Metagenomic sequencing suggests a diversity of RNA interference-like responses to viruses across multicellular eukaryotes

RNA interference (RNAi)-related pathways target viruses and transposable element (TE) transcripts in plants, fungi, and ecdysozoans (nematodes and arthropods), giving protection against infection and transmission. In each case, this produces abundant TE and virus-derived 20-30nt small RNAs, which provide a characteristic signature of RNAi-mediated defence. The broad phylogenetic distribution of the Argonaute and Dicer-family genes that mediate these pathways suggests that defensive RNAi is ancient, and probably shared by most animal (metazoan) phyla. Indeed, while vertebrates had been thought an exception, it has recently been argued that mammals also possess an antiviral RNAi pathway, although its immunological relevance is currently uncertain and the viral small RNAs (viRNAs) are not easily detectable. Here we use a metagenomic approach to test for the presence of viRNAs in five species from divergent animal phyla (Porifera, Cnidaria, Echinodermata, Mollusca, and Annelida), and in a brown alga-which represents an independent origin of multicellularity from plants, fungi, and animals. We use metagenomic RNA sequencing to identify around 80 virus-like contigs in these lineages, and small RNA sequencing to identify viRNAs derived from those viruses. We identified 21U small RNAs derived from an RNA virus in the brown alga, reminiscent of plant and fungal viRNAs, despite the deep divergence between these lineages. However, contrary to our expectations, we were unable to identify canonical (i.e. Drosophila- or nematode-like) viRNAs in any of the animals, despite the widespread presence of abundant micro-RNAs, and somatic transposon-derived piwi-interacting RNAs. We did identify a distinctive group of small RNAs derived from RNA viruses in the mollusc. However, unlike ecdysozoan viRNAs, these had a piRNA-like length distribution but lacked key signatures of piRNA biogenesis. We also identified primary piRNAs derived from putatively endogenous copies of DNA viruses in the cnidarian and the echinoderm, and an endogenous RNA virus in the mollusc. The absence of canonical virus-derived small RNAs from our samples may suggest that the majority of animal phyla lack an antiviral RNAi response. Alternatively, these phyla could possess an antiviral RNAi response resembling that reported for vertebrates, with cryptic viRNAs not detectable through simple metagenomic sequencing of wild-type individuals. In either case, our findings show that the antiviral RNAi responses of arthropods and nematodes, which are highly divergent from each other and from that of plants and fungi, are also highly diverged from the most likely ancestral metazoan state.

Development and application of a monoclonal-antibody technique for counting Aureococcus anophagefferens, an alga causing recurrent brown tides in the Mid-Atlantic United States

A method was developed for the rapid detection and enumeration of Aureococcus anophagefferens, the cause of harmful algal blooms called "brown tides" in estuaries of the Mid-Atlantic United States. The method employs a monoclonal antibody (MAb) and a colorimetric, enzyme-linked immunosorbent assay format. The MAb obtained exhibits high reactivity with A. anophagefferens and very low cross-reactivities with a phylogenetically diverse array of other protists and bacteria. Standard curves are constructed for each 96-well microtiter plate by using known amounts of a preserved culture of A. anophagefferens. This approach allows estimation of the abundance of the alga in natural samples. The MAb method was compared to an existing method that employs polyclonal antibodies and epifluorescence microscopy and to direct microscopic counts of A. anophagefferens in samples with high abundances of the alga. The MAb method provided increased quantitative accuracy and greatly reduced sample processing time. A spatial survey of several Long Island estuaries in May 2000 using this new approach documented a range of abundances of A. anophagefferens in these bays spanning nearly 3 orders of magnitude.

Phlorofucofuroeckol B suppresses inflammatory responses by down-regulating nuclear factor κB activation via Akt, ERK, and JNK in LPS-stimulated microglial cells

Microglial activation has been implicated in many neurological disorders for its inflammatory and neurotrophic effects. In this study, we investigated the effects of phlorofucofuroeckol B (PFF-B) isolated from Ecklonia stolonifera, on the production of inflammatory mediators in lipopolysaccharide (LPS)-stimulated microglia. PFF-B decreased secretion of pro-inflammatory cytokines including tumor necrosis factor α, interleukin (IL)-1β, and IL-6 and the expression of pro-inflammatory proteins such as cyclooxygenase-2 and inducible nitric oxide synthase in LPS-stimulated BV-2 cells. Profoundly, PFF-B inhibited activation of nuclear factor kappaB (NF-κB) by preventing the degradation of inhibitor κB-α (IκB-α), which led to prevent the nuclear translocation of p65 NF-κB subunit. Moreover, PFF-B inhibited the phosphorylation of Akt, ERK, and JNK. These results indicate that the anti-inflammatory effect of PFF-B on LPS-stimulated microglial cells is mainly regulated by the inhibition of IκB-α/NF-κB and Akt/ERK/JNK pathways. Our study suggests that PFF-B can be considered as a therapeutic agent against neuroinflammation by inhibiting microglial activation.

