CRISPR Flies Take Leaf Out of Butterfly Book to Exploit Predator-Deterring Toxins

An international team of researchers headed by scientists at the University of California (UC), Berkeley, has used CRISPR-Cas9 genome editing to turn fruit flies that might otherwise represent a handy snack for frogs and birds, into potentially poisonous prey that could cause anything that eats them—including humans—to vomit. The team, led by Noah K. Whiteman, PhD, principal investigator and an associate professor at UC Berkeley, introduced into the flies the same three mutations in a single gene that are carried by the monarch butterfly (Danaus plexippus), which can eat and sequester the poisonous plant milkweed as caterpillars, and then retain some of the toxin as adult butterflies, to deter predators. Milkweed is a highly toxic plant that would kill most animals, including humans. But like the monarch butterfly, the CRISPR-engineered fruit fly larvae were similarly able to eat milkweed and retain the plant’s toxins when they metamorphosed into now-poisonous adult “Monarch flies”. Critically, the mutations had to occur in the right sequence, otherwise the flies would not have survived the three separate mutational events.