Studies On Pyrethroid Insecticides Resistance Genes In Mosquitoes

Culex pipiens quinquefasciatus belongs to China's major home dwelling mosquito species,which is an important vector for filariasis and encephalitis;Aedes aegypti is widely distributed in Asia,Africa,the Pacific islands and the South America,and it is also a significant vector of dengue fever and dengue hemorrhagic fever.At present,chemical control is still one of the successful approaches for comprehensive prevention and control of mosquitoes.The widespread use of chemical pesticides has led to the occurrence and development of insecticide resistance.Therefore,there is an urgent need to study the mosquito resistance to insecticides in-depth.In this study,we studied Cx.pipiens quinquefasciatus possible new genes correlated with pyrethroid resistance,by using gene expression analysis.Moreover,we analyzed Ae.aegypti sodium channel gene mutations to study the correlation between mutation frequency and resistance.Our aims are to understand mechanisms of mosquito resistance against pyrethroid insecticides and to provide insight into insect resistance management.The main results of this study are as follows:1.Test results of Cx.pipiens quinquefasciatus and Ae.aegypti resistance levelBy using mosquito insecticides resistance bioassay,we got LC50 values of deltamethrin to Cx.pipiens quinquefasciatus larvae of F21,F23,F24,F26,F27 and F30,which are between 25.25-87.83 times of those to the resistant mosquitoes collected from Sanya.To compare with the susceptible strain of Ae.aegypti,LC50 values of deltamethrin,permethrin,and resmethrin to six resistant strains of Ae.aegypti are between 1-22.27,2.1-182.62,and 1.56-1486.92 times,respectively.2.The relationship between the 7 gene expressions and deltamethrin resistance of Cx.pipiens quinquefasciatusBy utilizing quantitative real-time PCR method,we identified that gene expressions of OBPjj7a,OBP28,E2 were positively correlated with deltamethrin resistance(R2=0.836,P=0.011;R2=0.788,P=0.018;R2=0.850,P= 0.009,respectively)of Cx.pipiens quinquefasciatus.Expressions of other 4 genes,H/ACA,S19,SAR2 and PGRP did not show any correlation with deltamethrin resistance.3?Ae.aegypti sodium channel gene mutationsBy applying molecular cloning techniques,we found three mutation sites of sodium channel gene of Ae.aegypti,they are I1011M:ATA to ATG;V10161:GTA toATA and F1534C:TTC to TGC.4.Calculation of Ae.aegypti sodium channel gene mutation frequencyThrough gene sequencing,it was indicated that mutation frequencies of the three sodium channel mutation sites were I1011M:0%-6.67%,V1016I:18.33%-48.33%,and F1534C:19.35%-85.94%.5.Correlation between the Ae.aegypti sodium channel gene mutation frequency and resistanceCorrelation analysis showed that the gene mutation frequencies of sodium channel on V1016I and F1534C positively correlated;11011M,V1016I and F1534C mutation frequencies respectively and deltamethrin,permethrin and resmethrin resistances positively correlated.The resistant mosquito showed cross-resistance to deltamethrin,permethrin and resmethrin.In summary,this study reported that three new genes of Cx.Pipiens quinquefasciatus might be involved in deltamethrin resistance;we found that sodium channel genes have three mutations sites,11011M,V10161 and F1534C respectively related to deltamethrin,permethrin and resmethrin resistances of Ae.aegypti.It will provide a theoretical basis for the control of mosquito resistance,and insight into resistance detection.