Evolutionary dynamics of sex-biased gene expression in a young XY system: insights from the brown alga genus Fucus.

Sex-biased gene expression is considered to be an underlying cause of sexually dimorphic traits. Although the nature and degree of sex-biased expression have been well documented in several animal and plant systems, far less is known about the evolution of sex-biased genes in more distant eukaryotic groups. Here, we investigate sex-biased gene expression in two brown algal dioecious species, Fucus serratus and Fucus vesiculosus, where male heterogamety (XX/XY) has recently emerged. We find that in contrast to evolutionary distant plant and animal lineages, male-biased genes do not experience high turnover rates, but instead reveal remarkable conservation of bias and expression levels between the two species, suggesting their importance in sexual differentiation. Genes with consistent male bias were enriched in functions related to gamete production, along with sperm competition and include three flagellar proteins under positive selection. We present one of the first reports, outside of the animal kingdom, showing that male-biased genes display accelerated rates of coding sequence evolution compared with female-biased or unbiased genes. Our results imply that evolutionary forces affect male and female sex-biased genes differently on structural and regulatory levels, resulting in unique properties of differentially expressed transcripts during reproductive development in Fucus algae.

Induction of Phlorotannins and Gene Expression in the Brown Macroalga Fucus vesiculosus in Response to the Herbivore Littorina littorea.

Mechanisms related to the induction of phlorotannin biosynthesis in marine brown algae remain poorly known. Several studies undertaken on fucoid species have shown that phlorotannins accumulate in the algae for several days or weeks after being exposed to grazing, and this is measured by direct quantification of soluble phenolic compounds. In order to investigate earlier inducible responses involved in phlorotannin metabolism, Fucus vesiculosus was studied between 6 and 72 h of grazing by the sea snail Littorina littorea. In this study, the quantification of soluble phenolic compounds was complemented by a Quantitative real-time PCR (qRT-PCR) approach applied on genes that are potentially involved in either the phlorotannin metabolism or stress responses. Soluble phlorotannin levels remained stable during the kinetics and increased significantly only after 12 h in the presence of grazers, compared to the control, before decreasing to the initial steady state for the rest of the kinetics. Under grazing conditions, the expression of vbpo, cyp450 and ast6 genes was upregulated, respectively, at 6 h, 12 h and 24 h, and cyp450 gene was downregulated after 72 h. Interestingly, the pksIII gene involved in the synthesis of phloroglucinol was overexpressed under grazing conditions after 24 h and 72 h. This study supports the hypothesis that phlorotannins are able to provide an inducible chemical defense under grazing activity, which is regulated at different stages of the stress response.

Bioprospecting of Less-Polar Constituents from Endemic Brown Macroalga Fucus virsoides J. Agardh from the Adriatic Sea and Targeted Antioxidant Effects In Vitro and In Vivo (Zebrafish Model).

The endemic brown macroalga Fucus virsoides J. Agardh from the Adriatic Sea was in the focus of the present research. The volatiles of fresh (FrFv) and air-dried (DrFv) samples of F. virsoides obtained by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) were analyzed by gas chromatography equipped with flame ionization detector and mass spectrometry (GC-FID/MS). The major HS-FrFv compound was pentadecane (61.90-71.55%) followed by pentadec-1-ene (11.00-7.98%). In HS-DrFv, pentadec-1-ene was not present, and few lower aliphatic compounds appeared, as well as benzaldehyde and benzyl alcohol. In HD-FrFv, particularly abundant were alkenes (such as pentadec-1-ene (19.32%), or (E)-pentadec-7-ene (8.35%)). In HD-DrFv, more oxidation products were present (e.g., carbonyl compounds such as tridecanal (18.51%)). The fatty acids profile of freeze-dried sample (FdFv) after conversion to methyl esters was determined by GC-FID, and oleic acid was dominant (42.28%), followed by arachidonic acid (15.00%). High-performance liquid chromatography-high-resolution mass spectrometry with electrospray ionization (HPLC-ESI-HRMS) was used for the screening of less polar fractions (F3 and F4) of F. virsoides. Mono- and diglycerides of stearic, palmitic, oleic, and arachidonic acids were found. Terpenoids and steroids comprised the compounds C20H30(32)O2 and C29H48O(2). Among carotenoids, fucoxanthin was identified. Chlorophyll derivatives were also found (C55H74(72)N4O(5-7)), dominated by pheophytin a. The antioxidant activity of the fractions was investigated by in vitro assays (oxygen radical absorbance capacity (ORAC), reduction of radical cation (ABTS•+), 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay, and ferric reducing antioxidant power (FRAP)) and by in vivo zebrafish model (along with fish embryotoxicity). In vitro experiments proved good radical scavenging abilities of F3 and F4 fractions, which were additionally supported by the protective effect against hydrogen peroxide-induced oxidative stress in zebrafish embryos.