Water soluble sulfated-fucans with immune-enhancing properties from Ecklonia cava

Water-soluble sulfated fucans isolated from Ecklonia cava were fractionated using an anion-exchange chromatography to investigate their molecular characteristics and immunomodulating activities. The crude fucoidan extract and purified fractions (EF1, EF2, and EF3) consisted mostly of different ratios of neutral sugars, proteins, sulfates, uronic acids, and their monosaccharide compositions were also significantly different. The backbone of the most immunoenhancing fraction, EF2, was mainly linked by (1→3)-linked fucopyranosyl and (1→4)-linked mannopyranosyl residues with sulfates at C-4 of fucopyranosyl units. The molecular weights of the crude fucoidan extract and purified fractions ranged from 8.3×10(3) to 442.6×10(3)g/mol. The crude extract, EF1 and EF2 stimulated RAW264.7 cells to produce considerable amounts of nitric oxide and cytokines. The treatment of cells with the sulfated fucans induced the degradation of Iκ-B and the phosphorylation of MAPK in RAW264.7 cells, implying that they might stimulate RAW264.7 cells through the activation of NF-κB and MAPK pathways.

Hemeoxygenase 1 partly mediates the anti-inflammatory effect of dieckol in lipopolysaccharide stimulated murine macrophages

Eisenia bicyclis is edible brown algae recognized as a rich source of bioactive derivatives mainly phlorotannins reported for their anti-oxidant properties. Of all phlorotannins identified so far, dieckol has shown the most potent effect in anti-inflammatory, radical scavenging and neuroprotective functions. However, whether dieckol up-regulates hemeoxygenase 1 (HO-1) and this mediates its anti-inflammatory effect in murine macrophages remains poorly understood. Dieckol (12.5-50 μM) inhibited nitric oxide production and attenuated inducible nitric oxide synthase, phospho (p)-PI-3K, p-Akt, p-IKK-α/β, p-IκB-α and nuclear p-NF-κBp65 protein expressions, and NF-κB transcriptional activity in LPS (0.1 μg/ml) stimulated murine macrophages. On the other hand, dieckol up-regulated HO-1 which partly mediated its anti-inflammatory effect in murine macrophages. Thus, dieckol appeared to be a potential therapeutic agent against inflammation through HO-1 up-regulation.

Rapid and label-free cell detection by metal-cluster-decorated carbon nanotube biosensors

In this paper, the use of carbon nanotube biosensors toward alga cell detection was examined. The biosensor devices were fabricated on complete 4 in. wafers by first growing carbon nanotubes (CNTs) and then depositing metal electrodes using a shadow mask. In addition, we decorated the biosensors with metal-clusters resulted in enhancing the sensitivity by 2000-folds and has enabled the detection of streptavidin down to 10 pM concentration. This sensitivity enhancement was attributed to activation of CNT channels due to formation of Schottky junctions between CNTs and metal-clusters. Real-time cell detection has been successfully carried out using the CNT biosensors for two kinds of alga related to brown tides: Aureococcus anophagefferens and BT3. Functionalization of the CNT biosensors with the monoclonal antibody for A. anophagefferens has led to detection at a concentration of 10(4) cells/ml, with sensitivity lower than 10(4) cells/ml projected based on the signal-to-noise ratio of the sensors. Further functionalization with tween 20 led to suppression of non-specific binding of BT3 and enabled label-free and selective detection of A. anophagefferens. These nanobiosensors may find potential applications for environmental monitoring and disease diagnosis.

Highly dynamic exon shuffling in candidate pathogen receptors ... what if brown algae were capable of adaptive immunity?

Pathogen recognition is the first step of immune reactions. In animals and plants, direct or indirect pathogen recognition is often mediated by a wealth of fast-evolving receptors, many of which contain ligand-binding and signal transduction domains, such as leucine-rich or tetratricopeptide repeat (LRR/TPR) and NB-ARC domains, respectively. In order to identify candidates potentially involved in algal defense, we mined the genome of the brown alga Ectocarpus siliculosus for homologues of these genes and assessed the evolutionary pressures acting upon them. We thus annotated all Ectocarpus LRR-containing genes, in particular an original group of LRR-containing GTPases of the ROCO family, and 24 NB-ARC-TPR proteins. They exhibit high birth and death rates, while a diversifying selection is acting on their LRR (respectively TPR) domain, probably affecting the ligand-binding specificities. Remarkably, each repeat is encoded by an exon, and the intense exon shuffling underpins the variability of LRR and TPR domains. We conclude that the Ectocarpus ROCO and NB-ARC-TPR families are excellent candidates for being involved in recognition/transduction events linked to immunity. We further hypothesize that brown algae may generate their immune repertoire via controlled somatic recombination, so far only known from the vertebrate adaptive immune systems.

