Resistance gene: 2 genes - 1

Crime is only resistant to a pesticide when there is a possibility of two resistance? That seems like a simple thing, even for mosquitoes. However, in fact, this change in insects weakens them in other ways, so the quantity is not everything. A new study brings the problem back to the starting point, given that two resistance genes are better, or at least not making insects pay more than just having one gene.

The war on insect repellent and other arthropods has helped more than 500 species with resistance to drugs. If viewed from an insect perspective, this resistance comes at a price. Insect-saving gene mutations in insecticide sprays make their metabolism and nervous system less effective in other clean environments.

Therefore, evolutionary biologists predict that these resistance will decrease when pesticides are not used. But no one can predict what will happen to insects with two genes that are resistant to taste at the same time. Is the price paid for each mutation doubled? Or will they cancel each other out?

To answer this question, medical entomologist Vincent Corbel of the Institute for Development Studies (IRD) Montpellier, France, and a group of researchers compared four Culex quinquefasciatus mosquitoes in the laboratory. These four varieties differ in their resistance to two insecticides used everywhere, from bed nets to fields. One breed of pyrenthroid-resistant mosquitoes, an organophosphate-resistant strain, one resistant to both and one with no resistance.

Many insecticide-resistant gene mutations can create a more supple mosquito.(Photo: Nil Rahola / IRD)

As expected, when the researchers raised four varieties of mosquitoes in the experimental environment without pesticides, the mosquitoes did not have the best survival resistance. Those with pyrenthroid resistance mutations have slightly lower survival rates while those with organophosphate resistance are the worst, with nearly 15% less survival than non-resistant mosquitoes. The surprise comes from mosquitoes with two genes that are resistant when their survival rate is equal to those of pyrenthroid-resistant mosquitoes, the team published on the BMC Evolutionary Biology evolutionary website.

While the mechanism of this result is still a mystery, Philip Agnew, an evolutionary biologist at the Institute for Genetics and Infectious Diseases (GEMI), Montpellier, and also involved In this experiment, it was suggested that a resistance gene mutation could partially compensate for the remaining gene mutation . A gene mutation causes the mosquito's movements to become jerky, the other mutation makes its nervous system more heavy and slow. 'It is possible that on individual mosquitoes carrying these genes, they are mutually exclusive,' said Philip Agnew. And that means these resistance genes will stay in the mosquito for a longer time, even if there is no toxic substance in the environment.

However, 'super mosquitoes' are not impossible to destroy. Although adult mosquitoes are resistant to each type of poison, a small dose of both compounds can easily destroy them. In fact, these two mosquitoes rarely combine. Mr. Cobel said that if carried out in an environment that is as effective as a laboratory, mixing these mosquitoes would provide a useful tool to destroy 'super mosquitoes'.

This is a very positive step in trying to understand the complex losses that mutations of many resistance genes cause at the same time, says entomologist Jeffrey Scott of Cornell University. He hopes scientists will continue the work with the gene mutations and other insects, and predict that the same mechanism exists in these species.