A gene within butterfly’s wings has been found to directly affect the manifestation of dorsal wing traits within the African squinting bush brown butterfly, Bicyclus anynana. These findings show that gene expression has great importance on the evolution of Bicyclus anynana.

Researchers from the National University of Singapore (NUS) discovered that when the gene, apterous A, was deleted from the butterfly’s genome, some features within the butterfly’s wings were repressed and activated, altering sex-specific wing traits and the appearance of the dorsal wings.

The discovery was made by Antonia Monteiro, associate professor, and her student, Anupama Prakash, both in the Department of Biological Sciences at the NUS Faculty of Science.

After removing the apterous A gene from the genome through a knockout process, Monteiro and Prakash noticed that the mutation of the gene resulted in defects in the wing’s development that caused a unique pattern.

The scientists explained that when the gene is present, it acts with other genes on the dorsal wing and results in a pattern. Without the gene, the particular pattern is inhibited.

Patterns on the ventral surface of the butterfly’s wing act as a defense against predators when it camouflages the butterfly, while the dorsal wing surface pattern is specifically meant to attract mates.

Additionally, the deletion of the gene allowed an eyespot pattern to develop, which is a marking similar to an eye pattern that has been common among dorsal wings surface patterns on butterflies, but was not present on Bicyclus anynana until the gene was mutated by the biologists.

When the gene is present in this particular butterfly, the common eyespots are blocked and make for a unique and uncommon development.

The mutation of apterous A was also found to alter sex-specific wing traits such as the repression of pheromone producing organs and the absence silver scale development on the dorsal forewing in male butterflies. For the female butterflies, removal of apterous A resulted in activation of the development of pheromone dispersing hairs and silver scale development.

In the male, removing the gene acted as a deactivator for gender-specific traits, while mutation of the gene was an activator in the female dorsal forewings.

The research produced from the study provides biologists a glimpse into understanding the role that cells play in altering colors and surface patters on butterfly wings.

“Since apterous A is expressed only in cells of the dorsal surface, we can now identify dorsal-specific cells based on this gene expression. This is very useful if, for example, we want to study how a certain color develops,” Prakash said.

The team of researchers at the university will proceed with further studies, based on their findings, including whether the gene impacts other families of butterflies and or butterflies without specific patterns on their wings, as well as how the gene inhibits the eyespot marking that is typical of butterflies.