Genetically Tweaking Flies to Save Livestock

Scientists are working on a clever way to control a nasty fly called the New World screwworm. This fly used to be a big problem in North and Central America, but it was wiped out by releasing sterile flies. However, releasing only male flies could make this method even better. Researchers have created special genetically modified flies. They used a system that turns off a gene using a substance called tetracycline. The goal is to make only male flies survive. They tried two different gene promoters to control when the gene turns off. One came from a similar fly species, and the other was from the screwworm itself. The idea is that the gene would be active in early embryos and turn off later. This would kill female flies before they develop, leaving only males. However, they found that the gene was also active in pupae, which was not expected. To make sure the female flies die, they tested different ways of giving doxycycline, a form of tetracycline, to the flies. They found that giving doxycycline at the right time could save the female flies by passing it from mother to offspring. But when they reduced the doxycycline, all the flies that survived were males. All the modified fly strains met the requirements for breeding in a colony. However, the modified males did not survive as well as the regular flies after removing doxycycline. In tests where males competed for mates, the modified flies did not do as well as the regular flies. One of the modified strains did as well as the regular flies in non-competitive tests, but all did poorly in competitive tests. This study shows how important it is to have precise control over gene activity and to carefully plan when to give antibiotics. It's a step towards making better genetic control methods for pests.