Researchers have made an unexpected discovery about the genetic processes that shape the colorful and intricate designs on butterfly wings. The team found that it’s an RNA molecule, not a protein as was commonly believed, that plays a key role in controlling how black pigment is spread across butterfly wings.
An international research team has revealed an unexpected genetic mechanism that affects the striking and intricate designs found on butterfly wings. In a study published in the Proceedings of the National Academy of Sciences, led by Luca Livraghi from George Washington University and the University of Cambridge, it was found that an RNA molecule, rather than a protein as previously assumed, is crucial for determining the distribution of black pigment on butterfly wings.
The fascinating ability of butterflies to create vivid patterns and colors on their wings has intrigued biologists for ages. The genetic material within the cells of growing butterfly wings is responsible for the specific arrangement of colors on the miniature scales of the wings—much like how colored pixels create an image on a digital screen. Decoding this genetic information is essential for understanding how our own genes contribute to our physical traits. In laboratory settings, scientists can alter this code in butterflies using gene-editing technology and observe how it affects visible characteristics, like wing coloration.
For a long time, it has been understood that protein-coding genes are vital to these processes. These genes generate proteins that dictate when and where a scale should produce a certain pigment. Researchers initially thought that the process for producing black pigments would follow the same pattern and focused on a protein-coding gene. However, the latest findings tell a different story.
The research team identified a gene that generates an RNA molecule—rather than a protein—that regulates the location of dark pigment formation during the development of butterflies. Through the use of the genome-editing method CRISPR, the researchers were able to show that when they eliminated the gene responsible for producing the RNA molecule, the butterflies entirely lost their black pigmented scales. This clearly demonstrated a connection between the functioning of RNA and the development of dark pigments.
“What we found was astonishing,” said Livraghi, a postdoctoral researcher at GW. “This RNA molecule directly affects where the black pigment shows up on the wings, influencing the butterfly’s color patterns in ways we did not expect.”
The research team further examined the role of the RNA molecule during the development of the wings. By studying its activity, they noted a perfect match between the locations where the RNA is active and where black scales appear.
“We were surprised to find that this gene activates exactly where the black scales will form on the wing, with remarkable precision,” said Arnaud Martin, an associate biology professor at GW. “In this sense, it acts as an evolutionary paintbrush, and it’s quite inventive considering its influence across various species.”
The researchers also looked into the newly identified RNA in other butterfly species that diverged evolutionarily about 80 million years ago. They discovered that, in each of these species, the RNA had adapted to control new positions for dark pigment patterns.
“The consistent findings from CRISPR mutants across multiple species clearly show that this RNA gene is not a recent development, but rather a fundamental ancestral mechanism for managing diversity in wing patterns,” noted Riccardo Papa, a biology professor at the University of Puerto Rico — RÃo Piedras.
“We, among others, have examined this genetic trait in various butterfly species and, quite impressively, it appears this same RNA is repeatedly utilized, from longwing butterflies to monarchs and painted ladies,” said Joe Hanly, a postdoctoral fellow and researcher at GW. “It’s evidently a critical gene for the evolution of wing patterns. I wonder what other similar occurrences scientists might have overlooked because they weren’t focusing on the unexplored aspects of the genome.”
The results not only challenge established beliefs about how genetic regulation works but also pave the way for new research into the evolution of noticeable traits in animals.
