New research led by the University of Colorado Boulder and the University of Texas at Arlington may shed light on how to bolster anti-venom treatments for snake bites.
The findings, published today in Nature Ecology and Evolution, how rattlesnakes maintain a broad and diverse toolkit of genes that encode snake venom, making it difficult for their prey to develop resistance to their deadly bite. They also overturn decades of thought on what factors shape venom gene evolution and venom variation.
"We found these rattlesnakes had a more diverse venom repertoire, more genetic tools in the toolkit, than their venom composition alone might suggest,” said Drew Schield, lead author on the paper and postdoctoral fellow in Ecology and Evolutionary Biology at CU Boulder.
Snake venom, an evolutionary adaptation, is made up of different enzymes and toxins that enable snakes to capture their prey. For decades, biologists have thought that snake venom continuously evolved to effectively kill specific prey while losing its genetic diversity along the way through a process known in evolutionary biology as “directional selection.”
The new study proposes that, instead, rattlesnake venom uses a mechanism known as “balancing selection”: a process where multiple versions of a gene—in this case, genes that encode venom proteins—are all maintained, providing an expanded venom arsenal.
This may be one reason that snakebite is notoriously difficult to treat.
“These evolutionary mechanisms ramp up the complexity that you're contending with when you develop antivenoms, as venom composition within the same species but in different geographic regions might be totally different,” said Schield.
Understanding how diverse venomous snake genomes truly are—from rattlesnakes to cobras and coral snakes—can inform advances in anti-venom therapeutics and save lives around the world, Schield said. (AP/Newswise)
