Recently, researchers noticed that only three amino acid changes were needed to make butterflies immune to chemicals called cardiac glycosides which are found in milkweed. Consequently, in October 2, 2019, researchers reported in Nature that they used gene editing to alter the genes of fruit flies to test if the changes in butterflies occurred by chance.
One characteristic of monarch butterflies is their ability to digest toxins in milkweed and become poisonous to their predators. With only three genetic changes, however, fruit flies were also able to develop this power as they transformed from maggots to adults. This seems like a definite evidence that the genetic changes in butterflies caused them to be immune, but researchers were still uncertain.
As a result, Noah Whiteman, an evolutionary biologist at the University of California, Berkeley, along with colleagues, utilized a gene editor called CRISPR/Cas9 to alter the genes of fruit flies. By reverting the amino acids one at a time, they were able to “go back in time” to see the changes that made monarch butterflies resistant to the chemicals.
After the research, the researchers concluded that all three amino acid changes are required to make fruit flies that are resistant to the chemicals. Simultaneously, they confirmed their previous belief that the amino acids that were involved in the research are a part of the protein called sodium pump alpha subunit. The sodium pump is also found in other cellular systems, and it moves charged sodiums and potassium atoms in and out of cells. The research proved that this connection is not coincidental.
The researchers also discovered that the fruit flies’ resistance to the chemicals had a cost. When the researchers slammed the vial that contained the ‘monarch flies,’ the flies became paralyzed. The flies now had a significantly lower stress capacity.
The change is still beneficial according to Whiteman. “The benefit of being noxious to predators is so much more valuable,” he says.
by SangHyun Kim