Nematocytes, the stinging cells of cnidarians, are the most evolutionarily ancient venom apparatus. These nanosyringelike weaponry systems reach pressures of approximately 150 atmospheres before discharging and punching through the outer layer of the prey or predator at accelerations of more than 5 million g, making them one of the fastest biomechanical events known. To gain better understanding of the function of the complex, phylum-specific nematocyst organelle, and its venom payload, we compared the soluble nematocyst's proteome from the sea anemone Anemonia viridis, the jellyfish Aurelia aurita, and the hydrozoan Hydra magnipapillata, each belonging to one of the three basal cnidarian lineages which diverged over 600 Ma. Although the basic morphological and functional characteristics of the nematocysts of the three organisms are similar, out of hundreds of proteins identified in each organism, only six are shared. These include structural proteins, a chaperone which may help maintain venon activity over extended periods, and dickkopf, an enigmatic Wnt ligand which may also serve as a toxin. Nevertheless, many protein domains are shared between the three organisms' nematocyst content suggesting common proteome functionalities. The venoms of Hydra and Aurelia appear to be functionally similar and composed mainly of cytotoxins and enzymes, whereas the venom of the Anemonia is markedly unique and based on peptide neurotoxins. Cnidarian venoms show evidence for functional recruitment, yet evidence for diversification through positive selection, common to other venoms, is lacking. The final injected nematocyst payload comprises a mixture of dynamically evolving proteins involved in the development, maturation, maintenance, and discharge of the nematocysts, which is unique to each organism and potentially to each nematocyst type.
Bibliographical noteFunding Information:
This work was supported by grant 1994/13 from the Israel Science Foundation to D.S. and by a postdoctoral fellowship from the Charney School of Marine Sciences to T.R. Sequencing was partly funded by the RBNI programat the Technion, Israel.
The authors thank Hila Wolf (Technion, Israel) for performing mass spectrometry analysis, Brian J. Haas (Broad Institute, USA), Leonid Brodsky and Amir Cohanim (University of Haifa, Israel) for help with transcriptome assembly, Assaf Malik and Noa Sher (University of Haifa Bioinformatics Support Unit) for help with bioinformatics analyses, and Uri Shavit (Technion, Israel) for assistance and collaboration. They also thank three anonymous referees who contributed significantly to this manuscript. This work was supported by grant 1994/13 from the Israel Science Foundation to D.S. and by a postdoctoral fellowship from the Charney School of Marine Sciences to T.R. Sequencing was partly funded by the RBNI program at the Technion, Israel. The authors declare no competing interests. T.R., T.L., and D.S. designed research; T.R., D.M., D.A., and V.B. performed research; T.R., D.M., T.L., and D.S. analyzed data and wrote the paper.
© The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved.
- Mass spectrometry
- Protein domain
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Molecular Biology