Influence of Fucoidan Extracts from Different Fucus Species on Adult Stem Cells and Molecular Mediators in In Vitro Models for Bone Formation and Vascularization.

Fucoidans, sulfated polysaccharides extracted from brown algae, are marine products with the potential to modulate bone formation and vascularization processes. The bioactivity and safety of fucoidans are highly associated with their chemical structure, which may vary with algae species and extraction method. Thus, in depth evaluation of fucoidan extracts in terms of endotoxin content, cytotoxicity, and their detailed molecular biological impact on the individual cell types in bone is needed. In this study, we characterized fucoidan extracts from three different Fucus species including Fucus vesiculosus (Fv), Fucus serratus (Fs), and Fucus distichus subsp. evanescens (Fe) for their chemical features, endotoxin content, cytotoxicity, and bioactive effects on human outgrowth endothelial cells (OEC) and human mesenchymal stem cells (MSC) as in vitro models for bone function and vascularization. Extracts contained mainly high molecular weight (HMW) fucoidans and were free of endotoxins that may cause inflammation or influence vascularization. OEC tolerated fucoidan concentrations up to 200 µg/mL, and no indication of cytotoxicity was observed. The inflammatory response, however, investigated by real-time PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) and endothelial barrier assessed by impedance measurement differed for the individual extracts. MSC in comparison with endothelial cells were more sensitive to fucoidans and showed partly reduced metabolic activity and proliferation at higher doses of fucoidans. Further results for MSC indicated impaired osteogenic functions in alkaline phosphatase and calcification assays. All tested extracts consistently lowered important molecular mediators involved in angiogenesis, such a VEGF (vascular endothelial growth factor), ANG-1 (angiopoietin 1), and ANG-2 (angiopoietin 2), as indicated by RT-PCR and ELISA. This was associated with antiangiogenic effects at the functional level using selected extracts in co-culture models to mimic bone vascularization processes during bone regeneration or osteosarcoma.

Antitumor Activity of Fucus vesiculosus-Derived Phlorotannins through Activation of Apoptotic Signals in Gastric and Colorectal Tumor Cell Lines.

Seaweeds are one of the largest producers of biomass in the marine environment and a source of multiple bioactive metabolites with valuable health benefits. Among these, phlorotannins have been widely recognized for their promising bioactive properties. The potential antitumor capacity of Fucus vesiculosus-derived phlorotannins remains, however, poorly explored, especially in gastrointestinal tract-related tumors. Therefore, this work aimed to evaluate the cytotoxic properties and possible mechanisms by which F. vesiculosus crude extract (CRD), phlorotannin-rich extract (EtOAc), and further phlorotannin-purified fractions (F1-F9) trigger cell death on different tumor cell lines of the gastrointestinal tract, using flow cytometry. The results indicate that F. vesiculosus samples exert specific cytotoxicity against tumor cell lines without affecting the viability of normal cells. Moreover, it was found that, among the nine different phlorotannin fractions tested, F5 was the most active against both Caco-2 colorectal and MKN-28 gastric cancer cells, inducing death via activation of both apoptosis and necrosis. The UHPLC-MS analysis of this fraction revealed, among others, the presence of a compound tentatively identified as eckstolonol and another as fucofurodiphlorethol, which could be mainly responsible for the promising cytotoxic effects observed in this sample. Overall, the results herein reported contribute to a better understanding of the mechanisms behind the antitumor properties of F. vesiculosus phlorotannin-rich extracts.

