Biology subjects

Macrander, J.

Publications and source records attributed to Macrander, J..

9 recordsLinked to original sources

bioRxiv2026

Stable yet Shifting: Early Toxin Dynamics in Typical and Atypical Clownfish-Anemone Symbioses

Among venomous animals, cnidarians represent the oldest metazoan lineage in which venom production and a specialized delivery system are defining synapomorphies. Cnidarians also represent the only venomous lineage for which mutualistic symbioses have evolved resulting in scenarios where mutualistic symbionts may also be targets of their venom. The most iconic example of this relationship is the mutualism between clownfish and their venomous sea anemone hosts. To investigate how symbiont presence and establishment influence toxin gene expression, we used a comparative TagSeq and RNA-Seq approach to quantify venom gene dynamics during the first 48 hours of clownfish-anemone symbiosis establishment in five anemone species. Our taxonomic sampling included three typical hosting species (Entacmaea quadricolor, Radianthus crispa, and Stichodactyla haddoni), each representing distinct evolutionary lineages of clownfish hosts, and two atypical Caribbean species (Condylactis gigantea and Stichodactyla helianthus) that do not host clownfish in nature, but have reported to host within the aquarium trade. Tentacle samples were collected prior to hosting, approximately 12 hours after initial symbiont establishment, and again 48 hours after symbiosis establishment. Our analyses revealed that overall toxin assemblages remained relatively stable during the early establishment phase, with no significant changes in the most highly expressed toxin gene candidates. However, subtle transcript-level shifts occurred within multi-copy toxin gene families, including cytolytic actinoporins and Sea Anemone 8 (SA8)-like toxins. Notably, one C. gigantea actinoporin transcript exhibited a [~]600-fold increase in expression in a single individual, which coincided with two clownfish mortalities prior to successful association, which subsequently decreased after establishment. Comparative sequence alignments suggest that amino acid substitutions in this transcript may be functionally relevant to symbiosis intolerance, as the amino acid substitutions were unique to this transcript, and not found in any other previously described cytolytic actinoporin. Together, these findings reveal that early toxin gene expression in clownfish-hosting sea anemones is largely stable, yet subtly dynamic at the transcript level. This study provides the first comparative transcriptomic insights into the molecular processes shaping symbiosis establishment in clownfish-anemone mutualisms, offering a framework for understanding venom evolution in the context of co-evolutionary interactions. HighlightsO_LIComparative gene expression survey reveals relatively stable toxin assemblages throughout the first 48 hours of establishing clownfish-anemone symbiosis. C_LIO_LISubtle shifts were observed among transcript variants in multi-gene copy variants, with potential implications for barriers to establishing symbiosis. C_LIO_LIAlthough toxin assemblages varied among species, sea anemone 8 (SA8) toxin-like transcripts were highly abundant in four of the focal taxa. C_LIO_LIThis is the first comparative gene expression analysis investigating molecular processes surrounding symbiosis establishment between clownfish and sea anemones. C_LIO_LIThese results provide insight into toxin dynamics surrounding the establishment of symbiosis, with particular insights into key evolutionary transitions resulting in symbiosis among atypical clownfish hosting species. C_LI

genetics↗

bioRxiv2023

Venom tradeoff shapes interspecific interactions, physiology and reproduction

The ability of an animal to effectively capture prey and defend against predators is pivotal for its survival. Venom, a mixture of many toxin proteins, shapes predator-prey interactions. Here, we use the sea anemone Nematostella vectensis to test how toxin genotypes impact predator-prey interactions. We developed a new genetic manipulation tool which significantly reduces both RNA and protein levels of Nv1, a major neurotoxin. In concert we recently discovered a native population of Nematostella that has lost Nv1.We demonstrate that these anemones lacking Nv1, have reduced ability to defend themselves against grass shrimp, a native predator. Additionally, secreted Nv1 can act indirectly in defense by attracting mummichog fish, which are known to prey on grass shrimp. This unravels a tritrophic interaction acting in animal defense at the molecular level. Additionally, our work reveals an evolutionary tradeoff, as the reduction of Nv1 levels causes faster growth and increased sexual and asexual reproductive rates.

