Characterizing Venom Variation in the Mexican Montane Pitvipers (Cerrophidion)

Hofmann, Erich P.

Rautsaw, Rhett M. Department of Biological Sciences

Clemson University

Clemson, South Carolina, USA

Grünwald, Christoph I. Jones, Jason M.

Franz-Chávez, Héctor

Ahumada-Carrillo, Ivan T

Ramírez Chaparro, Ricardo AC Villa del Álvarez, Colima, Mexico

de La Torre Loranca, Miguel Angel Instituto Lorancai

Km 32 Carretera Federal Orizaba-Zongolica Ocotepec Los Reyes, Veracruz, Mexico

Strickland, Jason L.

Mason, Andrew J.

Holding, Matthew L.*

Department of Biological Sciences Clemson UniversityClemson, South Carolina, USA

Borja, Miguel

Castañeda-Gaytán, Gamaliel Facultad de Ciencias Biológicas Universidad Juárez del Estado de Durango

Av. Universidad s/n. Fracc. Filadelfia - C.P. 35070 Gómez Palacio, Durango, Mexico

Rokyta, Darin R.

Department of Biological Science*

Florida State University Tallahassee, Florida, USA

Parkinson, Christopher L.

Department of Biological Sciences Department of Forestry and Environmental Conservation

Clemson University

Clemson, South Carolina, USA

Venom is highly adaptive, changing rapidly between species and between populations of the same species. Changes to venom are the result of adjustments in toxin gene expression and the underlying DNA sequence. However, the venom of many species remains uncharacterized, making it difficult to trace the evolutionary history of venom and provide adequate medical help to those bitten by uncharacterized species. Profiling toxin genes and their expression within and between species allows for the examination of venom variation and provides a better understanding of the full venom arsenal of a species. Here, we attempt to fill gaps in our understanding of venom evolution and variation by analyzing venom of three species of Cerrophidion from Mexico. We sequenced the venom-gland transcriptome for 12 individuals (six Cerrophidion godmani, three C. petlalcalensis, and three C. tzotzilorum) collected in southeastern Mexico, and tested for differences in the expression of toxin genes related to age class and locality. We found that the venom transcriptomes of these species are dominated by PLA2s and SVMPs, largely hemorrhagic toxins as expected, but individual variation was present in conspecific individuals. Both C. godmani and C. tzotzilorum displayed several toxins that were significantly differentially expressed between age classes, suggesting a possible ontogenetic shift. Interestingly, the most highly expressed PLA2 transcripts in C. godmani populations north and south of the Chiapan Depression were distinctly different, despite otherwise similar transcriptomic profiles. This might be evidence of local adaptation or early lineage diversification driving venom differences between these disjunct populations. Our data represent a broad examination of the venoms of Mexican Cerrophidion, characterizing the toxin gene repertoire of these species for the first time. Further sampling, proteomic confirmation, and additional analyses are underway to provide a more complete understanding of Cerrophidion venom evolution and variation across their range.

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