| Aphis gossypii Glover is a worldwide agricultural pest,which damages crops mainly by feeding and virus transmission.Due to a variety of factors such as strong reproductive capacity,short growth cycle and alternation of generations,cotton aphid has developed different levels of resistance to a variety of insecticides such as carbamate,pyrethroids,organophosphorus and so on,which has become one of the most difficult agricultural pests to control in the world.Cyantraniliprole is the second generation of ryanodine receptor agent insecticide.It has been used in the prevention and control of cotton aphid because of its unique action target,wide insecticidal spectrum,high efficiency and low toxicity.In this study,the cross-resistance of cotton aphid to other insecticides was determined.The mechanism of resistance of cotton aphid to cyantraniliprole was studied by synergist experiment,transcriptome data analysis and q-PCR.It provides a theoretical basis for prolonging the useful life of cyantraniliprole.The resistant strain has been selected with cyantraniliprole,and the resistance ratio was 15.71-fold.The cross-resistance of cyantraniliprole-resistant strains to other insecticides was determined.It was found that the resistant strain had medium-level cross-resistance to cyfluthrin(20.87-fold)and low-level cross-resistance to alphacypermethrin(9.14-fold),acephate(6.7-fold)and imidacloprid(6.86-fold).However,the resistant strain had no cross-resistance to dinotefuran,methomyl,thiamethoxam,acetamiprid,methidathion,chlorpyrifos,sulfoxaflor,bifenthrin,chlorfenapyr,emamectin benzoate,avermectin,clothianidin,omethoate,esfenvalerate and cyhalothrin.PBO can significantly enhance the toxicity of cyantraniliprole in resistant strain,and the synergic ratio is 2.68-fold.It can also significantly enhance the toxicity of cyfluthrin and esfenvalerate in resistant strain,and the synergic ratio is 11.06-fold and 11.60-fold.It indicates that cytochrome P450 plays a role in the cyantraniliprole resistance.The differentially expressed genes(DEGs)in CYR and SS were identified by high-throughput sequencing.A total of 53195332 and 68132233 reads were obtainedfrom SS and CYR cDNA libraries respectively.Compared with the SS strain,the number of differentially expressed genes in the CYR strain were 2016,with 1600 genes up-regulated and 416 genes down-regulated.There were 1094 genes annotated to GO and these genes were significantly enriched in metabolic processes,cellular process,membrane,membrane part,binding and catalytic activity.There were 961 genes annotated to the KOG database,which were mainly divided into three categories according to their functions: general function prediction only,signal transduction mechanisms and posttranslational modification,protein turnover,chaperones.There were 309 genes annotated to KEGG,the main metabolic pathway is spliceosome,glycolysis/ gluconeogenesis,purine metabolism,pentose,glucuronate interconversions and metabolism of xenobiotics by cytochrome P450.The significantly differentially expressed P450,UGTs,GSTs and ABC genes were screened and named by the naming committee.The names of P450 genes are as follows: CYP380C6,CYP6CY7,CYP6CY21,CYP380C12,CYP6CY12 and CYP4CJ5.Then these differentially expressed genes were verified by fluorescent quantitative PCR,and the results showed that the expression levels of all P450 genes were significantly up-regulated,which was consistent with transcriptome data.This suggests that these P450 genes may be involved in the detoxification and metabolism of cyantraniliprole.The research of cross-resistance provides theoretical guidance for the use of pesticides in the field and extends the useful life of pesticides.The research of up-regulation of P450 genes provides support for the study of resistance mechanism. |
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