Isotopically labelled macroalgae: A new method for determining sources of excess nitrogen pollution.

RATIONALE: Stable nitrogen isotope ratios (δ15 N) can be used to discern sources of excess nitrogen pollution in water. The δ15 N values of nitrate in water often do not reflect the true δ15 N source value owing to high temporal variation, and there are high analytical costs associated with obtaining δ15 N values from water nitrate. To find alternative solutions, we isotopically labelled macroalgae (i.e. seaweed) beyond natural variation as a new method for determining sources of excess nitrogen pollution in seawater. METHODS: Fucus vesiculosus (bladder wrack) non-fertile tips were collected from Easington Colliery, County Durham, UK, and cultured in two isotopically enriched solutions containing ammonium sulphate with δ15 N values of 170 ± 5‰ and -60 ± 3‰ for a period of 19 days. The macroalgae were cultured in separate opened glass jars in an incubator with set temperature (11°C) and light (125 µmol photons m-2 s-2 on a light/dark rhythm of 16 h/8 h). The oven-dried tips were analysed for δ15 N over the 19-day experiment. RESULTS: The macroalgal tips incorporated the isotopically enriched solutions rapidly, reaching 50% of the isotopically enriched seawater after ca 11 days for the 15 N-enriched solution and ca 15 days for the 14 N-enriched solution. δ15 N values were incorporated more into the torn base of the macroalgal tips than into the middle and apex regions. CONCLUSIONS: F. vesiculosus rapidly incorporates the isotopic ratio of the artificial seawater solution to which it is translocated. The laboratory-developed isotopically labelled macroalgae can be manufactured to generate 'unnatural' δ15 N values for translocation into coastal environments. This approach can provide an efficient, low-cost alternative to current analytical methods for determining and monitoring nitrogen pollution.

Bioactive Molecular Networking for Mapping the Antimicrobial Constituents of the Baltic Brown Alga Fucus vesiculosus.

The brown alga Fucus vesiculosus is common to the intertidal zones of the Baltic Sea, where it is exposed to high fouling pressures by microorganisms. Our previous studies showed, repeatedly, the consistent antimicrobial activity of F. vesiculosus crude extracts against human pathogens, while untargeted metabolomics analyses have revealed a variety of metabolites. In this study, we applied the UPLC-QToF-MS/MS-based "bioactive molecular networking" (BMN) concept on the most bioactive n-hexane and n-butanol subextracts of Baltic F. vesiculosus coupled with in silico dereplication tools to identify the compounds responsible for antimicrobial activity. The first antimicrobial cluster identified by BMN was galactolipids. Our targeted isolation efforts for this class led to the isolation of six monogalactosyldiacylglycerol (MGDG) derivatives (1-6) and one digalactosyldiacylglycerol (DGDG, 7). The MGDGs 5 and 6 and the DGDG 7 exhibited activity against Staphylococcus aureus. The second compound class with high bioactivity was phlorotannins. In particular, phlorethol-type phlorotannins showed high correlations with antimicrobial activity based on the BMN approach, and two phlorotannins (8-9) were isolated. This study shows that antimicrobial components of F. vesiculosus reside in the algal cell walls and membranes and that BMN provides a complementary tool for the targeted isolation of bioactive metabolites.

Microwave-Assisted Extraction of Phlorotannins from Fucus vesiculosus.

Microwave-assisted extraction (MAE) was carried out to maximize the extraction of phlorotannins from Fucus vesiculosus using a hydroethanolic mixture as a solvent, as an alternative to the conventional method with a hydroacetonic mixture. Optimal MAE conditions were set as ethanol concentration of 57% (v/v), temperature of 75 °C, and time of 5 min, which allowed a similar recovery of phlorotannins from the macroalgae compared to the conventional extraction. While the phlorotannins richness of the conventional extract was slightly superior to that of MAE (11.1 ± 1.3 vs. 9.8 ± 1.8 mg PGE/g DWextract), both extracts presented identical phlorotannins constituents, which included, among others, tetrafucol, pentafucol, hexafucol, and heptafucol structures. In addition, MAE showed a moderate capacity to scavenge ABTS•+ (IC50 of 96.0 ± 3.4 µg/mL) and to inhibit the activity of xanthine oxidase (IC50 of 23.1 ± 3.4 µg/mL) and a superior ability to control the activity of the key metabolic enzyme α-glucosidase compared to the pharmaceutical drug acarbose.

