RESUMO
Pyridalyl is one of the recently discovered insecticides which has shown toxicity against several insect pests with slight- or non-lethal effects against natural enemies. Cytotoxicity and prevention of protein synthesis have been reported as pyridalyl mode of action. In the current study, adults of Bacterocera oleae, as a major pest of olive, were fed on protein hydrolysate diet containing LC50 concentration of pyridalyl to determine the possible mode of action through gene expression and amino acid profile. Results showed that treated flies had significantly higher gene expressions of cytochrome P450, insulin receptor-like, antioxidant enzymes (catalase, peroxidase, superoxide dismutase) and the enzymes involved in cell death; caspase1, caspase3, caspase8 and caspase9 compared to control. Moreover, determination of amino acid profile in the whole body of both control and pyridalyl-treated B. oleae revealed the significant higher amounts of glutamic acid, glutamine, histidine, threonine, citrulin, arginine, taurine, alanine, tyrosine, α-amino butric acid, methionine and isoleucine in the treated adults while the control flies had the higher amounts of serine, glycine and tryptophane. No significant differences were found in the amounts of asparagine and phenylalanine between control and treatments. These results are in accordance with earlier findings on mode of action of pyridalyl through activation of cytochrome P450 system and alterations in protein synthesis machinery although here other mechanisms were also reported including activation of insulin receptor and antioxidant enzymes. Moreover, it is the first report on cytotoxicity through apoptosis with engagement of caspases.