Exotic myxozoan parasites establish complex life cycles in farm pond aquaculture.

Myxozoans are obligate parasites with complex life cycles, typically infecting fish and annelids. Here, we examined annelids from fish farm pond sediments in the Beit Shean Valley, in the Syrian-African Rift Valley, Israel, for myxozoan infections. We examined 1486 oligochaetes, and found 74 (5 %) were infected with actinospore stages. We used mitochondrial 16S sequencing to infer identity of 25 infected annelids as species of Potamothrix, Psammoryctides, Tubifex and Dero. We identified 7 myxozoan types from collective groups Neoactinomyxum and Sphaeractinomyxon, and characterized them by small subunit ribosomal DNA sequencing. The Neoactinomyxum type was genetically most similar (∼93 %) to cyprinid fish-infecting Myxobolus spp. The six Sphaeractinomyxon types were genetically similar (93-100 %) to Mugilid-infecting Myxobolus spp.; with one being the previously unknown actinospore stage of a myxospore that infects mullet from aquaculture from the Israeli coast of the Mediterranean Sea. As the farm pond system is artificial and geographically isolated from the Mediterranean, the presence of at least seven myxozoans in their annelid hosts demonstrates introduction and establishment of these parasites in a novel, brackish environment.

A remote sensing approach for exploring the dynamics of jellyfish, relative to the water current.

Drifting in large numbers, jellyfish often interfere in the operation of nearshore electrical plants, cause disturbances to marine recreational activity, encroach upon local fish populations, and impact food webs. Understanding the dynamic mechanisms behind jellyfish behavior is of importance in order to create migration models. In this work, we focus on the small-scale dynamics of jellyfish and offer a novel method to accurately track the trajectory of individual jellyfish with respect to the water current. The existing approaches for similar tasks usually involve a surface float tied to the jellyfish for location reference. This operation may induce drag on the jellyfish, thereby affecting its motion. Instead, we propose to attach an acoustic tag to the jellyfish's bell and then track its geographical location using acoustic beacons, which detect the tag's emissions, decode its ID and depth, and calculate the tag's position via time-difference-of-arrival acoustic localization. To observe the jellyfish's motion relative to the water current, we use a submerged floater that is deployed together with the released tagged jellyfish. Being Lagrangian on the horizontal plane while maintaining an on-demand depth, the floater drifts with the water current; thus, its trajectory serves as a reference for the current's velocity field. Using an acoustic modem and a hydrophone mounted to the floater, the operator from the deploying boat remotely changes the depth of the floater on-the-fly, to align it with that of the tagged jellyfish (as reported by the jellyfish's acoustic tag), thereby serving as a reference for the jellyfish's 3D motion with respect to the water current. We performed a proof-of-concept to demonstrate our approach over three jellyfish caught and tagged in Haifa Bay, and three corresponding floaters. The results present different dynamics for the three jellyfish, and show how they can move with, and even against, the water current.

The Molecular Mechanisms Employed by the Parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) from Invasion through Sporulation for Successful Proliferation in Its Fish Host.

Myxozoa is a unique group of obligate endoparasites in the phylum Cnidaria that can cause emerging diseases in wild and cultured fish populations. Recently, we identified a new myxozoan species, Myxobolus bejeranoi, which infects the gills of cultured tilapia while suppressing host immunity. To uncover the molecular mechanisms underlying this successful parasitic strategy, we conducted transcriptomics analysis of M. bejeranoi throughout the infection. Our results show that histones, which are essential for accelerated cell division, are highly expressed even one day after invasion. As the infection progressed, conserved parasitic genes that are known to modulate the host immune reaction in different parasitic taxa were upregulated. These genes included energy-related glycolytic enzymes, as well as calreticulin, proteases, and miRNA biogenesis proteins. Interestingly, myxozoan calreticulin formed a distinct phylogenetic clade apart from other cnidarians, suggesting a possible function in parasite pathogenesis. Sporogenesis was in its final stages 20 days post-exposure, as spore-specific markers were highly expressed. Lastly, we provide the first catalog of transcription factors in a Myxozoa species, which is minimized compared to free-living cnidarians and is dominated by homeodomain types. Overall, these molecular insights into myxozoan infection support the concept that parasitic strategies are a result of convergent evolution.