Fucoidans of Moroccan Brown Seaweed as Elicitors of Natural Defenses in Date Palm Roots.

Fucoidans from Moroccan brown seaweed Bifurcaria bifurcata and Fucus spiralis were tested for their elicitor activity after their purification and complete characterization. The fucoidans of B. bifurcata (BBF) and of F. spiralis (FSF) were extracted and purified then characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and size exclusion chromatography. The results show that BBF and FSF are mainly sulfated with 45.49 and 49.53% (w/w) sulfate, respectively. Analysis of neutral sugars determined by gas chromatography-mass spectrometry showed that FSF and BBF were mainly composed of 64% and 91% fucose and 20% and 6% galactose, respectively, with a few other sugars such as glucose (8% in FSF), rhamnose (1% in BBF) and mannose (8% in FSF and, 2% in BBF). The eliciting activity of these sulfated polysaccharides in stimulating the natural defenses of the date palm was evaluated through the activity of phenylalanine ammonia-lyase (PAL), and the increase in phenols and lignin content in the roots. The results obtained clearly show that the two fucoidans early and intensely stimulate the natural defenses of the date palm after 24 h of treatments. This remarkable elicitor effect seems to be linked to the sulfated groups compared to non-sulfate alginates extracted from the same algae. These results open promising perspectives for a biological control approach against date palm diseases.

Effect of Sulfated Polysaccharides from Marine Hydrobionts on Humoral Immune Response to Ovalbumin in Mice.

Adjuvant activity of fucoidans in experimental vaccine compositions with ovalbumin was studied on a mouse model. Compositions with sulfated polysaccharides from brown alga Fucus evanescens (native fucoidan in combination with polyphenols, and a product of fucoidan enzymatic hydrolysis) induced multiple productions of antigen-specific antibodies - total IgG, its isotypes IgG1 and, especially, IgG2a, in comparison with an individual ovalbumin. The adjuvant effect of native and structurally modified fucoidans is slightly inferior to that of the traditional licensed aluminum hydroxide adjuvant. The results indicate the prospects of using sulfated polysaccharides from F. evanescens as adjuvants in vaccines.

Distribution of natural ingredients suggests a complex network of metabolic transport between source and sink tissues in the brown alga Fucus vesiculosus.

MAIN CONCLUSION: Tight regulation of intra-thallus metabolite distribution in Fucus vesiculosus in late summer reveals the complex biochemical processes complying with reproduction and the preparation to the dark season. We used inductively coupled plasma atomic emission spectroscopy to study the tissue-specific elemental composition, and gas chromatography coupled to mass spectrometry to study the distribution of small-molecular weight primary and secondary metabolites of the brown alga Fucus vesiculosus thalli in the reproductive phase. Beyond general physiological requirements, the observed distribution of the analysed nutrients was also found to depend on characteristics related to the season of harvesting, i.e., the reproductive period. However, a particular curious result was the high metabolic activity found in the stipe of the plant. In conclusion, our data not only provide valuable information for industrial use of fucoids targeting specific algal ingredients, but also give highly interesting insights in the multifaceted system of intra-thallus biochemical interactions during reproduction of the brown algae.

Lipidomic Signatures Reveal Seasonal Shifts on the Relative Abundance of High-Valued Lipids from the Brown Algae Fucus vesiculosus.

