Venom of Tiger Rattlesnakes may advance genetic science

Among all rattlesnake species, the Tiger Rattlesnake has the simplest yet most lethal venom. Now, a new study performed by a team of researchers can describe the genetics behind the venomous bite of the Tiger Rattlesnake. The team was headed by a biologist from the University of South Florida (USF).

Mark Margres, assistant professor of biology photographs an Eastern Diamondback Rattlesnake at Caladesi Island, Florida. Image Credit: University of South Florida.

Reported in the latest edition of the Proceedings of the National Academy of Sciences, Mark Margres, Assistant Professor from the Department of Integrative Biology at USF, and collaborators across the south-eastern U.S., have sequenced the genome of the Tiger Rattlesnake to figure out the genotype of the venom trait.

The venom of the Tiger Rattlesnake is quite simple, but according to Margres, it is approximately 40 times more lethal when compared to the venom of the Eastern Diamondback Rattlesnakes found in Florida.

So far, the new study is the most comprehensive definition of the venom gene-regulatory network, and its detection of crucial mechanisms involved in creating the specifically toxic venom will allow investigators to explain many different queries related to genetics.

Simple genotypes can produce complex traits. Here, we have shown the opposite is also true - a complex genotype can produce simple traits.”

Mark Margres, Assistant Professor, Department of Integrative Biology, University of South Florida

Margres teamed up with collaborators from Clemson University, Florida State University, and the University of South Alabama in the study, which set out to understand whether trait variations are acquired from the variations in the number of genes, their sequence, and how they are controlled. The researchers’ study is only the second time in which a genome of the rattlesnake has been deciphered.

The genotype of an organism refers to the set of genes carried by it, and the phenotype of an organism refers to all of its detectable traits, which can be affected by several factors, including its genes and the environment in which it survives.

In this context, evolutionary biologists explore to figure out how genes have an impact on the phenotype variation among otherwise analogous organisms. In this example, the evolutionary biologists looked at why different types of rattlesnake species differ in terms of the toxicity and composition of venom.

Native to the Sonoran Desert of southern Arizona and northern Mexico, Tiger Rattlesnakes, specifically the comparatively small pit viper, preys on rodents and lizards.

Although certain species of Tiger Rattlesnakes have intricate venoms caused by an innumerable number of genes, Margres added that the venom of the Tiger Rattlesnake is rather simple—only 15 of its 51 toxin-producing genes intensely fuel the synthesis of peptides and proteins that attack the nervous system of its prey, forcing blood pressure to drop and stopping the blood clotting process.

The researchers observed that the number of venom genes considerably outpaces the number of proteins created in the basic phenotype; this suggests that a complex process was involved at the core of the lethal venom and, added to this, the Tiger Rattlesnakes still carry enough toxic genes.

Only about half of the venom genes in the genotype were expressed. To me, the interesting part is why are the non-expressed genes still present? These genes can make functional toxins, they just don’t. That needs to be explored further.”

Mark Margres, Assistant Professor, Department of Integrative Biology, University of South Florida

Apart from interpreting this specific species of poisonous snakes, the study will help improve genetic science by demonstrating the methods that are often utilized in genetic studies on fruit flies and mice—animals that are commonly employed in genetic research—and can even work when used in less-explored organisms, such as snakes, added Margres.

Genetic sequencing techniques, which are commonly used in human genetics studies, were used by the researchers and while doing so, they have paved the way for investigators to decode the relationship between the genotype and phenotype in several other organisms.

Another possible advantage of the study is that snake venom is utilized in medicine to help fight high blood pressure and stroke. A greater understanding of the venom will allow the medical engineering field to apply that information in the discovery and development of novel drugs, Margres concluded.

Video Credit: University of South Florida.