Selecting 16S rRNA Primers for Microbiome Analysis in a Host-Microbe System: The Case of the Jellyfish Rhopilema nomadica.

Amplicon sequencing of the 16S rRNA gene is extensively used to characterize bacterial communities, including those living in association with eukaryotic hosts. Deciding which region of the 16S rRNA gene to analyze and selecting the appropriate PCR primers remains a major decision when initiating any new microbiome study. Based on a detailed literature survey of studies focusing on cnidarian microbiomes, we compared three commonly used primers targeting different hypervariable regions of the 16S rRNA gene, V1V2, V3V4, and V4V5, using the jellyfish Rhopilema nomadica as a model. Although all primers exhibit a similar pattern in bacterial community composition, the performance of the V3V4 primer set was superior to V1V2 and V4V5. The V1V2 primers misclassified bacteria from the Bacilli class and exhibited low classification resolution for Rickettsiales, which represent the second most abundant 16S rRNA gene sequence in all the primers. The V4V5 primer set detected almost the same community composition as the V3V4, but the ability of these primers to also amplify the eukaryotic 18S rRNA gene may hinder bacterial community observations. However, after overcoming the challenges possessed by each one of those primers, we found that all three of them show very similar bacterial community dynamics and compositions. Nevertheless, based on our results, we propose that the V3V4 primer set is potentially the most suitable for studying jellyfish-associated bacterial communities. Our results suggest that, at least for jellyfish samples, it may be feasible to directly compare microbial community estimates from different studies, each using different primers but otherwise similar experimental protocols. More generally, we recommend specifically testing different primers for each new organism or system as a prelude to large-scale 16S rRNA gene amplicon analyses, especially of previously unstudied host-microbe associations.

The myxozoan parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) infection dynamics and host specificity in hybrid tilapia aquaculture.

Nile × blue tilapia hybrid (Oreochromis niloticus × O. aureus) has become an important food fish in intensive freshwater aquaculture. Recently, the parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) was found to infect hybrid tilapia gills at high prevalence, causing immune suppression and high mortality. Here, we explored additional characteristics of M. bejeranoi­tilapia interaction, which enable efficient proliferation of this parasite inside its specific host. Highly sensitive quantitative polymerase chain reaction (qPCR) and in situ hybridization analyses of fry collected from fertilization ponds provided evidence to an early-life infection of fish by a myxozoan parasite, occurring less than 3 weeks post-fertilization. Because Myxobolus species are highly host-specific, we next compared infection rates in hybrid tilapia and in both its parental species following a 1-week exposure to infectious pond water. Analysis by qPCR and histological sections showed that while blue tilapia was as susceptible to M. bejeranoi as the hybrid, Nile tilapia appeared to be resistant. This is the first report of differential susceptibility of a hybrid fish vs its parental purebreds to a myxozoan parasite. These findings advance our understanding of the relationship between M. bejeranoi and tilapia fish and raise important questions regarding the mechanisms that allow the parasite to distinguish between very closely related species and to infect a specific organ at very early-life stages.

Direct Electricity Production from Nematostella and Arthemia's Eggs in a Bio-Electrochemical Cell.

In recent years, extensive efforts have been made to develop clean energy technologies to replace fossil fuels to assist the struggle against climate change. One approach is to exploit the ability of bacteria and photosynthetic organisms to conduct external electron transport for electricity production in bio-electrochemical cells. In this work, we first show that the sea anemones Nematostella vectensis and eggs of Artemia (brine shrimp) secrete redox-active molecules that can reduce the electron acceptor Cytochrome C. We applied 2D fluorescence spectroscopy and identified NADH or NADPH as secreted species. Finally, we broaden the scope of living organisms that can be integrated with a bio-electrochemical cell to the sea anemones group, showing for the first time that Nematostella and eggs of Artemia can produce electrical current when integrated into a bio-electrochemical cell.