Fucus vesiculosus is an edible brown macroalga, with health benefits associated with its consumption and also a source of bioactive molecules. It is acknowledged that the biochemical composition of macroalgae changes when exposed to different environmental conditions occurring on different habitats, such as the water temperature, and light intensity. In the present study, the polar lipidome of Fucus vesiculosus was characterized for the first time using modern high-resolution HILIC-MS, and MS/MS approaches, to evaluate the phenotypic variability in two seasons of the year, e.g., winter and spring. A total of 187 molecular species were identified over eighteen classes of glycolipids, phospholipids and betaine lipids. Principal component analysis (PCA) multivariate statistical analysis and cluster analysis of polar lipid classes, polar lipid species and total fatty acids (FA) datasets, showed clustering according to the seasonal groups. While the lipid profile of Fucus vesiculosus harvested in the winter and spring yielded the same molecular species, the relative abundance of these species was significantly different. In the winter, changes were mainly due to the increased relative abundance of some molecular species of glycolipids and phospholipids, bearing octadeca(poly)enoic (18:3, 18:4) and eicosa(poly)enoic (20:4, 20:5) FA and betaine lipids species with short saturated FA (14:0) and polyunsaturated FA (PUFA). Importantly, glycolipids with n-3 PUFA and sulfolipids, have been reported to have important biological activities and therapeutic value. Overall, Fucus vesiculosus is a promising source of bioactive compounds that can be used as functional food or ingredients for human nutrition, feed, pharma, and cosmetic formulations. In this study, samples harvested in the winter season maximized yields of these bioactive components, when compared with samples harvested in the spring.

Variability in iodine in temperate seaweeds and iodine accumulation kinetics of Fucus vesiculosus and Laminaria digitata (Phaeophyceae, Ochrophyta).

The biogeochemistry of iodine in temperate coastal ecosystems is largely mediated by macroalgae, which act as a major biological sink and source of iodine. Their capacity to accumulate, retain and release iodine has been associated with abiotic and biotic stressors, but quantitative information is limited. We evaluated the seasonal iodine retention capacity of eleven macroalgal species belonging to different systematic groups, collected from two sites in Ireland. Iodine accumulation and retention were then further quantified in Fucus vesiculosus and Laminaria digitata in relation to I- concentrations in seawater and temperature. In general, iodine contents were ~101 -102  µmol · (g dw)-1 for Laminariales, 100 -101  µmol · (g dw)-1 for Fucales, 10-1 -100  µmol · (g dw)-1 for Rhodophyta, and 10-1  µmol · (g dw)-1 for Chlorophyta. Typically, algal iodine contents were above average in winter and below average in summer. Iodine accumulation in F. vesiculosus and L. digitata depended on I- availability and followed the Michaelis-Menten kinetic. The ratio of maximum accumulation rate to half accumulation coefficient (ρmax : Kt ) was 2.4 times higher for F. vesiculosus than for L. digitata, suggesting that F. vesiculosus was more efficient in iodine accumulation. Both species exhibited a temperature-dependent net loss of iodine, and only an exposure to sufficient external I- concentrations compensated for this loss. This study revealed that both environmental (e.g., I- in seawater, temperature) and organismal (e.g., the status of the iodine storage pool) variables determine retention and variability in iodine in temperate seaweeds.

Seasonal Variations in the Metabolome and Bioactivity Profile of Fucus vesiculosus Extracted by an Optimised, Pressurised Liquid Extraction Protocol.

The metabolism of seaweeds depends on environmental parameters, the availability of nutrients, and biotic/abiotic stresses; therefore, their chemical composition fluctuates throughout the year. This study investigated seasonal variations in the metabolome of the Baltic Sea brown alga Fucus vesiculosus and its potential relation to the bioactivity profile. By using a definitive screening design (DSD) combined with pressurised liquid extraction (PLE), an optimised protocol was developed to extract algal biomass monthly for a full calendar year. An untargeted metabolomics approach using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MSn)-based molecular networking and manual dereplication was employed. The extracts were simultaneously screened for their in vitro antimicrobial, anticancer/apoptotic, and free radical scavenging activities. 44 compounds were putatively dereplicated in the metabolome. Many compounds were found to vary with the sampling month; phlorotannin total ion count (TIC) was highest in summer, whilst chlorophylls, lipids, and carotenoids peaked in winter and spring. The greatest radical scavenging and apoptotic activities against pancreas cancer cells observed in the summer months were attributed to high phlorotannin TIC. Methicillin-resistant Staphylococcus aureus (MRSA) inhibitory activity was produced year-round without a clear seasonal trend. This is the first study applying DSD-based optimised PLE extraction combined with a metabolome analysis of F. vesiculosus for the identification of seasonal variations in both metabolome and bioactivity.

