Naturalist figured out how butterfly wings acquire their complicated pattern and varieties of colors such as red yellow white and black striping. In 2016 geneticists thought that most of the wing-pattern variations are encoded from protein producing gene called cortex. Three team have now instead proved that a different gene that was missed in previous researches is the key. The final product of the newly discovered gene is not a protein but RNA (lncRNA for long noncoding RNA), which function is to regulate and turn on and off genes that are responsible for the pigmentation of black and pattern on the wing.
The discovery was possible through a mutant butterfly that was put on sale on Ebay and bought from biologist Luca Livraghi of George Washington University after being flagged from a colleague. The butterfly in case was a completely white butterfly of the genus Heliconius. The team sequenced a dozen of those mutant ivory butterfly and realized that there was a deletion in the region of the cortex gene. The researchers then realized that the deletion of DNA included a sequence that encode the lncRNA that no one had examined before. The team then decided to expand the research to other species of butterflies. Using the gene editor CRISPR the team disabled the lncRNA gene in painted lady butterflies (Vanessa cardui) which are easy to breed in lab and had colorful wings. The CRISPR edit produced white-winged painted lady butterflies just like the Heliconius. Moreover the team tried to disable the cortex gene and realized that it doesn’t affect the color of the wings.
The results of this study were also proofed to be right and can be extended to other butterfly species that are distantly related to it. A Cornell evolutionary biologist (Robert Reed), joined effort with Livraghi and used the same CRISPR techniques on buckeye butterfly. By cutting different parts of the lncRNA, Reed was able to produce butterfly with little or no color. Moreover, Antonia Monterey and Shen Tian from National University of Singapore, while focusing on microRNA found that one of those short RNA sequence was active on bush brown butterfly (Bicyclus anynana) just like Livraghi found for his butterfly. The Singapore team disabled in an experiment the DNA that encoded the microRNA, called mir-193 and the bush brown butterfly wings became lighter just as predicted from the other team. The experiment was then repeated by cutting mir-193 on Indian cabbage white( Pieris canidia) and changed the wings from black-patterned to white. This confirmed that the microRNA was a short part of the longer lncRNA.
It is crazy to think how such a short piece of information can change drastically the phenotype of butterfly species that are very distantly related. Because the microRNA mir-193 is proven to be conserved in animal kingdom, scientists and researchers think that this small piece of RNA can be used in other species to regulates genes. Moreover, the focus is always have been on DNA but RNA turned out to be as much as important as DNA not only for transcription and translation but also for gene regulation.
I think it is fascinating that the effect of the IncRNA on butterfly color seems to be standardized across multiple butterflies. I have been somewhat noticing a pattern lately the more I observe current genetics research related to your last statement. Researchers have always been focused on the effects of DNA on gene regulation but lately seemed to have discovered in various ways that RNA may be just as important. There may be a trend beginning toward increased research surrounding the effects of RNA on gene regulation.
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