. DEHU was hitherto reported to be reduced to 2-keto-3-deoxy-gluconate (KDG) by a DEHU-specific reductase with NAD(P)H in alginate-assimilating organisms and its metabolism in alginate-producing organisms is unknown. Here, we report the functional identification of a DEHU reductase, SjRed, in S. japonica. Among the 14 tested compounds, only DEHU was used as a substrate and was converted to KDG in the presence of NADPH. Optimum temperature, pH, and KCl concentration required for SjRed activity were determined to be 25 °C, 7.2, and 100 mM, respectively. SjRed consists of 341 amino acid residues and is proposed to be a member of the aldo-keto reductase superfamily. Sequencing of SjRed revealed that it is composed of at least three exons. These results indicate the existence of an enzyme that reduces DEHU to KDG in S. japonica. This is the first report on the functional identification of a DEHU-reductase in alginate-producing organisms. • Novel DEHU reductase, SjRed, was functionally identified from a brown alga. • SjRed belongs to the aldo-keto reductase superfamily. • SjRed is the first DEHU reductase discovered in any alginate-producing organisms. [ABSTRACT FROM AUTHOR]

It has been reported that there was a linkage of 5S rRNA gene to 18S-5.8S-25S rRNA gene in a few of species in Ochrophyta. In regard to the usual two positions of linked 5S rDNA to the 3′ end of 25S rDNA, two pairs of primers were designed for amplification to verify this linkage of two genes in a kelp cultivar of Saccharina japonica, one of species in Ochrophyta. This result supplemented the previous report that 5S rDNA was unlinked to 25S rDNA in this kelp. In order to simultaneously visualize this unlinkage of two genes, dual-color fluorescence in situ hybridization (FISH) technique was applied to the cytogenetics of S. japonica. Dual-color FISH images showed that two and four hybridization signals were present in the kelp gametophyte and sporophyte, respectively, metaphase nuclei hybridized simultaneously with the labeled probes of 18S rDNA and 5S rDNA. Both haploid and diploid karyotypes in decreasing length of chromosomes showed that 18S-5.8S-25S rDNA was localized at the interstitial region of Chromosome 23, whereas 5S rDNA resided at the sub-telomeric region of Chromosome 27. These karyotypes suggested that the kelp nuclear genome had only one locus of each rRNA gene, and their loci on different chromosomes indicated the physical unlinkage of 5S rDNA to 18S-5.8S-25S rDNA in this kelp. Therefore, dual-color FISH seems to be a powerful technique for the discrimination and pairing of chromosomes featured in both small size and nearly identical shape in S. japonica. [ABSTRACT FROM AUTHOR]

Saccharina japonica is an important large brown alga and a major component of productive beds on the northwest coast of the Pacific Ocean. Abiotic stress response mechanisms are receiving considerable attention because global climate change is increasing their abiotic stress levels. However, our knowledge of how S. japonica broadly responds to stress is limited. In this study, we investigated the S. japonica responsive genes underlying acclimation to diverse stressors of acidification, high light, high temperature, hypersalinity, and hyposalinity and identified 408 core genes constantly and differentially expressed in response to all stressors. Our results confirm that stressors had strong effects on genes participating in photosynthesis, amino acid metabolism, carbohydrate metabolism, halogen metabolism, and reactive oxygen species defense. These findings will improve our understanding of brown algal response mechanisms linked to environmental stress and provide a list of candidate genes for improving algal stress tolerance in light of environmental stress in future studies. [ABSTRACT FROM AUTHOR]

Periplasmic or external carbonic anhydrases (CAs) have been well accepted as playing a crucial role in the acquisition of dissolved inorganic carbon; however, no cytological evidence or molecular information on these enzymes has been reported in seaweeds to date. In this study, the full‐length cDNA sequence coding for a putative periplasmic Sjα‐CA2 was cloned from the gametophytes of Saccharina japonica, an industrial brown seaweed. It was 1,728 bp in length and included a 263‐bp 5′‐untranslated region (UTR), a 577‐bp 3′‐UTR, and an 888‐bp open reading frame encoding a protein precursor consisting of 295 amino acids. The mature protein, after removal of a predicted 28‐residue signal peptide, was composed of 267 amino acids with a relative molecular weight of 29.27 kDa. Multisequence alignment and phylogenetic analysis indicated that it was a member of the α‐CA family. Enzyme activity assays showed that the recombinant Sjα‐CA2 in Escherichia coli possessed CO2 hydration and esterase activities, thus identifying this gene Sjα‐CA2 in function. Immunogold electron microscopic observations with the prepared anti‐Sjα‐CA2 polyclonal antibody illustrated that Sjα‐CA2 was located in periplasmic space of the kelp gametophyte cells. Quantitative real‐time PCR results revealed that the transcription of Sjα‐CA2 was induced by elevated HCO3‐ levels, but it was little changed while the kelp gametophytes were subjected to elevated CO2 concentrations. This study suggests that the periplasmic Sjα‐CA2 might play a role in adapting to elevated environmental levels of HCO3‐ by dehydration of HCO3‐ to generate CO2, which could be readily taken up by S. japonica gametophytes. [ABSTRACT FROM AUTHOR]

