The Role Of TRE1 And CHS1 Genes In Mosquito Resistance

As a class of important medical insects,mosquitoes spread a variety of diseases,such as malaria,dengue fever,yellow fever,West nile feverand encephalitis B.The main strategy of mosquito-borne diseases control is to cut off the transmission route.And the chemical controlhas always been used as the main strategy of mosquito control because of its fast,efficient and economical convenience.With the extensive use of insecticides,mosquito resistance showeda sharp increase in growth rate.Therefore,the development andregulation mechanism of mosquitoinsecticide resistance have become the focus of research.Insect epidermis plays a vital role in the formation of insecticide resistance.At present,the research on the resistance of insect epidermis is mainly focused on the epidermal protein,and the role of chitin synthesis enzymes in insecticide resistance has not been reported,and further research is needed.Using high-throughput sequencing technology,our previous study analyzed the whole genome expression profile of susceptible and resistant strains of Culex pipiens pollens.In those differentially expressed genes,trehalase and chitin synthase genes were upregulated in resistant strain.In this study,we first verified the differences in the expression of trehalase and chitin synthase in susceptible and resistant strainswith RTqPCR.Subsequently,we verified the content of chitin in susceptible and resistant strains using chitin extraction and Morgan-Elson analysis.Last,the relationship between trehalase and chitin synthase genes and deltamenthrin resistance was identified by microinjecting dsRNA.The resultsshowed that trehalase gene and chitin synthase gene were up-regulated 1.65-fold and 1.74-fold in resistant strain than in the susceptible strain(P<0.05).And chitin extraction and Morgan-Elson analysis confirmed thatthe chitin content was 1.4-fold in the resistant strain than in the susceptible strain(P<0.05).The dsRNAof the trehalase gene was injected into the mosquito,and RTqPCR and chitin analysis results showed that the dsTREl injected group showed a reduction of 46%in mRNA level and a reduction of 14%in chitin contents compared to the control group(P<0.05).And the results of CDC bottle showed that the mortality of dsTRE1 injection group was higher than that of control group(P<0.05),suggesting TRE1 was related to deltamenthrin resistance.Similarly,the dSCHS1 injected group showed a reduction of 49%in mRNA level and a reduction of 19.5%in chitin contents compared to the control group(P<0.05).CDC bottle bioassay showed that dsCHS1-injected group was less resistant to deltamethrin compared with the control groups(P<0.05),suggesting CHS1 was related to deltamenthrin resistance.In this paper,we found that the mRNA level of CHS1 gene decreased 24%after dsTRE1 injection(P<0.05),while the expression of TRE1 gene did not change after dsCHS1 injection.This result suggestedthat the change of the upstream gene(trehalase gene)in the chitin synthesis pathway affected the expression of the downstream gene(chitin synthase gene),which affected the formation of mosquito resistance.Taken together,our results suggest that TRE1 and CHS1 genes are involved in the formation of insecticide resistance,which improves a scientific basis for further elucidating the molecular mechanism of insecticide resistance,and provides a new clue for the comprehensive management of mosquitoes.