Molecular characterization of pyrethroid resistance in the olive fruit fly Bactrocera oleae

Α reduction of pyrethroid efficacy has been recently recorded in the olive fruit fly Bactrocera oleae, the most destructive insect pest of olives worldwide. We analyzed the transcriptomic differences between two highly pyrethroid resistant populations versus a relatively susceptible field population and two laboratory strains to gain more insight into the molecular mechanism of resistance. A large number of genes was found to be significantly differentially transcribed across the pairwise comparisons between resistant and susceptible insect populations. Interestingly, gene set analysis revealed that genes of the ‘electron carrier activity’ GO group were enriched in one specific pairwise transcriptomic comparison. As P450 monooxygenase enzymes are typically associated with this Molecular Function GO-group, this might reflect a P450-mediated resistance mechanism. These results suggest that transcriptional induction of the CYP6 P450s might be an important mechanism of pyrethroid resistance in B. oleae and pave the way for the development of synergists and molecular diagnostics for insecticide resistance management. Four biological replicates from the B. olaea population LAB, AN12, AN14, and FOK14 (each consisting of 10 pooled one-to-three days old females) were collected. In total, three major comparisons were performed; AN12 vs HYB, AN14 vs LAB, and AN14 vs FOK14.