Proteo-Transcriptomic Analysis Identifies Potential Novel Toxins Secreted by the Predatory, Prey-Piercing Ribbon Worm Amphiporus lactifloreus

Mar Drugs. 2020 Aug 1;18(8):407. doi: 10.3390/md18080407.

Abstract

Nemerteans (ribbon worms) employ toxins to subdue their prey, but research thus far has focused on the small-molecule components of mucus secretions and few protein toxins have been characterized. We carried out a preliminary proteotranscriptomic analysis of putative toxins produced by the hoplonemertean Amphiporus lactifloreus (Hoplonemertea, Amphiporidae). No variants were found of known nemertean-specific toxin proteins (neurotoxins, cytotoxins, parbolysins or nemertides) but several toxin-like transcripts were discovered, expressed strongly in the proboscis, including putative metalloproteinases and sequences resembling sea anemone actitoxins, crown-of-thorn sea star plancitoxins, and multiple classes of inhibitor cystine knot/knottin family proteins. Some of these products were also directly identified in the mucus proteome, supporting their preliminary identification as secreted toxin components. Two new nemertean-typical toxin candidates could be described and were named U-nemertotoxin-1 and U-nemertotoxin-2. Our findings provide insight into the largely overlooked venom system of nemerteans and support a hypothesis in which the nemertean proboscis evolved in several steps from a flesh-melting organ in scavenging nemerteans to a flesh-melting and toxin-secreting venom apparatus in hunting hoplonemerteans.

Keywords: actitoxins; hoplonemerteans; inhibitor cystine knot/knottin; nemertean toxins; nemertotoxins; plancitoxins; proteomics; transcriptomics.

MeSH terms

  • Animals
  • Databases, Genetic
  • Gene Expression Profiling*
  • Invertebrates / genetics*
  • Invertebrates / metabolism*
  • Marine Toxins / genetics*
  • Marine Toxins / metabolism*
  • Proteome*
  • Proteomics*
  • Transcriptome*

Substances

  • Marine Toxins
  • Proteome