Infection by the Parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) Suppresses the Immune System of Hybrid Tilapia.

Myxozoa (Cnidaria) is a large group of microscopic obligate endoparasites that can cause emerging diseases, affecting wild fish populations and fisheries. Recently, the myxozoan Myxobolus bejeranoi was found to infect the gills of hybrid tilapia (Nile tilapia (Oreochromis niloticus) × Jordan/blue tilapia (O. aureus)), causing high morbidity and mortality. Here, we used comparative transcriptomics to elucidate the molecular processes occurring in the fish host following infection by M. bejeranoi. Fish were exposed to pond water containing actinospores for 24 h and the effects of minor, intermediate, and severe infections on the sporulation site, the gills, and on the hematopoietic organs, head kidney and spleen, were compared. Enrichment analysis for GO and KEGG pathways indicated immune system activation in gills at severe infection, whereas in the head kidney a broad immune suppression included deactivation of cytokines and GATA3 transcription factor responsible for T helper cell differentiation. In the spleen, the cytotoxic effector proteins perforin and granzyme B were downregulated and insulin, which may function as an immunomodulatory hormone inducing systemic immune suppression, was upregulated. These findings suggest that M. bejeranoi is a highly efficient parasite that disables the defense mechanisms of its fish host hybrid tilapia.

Amplicon sequence variant-based meiofaunal community composition revealed by DADA2 tool is compatible with species composition.

The present study is aimed at implementing the morphological identification-free amplicon sequence variant (ASV) concept for describing meiofaunal species composition, while strongly indicating reasonable compatibility with the underlying species. A primer pair was constructed and demonstrated to PCR amplify a 470-490 bp 18S barcode from a variety of meiofaunal taxa, high throughput sequenced using the Illumina 300 × 2 bps platform. Sixteen 18S multi-species HTS assemblies were created from meiofaunal samples and merged to one assembly of ~2,150,000 reads. Five quality scores (q = 35, 30, 25, 20, 15) were implemented to filter five 18S barcode assemblies, which served as inputs for the DADA2 software, ending with five reference ASV libraries. Each of these libraries was clustered, applying 3% dissimilarity threshold, revealed an average number of 1.38 ±â€¯0.078 ASVs / cluster. Hence, demonstrating high level of ASV uniqueness. The libraries which were based on q ≤ 25 reached a near-asymptote number of ASVs which together with the low average number of ASVs / cluster, strongly indicated fair representation of the actual number of the underlying species. Hence, the q = 25 library was selected to be used as metabarcoding reference library. It contained 461 ASVs and 342-3% clusters with average number of 1.34 ±â€¯1.036 ASV / cluster and their BLASTN annotation elucidated a variety of expected meiofaunal taxa. The sixteen assemblies of sample-specific paired reads were mapped to this reference library and sample ASV profiles, namely the list of ASVs and their proportional copy numbers were created and clustered.

Contribution of Maternal and Paternal Transmission to Bacterial Colonization in Nematostella vectensis.

