King Cobra Genome Sequenced, Shedding Light on Evolution of Snake Venom

The king cobra is one of the most deadly snakes on Earth. Able to grow up to 18 feet in length and with enough venom in a bite to kill up to 20 people, this snake is certainly one that should be avoided. Now, though, scientists have learned a bit more about this king of snakes; they've sequenced its genome, revealing the dynamic evolution and adaptation in the snake venom system.

Snake venoms are complex protein mixtures encoded by several gene families. These proteins function synergistically to cause rapid paralysis or death in prey. Although previous research hypothesized that venom genes evolved "early" in the lineage leading to snakes, the new genome sequencing revealed that venom gene families actually do not duplicate early. In fact, the rapid and extensive expansion of functionally important venom toxin families is restricted to the venomous "advanced" snake lineage.

That's not all the researchers found, though. The diversification of these toxins correlates directly with their functional importance in prey capture. For example, the most pathogenic king cobra toxin family have undergone massive expansion. In contrast, venom proteins will less important functions do not participate in the evolutionary arms race that occurs between snakes and their prey.

"These are the first snake genomes to be sequenced and fully annotated and our results in relation to the king cobra provide a unique view of the origin and evolution of snake venom, including revealing multiple genome-level adaptive responses to natural selection in this complex biological weapon system," said Nicholas Casewell, one of the researchers, in a news release. "These adaptations include the massive and rapid expansion of gene families that produce venom toxins, providing the snake with a highly toxic protein mixture required to overcome a variety of different prey and also circumvent any resistance to venom that may have developed in such prey."

The findings reveal a new genome-wide perspective on snake adaptations and, more specifically, shed some light on the venom systems that these reptiles use. This could show a bit more about the evolutionary history of snakes.

The findings are published in the journal Proceedings of the National Academy of Sciences.