Size matters: an evaluation on the molecular basis of ontogenetic modifications in the composition of Bothrops jararacussu snake venom

Ontogenetic changes in venom composition have been described in Bothrops snakes but only a few studies have attempted to identify the targeted paralogues or the molecular mechanisms involved in venom modifications of gene expression during ontogeny. In this study, we decoded B. jararacussu venom gland transcripts from six specimens of varying sizes and analyzed the variability in the composition of independent venom proteomes from 19 individuals. We identified 125 distinct putative toxin transcripts, and of these, 73 were detected in venom proteomes and only 10 were involved in the ontogenetic changes. Ontogenetic variability was linearly related to snake size and did not correspond to the maturation of the reproductive stage. Changes in the transcriptome were highly predictive of changes in the venom proteome. The basic myotoxic PLA2s were the most abundant components in larger snakes while in venoms from smaller snakes, PIII-class SVMPs were the major components. The SVMPs identified corresponded to novel sequences and conferred both pro-coagulant and hemorrhagic functions to the venom of small snakes. The mechanisms modulating venom variability are predominantly related to transcriptional events and may be related to the advantage of coagulant and hemorrhagic venoms from small snakes to predatory function.