On snake venom

Here is an interesting snake-related paper I came across in BMC Genomics this week:

Venom gland transcriptomes of two Elapid snakes (Bungarus multicinctus and Naja atra) and evolution of toxin genes

This paper is cool because the authors wanted to understand the genetics and evolutionary patterns of venom in two species of snake: the many-banded krait (Bungarus multicinctus) and the Chinese cobra (Naja atra).

Venom is an adaptation involving thousands of complex proteins and enzymes, so the scientists wanted to compare gene expression in venom gland tissue. To do this they sequence the transcriptome, or only the information in the genome that is transcribed into mRNA (such as in exons) that will be translated by the cellular ribosomal machinery into amino acids. The DNA “translation” of  mRNA is known as a cDNA library. The scientists do a BLAST search to compare their sequences to a database of known proteins. The krait venom is composed of neurotoxin while the cobra venom contains both neurotoxin and cytotoxin, which causes the very cells of the prey to simply die.

As rare as they are, a bite from a venomous snake can kill a human one way, another way, or in a multitude of ways, depending on the snake.

When did venom first evolve? Probably way before snakes did.

According a 2006 paper in Nature, early in lizard evolution 200 million years ago there arose a “venom clade” that was the first to integrate toxicity and prey acquisition.  The descendants of those early squamates include all modern snakes, as well as anguimorph lizards – such as monitors (like the Komodo Dragon) and Gila monsters – and iguanians (they found venom proteins in the adorable Bearded Dragon!).

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