Lepidopterans are well known for their colorful and patterned wings. Be it black and white, or dark and bright, these patterns arise due to a pigment in their body- Melanin. Yes, the same pigment that makes your hair grey or black! These winged beauties are used as classic examples to explain evolution and natural selection. We now know the ecological factors behind the different wing patterns. However, to date, we do not understand how the color change happens at a molecular level. Thanks to a team of researchers from the National University of Singapore, we are close to finding the answer. Let us dive deep into their work and find the molecular basis of color change in the wings of lepidopterans.
What did they previously assume?
Over the past two decades, many scientists attributed a tiny gene- cortex that acted as a melanic switch I.e. the protein that controls the turning on and off of the melanin pigment thereby contributing to the colored patterns.
What do we now know?
Through a recent research work, a paper published in the journal Science showed that a ‘previously ignored’ miRNA was the actual melanic switch. Dr. Tian, the lead author of this work took inspiration from piles of information claiming the cortex was the melanic switch. He studied the genomic features of this particular genomic region- the miRNA.
miRNA could be the possible melanic switch
Upon disrupting a specific miRNA, they identified that the dark coloration of wings disappeared. They then concluded that the mir-193 located very close to the cortex gene was found to be responsible for the black and dark-colored wings. Interestingly, disrupting the cortex and three of its associated protein-coding genes did not affect the wing color.
Role of ivory in mir-193
The miRNA was processed by an RNA- ivory. Its main function is to repress not just melanin but also other pigmentation genes. Interestingly, the sequence of the mir-193 was highly conserved throughout the animal kingdom including drosophila.
Little did we believe that a tiny non-coding RNA molecule could be the reason behind the colorful patterns of butterfly wings. They act as a switch between light and dark colors by shuttling between their expression and non-expression state.
These unsung heroes (miRNAs) should never be ignored and could possibly be an answer to some unanswered questions in biology. We touched upon this in a previous article on BioDiaries. Check it out here.
What do you think about this fascinating discovery?
Fascinating!