A new genetic study shows that the protein cryptochrome 4 in birds’ eyes is key to their magnetic navigation abilities, and evolutionary changes highlight the role of birds in adapting to different environments.
Migratory birds have the ability to navigate long distances with extreme precision using a variety of mechanisms, including a magnetic compass. In a recent study, biologists Dr. Corinna Langebreik and Dr. A team led by Miriam Lidvogel compared the genomes of several hundred bird species and found significant evolutionary changes in the gene responsible for coding the cryptochrome 4 protein. The eyes are believed to be an important magnetoreceptor that controls navigation abilities.
Cryptochrome 4 as a candidate magnetoreceptor
These findings suggest adaptation to different environmental conditions and support the theory that cryptochrome 4 functions as a sensor protein, the team writes in a paper recently published in the Royal Society Research Journal. Proceedings of the Royal Society B Biological Sciences .
The research was prompted by research from the Universities of Oldenburg and Oxford, which showed that magnetoreception relies on a complex quantum mechanical process that occurs in specific cells in the retina of migratory birds. These findings, published by a scientific journal in 2021 Nature, provided evidence supporting the hypothesis that cryptochrome 4 was the magnetoreceptor they were looking for. They proved that cryptochrome 4 is present in the retina of the bird eye. In addition, both experiments with bacterial proteins and model calculations showed that cryptochrome 4 exhibits a suspicious quantum effect in response to magnetic fields.
Comparative susceptibility across bird species
A previous study also found that cryptochrome 4 showed greater sensitivity to magnetic fields in migratory birds such as robins compared to sedentary species such as chickens and pigeons. “Therefore, the reason why cryptochrome 4 is more sensitive in robins than in chickens and pigeons must be found in the DNA sequence of the protein,” says Langebreik, the study’s lead author. “The sorting was probably optimized by the evolutionary processes of these nocturnal migratory birds,” he adds.
In the current study, the team examined magnetic sensing from an evolutionary perspective for the first time. Researchers analyzed the cryptochrome genes of 4,363 bird species. First, they compared the rate of protein evolution with that of two related cryptochromes and found that the gene sequences of the cryptochromes used for comparison were very similar across all bird species. They appear to have changed little during evolution. This is most likely due to their key role in regulating the internal clock, a mechanism that is important for all birds and where changes can lead to extremely negative consequences.
Cryptochrome 4, on the other hand, turned out to be very volatile. “This shows that the protein is important for adaptation to certain environmental conditions,” explains Lidvogel, professor of ornithology at the University of Oldenburg and director of the Bird Research Institute. The specialty taken may be magnetoreception. “A similar pattern has been observed in other sensory proteins, such as photosensitive pigments in the eye,” he explains.
The researchers then took a closer look at how the cryptochrome 4 gene sequence evolved over the evolutionary history of birds. Their analysis revealed a distinct trend, especially in Passeriformes, where the protein had undergone significant optimization due to rapid selection. “Our results suggest that evolutionary processes may have led to the specialization of cryptochrome 4 as a magnetoreceptor in songbirds,” says Langebreak.
Oppressors lost a suspicious protein
The study found that cryptochrome 4 was absent in certain bird species, such as parrots, hummingbirds, and suboscines. This suggests that it does not play a vital role in their survival. However, while parrots and hummingbirds are sedentary, some tyrannies are long-distance migrants that can fly both day and night, such as small European songbirds. “The fact that they do not have cryptochrome 4, unlike the archaeon, makes them an ideal system to study different hypotheses regarding magnetoreception,” says Langebreak.
This raises the question: Have bullies evolved a magnetic sense of smell that works independently of cryptochrome 4, or are they able to navigate without a magnetic sense of smell? Another possibility is that their magnetic sense of smell has the same properties as those of robins; this sense depends on light and can be disrupted by radio waves. “While the first two scenarios convincingly support the cryptochrome 4 hypothesis, the third poses a problem for the theory,” the biologist emphasizes.
In the future, the research team plans to study the magnetic orientation of the tires and determine whether they have magnetic hearing. “Rainbows provide us with a natural tool to understand the function of cryptochrome 4 and the importance of magnetic sensing in migratory birds,” says Lidvogel.
Source: Port Altele
