A RNA-seq approach to identify putative toxins from acrorhagi in aggressive and non-aggressive Anthopleura elegantissima polyps

Abstract

BackgroundThe use of venom in intraspecific aggression is uncommon and venom-transmitting structures specifically used for intraspecific competition are found in few lineages of venomous taxa. Next-generation transcriptome sequencing allows robust characterization of venom diversity and exploration of functionally unique tissues. Using a tissue-specific RNA-seq approach, we investigate the venom composition and gene ontology diversity of acrorhagi, specialized structures used in intraspecific competition, in aggressive and non-aggressive polyps of the aggregating sea anemone Anthopleura elegantissima (Cnidaria: Anthozoa: Hexacorallia: Actiniaria: Actiniidae).ResultsCollectively, we generated approximately 450,000 transcripts from acrorhagi of aggressive and non-aggressive polyps. For both transcriptomes we identified 65 candidate sea anemone toxin genes, representing phospholipase A2s, cytolysins, neurotoxins, and acrorhagins. When compared to previously characterized sea anemone toxin assemblages, each transcriptome revealed greater within-species sequence divergence across all toxin types. The transcriptome of the aggressive polyp had a higher abundance of type II voltage gated potassium channel toxins/Kunitz-type protease inhibitors and type II acrorhagins. Using toxin-like proteins from other venomous taxa, we also identified 612 candidate toxin-like transcripts with signaling regions, potentially unidentified secretory toxin-like proteins. Among these, metallopeptidases and cysteine rich (CRISP) candidate transcripts were in high abundance. Furthermore, our gene ontology analyses identified a high prevalence of genes associated with “blood coagulation” and “positive regulation of apoptosis”, as well as “nucleoside: sodium symporter activity” and “ion channel binding”. The resulting assemblage of expressed genes may represent synergistic proteins associated with toxins or proteins related to the morphology and behavior exhibited by the aggressive polyp.ConclusionWe implement a multifaceted approach to investigate the assemblage of expressed genes specifically within acrorhagi, specialized structures used only for intraspecific competition. By combining differential expression, phylogenetic, and gene ontology analyses, we identify several candidate toxins and other potentially important proteins in acrorhagi of A. elegantissima. Although not all of the toxins identified are used in intraspecific competition, our analysis highlights some candidates that may play a vital role in intraspecific competition. Our findings provide a framework for further investigation into components of venom used exclusively for intraspecific competition in acrorhagi-bearing sea anemones and potentially other venomous animals.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1417-4) contains supplementary material, which is available to authorized users.

The draft genome of Actinia tenebrosa reveals insights into toxin evolution

“…Many of these cnidarian-specific genes expressed in the cnidocytes encode for toxin peptides Sebé-Pedrós et al, 2018). This is consistent with evidence that acrorhagin 1 and acrorhagin 2 are novel toxincoding genes which are localized to the acrorhagi, a morphological structure used for envenomation that is unique to sea anemones from Actinioidea (Honma et al, 2005;Macrander, Brugler, & Daly, 2015). This is consistent with evidence that acrorhagin 1 and acrorhagin 2 are novel toxincoding genes which are localized to the acrorhagi, a morphological structure used for envenomation that is unique to sea anemones from Actinioidea (Honma et al, 2005;Macrander, Brugler, & Daly, 2015).…”

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.…”