D.G.R.P. - G.W.A.S
What is the genetic basis of insecticide resistance?
The scientic literature abounds with examples of insects evolving resistance to insecticides. The resistance mechanisms vary but includes:
1. Behavioural modifications to avoid chemicals
2. Cuticular modification (also known as 'penetration resistance')
3. Enhanced excretory systems
4. Increased detoxification mechanisms. This is a common mechanism often involving cis-regulatory changes of genes encoding enzymes (P450s, Carboylesterases, Glutathione S-transferases)
5. Modification of the molecular target of the insecticide
6. Potentially other mechanisms
A common limitation of many studies of insecticide resistance is that they have focussed in single genes of large effect (they are easier to detect and have a greater impact on insect control). However if we are to properly understand the perturbation that insecticides impose on insects, the genetic response of insects to insecticides, and the evolutionary processes at play in the evolution of insecticide resistance, we need to get more quantitative. We want to know all the genes, their individual effect sizes, how they interact with each other, what effect they have on other traits, how they are influenced by the environment, how they vary in natural population etc.
We have been using the wonderful Drosophila Genetic Reference Panel (DGRP) developed by Trudy Mackay to interrogate the insecticide biology of the model insect: Drosophila melanogaster, using a genetic technique called Genome Wide Association Studies (GWAS). We have screened the DGRP for many class of insecticides and are starting to see the similarities and differences in the way they act.