Microbial communities confer multiple beneficial effects to their multicellular hosts. To evaluate the evolutionary and ecological implications of the animal-microbe interactions, it is essential to understand how bacterial colonization is secured and maintained during the transition from one generation to the next. However, the mechanisms of symbiont transmission are poorly studied for many species, especially in marine environments, where the surrounding water constitutes an additional source of microbes. Nematostella vectensis, an estuarine cnidarian, has recently emerged as model organism for studies on host-microbes interactions. Here, we use this model organism to study the transmission of bacterial colonizers, evaluating the contribution of parental and environmental transmission to the establishment of bacterial communities of the offspring. We induced spawning in adult male and female polyps of N. vectensis and used their gametes for five individual fertilization experiments. While embryos developed into primary polyps, we sampled each developmental stage and its corresponding medium samples. By analyzing the microbial community compositions of all samples through 16S rRNA gene amplicon sequencing, we showed that all host tissues harbor microbiota significantly different from the surrounding medium. Interestingly, oocytes and sperms are associated with distinct bacterial communities, indicating the specific vertical transmission of bacterial colonizers by the gametes. These differences were consistent among all the five families analyzed. By overlapping the identified bacterial ASVs associated with gametes, offspring and parents, we identified specific bacterial ASVs that are well supported candidates for vertical transmission via mothers and fathers. This is the first study investigating bacteria transmission in N. vectensis, and among few on marine spawners that do not brood larvae. Our results shed light on the consistent yet distinct maternal and paternal transfer of bacterial symbionts along the different life stages and generations of an aquatic invertebrate.

Cellular pathways during spawning induction in the starlet sea anemone Nematostella vectensis.

In cnidarians, long-term ecological success relies on sexual reproduction. The sea anemone Nematostella vectensis, which has emerged as an important model organism for developmental studies, can be induced for spawning by temperature elevation and light exposure. To uncover molecular mechanisms and pathways underlying spawning, we characterized the transcriptome of Nematostella females before and during spawning induction. We identified an array of processes involving numerous receptors, circadian clock components, cytoskeleton, and extracellular transcripts that are upregulated upon spawning induction. Concurrently, processes related to the cell cycle, fatty acid metabolism, and other housekeeping functions are downregulated. Real-time qPCR revealed that light exposure has a minor effect on expression levels of most examined transcripts, implying that temperature change is a stronger inducer for spawning in Nematostella. Our findings reveal the potential mechanisms that may enable the mesenteries to serve as a gonad-like tissue for the developing oocytes and expand our understanding of sexual reproduction in cnidarians.

The cnidarian parasite Ceratonova shasta utilizes inherited and recruited venom-like compounds during infection.

BACKGROUND: Cnidarians are the most ancient venomous organisms. They store a cocktail of venom proteins inside unique stinging organelles called nematocysts. When a cnidarian encounters chemical and physical cues from a potential threat or prey animal, the nematocyst is triggered and fires a harpoon-like tubule to penetrate and inject venom into the prey. Nematocysts are present in all Cnidaria, including the morphologically simple Myxozoa, which are a speciose group of microscopic, spore-forming, obligate parasites of fish and invertebrates. Rather than predation or defense, myxozoans use nematocysts for adhesion to hosts, but the involvement of venom in this process is poorly understood. Recent work shows some myxozoans have a reduced repertoire of venom-like compounds (VLCs) relative to free-living cnidarians, however the function of these proteins is not known. METHODS: We searched for VLCs in the nematocyst proteome and a time-series infection transcriptome of Ceratonova shasta, a myxozoan parasite of salmonid fish. We used four parallel approaches to detect VLCs: BLAST and HMMER searches to preexisting cnidarian venom datasets, the machine learning tool ToxClassifier, and structural modeling of nematocyst proteomes. Sequences that scored positive by at least three methods were considered VLCs. We then mapped their time-series expressions in the fish host and analyzed their phylogenetic relatedness to sequences from other venomous animals. RESULTS: We identified eight VLCs, all of which have closely related sequences in other myxozoan datasets, suggesting a conserved venom profile across Myxozoa, and an overall reduction in venom diversity relative to free-living cnidarians. Expression of the VLCs over the 3-week fish infection varied considerably: three sequences were most expressed at one day post-exposure in the fish's gills; whereas expression of the other five VLCs peaked at 21 days post-exposure in the intestines, coinciding with the formation of mature parasite spores with nematocysts. Expression of VLC genes early in infection, prior to the development of nematocysts, suggests venoms in C. shasta have been repurposed to facilitate parasite invasion and proliferation within the host. Molecular phylogenetics suggested some VLCs were inherited from a cnidarian ancestor, whereas others were more closely related to sequences from venomous non-Cnidarian organisms and thus may have gained qualities of venom components via convergent evolution. The presence of VLCs and their differential expression during parasite infection enrich the concept of what functions a "venom" can have and represent targets for designing therapeutics against myxozoan infections.

