By making changes to just two genes, researchers have managed to alter the design of eyespots on butterfly wings. The findings, published in Nature Communications last week, could help us understand how color patterns evolved.
"Variation is the raw material of evolution," Cornell University’s Robert Reed said in a statement. Butterfly wing designs are an accessible model for researchers trying to study how natural selection favors some variations over others. Their wings can serve many functions, ranging from mimicry to warning signs that ward off would-be predators The vivid orange-and-black markings on monarchs advertise their noxious taste, for example, while eyespots that adorn the wings of Caligo owl butterflies resemble the eyes of birds of prey. Previous work identified two genes that are expressed during early eyespot determination: spalt and Distal-less.
So Reed and Linlin Zhang also of Cornell used genome editing technology to tweak the genes of the painted lady butterfly (Vanessa cardui) and the buckeye (Junonia coenia). By cutting out the gene spalt, the team produced butterflies with fewer eyespots and those with none at all. When they deleted the gene Distal-less, they produced butterflies with both more and larger eyespots.
"People suspected these genes had something to do with wing patterns but nobody had proved it," Reed said. "It probably takes dozens or hundreds of genes to make an eyespot, so it was remarkable to find that only one or two genes are required to add or subtract these complex patterns. It is a beautiful demonstration of how animals are assembled as modules, much like a model kit.”
Additionally, the distal-less gene played key roles in shaping several other parts of the body: Removing the gene resulted in butterflies with shorter legs and antennae.
Image in the text: Normal and engineered wing patterns shown here as mirror images. Cornell University