Study Suggests

Butterflies have long fascinated biologists, not just for their beauty but for the incredible diversity in the patterns and colors of their wings. How do these intricate designs come to be, and what genetic mechanisms drive their evolution? A new study has unearthed an unexpected answer: an RNA molecule, not a protein as previously thought, plays a critical role in determining the distribution of black pigment on butterfly wings.

The Hidden Role of RNA

Scientists have known for some time that protein-coding genes are involved in the development of butterfly wing patterns, dictating when and where specific pigments form. But this new research, published in the Proceedings of the National Academy of Sciences and led by a team from George Washington University, has found that an RNA molecule controls the process instead.

The researchers used CRISPR gene-editing technology to remove the gene responsible for producing the RNA molecule. The result? Butterflies completely lost their black-pigmented scales, showing a clear link between RNA activity and pigment distribution. This discovery rewrites the previous understanding of how butterfly coloration evolves.

A Key to Evolutionary Diversity

The researchers didn’t stop at one species. They examined this RNA gene in several butterfly species that diverged around 80 million years ago, from monarchs to longwing butterflies. They found that in every case, the same RNA molecule played a crucial role in regulating wing patterning. The fact that this mechanism has been conserved across so many species suggests that it’s an ancient and fundamental part of butterfly evolution.

“This RNA molecule acts like an evolutionary paintbrush,” says Arnaud Martin, associate professor of biology at George Washington University. “It precisely controls where dark pigments will appear on butterfly wings, creating patterns with incredible precision.”

Genomic Dark Matter: A New Frontier

The researchers describe this RNA molecule as part of the genome’s “dark matter”—non-coding regions of the genome that don’t produce proteins but still have important regulatory functions. These findings challenge long-standing assumptions about the role of protein-coding genes in evolution and open new avenues for studying how other visible traits, such as color and patterns, evolve in animals.

“We’ve only scratched the surface of understanding the dark matter of the genome,” says lead author Luca Livraghi. “This discovery could be the tip of the iceberg when it comes to how RNA influences evolution.”