ABSTRACT
The enzyme NADPH-cytochrome P450 reductase (CPR) plays a central role in cytochromes P450 activity. Gene expression analysis of cytochromes P450 and CPR in deltamethrin-resistant and susceptible populations revealed that P450s genes are involved in the development of insecticide resistance in Triatoma infestans. To clarify the role of cytochromes P450 in insecticide resistance, it was proposed to investigate the effect of CPR gene silencing by RNA interference (RNAi) in a pyrethroid resistant population of T. infestans. Silencing of the CPR gene showed a significant increase in susceptibility to deltamethrin in the population analysed. This result support the hypothesis that the metabolic process of detoxification mediated by cytochromes P450 contributes to the decreased deltamethrin susceptibility observed in the resistant strain of T. infestans.
Subject(s)
Chagas Disease , Insecticides , Pyrethrins , Triatoma , Animals , Insecticides/pharmacology , RNA Interference , Pyrethrins/pharmacology , Chagas Disease/genetics , Nitriles/pharmacology , Insecticide Resistance/genetics , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , Cytochrome P-450 Enzyme System/pharmacologyABSTRACT
Pyrethroid resistance has been detected in Triatoma infestans, which in part has been attributed to increased oxidative metabolism of the insecticide by cytochrome P450s. Nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome P450 reductase (CPR) catalyzes electron transfer from NADPH to all known cytochrome P450s. In this study, the expression of the CPR gene at transcriptional level was determined in different tissues and two life stages. The expression patterns showed differences in the tissues and stages studied, suggesting differential metabolic requirements. On the other hand, to investigate the presence of rhythms in the expression of genes related with insecticide resistance, we explored the daily expression profile of the CPR gene and a P450 gene (CYP4EM7) in fat body from adults of T. infestans under different dark/light regimes. The results suggest that CPR gene expression is under endogenous clock regulation and show a rhythmic profile in the expression of the CYP4EM7 gene.
Subject(s)
Chagas Disease/transmission , Circadian Clocks/physiology , Insect Vectors/genetics , Insecticide Resistance/genetics , Triatoma/genetics , Animals , Gene Expression Regulation/physiology , Insect Proteins/genetics , Insect Proteins/metabolism , Insect Vectors/drug effects , Insecticides/pharmacology , NADPH-Ferrihemoprotein Reductase/genetics , Photoperiod , Pyrethrins/pharmacology , RNA, Messenger/genetics , RNA, Messenger/metabolism , Triatoma/drug effectsABSTRACT
Pyrethroid resistance has been detected in Triatoma infestans (Hemiptera: Reduviidae), which was atributed to target site insensitivity and increased oxidative metabolism of the insecticide by cytochrome P450s. Nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome P450 reductase (CPR) plays an essential role in transferring electrons from NADPH to the P450-substrate complex. In this study, the full length CPR cDNA of T. infestans was isolated and gene expression was determined by quantitative polymerase chain reaction. The open reading frame is 2,046 bp long, encoding a protein of 682 amino acids. Amino acid sequence analysis indicates that the T. infestans CPR and the putative Rhodnius prolixus and Triatoma dimidiata CPRs present conserved ligand-binding domains. Congruent with a previous study of our laboratory, in which the expression of three cytochrome P450 genes (CYP4EM7, CYP3085B1, and CYP3092A6 genes) was induced by deltamethrin, the levels of T. infestans CPR mRNA were upregulated in the fat body of fifth instar nymphs after topical application of deltamethrin. Besides, as it was observed in the CYP4EM7 gene, it was detected overexpression of the CPR gene in the most resistant strain of T. infestans included in the study. These results suggest that CPR plays an essential role in P450-mediated resistance of T. infestans to insecticides.
