This month, UC Berkeley scientists genetically modified fruit flies using CRISPR-Cas9 gene-editing technology, granting the flies immunity to toxic milkweed and allowing them to use the toxins from the milkweed as a defense mechanism against predators.
According to Berkeley News, these fruit flies were genetically modified to copy genomes of the monarch butterfly that allow them to eat the toxic milkweed. UC Berkeley associate integrative biology professor and principal investigator on the project, Noah Whiteman, explained that his research finds its roots in the fundamental question of evolution and understanding adaptation. With this research, researchers were able to test evolution in a way that would not have been possible without the ability to create mutations with the use of CRISPR-Cas9, according to Whiteman.
According to Michael Astourian, a researcher on the project and campus junior, there are three known mutations in the monarch butterfly genome that make it immune to milkweed toxins. Using CRISPR technology, researchers were able to replicate the same three mutations in a model fruit fly, known taxonomically as Drosophila melanogaster.
“We found that with all three of these mutations, the flies were able to not only eat Milkweed and other ouabain medias, but were able to store low levels of the toxin,” Astourian said in an email. “This means that there are strictly 3 mutations separating toxin eating super-flies from your average fruit fly!”
One of the main concerns with these flies, however, is the toxicity aspect. These genetically modified flies have proved to elicit violent reactions from those that consume them, according to Whiteman.
According to Astourian, when monarch caterpillars feed on milkweed and emerge as butterflies, the toxins from the milkweed are stored in their wings. When predators prey on these butterflies, they begin to feel nauseous as the toxins take effect.
“Entomologist Lincoln Brower and his wife discovered back in the ‘60s that birds are aversive to eating the butterflies — they throw up when they eat them, so if enough gets into the human system, they will respond in the same way, but nothing that is life-threatening,” Whiteman said.
For those concerned about the dangers of these flies, UC Berkeley assistant professor of integrative biology Caroline Williams assured that these flies will not be released into the wild.
Despite the potential hazardous aspects of these flies, the research has proven to be unlike anything seen before in this field of science, according to Williams.
“The research is important because it shows that you can recapitulate the evolutionary processes that led to becoming resistant to the milkweed toxins by introducing just a few new mutations in Drosophila,” Williams said in an email. “There aren’t too many examples like this of where we can ‘replay the tape of evolution’ to find out how organisms adapt to their environment.”