The Middle Eastern Cousin: Comparative Venomics of and .

Among the medically most important snakes in the world, the species belonging to the genus have been attributed to the highest number of human envenomings, deaths and disabilities. Given their significant clinical relevance, the venoms of Russell's vipers ( and ) have been the primary focus of research. In contrast, the composition, activity, ecology and evolution of venom of its congener, the Palestine viper (), have remained largely understudied. Therefore, to unravel the factors responsible for the enhanced medical relevance of in comparison to , we comparatively evaluated their venom proteomes, biochemical activities, and mortality and morbidity inflicting potentials. Furthermore, the synthesis and regulation of venom in snakes have also remained underinvestigated, and the relative contribution of each venom gland remains unclear. We address this knowledge gap by sequencing the tissue transcriptomes of both venom glands of , and comparatively evaluating their contribution to the secreted venom concoction. Our findings highlight the disparity in the venom composition, function and toxicities of the two species. We also show that toxin production is not partitioned between the two venom glands of .