Humans and other mammals have the potential to evolve and become venomous, thanks to a genetic foundation that is present in both reptiles and mammals, a report says.
Scientists from Okinawa Institute of Science and Technology Graduate University (OIST), along with the Australian National University, made this discovery when they compared mammal salivary gland tissues and venom glands of snakes.
They found that mammals’ genes had a similar pattern of activity that is present in snakes’ glands, which is why they assume that both species share an ancient functional core that has been retained since the two lineages divided hundreds of millions of years ago, EurekAlert! stated.
“Many scientists have intuitively believed this is true, but this is the first real solid evidence for the theory that venom glands evolved from early salivary glands,” Agneesh Barua, first author and a Ph.D. student at OIST, shared with his university.
The research also provides clear evidence of an “underlying molecular link” between the venom glands of snakes and the salivary glands of mammals.
“Venoms are a cocktail of proteins that animals have weaponized to immobilize and kill prey, as well as for self-defence,” Barua told OIST.
“What’s interesting about venom is that it has arisen in so many different animals: jellyfish, spiders, scorpions, snakes, and even some mammals.”
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This latest study about snakes unveils the ancient foundation of oral venoms, although scientists have yet to discover their origin.
Previous research explored the genes that code the proteins that form venom.
However, the oral venom system was established before many venom toxins were incorporated in it, which is why researchers needed to look at the genes that existed before venom’s origins, “genes which enabled the rise of venom systems,” Barua said, according to OIST.
This time, the scientific team searched for genes that work and interact strongly with the venom genes, using venom glands taken from the Habu snake in Taiwan, a type of pit viper from Asia.
Researchers detected nearly 3,000 “co-operating genes” and found that they played crucial roles in protecting the cells from the stress linked to the production of the proteins. The same genes were also key in regulating protein modification and folding, the study states.
First real solid evidence for the theory that venom glands evolved from early salivary glandsAgneesh Barua
When making proteins, the chains of amino acids are folded in a particular manner; otherwise, proteins will not take the form that is necessary for their proper functioning – just like a wrong fold can ruin origami. Moreover, mis-folded proteins can build up and harm the cells, EurekAlert! stated.
“The role of these genes in the unfolded protein response pathway makes a lot of sense as venoms are complex mixtures of proteins. So to ensure you can manufacture all these proteins, you need a robust system in place to make sure the proteins are folded correctly so they can function effectively,” Barua told OIST.
When the scientists explored the genomes and salivary gland tissues of other animals, such as dogs, chimpanzees and humans, they found that those species incorporated their own versions of “co-operating genes,” which had a similar pattern of activity that snakes have in their venom glands. This discovery raised theories about the ancient functional core that both mammals and snakes have shared for hundreds of millions of years.
“While snakes then went crazy, incorporating many different toxins into their venom and increasing the number of genes involved in producing venom, mammals like shrews produce simpler venom that has a high similarity to saliva,” Barua said, according to the report.
Scientists’ discovery about salivary glands could mean they will look at other mammals in an “unsettling new light.”
“There were experiments in the 1980s that showed that male mice produce compounds in their saliva that are highly toxic when injected into rats,” said Barua, according to the report.
“If under certain ecological conditions, mice that produce more toxic proteins in their saliva have better reproductive success, then in a few thousand years, we might encounter venomous mice.”
And if the right ecological conditions ever existed, humans could also be venomous, although it is very unlikely, the report states.
“It definitely gives a whole new meaning to (the phrase) ‘a toxic person’,” added Barua.