For many years, the colorful and intricate patterns on the wings of butterflies were thought by scientists to be controlled by many genes. This was believed because of their complexity and vast amounts of variation. But now, entomologists believe that just two genes control the vast array of colors found in a butterfly’s wings. This conclusion was reached thanks to research done with the famous, pioneering, and controversial CRISPR technique.
The Two Genes, a Genetic Master Switch for the Colors and Patterns
One of the two studies on the matter, both published in the journal Proceedings of the National Academy of Sciences, was conducted by Bob Reed, an evolutionary development biologist, and an international team of scientists based at Cornell University in Ithaca, New York. The team first looked at the much beloved and very endangered monarch butterfly. It then moved on to several other species, and their findings helped confirm the initial study results.
Within the DNA of the butterflies, just two complementary genes called WntA and optix seemed to handle most of the outward expression of the patterns and colors on the wings of the butterflies. These two genes appear to be the so-called “adaptive hotspots”. This means that their expression is affected by the butterfly’s environment.
Such adaptations allow the insect to better mask itself within whatever field of wildflowers or bush, for example, it might be happening to live in or pass by.
“The two different genes are complementary. They are painting genes specialized, in a way, for making patterns,” states Arnaud Martin, the lead author of the other study and a developmental biologist at the George Washington University.
Whenever the scientists turned off the WntA gene, boundaries and shapes in the wing patterns became less vibrant. The dark contouring of the monarch’s wing, for example, faded to a pale gray.
When they turned off the optix, the colors in the center of the wings disappeared almost entirely. Butterflies with typically bright red and yellow wings turned out gray and brown.
However, altering this gene in bland species led to the exact opposite effect. In the Junonia coenia, for example, it resulted in the appearance of bright blue spots. The results seem to indicate that the optix gene may be about more than just pigmentation, as it might even have a role in other physical expressions as well.
Image Source: Wikimedia