Evolutionary Changes in Gene Expression, Coding Sequence and Copy-Number at the Cyp6g1 Locus Contribute to Resistance to Multiple Insecticides in Drosophila
Figure 3
Overexpression of different Cyp6g1 orthologs confers resistance to different insecticides.
A) Changes in survival following exposure to three classes of insecticide by expression of Cyp6g1 orthologs from D. melanogaster, D. simulans, D. willistoni and D. virilis in a consistent genetic background. Resistance ratio (RR) was calculated by comparing the concentration of insecticide that killed 50% of insects (the LC50) between the line expressing the ortholog and the background strain, 86Fb, which was genetically identical except for the absence of the Cyp6g1 construct. Results marked with an asterisk were statistically significant (p<0.05). Orthologs from D. melanogaster and D. simulans were functionally identical at a qualitative level, both providing resistance to all three chemicals, but the resistance profile varied between the other three orthologs. B) Comparison of the potential of the CYP6G1 orthologs to cause resistance when overexpressed. D. melanogaster and D. simulans orthologs cause resistance to a range of chemicals, whilst the ortholog from D. willistoni and the two paralogs from D. virilis only conferred resistance to one of the chemicals tested. These results suggest that adaptation of the protein has occurred repeatedly in Drosophila. The scale bar indicates the number of substitutions per four-fold degenerate site in the genomes of the species (inferred from Stark et al. [21]).