Insecticides have long been a weapon against pests that threaten crops. However, over time, insects such as beetles, moths, and flies have developed genetic mutations that make these chemicals ineffective. This escalating resistance has led farmers and pest control experts to use more potent and frequent applications of these harmful compounds, risking human health and environmental damage as these insecticides often kill beneficial insects as well.
In answer to this problem, researchers have created a sophisticated technology that can genetically alter insecticide-resistant genes, replacing them with genes susceptible to pesticides. These gene-editing technologies, based on CRISPR, could protect crops and significantly decrease the amount of chemical pesticides needed to combat pests.
Yet, concerns have been raised about these gene-editing systems. Critics argue that once introduced into a population, they could spread uncontrollably.
In response to this concern, geneticists at the University of California San Diego have developed a solution. In a study published in the journal Nature Communications, Postdoctoral Scholar Ankush Auradkar and Professor Ethan Bier developed a new genetic mechanism that reverses insecticide resistance in pests and then vanishes, leaving a population of insects with restored susceptibility to insecticides.
“We’ve created an efficient biological method to reverse insecticide resistance without causing additional environmental disruption,” said Bier, referring to the self-eliminating gene-editing technique, also known as “e-Drive.” He added that the e-Drive is programmed to act transiently and then disappear from the population.
The researchers designed a small group of DNA elements, termed a “cassette,” and inserted it into fruit flies as a test case. This e-Drive targets a specific gene, vgsc, crucial for proper nervous system function. Through CRISPR gene-editing, the insecticide-resistant vgsc gene is replaced with a version susceptible to insecticides.
When insects carrying this cassette are introduced into a population, they mate randomly, passing on the e-Drive to their offspring. To control the spread of the e-Drive, the researchers imposed a ‘fitness check’ on those carrying the cassette, which either limited viability or fertility. Over generations, the frequency of the cassette in the population decreases until it disappears completely.
Lab experiments showed that all offspring were converted to the original genes in eight-to-ten generations, or approximately six months in flies.
Auradkar noted, “Because the gene cassette places a significant fitness cost on insects, it’s rapidly eliminated from the population, lasting only until the insecticide-resistant genes are fully converted back to their original state.”
The temporary nature of the e-Drive means it can be reintroduced as necessary and modified to work with different types of pesticides. The team is now working on applying this technique to mosquitoes to help curb the spread of diseases like malaria.
The study, co-authored by close collaborators Rodrigo Corder of the University of São Paulo’s Institute of Biomedical Science and John Marshall of the Innovative Genomics Institute, utilized sophisticated mathematical modeling to reveal key aspects of the e-Drive system, including its ability to efficiently eliminate individuals where the gene-editing process did not occur.