Key aspects of the iodine metabolism in brown algae: a brief critical review

Brown algae include the strongest accumulators of iodine known among living systems. This paper reviews the current state of bioinorganic research in the field, focusing on the models Laminaria digitata, Macrocystis pyrifera and Ectocarpus siliculosus, and covering uptake and efflux, localization and biological significance of storage, as well as marine and atmospheric chemistry of iodine.

From Ecology to Biotechnology, Study of the Defense Strategies of Algae and Halophytes (from Trapani Saltworks, NW Sicily) with a Focus on Antioxidants and Antimicrobial Properties

This study aimed at the characterization of the antioxidant power of polyphenol extracts (PE) obtained from the algae Cystoseira foeniculacea (CYS) (Phaeophyta) and from the halophyte Halocnemum strobilaceum (HAL), growing in the solar saltworks of western Sicily (Italy), and at the evaluation of their anti-microfouling properties, in order to correlate these activities to defense strategies in extreme environmental conditions. The antioxidant properties were assessed in the PE based on the total antioxidant activity test and the reducing power test; the anti-microfouling properties of the two PE were evaluated by measuring the growth inhibition of marine fish and shellfish pathogen bacteria as well as marine surface fouling bacteria and microalgae exposed to the fractions. Similar polyphenol content (CYS 5.88 ± 0.75 and HAL 6.03 ± 0.25 mg gallic acid equivalents (GAE) g-1 dried weight, DW) and similar reducing power percentage (93.91 ± 4.34 and 90.03 ± 6.19) were recorded for both species, even if they exhibited a different total antioxidant power (measured by the percentage of inhibition of the radical 2,2 diphenyl-1-picrylhydrazyl DPPH), with CYS (79.30) more active than HAL (59.90). Both PE showed anti-microfouling properties, being inhibitors of adhesion and growth of marine fish and shellfish pathogen bacteria (V. aestuarianus, V. carchariae, V. harveyi, P. elyakovii, H. aquamarina) and fouling bacteria (V. natriegens, V. proteolyticus, P. iirgensii, R. litoralis) with minimum inhibitory concentrations comparable to the commercial antifouling products used as a positive control (SEA-NINE™ 211N). Only CYS was a significant inhibitor of the microalgae strains tested, being able to reduce E. gayraliae and C. closterium growth (MIC 10 µg·mL-1) and the adhesion of all three strains tested (E. gayraliae, C. closterium and P. purpureum), suggesting its promise for use as an antifouling (AF) product.

Downregulation of Microparticle Release and Pro-Inflammatory Properties of Activated Human Polymorphonuclear Neutrophils by LMW Fucoidan

Exposition of neutrophils (polymorphonuclear neutrophils, PMNs) to bacterial products triggers exacerbated activation of these cells, increasing their harmful effects on host tissues. We evaluated the possibility of interfering with the classic immune innate responses of human PMNs exposed to bacterial endotoxin (lipopolysaccharide, LPS), and further stimulated with bacterial formyl peptide (N-formyl-methionine-leucine-phenylalanine, fMLP). We showed that the low- molecular-weight fucoidan (LMW-Fuc), a polysaccharide extracted from brown algae, attenuated the exacerbated activation induced by fMLP on LPS-primed PMNs, in vitro, impairing chemotaxis, NET formation, and the pro-survival and pro-oxidative effects. LMW-Fuc also inhibited the activation of canonical signaling pathways, AKT, bad, p47phox and MLC, activated by the exposition of PMN to bacterial products. The activation of PMN by sequential exposure to LPS and fMLP induced the release of L-selectin+ microparticles, which were able to trigger extracellular reactive oxygen species production by fresh PMNs and macrophages. Furthermore, we observed that LMW-Fuc inhibited microparticle release from activated PMN. In vivo experiments showed that circulating PMN-derived microparticles could be detected in mice exposed to bacterial products (LPS/fMLP), being downregulated in animals treated with LMW-Fuc. The data highlight the autocrine and paracrine role of pro-inflammatory microparticles derived from activated PMN and demonstrate the anti-inflammatory effects of LMW-Fuc on these cells.

