The eye has always been annoying. Even Charles Darwin’s theory of evolution struggled to explain the complex evolution of the eyeball. A new discovery in which bacteria over 500 million years old play a significant role now makes it even clearer.
American researchers I found the evidence To exchange gene packages between bacteria and vertebrates. Their new study focuses on a particular example of this: the IRBP gene (protein binding to retinoid receptors)which contains the code for making a protein, forms an important link in eye development and light perception. Scientists have used the computing power of the advanced computer model IQ-TREE to understand the evolutionary history of the origin of the eye in vertebrates, and have come across more bacterial gene sequences in humans that were not present in our distant ancestors.
Borrowing genes from other life forms
The idea of genetic cross-pollination between bacteria and vertebrates is not new. When the human gene was first sequenced in 2001, scientists thought they were dealing with more than 200 “bacterial” genes. However, many of these microbial genetic connections did not hold up in follow-up research. Researcher Matthew Dougherty and colleagues from University of California Delve deeper into human DNA with a new computer program and compare DNA fragments to similar genetic sequences from hundreds of other species. Genes that could not be found in distant ancestors were classified as interesting. According to the researchers, these would be good candidates for jumping directly from bacteria to vertebrates. “Of the dozens of possible abnormal genes, one stood head and shoulders above the rest,” says Dougherty.
This was the gene IRBP, which was already known to be an important link for vision. The protein that can be synthesized does its work in the space between the retina and the retinal pigment epithelium (RPE), a single-celled layer on the retina connected to the sensorineural retina. When light hits a photosensitive photoreceptor, the vitamin A compounds present cause it to “twist,” triggering an electrical impulse that activates the optic nerve. IRBP ensures that the twisting in these molecules disappears and the vitamin A complex returns to its old form. The researchers therefore argue that IRBP is essential for the vision of all vertebrates.
From protein recycling to vision
IRBP is very similar to a group of bacterial gene sequences called peptidases. These enzymes are known for their ability to recycle protein. The peptidase gene is thought to have jumped from a microbe to an ancient ancestor of all modern vertebrates more than 500 million years ago. Once this gene was encapsulated in its new location, it replicated itself twice. After that, it lost its protein recycling function and took on a visual role by binding to light-sensitive molecules, the study says.
The primary role of IRBP is not undisputed. Some biologists in the field disagree with the California researchers’ theory. But this horizontal exchange of genes takes place between completely different forms of life, that’s for sure. When a gene sequence takes root in a new species, the evolutionary process can run wild with it, and sometimes entirely new possibilities emerge or the recipient’s existing skills get a huge boost. It’s a great concept that will undoubtedly require more research.
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