Tissue-Specific Venom Composition and Differential Gene Expression in Sea Anemones

Abstract

Cnidarians represent one of the few groups of venomous animals that lack a centralized venom transmission system. Instead, they are equipped with stinging capsules collectively known as nematocysts. Nematocysts vary in abundance and type across different tissues; however, the venom composition in most species remains unknown. Depending on the tissue type, the venom composition in sea anemones may be vital for predation, defense, or digestion. Using a tissue-specific RNA-seq approach, we characterize the venom assemblage in the tentacles, mesenterial filaments, and column for three species of sea anemone (Anemonia sulcata, Heteractis crispa, and Megalactis griffithsi). These taxa vary with regard to inferred venom potency, symbiont abundance, and nematocyst diversity. We show that there is significant variation in abundance of toxin-like genes across tissues and species. Although the cumulative toxin abundance for the column was consistently the lowest, contributions to the overall toxin assemblage varied considerably among tissues for different toxin types. Our gene ontology (GO) analyses also show sharp contrasts between conserved GO groups emerging from whole transcriptome analysis and tissue-specific expression among GO groups in our differential expression analysis. This study provides a framework for future characterization of tissue-specific venom and other functionally important genes in this lineage of simple bodied animals.

Evolution of the Cytolytic Pore-Forming Proteins (Actinoporins) in Sea Anemones

“…Transcriptomes and genomes from 25 species of sea anemones ( Nematostella vectensis [48], Edwardsiella lineata [49], Stomphia coccinea , Actinia equina , Anemonia sulcata [44], Anthopleura elegantissima [46], Bunodosoma cavernata , Condylactis gigantea , Entacmaea quadricolor , Epiactis japonica , Epiactis prolifera , Macrodactyla doreensis , Heteractis crispa [44], Bartholomea annulata , Exaiptasia pallida [47], Andvakia discipulorum , Diadumene leucolena , Diadumene lineata , Calliactis polypus , Haloclava producta , Metridium senile , Sagartia elegans , and Triactis producta ) were used to identify candidate cytolysins and cytolysin-like sequences. The unpublished transcriptomes’ RNA isolation and sequencing were carried out similar to what was published previously [44,46].…”

“…The unpublished transcriptomes’ RNA isolation and sequencing were carried out similar to what was published previously [44,46]. In brief, specimens were frozen in liquid nitrogen or placed in RNALater (QIAGEN, Hilden, Germany) immediately after being collected.…”

Sequencing and de novo transcriptome assembly of Anthopleura dowii Verrill (1869), from Mexico

“…Nonetheless, only a limited number of transcriptomes from sea anemones have been sequenced so far [6], [7], [8], [9], [10], [11] Here we performed de novo transcriptome assembly for the sea anemone Anthopleura dowii Verrill (1869) (Actiniaria: Enthemonae: Actinioidea: Actiniidae) by next-generation sequencing.…”

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

“…Beyond individual transcripts we evaluated changes in functional Gene Ontology groups (GO) between the different populations across control and stressed environments. This was done by two different approaches, first we used custom Python scripts as previously described in [41], which divided TMM values across associated GO terms. The GO groups were then grouped based on semantic similarity and identified using REVIGO [42].…”