SUMMARY The sugar kelp Saccharina latissima experiences a wide range of environmental conditions along its geographical and vertical distribution range. Temperature and salinity are two critical drivers influencing growth, photosynthesis and biochemical composition. Moreover, interactive effects might modify the results described for single effects. In shallow water coastal systems, exposure to rising temperatures and low salinity are expected as consequence of global warming, increased precipitation and coastal run‐off. To understand the acclimation mechanisms of S. latissima to changes in temperature and salinity and their interactions, we performed a mechanistic laboratory experiment in which juvenile sporophytes from Brittany, France were exposed to a combination of three temperatures (0, 8 and 15°C) and two salinity levels (20 and 30 psu (practical salinity units)). After a temperature acclimation of 7 days, sporophytes were exposed to low salinity (20 psu) for a period of 11 days. Growth, and maximal quantum yield of photosystem II (Fv/Fm), pigments, mannitol content and C:N ratio were measured over time. We report for the first time in S. latissima a fivefold increase in the osmolyte mannitol in response to low temperature (0°C) compared to 8 and 15°C that may have ecological and economic implications. Low temperatures significantly affected all parameters, mostly in a negative way. Chlorophyll a, the accessory pigment pool, growth and Fv/Fm were significantly lower at 0°C, while the de‐epoxidation state of the xanthophyll cycle was increased at both 0 and 8°C compared to 15°C. Mannitol content and growth decreased with decreased salinity; in contrast, pigment content and Fv/Fm were to a large extent irresponsive to salinity. In comparison to S. latissima originating from an Arctic population, despite some reported differences, this study reveals a remarkably similar impact of temperature and salinity variation, reflecting the large degree of adaptability in this species. [ABSTRACT FROM AUTHOR]

Saccharina japonica is a brown macroalga that has been commercially cultivated in China for almost a century. As a natural raw material, it is widely used in the food and pharmaceutical industries, and it may potentially be useful for biofuel production. However, little is known about the genes involved in carbohydrate biosynthesis, and their regulation is less understood. In this study, the analysis of growth traits and alginate and mannitol contents suggested that sporophyte development could be divided into four stages. Accordingly, we performed transcriptome analysis of the S. japonica sporophyte. In total, 589 million clean reads were generated, and 4,514 novel genes were identified. Gene expression analysis revealed that 2,542 genes were differentially expressed. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that these genes were significantly enriched in "Carbon metabolism," "Photosynthesis," and "Photosynthesis‐antenna proteins" pathways, which are important for metabolism of various carbohydrates during sporophyte development. Systematic analysis identified the genes encoding enzymes for the biosynthesis of cell wall carbohydrates (including alginate, fucoidan, and cellulose) and cytoplasm storage carbohydrates (mannitol, laminarin, and trehalose). Among them, some key genes associated with carbohydrate content were further identified based on detailed expression profiling, representing good candidates for further functional studies. This study provides a global view of the carbohydrate metabolism process and an important resource for functional genomics studies in S. japonica. The results obtained lay the basis for elucidating the molecular mechanism of carbohydrate biosynthesis and for genetic breeding of carbohydrates‐related traits in kelp. [ABSTRACT FROM AUTHOR]