Ectopic activation of GABAB receptors inhibits neurogenesis and metamorphosis in the cnidarian Nematostella vectensis.

The metabotropic gamma-aminobutyric acid B receptor (GABABR) is a G protein-coupled receptor that mediates neuronal inhibition by the neurotransmitter GABA. While GABABR-mediated signalling has been suggested to play central roles in neuronal differentiation and proliferation across evolution, it has mostly been studied in the mammalian brain. Here, we demonstrate that ectopic activation of GABABR signalling affects neurogenic functions in the sea anemone Nematostella vectensis. We identified four putative Nematostella GABABR homologues presenting conserved three-dimensional extracellular domains and residues needed for binding GABA and the GABABR agonist baclofen. Moreover, sustained activation of GABABR signalling reversibly arrests the critical metamorphosis transition from planktonic larva to sessile polyp life stage. To understand the processes that underlie the developmental arrest, we combined transcriptomic and spatial analyses of control and baclofen-treated larvae. Our findings reveal that the cnidarian neurogenic programme is arrested following the addition of baclofen to developing larvae. Specifically, neuron development and neurite extension were inhibited, resulting in an underdeveloped and less organized nervous system and downregulation of proneural factors including NvSoxB(2), NvNeuroD1 and NvElav1. Our results thus point to an evolutionarily conserved function of GABABR in neurogenesis regulation and shed light on early cnidarian development.

A comparison of the structure and function of nematocysts in free-living and parasitic cnidarians (Myxozoa).

Myxozoans are obligate parasites that have complex life cycles requiring alternate vertebrate and invertebrate hosts, with transmission via microscopic waterborne spores. Unusually for parasites, they belong to the phylum Cnidaria, alongside thousands of free-living corals, sea anemones, jellyfish and hydrozoans. Their cnidarian affinity is affirmed by genetic relatedness and the presence of nematocysts, historically called "polar capsules" in myxozoan research. Free-living cnidarians utilise this cellular weaponry for defence, predation and adhesion, whereas myxozoans use it to anchor to their hosts as the first step in infection. Despite the ~650 million years of divergence between free-living cnidarians and myxozoans, their nematocysts retain many shared morphological and molecular characters. Both are intra-cellular capsules with a single opening, and contain a coiled, evertable tubule. They are composed of unique nematocyst proteins, nematogalectin and minicollagen, and both likely contain an internal matrix of metal cations covalently bound to the anionic polymer poly-gamma glutamate. The rapid dissociation of this matrix and the resulting increase in internal osmotic potential is the driving force behind tubule elongation during discharge. In this review, we compare the structure and function of nematocysts in Myxozoa and free-living Cnidaria, incorporating recent molecular characterizations. We propose that terminology for homologous myxozoan structures be synonymized with those from other Cnidaria, hence, "polar capsule" as a taxon-specific nematocyst morphotype and "polar filament" as "tubule." Despite taxonomic divergence, genome reduction and an evolution to parasitism, myxozoans maintain nematocysts that are structurally and functionally homologous to those of their free-living cnidarian relatives.

In vitro and in vivo assays reveal that cations affect nematocyst discharge in Myxobolus cerebralis (Cnidaria: Myxozoa).

