A bacterial gene contributed to evolution of the vertebrate eye

What is it about?

Animals usually evolve by inheriting genes from their parents. This type of vertical inheritance means that evolution of novel features usually evolves by "tinkering" with genes that came from previous generations. Here we found that a major innovation in the evolution of the vertebrate eye did not come by "tinkering" with genes that exist in other animals, but by taking up a gene from bacteria and using that to evolve a new function. This type of horizontal gene transfer (HGT) from bacteria is rare in animals, but can lead to large evolutionary innovations such as altering the structure of the eye.

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Photo by Colin Lloyd on Unsplash

Photo by Colin Lloyd on Unsplash

Why is it important?

The vertebrate eye was described by Charles Darwin as one of the greatest potential challenges to a theory of natural selection by stepwise evolutionary processes. Our work shows that the complexity of the eye has evolved not only by stepwise repurposing of genes that preexisted in animals but but by acquiring novel DNA from bacteria. More broadly, our work highlights the impact that microbial DNA can have on evolution of complex systems in animals and suggests that many other cases of bacteria-to-animal HGT (horizontal gene transfer) likely remain to be discovered.