Mass mortality of the long line culture of the sea urchin Strongylocentrotus intermedius in summer, which is greatly associated with their disease, energy storage and resistant abilities, is the most serious problem for the development of the aquaculture. Here, a feeding experiment was conducted for ~ 9 weeks to investigate the survival, growth and gonadal development of small S. intermedius (~ 3 cm) fed either brown algae Sargassum horneri or Saccharina japonica. Subsequently, we assessed their resistant abilities via observing the behaviors of righting, tube feet extension and Aristotle's lantern reflex at both moderately elevated and acutely changed water temperatures. Sea urchins fed S. horneri showed significantly fewer diseased individuals and slower gonadal development than those fed S. japonica. Consistently, significantly greater Aristotle's lantern reflex occurred in sea urchins fed S. horneri at moderately elevated temperatures. These findings suggest that S. horneri has direct application potential as food for the long line culture of S. intermedius in summer because of the advantage in health, energy storage (avoid the energy loss caused by gonadal development at small body sizes) and resistance abilities. In comparison, sea urchins fed S. japonica outperformed those fed S. horneri for all experimental behaviors under the acutely changed water temperatures. These findings clearly suggest that S. intermedius fed S. japonica is more suitable for the areas with cold water mass in summer, because it can effectively avoid or reduce the negative impacts of acute changes of water temperature on sea urchins. The present study provides valuable information into the management of the long line culture of S. intermedius in summer. [ABSTRACT FROM AUTHOR]

Understanding the physiological responses of kelp to environmental parameters is essential for the conservation of natural kelp beds and increased cultivation yield. We investigated the effects of photosynthetically active radiation (PAR) and temperature on photosynthesis of a subarctic edible brown alga, Saccharina sculpera (Laminariales), using pulse amplitude modulation (PAM)–chlorophyll fluorometry and optical dissolved oxygen sensors. Photosynthesis–PAR experiments at 8 °C, 15 °C, and 22 °C revealed the highest net photosynthetic rates at 22 °C. Values for compensation (Ec) and saturation (Ek) indicated a high affinity for a light environment that reflected the natural vertical habitat of this alga. The photosynthetic response of S. sculpera to temperature indicated that the optimum temperature for oxygenic photosynthesis ( K o p t G P ) was 22.9 °C, which was consistent with the highest seawater temperature in Japanese distribution range for this subarctic species. The alga survived for 168 h at 24 °C in darkness. Continuous 6 h exposure to PAR of 100 µmol (low) and 1000 µmol (high) photons m–2 s–1 at 8 °C, 15 °C, and 22 °C induced chronic photoinhibition in the alga, with greater declines in effective quantum yields of photosystem II (ΦPSII). Failure to recover Fv/Fm after dark acclimation at low and high PAR was observed, except for low PAR at 8 °C. The physiological performance of S. sculpera indicates an affinity for a low light environment. We expect that our results will lead to an improvement in aquaculture techniques through the regulation of cultivation depth. [ABSTRACT FROM AUTHOR]

Kelp life‐cycle transitions are complex and susceptible to various (a)biotic controls. Understanding the microscopic part of the kelp's lifecycle is of key importance, as gametophytes form a critical phase influencing, among others, the distributional limits of the species. Many environmental controls have been identified that affect kelp gametogenesis, whose interactive effects can be subtle and counterintuitive. Here we performed a fully factorial experiment on the (interactive) influences of light intensity, light quality, and the Initial Gametophyte Density (IGD) on Saccharina latissima reproduction and vegetative growth of delayed gametophytes. A total of 144 cultures were followed over a period of 21 d. The IGD was a key determinant for reproductive success, with increased IGDs (≥0.04 mg DW · mL−1) practically halting reproduction. Interestingly, the effects of IGDs were not affected by nutrient availability, suggesting a resource‐independent effect of density on reproduction. The Photosynthetically Usable Radiation (PUR), overarching the quantitative contribution of both light intensity and light quality, correlated with both reproduction and vegetative growth. The PUR furthermore specifies that the contribution of light quality, as a lifecycle control, is a matter of absorbed photon flux instead of color signaling. We hypothesize that (i) the number of photons absorbed, independent of their specific wavelength, and (ii) IGD interactions, independent of nutrient availability, are major determinants of reproduction in S. latissima gametophytes. These insights help understand kelp gametophyte development and dispersal under natural conditions, while also aiding the control of in vitro gametophyte cultures. [ABSTRACT FROM AUTHOR]

The Arctic region is currently facing substantial environmental changes due to global warming. Melting glaciers cause reduced salinity environments in coastal Arctic habitats, which may be stressful for kelp beds. To investigate the responses of the kelp Saccharina latissima to the warming Arctic, we studied the transcriptomic changes of S. latissima from Kongsfjorden (Svalbard, Norway) over a 24‐hour exposure to two salinities (Absolute Salinity [SA] 20 and 30) after a 7‐day pre‐acclimation at three temperatures (0, 8 and 15°C). In addition, corresponding physiological data were assessed during an 11‐days salinity/temperature experiment. Growth and maximal quantum yield for photosystem II fluorescence were positively affected by increased temperature during acclimation, whereas hyposalinity caused negative effects at the last day of treatment. In contrast, hyposalinity induced marked changes on the transcriptomic level. Compared to the control (8°C – SA 30), the 8°C – SA 20 exhibited the highest number of differentially expressed genes (DEGs), followed by the 0°C – SA 20. Comparisons indicate that S. latissima tends to convert its energy from primary metabolism (e.g. photosynthesis) to antioxidant activity under hyposaline stress. The increase in physiological performance at 15°C shows that S. latissima in the Arctic region can adjust and might even benefit from increased temperatures. However, in Arctic fjord environments its performance might become impaired by decreased salinity as a result of ice melting. [ABSTRACT FROM AUTHOR]