Myxozoans are parasitic, microscopic cnidarians that have retained the phylum-characteristic stinging capsules called nematocysts. Free-living cnidarians, like jellyfish and corals, utilize nematocysts for feeding and defence, with discharge powered by osmotic energy. Myxozoans use nematocysts to anchor to their fish hosts in the first step of infection, however, the discharge mechanism is poorly understood. We used Myxobolus cerebralis, a pathogenic myxozoan parasite of salmonid fishes, and developed two assays to explore the nature of its nematocyst discharge. Using parasite actinospores, the infectious stage to fish, we stimulated discharge of the nematocysts with rainbow trout mucus in vitro, in solutions enriched with chloride salts of Na+, K+, Ca2+ and Gd3+, and quantified discharge using microscopy. We then used quantitative polymerase chain reaction to evaluate the in vivo effects of these treatments, plus Mg2+ and the common aquaculture disinfectant KMnO4, on the ability of M. cerebralis actinospores to infect fish. We found that Mg2+ and Gd3+ reduced infection in vivo, whereas Na+ and K+ over-stimulated nematocyst discharge in vitro and reduced infection in vivo. These findings align with nematocyst discharge behaviour in free-living Cnidaria, and suggest phylum-wide commonalties, which could be exploited to develop novel approaches for controlling myxozoan diseases in aquaculture.

The Levantine jellyfish Rhopilema nomadica and Rhizostoma pulmo swim faster against the flow than with the flow.

Jellyfish locomotion and orientation have been studied in the past both in the laboratory, testing mostly small jellyfish, and in the field, where it was impossible to control the seawater currents. Utilizing an outdoor water flume, we tested the locomotion of jellyfish when swimming against and with currents of up to 4.5 cm s-1. We used adult jellyfish from two of the most abundant species in the eastern Mediterranean, Rhopilema nomadica and Rhizostoma pulmo, and measured their pulsation frequency and swimming speed relative to the water. While pulsation frequency was not affected by the water velocity, jellyfish swam faster against the current than with it. This finding suggests that jellyfish possess a sensory ability, whose mechanism is currently unknown, enabling them to gauge the flow and react to it, possibly in order to reduce the risk of stranding.

Myxozoans: Ancient metazoan parasites find a home in phylum Cnidaria.

Myxozoans are endoparasites with complex life cycles that alternate between invertebrate and vertebrate hosts. Though considered protozoans for over 150 years, they are now recognized as metazoans, given their multicellularity and ultrastructural features. In recognition of synapomorphies and cnidarian-specific genes, myxozoans were placed recently within the phylum Cnidaria. Although they have lost genetic and structural complexity on the path to parasitism, myxozoans have retained characteristic cnidarian cnidocysts, but use them for initiating host infection. Myxozoans represent at least 20% of phylum Cnidaria, but as a result of rapid evolution, extensive diversification and host specialization, they are probably at least as diverse as their free-living relatives. The ability of myxozoans to infect freshwater, marine and terrestrial hosts implies that Cnidaria are no longer constrained to the aquatic environment.

Morphological and molecular characterization of a novel myxosporean parasite Myxobolus bejeranoi n. sp. (Cnidaria: Myxosporea) from hybrid tilapia in Israel.

Myxosporean infections can cause severe damage to commercially grown tilapia. Here, we report a novel myxosporean that was found in gills of Oreochromis aureus male × Oreochromis niloticus female, which is an important aquaculture tilapia hybrid in Israel. Three-month-old fish were found to have cysts located in gill muscle tissue, which were filled with both immature and mature spores. Affected fish displayed higher mortality rate. Spore dimensions (10.8 ± 0.7 µm length × 6.8 ± 0.6 µm width) and molecular characterization using 18S ribosomal DNA revealed that the unknown parasite belongs in the Myxobolus clade. Based on the infection site, spore morphology and molecular characterization, we describe this parasite as Myxobolus bejeranoi n. sp. (MF401455). Phylogenetic analysis showed that the new species is most closely related to two Myxobolus spp. from O. niloticus in Egypt and Ghana.

