Examining Venom Diversification through Comparative Venom Gland Transcriptomics of Palm-Pitvipers

Mason, Andrew                                                                                                                          

ajmason@clemson.edu

Department of Biological Sciences                                                                                                              

Clemson University                                                                                                                                      

Clemson, South Carolina, USA

 

Sasa, Mahmood                                                                                                                                                           Instituto Clodomiro Picado                                                                                                                                       

Facultad de Microbiología                                                                                                                                   Universidad de Costa Rica                                                                                                                                            San José, Costa Rica

 

Rokyta, Darin

Department of Biological Science                                                                                                                               Florida State University                                                                                                                                          Tallahassee, Florida, USA

 

Parkinson, Christopher 

Department of Forestry and Environmental Conservation                                                                           Clemson University

Clemson, South Carolina, USA

 

Identifying the evolutionary mechanisms generating diverse phenotypes is key to understanding the origins of biodiversity through speciation and adaptation. Pitviper venoms are composite phenotypes of 10-100 individual toxins, most of which are the product of single genes. This allows for each toxin’s protein phenotype to be linked to their genetic origins with relative ease, facilitating evolutionary inference. Venoms are often highly variable among species, as is seen in Middle American palm-pitvipers (Bothriechis spp), though patterns of interspecific venom evolution and toxin diversification have been difficult to discern. To examine venom evolution in palm-pitvipers we generated venom gland transcriptomes from each of the 11 species of Bothriechis. We examine these data in relation to the species phylogeny and biogeography and identified orthologous groups of toxins to infer relative frequencies of toxin gains/losses. Venoms compositions were highly variable among species at the toxin-family and transcript-specific levels. The apparent prevalence of species-specific toxins suggested that toxins genes gains and/or loss occur relatively frequently, though the identification of toxins conserved among nearly all lineages suggests a primary role of regulatory evolution in shaping venom phenotypes. These results have further demonstrated that venom evolution occurs through multiple molecular mechanisms, all of which must be considered for a thorough understanding of the evolution of complex phenotypes.

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