The aquaculture of macroalgae for human consumption and other high-end applications is experiencing unprecedented development in European countries, with the brown algae Saccharina latissima being the flag species. However, environmental conditions in open sea culture sites are often unique, which may impact the biochemical composition of cultured macroalgae. The present study compared the elemental compositions (CHNS), fatty acid profiles, and lipidomes of S. latissima originating from three distinct locations (France, Norway, and the United Kingdom). Significant differences were found in the elemental composition, with Norwegian samples displaying twice the lipid content of the others, and significantly less protein (2.6%, while French and UK samples contained 6.3% and 9.1%, respectively). The fatty acid profiles also differed considerably, with UK samples displaying a lower content of n-3 fatty acids (21.6%), resulting in a higher n-6/n-3 ratio. Regarding the lipidomic profile, samples from France were enriched in lyso lipids, while those from Norway displayed a particular signature of phosphatidylglycerol, phosphatidylinositol, and phosphatidylcholine. Samples from the UK featured higher levels of phosphatidylethanolamine and, in general, a lower content of galactolipids. These differences highlight the influence of site-specific environmental conditions in the shaping of macroalgae biochemical phenotypes and nutritional value. It is also important to highlight that differences recorded in the lipidome of S. latissima make it possible to pinpoint specific lipid species that are likely to represent origin biomarkers. This finding is relevant for future applications in the field of geographic origin traceability and food control. [ABSTRACT FROM AUTHOR]

Summary: Brown algae have convergently evolved plant‐like body plans and reproductive cycles, which in plants are controlled by differential DNA methylation. This contribution provides the first single‐base methylome profiles of haploid gametophytes and diploid sporophytes of a multicellular alga.Although only c. 1.4% of cytosines in Saccharina japonica were methylated mainly at CHH sites and characterized by 5‐methylcytosine (5mC), there were significant differences between life‐cycle stages. DNA methyltransferase 2 (DNMT2), known to efficiently catalyze tRNA methylation, is assumed to methylate the genome of S. japonica in the structural context of tRNAs as the genome does not encode any other DNA methyltransferases. Circular and long noncoding RNA genes were the most strongly methylated regulatory elements in S. japonica.Differential expression of genes was negatively correlated with DNA methylation with the highest methylation levels measured in both haploid gametophytes. Hypomethylated and highly expressed genes in diploid sporophytes included genes involved in morphogenesis and halogen metabolism.The data herein provide evidence that cytosine methylation, although occurring at a low level, is significantly contributing to the formation of different life‐cycle stages, tissue differentiation and metabolism in brown algae. [ABSTRACT FROM AUTHOR]

Alginates are valued in many industries, due to their versatile properties. These polysaccharides originate from brown algae (Phaeophyceae) and some bacteria of the Azotobacter and Pseudomonas genera, consisting of 1 → 4 linked β- d -mannuronic acid (M), and its C5-epimer α- l -guluronic acid (G). Several applications rely on a high G-content, which confers good gelling properties. Because of its high natural G-content (F G = 0.60–0.75), the alginate from Laminaria hyperborea (LH) has sustained a thriving industry in Norway. Alginates from other sources can be upgraded with mannuronan C-5 epimerases that convert M to G, and this has been demonstrated in many studies, but not applied in the seaweed industry. The present study demonstrates epimerisation directly in the process of alginate extraction from cultivated Saccharina latissima (SL) and Alaria esculenta (AE) , and the lamina of LH. Unlike conventional epimerisation, which comprises multiple steps, this in-process protocol can decrease the time and costs necessary for alginate upgrading. In-process epimerisation with AlgE1 enzyme enhanced G-content and hydrogel strength in all examined species, with the greatest effect on SL (F G from 0.44 to 0.76, hydrogel Young's modulus from 22 to 34 kPa). As proof of concept, an upscaled in-process epimerisation of alginate from fresh SL was successfully demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]