In vivo uptake of iodine from a Fucus serratus Linnaeus seaweed bath: does volatile iodine contribute?

Seaweed baths containing Fucus serratus Linnaeus are a rich source of iodine which has the potential to increase the urinary iodide concentration (UIC) of the bather. In this study, the range of total iodine concentration in seawater (22-105 µg L-1) and seaweed baths (808-13,734 µg L-1) was measured over 1 year. The seasonal trend shows minimum levels in summer (May-July) and maximum in winter (November-January). The bathwater pH was found to be acidic, average pH 5.9 ± 0.3. An in vivo study with 30 volunteers was undertaken to measure the UIC of 15 bathers immersed in the bath and 15 non-bathers sitting adjacent to the bath. Their UIC was analysed pre- and post-seaweed bath and corrected for creatinine concentration. The corrected UIC of the population shows an increase following the seaweed bath from a pre-treatment median of 76 µg L-1 to a post-treatment median of 95 µg L-1. The pre-treatment UIC for both groups did not indicate significant difference (p = 0.479); however, the post-treatment UIC for both did (p = 0.015) where the median bather test UIC was 86 µg L-1 and the non-bather UIC test was 105 µg L-1. Results indicate the bath has the potential to increase the UIC by a significant amount and that inhalation of volatile iodine is a more significant contributor to UIC than previously documented.

Nutrients influence the thermal ecophysiology of an intertidal macroalga: multiple stressors or multiple drivers?

Urbanization of coastlines is leading to increased introduction of nutrients from the terrestrial environment to nearshore habitats. While such nutrient influxes can be detrimental to coastal marine organisms due to increased eutrophication and subsequent reduced oxygen, they could also have positive effects (i.e., increased food availability) on species that are nitrogen-limited such as macroalgae. Nutrient enrichment in this environment thus has the potential to counteract some of the negative impacts of increasing temperatures, at least for some species. Characterizing the physiological response of organisms to simultaneous changes in multiple drivers such as these is an important first step in predicting how global climate change may lead to ecological responses at more local levels. We evaluated how nutrient enrichment (i.e., nitrogen availability) affected the growth of Fucus vesiculosus, a foundational macroalgal species in the North Atlantic rocky intertidal zone, and found that nutrient-enriched algal blades showed a significant increase in tissue growth compared to individuals grown under ambient conditions. We further quantified net photosynthesis by ambient and nutrient-enriched tissues at saturating irradiance over a range of temperature conditions (6-30°C). Respiration was unaffected by nutrient treatment; however, there was a significant increase in photosynthetic oxygen production for nutrient-enriched tissue compared to ambient, but only at elevated (≥18°C) temperatures. This study contributes to a growing body of literature showing the complexity of responses to changes in multiple drivers, and highlights the importance of studying the impacts of global climate change within the context of more local environmental conditions.

Early Embryogenesis of Brown Alga Fucus vesiculosus L. is Characterized by Significant Changes in Carbon and Energy Metabolism.

Brown algae have an important role in marine environments. With respect to their broad distribution and importance for the environment and human use, brown algae of the order Fucales in particular became a model system for physiological and ecological studies. Thus, several fucoids have been extensively studied for their composition on the molecular level. However, research of fucoid physiology and biochemistry so far mostly focused on the adult algae, so a holistic view on the development of these organisms, including the crucial first life stages, is still missing. Therefore, we employed non-targeted metabolite profiling by gas chromatography coupled to mass spectrometry to create a non-biased picture of the early development of the fucoid alga Fucus vesiculosus. We found that embryogenic physiology was mainly dominated by a tight regulation of carbon and energy metabolism. The first dramatic changes of zygote metabolism started within 1 h after fertilization, while metabolism of 6-9 days old embryos appeared already close to that of an adult alga, indicated by the intensive production of secondary metabolites and accumulation of mannitol and citric acid. Given the comprehensive description and analysis we obtained in our experiments, our results exhibit an invaluable resource for the design of further experiments related to physiology of early algal development.

