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Abstract

Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard)1. Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species)2,3,4,5. In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system1. Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards (including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular (lower) or maxillary (upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins.

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Acknowledgements

We thank the following persons and institutions who helped us or contributed tissue samples used in this study: A. Fry, Alice Springs Reptile Centre, Australian Reptile Park, M. A. G. de Bakker, R. L. Bezy, B. Branch, J. Campbell, N. Clemann, C. Clemente, C. Cicero, K. Daoues, A. S. Delmas, B. Demeter, J. Haberfield, A. Hassanin, Healesville Sanctuary, M. Hird, Louisiana State University Museum of Zoology, P. Moler, T. Moncuit, P. Moret, National Museum of Natural History Naturalis Leiden (J. W. Arntzen), T. Pappenfus, J.-C. Rage, C. Skliris, J. Smith, S. Sweet, Ultimate Reptiles (South Australia), University of California Museum of Vertebrate Zoology (Berkeley), J. Walker, R. Waters, J. Weigel and B. Wilson. We also thank A. Webb and T. Purcell for providing HPLC access; N. Williamson for help with preliminary mass spectrometry characterization; E. V. Grishin for help in obtaining the references in Russian; S. Edwards for comments; and T. van Wagner and V. Wexler for artwork. This work was funded by the Service de Systématique moléculaire of the Muséum National d'Histoire Naturelle, Institut de Systématique (N.V.) and by grants from the Australian Academy of Science (B.G.F.), Australian Geographic Society (B.G.F.), Australia & Pacific Science Foundation (B.G.F.), Australian Research Council (B.G.F.), CASS Foundation (B.G.F.), Commonwealth of Australia Department of Health and Aging (B.G.F.), Ian Potter Foundation (B.G.F.), International Human Frontiers Science Program Organisation (B.G.F.), Leiden University (F.J.V., M.K.R.), NASA Astrobiology Institute (S.B.H.), National Science Foundation (S.B.H.) and University of Melbourne (B.G.F.). We thank the relevant wildlife departments for granting the scientific permits for field collection of required specimens.

Author information

Affiliations

  1. Australian Venom Research Unit, Level 8, School of Medicine, University of Melbourne, Parkville, Victoria 3010, Australia

    • Bryan G. Fry
    •  & S. F. Ryan Ramjan
  2. Population and Evolutionary Genetics Unit, Museum Victoria, GPO Box 666E, Melbourne, Victoria 3001, Australia

    • Bryan G. Fry
    •  & Janette A. Norman
  3. Department of Biology and Astrobiology Research Center, 208 Mueller Lab, Pennsylvania State University, University Park, Pennsylvania 16802-5301, USA

    • Nicolas Vidal
    •  & S. Blair Hedges
  4. UMS 602, Taxonomie et collections, Reptiles-Amphibiens, Département Systématique et Évolution, Muséum National d'Histoire Naturelle, 25 Rue Cuvier, Paris 75005, France

    • Nicolas Vidal
  5. Institute of Biology, Leiden University, Kaiserstraat 63, PO Box 9516, 2300 RA, Leiden, The Netherlands

    • Freek J. Vonk
    •  & Michael K. Richardson
  6. Department of Structural Biology and Bioinformatics, University of Geneva and Swiss Institute of Bioinformatics, Centre Médical Universitaire, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland

    • Holger Scheib
  7. SBC Lab AG, Seebüelstrasse 26, 8185 Winkel, Switzerland

    • Holger Scheib
  8. Monash Venom Group, Department of Pharmacology, Monash University, Clayton, Victoria 3800, Australia

    • Sanjaya Kuruppu
    •  & Wayne. C. Hodgson
  9. Molecular and Health Technologies, CSIRO, 343 Royal Parade, Parkville, Victoria 3010, Australia

    • Kim Fung
  10. Department of Pathology, University of Melbourne, Parkville, Victoria 3010, Australia

    • Vera Ignjatovic
    •  & Robyn Summerhayes
  11. Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Victoria 3052, Australia

    • Vera Ignjatovic
    •  & Robyn Summerhayes
  12. Department of Zoology, Tel Aviv University, Tel Aviv 69978, Israel

    • Elazar Kochva

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Competing interests

The sequences of the cDNA clones have been deposited in GenBank (accession numbers DQ139877–DQ139931 and DQ184481), as have the nuclear gene sequences (DQ119594–DQ119641). Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Corresponding author

Correspondence to Bryan G. Fry.

Supplementary information

PDF files

  1. 1.

    Supplementary Figures

    This file contains 13 Supplementary Figures, including the molecular phylogenetic analysis of squamate nuclear genes, the phylogenetic analyses and sequence alignments of the toxin types analysed in this study as well as the liquid chromatography-mass spectrometry analysis of Varanus varius (Lace monitor) venom.

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    Supplementary Methods

    This file contains detailed descriptions of materials and methods not already described in the main article.

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DOI

https://doi.org/10.1038/nature04328

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