Sensitivity Of Symbionts In Bemisia Tabaci MED Cryptospecies To Sulfoxaflor

Chemical control is currently the most widely used and effective method of pest control in agricultural production,but it has also caused a series of problems with increased insect resistance,therefore,in agricultural production,we urgently need to find ways to address insect resistance.Many studies have demonstrated that symbionts may be related to insect drug resistance,we hope to identify the key factors affecting the drug resistance of B.tabaci from the perspective of symbionts,and be able to use symbionts to play a role in the field control of B.tabaci,therefore,this study focused on the species composition,diversity,abundance,and interrelationship of the symbionts of Bemisia tabaci,which are resistant population to sulfoxaflor（BR）and susceptible population（BS）,and screened out the antibiotics that inhibit their symbionts and their dosage,the susceptibility of resistant strains to four pesticides and the activities of four detoxification metabolic enzymes before and after bacteriostasis were measured,the differentially expressed genes of different strains were analyzed from the transcriptomic level,the research results are helpful in revealing the relationship between symbionts and insect resistance,providing a reference basis for the interaction between symbionts and host insects,and providing new ideas for using symbionts to control field pests.The main research results are as follows:1.Comparative analysis of microbial diversity among susceptible and resistant strains of sulfoxaflor in B.tabaci was conducted using amplified sequence technology,it was found that the symbionts carried by the two strains of B.tabaci included the primary bacteria Portiera,the secondary bacteria Rickettsia,Hamiltonella,Hemipteriphilus,Fritsche,Geomicrobium,Nesterenkonia and Bacillus;the contents of Portiera,Rickettsia,Hamiltonella and Hemipteriphilus in resistant population were significantly higher than those in susceptible population,and the content of Rickettsia was the highest;the species richness（Ace index）and species diversity（shannon index）of microorganisms in resistant population are higher than those in susceptible population,microbial species are mainly concentrated in the three phylum of Proteobacteria,Firmicutes,and Actinobacteriota,with Proteobacteria having the highest abundance;the correlation between different species is strong and complex,while the correlation between symbionts in susceptible populations is weak and simple.2.The symbionts in B.tabaci were removed by feeding rifampicin,ampicillin,tetracycline hydrochloride and kanamycin sulfate,and the bacterial load of symbionts in B.tabaci was detected by fluorescence quantitative PCR.The results showed that rifampicin had the best removal effect on the symbionts of B.tabaci.With the increase of antibiotic treatment concentration,the removal efficiency of symbionts in B.tabaci increased.It was determined that the optimal treatment concentration and treatment time for rifampicin were 100 mg/L and 48 h,respectively.3.The two strains were treated with selected antibiotics,and the diversity of microorganisms in the two strains was analyzed.The results showed that after antibiotic treatment,the microbial richness and diversity in the resistant and susceptible strains were significantly decreased,and the decline of the resistant strain was more significant;In the susceptible strain,the contents of Bacillus and Geomicrobium did not decrease significantly,but the contents of the other six kinds of bacteria decreased significantly,while the contents of eight kinds of bacteria in the resistant population decreased significantly,especially Portiera,Rickettsia and Hamiltonella,decreased by 80%,85%,and 81%respectively.The results of PCo A analysis showed that the species composition of the two strains were obviously different before and after antibiotic treatment.4.The sensitivity of the resistant and susceptible strains treated with rifampicin to the sublethal concentration LC₃₀of four drugs,namely,sulfoxaflor,imidacloprid,thiamethoxam and cyantraniliprole,was determined by the agar moisturizing method.The results showed that the antibiotic treated resistant strain of B.tabaci significantly increased their sensitivity to all four insecticides,while the treated susceptible strain only significantly increased their sensitivity to sulfoxaflor and cyantraniliprole,with no significant changes in the sensitivity to thiamethoxam and imidacloprid.The activities of glutathione S-transferase（GST）,carboxylesterase（Car E）,acetylcholinesterase（Ach E）and cytochrome oxidase（P450）in the resistant and susceptible strains were further measured before and after antibiotic treatment,the results showed that the activities of Ach E and Car E in the resistant strain did not change significantly compared with the susceptible strain,while the activities of GST and P450 increased significantly;after antibiotic treatment,the activities of Ach E,Car E and GST had no significant change,but the activity of P450 decreased significantly.it is speculated that the factors mediating the resistance of B.tabaci to sulfoxaflor may be related to the change of P450 activity.5.After feeding the resistant population B.tabaci treated with cotton and nutrient solution,It was found that the content of symbionts in B.tabaci fed with cotton and nutrient solution did not recover within 48 hours,which may be related to the persistence of rifampicin in B.tabaci.the symbionts in B.tabaci fed with cotton did not recover at 72hours and 96 hours,however,the B.tabaci fed with nutrient solution recovered obviously at 72 hours and 96 hours.It was found that the sensitivity of B.tabaci to sulfoxaflor and cyantraniliprole decreased after the recovery of the symbionts fed with the nutrient solution,while the sensitivity of B.tabaci to sulfoxaflor and cyantraniliprole did not recover after the feeding of cotton,at the same time,the sensitivity of B.abaci to sulfoxaflor and cyantraniliprole did not change significantly,which indicated that the increase of resistant symbionts gave B.abaci drug resistance.6.Transcriptome analysis of the resistant and susceptible strains before and after treatment with rifampicin showed that the differentially expressed genes in the resistant and susceptible strains were mainly concentrated in regulating detoxification metabolism,energy metabolism,and immune system pathways.Compared with the susceptible strain,most of these differentially expressed genes related to detoxification metabolism in the resistant strain were up-regulated;after antibiotic treatment,most of these differentially expressed genes in the susceptible strain and the resistant strain were down-regulated.The key genes were UDP-glucuronosyltransferase UGT2B18,UGT2B7 and P450 cytochrome oxidase CYP6D4,CYP6A14,CYP6K1,CYP6A20,at the same time,these genes were significantly expressed with the increase of the content of symbionts,and significantly down-regulated with antibiotic treatment,it is suggested that the symbionts of B.tabaci may regulate the expression of the detoxification metabolic enzyme gene of the host,and then participate in the resistance of B.tabaci to sulfoxaflor.The above results indicate that the abundance,diversity,and correlation of microorganisms in the body of B.tabaci are all related to insect drug resistance.Antibiotic treatment of B.tabaci can significantly increase its sensitivity to pesticides,by increasing the content of symbionts related to host resistance（such as Portiera,Rickettsia,Hamiltonella,and other symbionts of the Proteobacteria）,significant expression of detoxification and metabolic enzyme genes dominated by P450 and UGT can be regulated to improve the drug resistance of B.tabaci,confirming that symbionts can affect the drug resistance of B.tabaci,which is of great significance for the application of symbionts to control of B.tabaci.