title: Nemertean toxin genes revealed through transcriptome sequencing.
abstract: Nemerteans are one of few animal groups that have evolved the ability to utilize toxins for both defense and subduing prey, but little is known about specific nemertean toxins. In particular, no study has identified specific toxin genes even though peptide toxins are known from some nemertean species. Information about toxin genes is needed to better understand evolution of toxins across animals and possibly provide novel targets for pharmaceutical and industrial applications. We sequenced and annotated transcriptomes of two free-living and one commensal nemertean and annotated an additional six publicly available nemertean transcriptomes to identify putative toxin genes. Approximately 63-74% of predicted open reading frames in each transcriptome were annotated with gene names, and all species had similar percentages of transcripts annotated with each higher-level GO term. Every nemertean analyzed possessed genes with high sequence similarities to known animal toxins including those from stonefish, cephalopods, and sea anemones. One toxin-like gene found in all nemerteans analyzed had high sequence similarity to Plancitoxin-1, a DNase II hepatotoxin that may function well at low pH, which suggests that the acidic body walls of some nemerteans could work to enhance the efficacy of protein toxins. The highest number of toxin-like genes found in any one species was seven and the lowest was three. The diversity of toxin-like nemertean genes found here is greater than previously documented, and these animals are likely an ideal system for exploring toxin evolution and industrial applications of toxins.
authors.affiliation: Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama nwhelan@auburn.edu ken@auburn.edu.
authors.forename: Nathan V
authors.initials: NV
authors.lastname: Whelan
authors.affiliation: Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama Present address: School of Biological Sciences, University of Queensland, Brisbane, QLD, Australia.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Kocot
authors.affiliation: Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Santos
authors.affiliation: Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama nwhelan@auburn.edu ken@auburn.edu.
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Halanych
mesh_terms: D000818:Animals; D000845:Annelida / Q000235:genetics*; D004474:Ecthyma, Contagious; D008387:Marine Toxins / Q000235:genetics*; D017423:Sequence Analysis, RNA; D059467:Transcriptome; D014688:Venoms / Q000235:genetics*
chemical_list: D008387:Marine Toxins; D014688:Venoms
keywords: Nemertea; cytotoxin; hepatotoxin; ribbon worm; toxin; transcriptome