Whole-cell sensing for a harmful bloom-forming microscopic alga by measuring antibody--antigen forces

Aureococcus anophagefferens, a harmful bloom-forming alga responsible for brown tides in estuaries of the Middle Atlantic U.S., has been investigated by atomic force microscopy for the first time, using probes functionalized with a monoclonal antibody specific for the alga. The rupture force between a single monoclonal antibody and the surface of A. anophagefferens was experimentally found to be 246 +/- 11 pN at the load rate of 12 nN/s. Force histograms for A. anophagefferens and other similarly-sized algae are presented and analyzed. The results illustrate the effects of load rates, and demonstrate that force-distance measurements can be used to build biosensors with high signal-to-noise ratios for A. anophagefferens. The methods described in this paper can be used, in principle, to construct sensors with single-cell resolution for arbitrary cells for which monoclonal antibodies are available.

Hypersensitivity pneumonitis induced by Konjak flour and powdered Hijikia fusiforme

This is a report of a patient with occupational hypersensitivity pneumonitis (HP) caused by Konjak flour and powdered Hijikia fusiforme. A 56-year-old man had worked as a Konnyaku manufacturer for 38 years, and suffered from dyspnea on exertion. Konnyaku is a paste made from Konjak flour, powdered Hijikia fusiforme, quicklime, and powdered scallop shell. The diagnosis of HP was confirmed immunologically by the detection of serum precipitins to powdered Hijikia fusiforme, and by the positive result of in vitro lymphocytic proliferative response for Konjak flour using peripheral blood lymphocytes. To our knowledge, this is the first case report of Konnyaku manufacturer's lung.

Elastin peptide receptor-directed monocyte chemotactic polysaccharides derived from seaweed sporophyll and from infectious fungus

We discovered that a seaweed sporophyll-derived polysaccharide of brown alga, Wakame (Undaria pinnatifida) bound to monocytes and attracted them in vitro and in vivo. Physicochemical properties, affinity to a lectin-bead column and sugar composition of the chemotactic polysaccharide indicated this molecule to be a highly sulfated fucogalactan. We then identified the monocyte receptor of the sulfated fucogalactan as the elastin peptide receptor by prophylactic inhibition of the binding and the chemoattraction with lactose and the synthetic elastin peptide, Val-Gly-Val-Ala-Pro-Gly. We assume that the galactose-binding lectin, which is a component of the elastin peptide receptor complex, would recognize a Gal residue of the sulfated fucogalactan. We also observed a similar chemoattracting polysaccharide in a pathogenic fungus, Candida albicans, although the content of it was much lower than in the case of seaweed sporophyll. We speculate that the chemotactic response of monocytes to the sulfated fucogalactan is part of the innate immune system to fungal infection.

Fertilization in brown algae. IV. Appearance of sperm-specific antigens on fertilized eggs

Flagella antigens from sperm of Fucus serratus have been used to raise antibodies in rabbits. The immunoglobulin G fraction inhibits fertilization with some degree of species specificity. The antigens detected on sperm are not present on unfertilized egg membranes, but appear after fertilization. The common antigens on the fertilized egg can be distinguished from the cell wall material that is also released on fertilization.

[Homology between antigenic determinants of bovine clathrin and clathrin from the brown alga Laminaria digitata]

Coated vesicles, essential organelles of intracellular membrane traffic, have been extensively studied in animal and higher plant cells. In the algae, cytological studies only have been performed which demonstrate the presence of such coated vesicles with their surrounding clathrin lattice. The present work has been carried out on coated vesicles isolated for the first time from the brown algae Laminaria digitata. For comparison of the antigenic characteristics of clathrin prepared from the Bovine brain or adrenocortical cells and the clathrin prepared from algae, polyclonal antibodies have been raised to a purified Bovine brain clathrin in Goat and to Bovine adrenocortical clathrin in Rabbit. The positive immunological responses of the coated vesicles and the clathrin from Algae to these antibodies, evidence an homology between antigenic determinants of clathrin from animal and vegetal cells.

[Agglutinins in marine brown algae. Dedicated to Professor Dr. H. Knöll on his 65th birthday]

Extracts from the brown algae Fucus vesiculosus, F. serratus, and Halidrys siliquosa agglutinated human erythrocytes of groups A, B, O, and AB as well as erythrocytes from some animal species, ascites tumour cells from mice, and streptococci of many groups of the LANCEFIELD system. The extract of Chorda filum did not show haemagglutination but agglutinated ascites tumour cells and streptococci of a few groups.