An Investigation Reveals RNA Molecule's Influence on Butterfly Wing Pigmentation

An international team of researchers has uncovered a surprising genetic mechanism determining butterfly wing patterns and coloration. The findings, published in the Proceedings of the National Academy of Sciences and led by Luca Livraghi of George Washington University and the University of Cambridge, reveal that an RNA molecule plays a crucial role in controlling the distribution of black pigment on butterfly wings, a role previously attributed to proteins.

For centuries, biologists have been captivated by how butterflies create their vivid patterns. The genetic code within the cells of developing butterfly wings dictates the arrangement of color on these wing scales – akin to the arrangement of pixels in a digital image. Manipulating this code using gene-editing tools like CRISPR in the laboratory can help researchers observe the effects on visible traits such as wing coloration. Historically, protein-coding genes were considered fundamental to these processes, generating proteins responsible for pigment creation. However, this new research presents a different narrative.

The team uncovered a specific gene that produces an RNA molecule, not a protein, which influences where dark pigments form during metamorphosis. They demonstrated with CRISPR that removing this gene causes butterflies to entirely lose their black pigmented scales, establishing a direct link between RNA activity and black pigment development. "What we found was astonishing," Livraghi noted. "This RNA molecule determines the exact location of black pigment on the wings, shaping color patterns in unexpected ways."

By investigating this RNA molecule's activity during wing development, the researchers found precise correlations between its expression and the formation of black scales. "It’s an evolutionary paintbrush," said Arnaud Martin, an associate professor of biology at GW. Interestingly, this RNA was found performing similar roles in various butterfly species whose evolutionary paths diverged about 80 million years ago, indicating its long-standing evolutionary significance.

According to Riccardo Papa of the University of Puerto Rico—Río Piedras, "The consistent results from CRISPR mutants in several species show that this RNA gene is an ancient mechanism regulating wing pattern diversity." Further research by Joe Hanly, a visiting fellow at GW, noted the repeated use of the same RNA across different butterfly species, emphasizing its critical role in wing pattern evolution. He suggested that other significant phenomena might have been overlooked because they were not focusing on genetic ‘dark matter’.

Ultimately, these findings overturn longstanding beliefs about genetic regulation and open up new avenues for studying how traits evolve within the animal kingdom, providing significant insight into genetic control mechanisms that govern observable characteristics in butterflies and potentially other species.

Earlier, SSP wrote that a new algorithm can predict major earthquakes months ahead.