We Might be Repelled to Something that Even Fruit Flies Are Not!

Yuying Wang ‘23

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On October 2, 2019, researchers from the University of Berkley published a new study that left everyone in awe. With the help of advanced editing software, they were able to model fruit flies after the monarch butterfly and modify their species to become resistant to the toxins found particularly in milkweed. This accomplishment also leads them to many additional findings that changed their view of the internal composition of species and their ability to evolve from their surroundings. 

 

Milkweed is a type of plant that contains harmful toxins, mostly from digitoxin. Digitoxin is the main component of the plant. This poisonous substance harmful to numerous species because it interferes with sodium/potassium pump, which most of the body’s cells use to move sodium ions out and potassium ions in, sending the balance of ion concentration out of control. The imbalance of ion concentration leads to a rapid increase in heartbeats, thus leading to heart failure, and death is caused by cardiac arrest.

 

While this does keep a majority of the predators away, monarch butterflies are an exception to this statement. They seem to have developed an immunity to the toxic components of the plant, and the species has included milkweed as a staple in their diet. Although other animals make a clear avoidance of this threat, monarch butterflies don’t. This raised several questions among researchers, which ultimately lead them to discover that it basically came down to three single-nucleotide substitutions that would allow fruit flies to digest milkweed.

 

Whiteman, an associate professor of integrative biology who had an impactful role in this journal stated: “All we [they] did was change three sites, and we made these superflys.” Having said it so easily, Whiteman’s team tested a bunch of experiments utilizing CRISPR-Cas9, a gene-editing platform. Specifically, they copied six variations of a monarch butterfly’s genes and input it the composition of the fruit fly, then, they fed each variable an amount of milkweed powder and observed the ones that were able to resist. Those turned out to be a mixture of three mutations that turned them into “superflies.” But, after having produced batches of successful results, they managed to show that 20 other insect groups were able to eat milkweed and compared to an ordinary fruit fly (the constant group) they were almost 1,000 times less sensitive to the toxins. Also, surprisingly, they were also able to ingest other types of plants that were also deemed to be poisonous. These species include moths, beetles, wasps, flies, aphids, a weevil and a true bug (a more general category of insects that had similar mouth sucking part). Researchers think that monarch butterflies have drastically evolved and adapted to avoid any potential predators, making them have a stronger resistance to milkweed toxins. 

 

The successes from this finding are honestly astonishing for researchers, and with the principle that for insects, it takes at a minimum of only three mutations for them to resist the risk-taking threats of a toxic plant. Whiteman had made it clear that “complex organismal traits can evolve by following simple rules.”

 

[1] https://www.vice.com/en_us/article/j5yvkd/scientists-edited-fruit-fly-genes-to-give-them-butterflies-toxic-abilities

[2] https://www.sciencenews.org/article/gene-editing-can-make-fruit-flies-into-monarch-flies

[3] https://www.sciencemag.org/news/2019/10/how-monarch-butterfly-evolved-its-resistance-toxic-milkweed

[4] https://the-natural-web.org/2013/08/19/milkweed-its-not-just-for-monarchs/

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