Functional and proteomic analysis of Ceratonova shasta (Cnidaria: Myxozoa) polar capsules reveals adaptations to parasitism.

Myxozoa is a diverse, speciose group of microscopic parasites, recently placed within the phylum Cnidaria. Myxozoans are highly reduced in size and complexity relative to free-living cnidarians, yet they have retained specialized organelles known as polar capsules, akin to the nematocyst stinging capsules of free-living species. Whereas in free-living cnidarians the stinging capsules are used for prey capture or defense, in myxozoans they have the essential function of initiating the host infection process. To explore the evolutionary adaptation of polar capsules to parasitism, we used as a model organism Ceratonova shasta, which causes lethal disease in salmonids. Here, we report the first isolation of C. shasta myxospore polar capsules using a tailored dielectrophoresis-based microfluidic chip. Using electron microscopy and functional analysis we demonstrated that C. shasta tubules have no openings and are likely used to anchor the spore to the host. Proteomic analysis of C. shasta polar capsules suggested that they have retained typical structural and housekeeping proteins found in nematocysts of jellyfish, sea anemones and Hydra, but have lost the most important functional group in nematocysts, namely toxins. Our findings support the hypothesis that polar capsules and nematocysts are homologous organelles, which have adapted to their distinct functions.

Dielectrophoretic characterization and isolation of jellyfish stinging capsules.

Jellyfish stinging capsules known as nematocysts are explosive, natural-injection systems with high potential as a natural drug-delivery system. These organelles consist of a capsule containing a highly folded thin needle-like tubule and a matrix highly concentrated with charged constituents that enable the tubule to fire and penetrate a target. For the purpose of using these nematocysts as drug delivery system it is first required to purify subpopulations from heterogeneous population of capsules and to investigate each subpopulation's distinct function and characteristics. Here, the nematocysts' dielectric properties were experimentally investigated using dielectrophoretic and electrorotational spectra with best fits derived from theoretical models. The dielectric characterization adds to our understanding of the nematocysts' structure and function and is necessary for the dielectrophoretic isolation and manipulation of populations. As expected, the effect of monovalent and divalent exchange cations resulted in higher inner conductivity for the NaCl treated capsules; this result stands in agreement with their relative higher osmotic pressure. In addition, an efficient dielectrophoretic isolation of different nematocyst subpopulations was demonstrated, paving the way to an understanding of nematocysts' functional diversity and the development of an efficient drug delivery platform.

Regulation of AP-1 by MAPK Signaling in Metal-Stressed Sea Anemone.

BACKGROUND/AIMS: AP-1 transcription factor plays a conserved role in the immediate response to stress. Activation of AP-1 members jun and fos is mediated by complex signaling cascades to control cell proliferation and survival. To understand the evolution of this broadly-shared pathway, we studied AP-1 regulation by MAPK signaling in a basal metazoan. METHODS: Metal- stressed cnidarian Nematostella vectensis anemones were tested with kinase inhibitors and analyzed for gene expression levels and protein phosphorylation. RESULTS: We show that in cnidarian, AP-1 is regulated differently than in bilaterian models. ERK2 and ERK5, the main MAPK drivers of AP-1 activation in Bilateria, down-regulated fos1 and jun1 transcription in anemones exposed to metal stress, whereas p38 MAPK, triggered transcription of jun1 but not fos1. Furthermore, our results reveal that GSK3-ß is the main driver of the immediate stress response in Nematostella. GSK3-ß triggered transcription of AP-1 and two other stress-related genes, egr1 and hsp70. Finally, phylogenetic analysis and protein characterization show that while MAPKs and GSK3-ß are evolutionarily conserved, Fos and Jun proteins in Nematostella and other cnidarians lack important regulatory and phosphorylation sites found in Bilateria. CONCLUSION: These findings reveal alternative network interactions of conserved signaling kinases, providing insight into the evolutionary plasticity of immediate stress response mechanisms.