Woodrats, small rodents that weigh less than half a pound, can survive venomous rattlesnake bites that would hospitalize or kill a full-grown human. New research published in Molecular Biology and Evolution links this resistance to changes in a family of genes called SERPINs and, in particular, to multiple copies of SERPINA3.
The study found that woodrats carry 12 copies of SERPINA3. These copies arose through tandem duplication, where an extra gene copy is inserted into the genome; the original gene continues its normal role while the new copy can evolve a different function. The research team, led by Matthew Holding and co-led by Meilyn Ward in David Ginsburg’s lab at the University of Michigan Life Sciences Institute, tested the proteins encoded by each SERPINA3 gene with venom collected from the rattlesnakes that hunt these rodents.
Many SERPINA3 proteins bound directly to venom components and blocked their toxic effects, but the proteins showed substantial variation in activity. Some did not interact with venom, implying different biological roles, while one protein inhibited two distinct components that underlie venom toxicity. The authors note that tandem duplication also occurs frequently in snake venom genes, and they suggest the SERPINA3 duplications may reflect a coevolutionary response as prey evolve resistance and venom proteins diversify. The study received support from the National Institutes of Health and the University of Michigan’s Honors Summer Fellowship.
Difficult words
- resistance — ability to withstand damage or harmful effects
- tandem duplication — when an extra gene copy appears next to original
- bind — to attach firmly to another moleculebound
- inhibit — to prevent or reduce a biological activityinhibited
- coevolutionary — involving mutual evolutionary change between species
- diversify — to become more varied in type or form
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Discussion questions
- How could multiple copies of a gene help an animal survive threats such as venom? Give reasons from the article.
- The authors suggest coevolution between prey and predators. What example from the article supports this idea, and why might coevolution matter?
- What practical benefits could come from understanding how SERPINA3 proteins block venom? Give possible research or medical uses.
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