evolutionary biology↗

bioRxiv2022

A cnidarian phylogenomic tree fitted with hundreds of 18S leaves

Cnidarians are critical members of aquatic communities and have been an experimental system for a diversity of research areas ranging from development to biomechanics to global change biology. Yet we still lack a well-resolved, taxonomically balanced, cnidarian tree of life to place this research in appropriate phylogenetic context. To move towards this goal, we combined data from 26 new anthozoan transcriptomes with 86 previously published cnidarian and outgroup datasets to generate two 748-locus alignments containing 123,051 (trimmed) and 449,935 (untrimmed) amino acids. We estimated maximum likelihood phylogenies for both matrices under partitioned and unpartitioned site-homogeneous and site-heterogenous models of substitution. We used the resulting topology to constrain a phylogenetic analysis of 1,814 small subunit ribosomal (18S) gene sequences from GenBank. Our results confirm the position of Ceriantharia (tube-dwelling anemones), a historically recalcitrant group, as sister to the rest of Hexacorallia across all phylogenies regardless of data matrix or model choice. We also find unanimous support for the sister relationship of Endocnidozoa and Medusozoa and propose the name Operculozoa for the clade uniting these taxa. Our 18S hybrid phylogeny provides insight into relationships of 15% of extant taxa. Together these data are an invaluable resource for comparative cnidarian research and provide perspective to guide future refinement of cnidarian systematics.

evolutionary biology↗

bioRxiv2022

Exploring Differential Gene Expression Profiles Of Dero (Allodero) Hylae In Their Parasitic And Free-Living Forms

Parasitism is ubiquitous in nature, yet little is known about the evolutionary mechanisms that lead to a parasitic lifestyle. Facultative parasites can switch between free-living and parasitic lifestyles, which may provide an opportunity to study the genetic mechanisms underlying a transition to parasitism. The oligochaete Dero (Allodero) hylae is a facultative parasite commonly found within the ureter of various anuran species, such as the Cuban Tree Frog (Osteopilus septentrionalis). Dero hylae makes passage through the frogs cloaca, where it then infects the ureter. In the ureter, the worm loses free-living characteristics such as hair setae, dorsal setae, a digestive tract, and fossa with gills as it transitions to a parasitic lifestyle. Dero hylae may be expelled from its host during urination, when this occurs the worm will reacquire free-living characteristics. The focus of this study is to compare the differential gene expression profiles observed when this rapid morphological change takes place. Specimens of D. hylae were collected from wild Cuban Tree Frogs and either flash-frozen for their parasitic stage RNA profile or cultured for two weeks to produce their free-living stage and then flash-frozen. Using the sequenced RNA, a de novo transcriptome was assembled and differential gene expression RNA Tag-Seq analysis between the free-living and parasitic life forms was analyzed. Based on these results, we have identified 213 genes differentially expressed transcripts between the two life forms, 190 of these being up-regulated in the free-living life form. While over half of the differential genes recovered did not recover any significant BLAST hits, many of these genes did provide insight into which molecular signals are potentially used by D. hylae to lose and subsequently regrow their setae, digestive tract, and gills. This analysis provides significant insight into which differentially expressed genes are linked to drastic morphological changes observed in this rare oligochaete parasitism across the free-living and parasitic forms of D. hylae.

genetics↗

bioRxiv2022

Dominant toxin hypothesis: unravelling the venom phenotype across micro and macroevolution

Venom is a complex trait with substantial inter- and intraspecific variability resulting from strong selective pressures acting on the expression of many toxic proteins. However, understanding the processes underlying the toxin expression dynamics that determine the venom phenotype remains unresolved. Here, we use comparative genomics and transcriptomics to reveal that toxin expression in sea anemones evolves rapidly with little constraint and that a single toxin family dictates the venom phenotype in each species. This dominant toxin family is characterized by massive gene duplication events. In-depth analysis of the sea anemone, Nematostella vectensis, revealed significant variation in the number of copies of the dominant toxin (Nv1) across populations, corresponding to significant differences in Nv1 expression at both the transcript and protein levels. These differences in Nv1 copies are driven by independent expansion events, resulting in distinct haplotypes that have a restricted geographical distribution. Strikingly, one population has undergone a severe contraction event, causing a near-complete loss of Nv1 production. Our findings across micro- and macroevolutionary scales in sea anemones complement observations of single dominant toxin family present in other venomous organisms and establishes the dominant toxin hypothesis whereby venomous animals have convergently evolved a similar strategy in shaping the venom phenotype.

