#Singapore #microRNA #Lepidoptera #NUS Study

Unveiling the Coloration Mystery of Butterflies and Moths

Butterflies and moths, belonging to the order Lepidoptera, are renowned for their striking wing color patterns which showcase a kaleidoscope of colors. From the vibrant blues of Morpho butterflies to the muted tones of night-flying moths, their wings serve not only as decoration but also crucial functions in survival and reproduction. Yet despite extensive research into the ecological implications of wing coloration, the genetic underpinnings behind these dazzling displays have remained elusive until now.

A pivotal study led by researchers from the National University of Singapore (NUS), in collaboration with institutions in Japan and the United States, has shed light on an essential factor in this evolutionary puzzle. The research, recently published in Science, has revealed that a specific microRNA (miRNA) plays a crucial role in determining whether these insects display black or white coloration in their wings, upending previous theories that centered on a gene known as cortex.

The Search for Color Control

Over the past two decades, it has been presumed that the gene cortex was responsible for the melanic (dark-colored) variations in Lepidopteran wing patterns. This assumption was vividly illustrated with historical accounts such as the case of the British peppered moth, Biston betularia, which underwent rapid evolutionary change in response to industrial pollution in the late 1800s. The concept highlighted the interplay between environment and genetic expression, showcasing the direct influence of natural selection on species adaptation.

However, skepticism toward the cortex-centric view has been brewing among scientists. Dr. Shen Tian, the primary investigator of the study and a postdoctoral researcher at Duke University, remarked, “Several studies raised doubts about cortex being the sole melanic switch, prompting us to explore other potential genomic elements.”

The team focused on an adjacent miRNA, mir-193, previously overlooked in discussions about wing coloration. Utilizing the CRISPR-Cas9 gene-editing technology, they performed targeted disruptions of mir-193 across three diverse butterfly species: the African squinting bush brown butterfly (Bicyclus anynana), the Indian cabbage white butterfly (Pieris canidia), and the common mormon butterfly (Papilio polytes). The results were striking: complete disruption of mir-193 led to the absence of dark and melanic wing colors, whereas alterations to cortex had no noticeable effect.

A Broader Impact of MicroRNA

The implications of these findings extend beyond Lepidoptera. Mir-193’s sequence is not only conserved among butterflies but also across various animal species, suggesting its role as a fundamental regulator of melanic coloration. Further tests in common fruit flies (Drosophila melanogaster) revealed that mir-193 similarly influenced coloration in these organisms, indicating a universal mechanism underlying color expression within the animal kingdom.

Professor Antónia Monteiro, who co-led the study, concluded, “This research flips the traditional understanding of color variation in butterflies and moths on its head. It demonstrates how essential non-coding RNAs like miRNAs can significantly influence phenotype and should not be disregarded in genetic studies.”

This study not only enhances our understanding of the intricate genetic mechanisms behind wing coloration but also serves as a catalyst for future research endeavors delving into the largely unexplored realm of non-coding RNAs. Dr. Tian stresses the importance of this investigation, indicating that these small but mighty molecules could unravel more evolutionary secrets, prompting dire need for further studies involving miRNAs in phenotypic diversity across a spectrum of life forms.

In conclusion, as researchers continue to probe the nuanced tapestry of evolution, the revelation of mir-193 as a key player in the coloration of butterflies and moths stands as a testament to the ever-evolving field of genetics and the intricate dance between DNA and phenotype.