Opsin, Involved In Mosquito Resistance To Deltamethrin

Frequent and wide application of insecticides has resulted in the emergence andspread of insecticide resistance in insect populations. Understanding the mechanismsof insecticide resistance is critical to vector control.A new opsin gene（NCBI/GenBank JQ354934，2012） was cloned from Aedesalbopictus C6/36cells. An open reading frame (ORF) of1122bp was found to encodea putative373amino acids protein that exhibits95%,91%and87%identity withopsins from Ae. aegypti, Anopheles gambiae and Culex pipiens pallens respectively.Over-expression of Ae. albopictus’s opsin gene by transfection increasedmosquito cell viabilities to deltamethrin at the concentrations of101.5μg/mL，102.0μg/mLå'Œ102.5μg/mL, and knock down of opsin by siRNA decreased mosquitocell viabilities to deltamethrin at the same three concertrations(p<0.05). The resultindicates that opsin gene is related to deltamethrin resistance.To further investigate the resistance mechanism related to opsin, thetranscriptional levels of Arrestin, Gqαand CYP6A1were detected by real-timequantitative PCR in mosqito cells with transfection and siRNA of opsin. Theactivities of PLC were also assayed. Over-expression of opsin by transfectionincreased the activity of PLC and the transcriptional levels of Gqα, CYP6A1but notArrestin. Knock down of Opsin by siRNA decreased the activity of PLC and thetranscriptional mRNA levels of Gqα, CYP6A1but not Arrestin. Interestingly,over-expression of Arrestin increased cell viability and mRNA levels of Opsin andCYP6A1in mosqito cells. On the other hand, knok down of Arrestin by siRNAdecreased cell viability and mRNA levels of Opsin and CYP6A1in C6/36cells. It isindicated that Opsin, which may be affected by Arrestin, may regulate expressionlevel of Gqαand activity of PLC, thus affect expression of CYP6A1, and finally is involved in insecticide resistance.The high mRNA levels of opsin, Arrestin, GqαandPLC between resistant and susceptible Culex mosquitoes further suggest that Opsin,together with other related genes, such as Arrestin, Gqα, PLC in GPCR signaltransportation, may be involved in a new mechanism in deltamethrin resistance.The mRNA levels of Opsin gene from deltamethrin-resistant and–susceptible Cx.pipiens pallens in different regions, from5strains selected with differentdeltamethrin-resistant levels by generations and from strains resistant to cypermethrin,propoxur and DDVP were detected by real-time quantitative PCR. The results shownup-regulated mRNA levels of Opsin gene in resistant mosquitoes compared to that ofsusceptible ones. Western blotting implicated up-expression levels of Opsin betweenresistant and susceptible mosquitoes in two regions. These results indicate that Opsinmight be used as a marker in insecticide-resistance detection.