Differences in Metal Accumulation in the Growing Shoot Tips and Remaining Shoot Tissue in Three Species of Brown Seaweeds.

In this study we compared the accumulation of eight metals and two metalloids in the growing tips and the remaining shoot tissue of three species of brown seaweeds commonly used in biomonitoring studies (Fucus ceranoides, Fucus spiralis and Ascophyllum nodosum). Regression analysis of the data obtained showed that there was no statistically significant difference in accumulation in numerous cases; although most of the relationships were significant, many of the coefficients of determination were low. However, the concentrations of Mn and Zn in the growing tips were closely related to the concentrations in the rest of the tissue in all three species, possibly due to redistribution of these elements. Interspecies differences in bioconcentration of the elements may be partly explained by differences in the relative growth rates.

Immunolocalization of cell wall carbohydrate epitopes in seaweeds: presence of land plant epitopes in Fucus vesiculosus L. (Phaeophyceae).

MAIN CONCLUSION: Land plant cell wall glycan epitopes are present in Fucus vesiculosus. RG-I/AG mAbs recognize distinct glycan epitopes in structurally different galactans, and 3-linked glucans are also present in the cell walls. Cell wall-directed monoclonal antibodies (mAbs) have given increased knowledge of fundamental land plant processes but are not extensively used to study seaweeds. We profiled the brown seaweed Fucus vesiculosus glycome employing 155 mAbs that recognize predominantly vascular plant cell wall glycan components. The resulting profile was used to inform in situ labeling studies. Several of the mAbs recognized and bound to epitopes present in different thallus parts of Fucus vesiculosus. Antibodies recognizing arabinogalactan epitopes were divided into four groups based on their immunolocalization patterns. Group 1 bound to the stipe, blade, and receptacles. Group 2 bound to the antheridia, oogonia and paraphyses. Group 3 recognized antheridia cell walls and Group 4 localized on the antheridia inner wall and oogonia mesochite. This study reveals that epitopes present in vascular plant cell walls are also present in brown seaweeds. Furthermore, the diverse in situ localization patterns of the RG-I/AG clade mAbs suggest that these mAbs likely detect distinct epitopes present in structurally different galactans. In addition, 3-linked glucans were also detected throughout the cell walls of the algal tissues, using the ß-glucan-directed LAMP mAb. Our results give insights into cell wall evolution, and diversify the available tools for the study of brown seaweed cell walls.

Dynamics of cell wall assembly during early embryogenesis in the brown alga Fucus.

Zygotes from Fucus species have been used extensively to study cell polarization and rhizoid outgrowth, and in this model system cell wall deposition aligns with the establishment of polarity. Monoclonal antibodies are essential tools for the in situ analysis of cell wall glycans, and here we report the characteristics of six monoclonal antibodies to alginates (BAM6-BAM11). The use of these, in conjunction with monoclonal antibodies to brown algal sulfated fucans, has enabled the study of the developmental dynamics of the Fucus zygote cell walls. Young zygotes are spherical and all alginate epitopes are deposited uniformly following cellulose deposition. At germination, sulfated fucans are secreted in the growing rhizoid wall. The redistribution of cell wall epitopes was investigated during treatments that cause reorientation of the growth axis (change in light direction) or disrupt rhizoid development (arabinogalactan-protein-reactive Yariv reagent). Alginate modeling was drastically impaired in the latter, and both treatments cause a redistribution of highly sulfated fucan epitopes. The dynamics of cell wall glycans in this system have been visualized in situ for the first time, leading to an enhanced understanding of the early developmental mechanisms of Fucus species. These sets of monoclonal antibodies significantly extend the available molecular tools for brown algal cell wall studies.