evolutionary biology↗

bioRxiv2020

Transcriptomic analysis of four cerianthid (Cnidaria, Ceriantharia) venoms

Tube anemones, or cerianthids, are a phylogenetically informative group of cnidarians with complex life histories, including a pelagic larval stage and tube-dwelling adult stage, both known to utilize venom in stinging-cell rich tentacles. Cnidarians are an entirely venomous group that utilize their proteinaceous-dominated toxins to capture prey and defend against predators, in addition to several other ecological functions, including intraspecific interactions. At present there are no studies describing the venom for any species within cerianthids. Given their unique development, ecology, and distinct phylogenetic-placement within Cnidaria, our objective is to evaluate the venom-like gene diversity of four species of cerianthids from newly collected transcriptomic data. We identified 525 venom-like genes between all four species. The venom-gene profile for each species was dominated by enzymatic protein and peptide families, which is consistent with previous findings in other cnidarian venoms. However, we found few toxins that are typical of sea anemones and corals, and furthermore, three of the four species express toxin-like genes closely related to potent pore-forming toxins in box jellyfish. Our study is the first to provide a survey of the putative venom composition of cerianthids, and contributes to our general understanding of the diversity of cnidarian toxins.

evolutionary biology↗

bioRxiv2020

Toxin-like neuropeptides in the sea anemone Nematostella unravel recruitment from the nervous system to venom

The sea anemone Nematostella vectensis (Anthozoa, Cnidaria) is a powerful model system for characterizing the evolution of genes functioning in venom and nervous systems. Despite being an example for evolutionary novelty, the evolutionary origin of most toxins remains unknown. Here we report the first bona fide case of protein recruitment from the cnidarian nervous to venom system. The ShK-like1 peptide has ShKT cysteine motif, is lethal for fish larvae and packaged into nematocysts, the cnidarian venom-producing stinging capsules. Thus, ShK-like1 is a toxic venom component. Its paralog, ShK-like2, is a neuropeptide localized to neurons and is involved in development. Interestingly, both peptides exhibit similarities in their functional activities: both of them provoke contraction in Nematostella polyps and are toxic to fish. Because ShK-like2 but not ShK-like1 is conserved throughout sea anemone phylogeny, we conclude that the two paralogs originated due to a Nematostella-specific duplication of a ShK-like2 ancestor, a neuropeptide-encoding gene, followed by diversification and partial functional specialization. Strikingly, ShK-like2 is represented by two gene isoforms controlled by alternative promoters conferring regulatory flexibility throughout development. Additionally, we characterized the expression patterns of four other peptides with structural similarities to studied venom components, and revealed their unexpected neuronal localization. Thus, we employed genomics, transcriptomics and functional approaches to reveal one new venom component, five neuropeptides with two different cysteine motifs and an evolutionary pathway from nervous to venom system in Cnidaria.

evolutionary biology↗

bioRxiv2020

Population Specific Adaptations in Venom Production to Abiotic Stressors in a Widely Distributed Cnidarian

Nematostella vectensis is a sea anemone (Actiniaria, Cnidaria) inhabiting estuaries over a broad geographic range where environmental conditions such as temperatures and salinity vary widely. In cnidarians, antagonistic interactions with predators and prey are mediated by their venom, which may be metabolically expensive. In this study, we challenged Nematostella polyps with heat, salinity, UV light stressors and a combination of all three to determine how abiotic stressors impact toxin expression for individuals collected across this species range. Transcriptomics and proteomics revealed that the highly abundant toxin Nv1 was the most downregulated gene under heat stress conditions in multiple populations. Physiological measurements demonstrated that venom is metabolically costly to produce suggesting that downregulating venom expression under stressful conditions may be advantageous. Strikingly, under a range of abiotic stressors, individuals from different geographic locations along this latitudinal cline modulate venom production levels differently in a pattern reflecting local adaptation.

evolutionary biology↗

bioRxiv2017

A microbial perspective on the life-history evolution of marine invertebrate larvae: if, where, and when to feed

The feeding environment for planktotrophic larvae has a major impact on development and progression towards competency for metamorphosis. High phytoplankton environments that promote growth often have a greater microbial load and incidence of pathogenic microbes, while areas with lower food availability have a lower number of potential pathogens. Trade-offs between metabolic processes associated with growth and immune functionality have been described throughout the animal kingdom and may influence the life-history evolution of marine invertebrate planktotrophic larvae in these environments. Namely, to avoid potential incidences of microbial-mediated mortality and/or dysbiosis, larvae should regulate time spent between these two feeding environments. We describe here transcriptomic and microbiome data that supports this trade-off in larvae, where larvae in a well-fed environment upregulate genes associated with metabolism and may regularly enter a state of dysbiosis, resulting in mortality. To address the hypothesis that the environmental microbiota is a selective force on if, where, and when planktotrophic larvae should feed, we present a strategy for determining the specific interactions of larvae and microbes at a scale representative of their larger pelagic environment.

evolutionary biology↗