Mechanism Of Resistance To Nitenpyram Mediated By Symbionts In Nilaparvata Lugens

Insecticide resistance is broadly recognized as an ecological rebound phenomenon resulting from insecticide use and is a challenging problem facing integrated pest management.It has been reported that symbionts in insects mediated insecticide resistance.Nilaparvata lugens,a major threat to rice production,has developed different degrees of resistance to 33 kinds of insecticide compounds.It is necessary to overcome the resistance of N.lugens to insecticides.In the present study,the mechanism of symbionts-mediated resistance to nitenpyram of N.lugens is explored.The main findings are as following:1.The comparison of microbiome based on amplicon sequencing of nitenpyramsusceptible and nitenpyram-resistant populations.Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes were found to be the main bacteria of N.lugens.Among these,the abundance of Actinobacteria and Bacteroidetes in the resistant population was significantly higher than that of the susceptible one,and the bacteria of the susceptible population mainly belong to Proteobacteria.In addition,evenness and species number of the microbial community in the resistant population were significantly higher than the susceptible one,and significant differences in microbial community structure were observed,suggesting that an elevated microbiome alpha diversity and an altered microbial community structure were associated with insecticide screening in N.lugens.2.Rice dipping and topical application method were applied to assess the susceptibility of N.lugens to nitenpyram after the treatment of mixed antibiotics.The results showed that the susceptibility of the resistant population treated with mixed antibiotics to nitenpyram was significantly increased,but it was not observed in susceptible populations.After measurement of detoxification enzymes activity,it was found that the activity of esterase in the susceptible population was significantly decreased after treatment with mixed antibiotics,but there was no significant difference in expression of the enzyme genes related to nitenpyram resistance,which is coordinated with the results of biological activity measurements.In the resistant population,the activity of cytochrome P450 was decreased after treatment of mixed antibiotics,and the expression of the enzyme genes involved in resistance to nitenpyram decreased significantly,including Car E17,Car E19,CYP418A1,CYP4C76,CYP4C77,CYP4CE1,CYP6ER1,CYP6FL3 and CYP6FL4.3.Mixed rearing of newly-hatched nymphs from the susceptible population and high-instar nymphs from the resistant population resulted in a symbiotic structure in the susceptible population similar to that of the resistant population.The bioassay results of rice dipping and topical application method showed that resistance of the susceptible population to nitenpyram significantly increased after rearing of combination of the resistant population.Detoxification enzymes activity was measured,and the activity of cytochrome P450 in the susceptible population with mixed rearing was significantly increased,and expression of CYP4CE1,CYP6ER1 and CYP6FL3 was significantly upregulated.However,the resistance of the susceptible population with mixed rearing to nitenpyram was recovered after the treatment of mixed antibiotics.These findings suggest that symbionts mediate resistance to nitenpyram of N.lugens by upregulating the expression of detoxification enzymes genes.