The Action Mode Of Destruxin Inhibiting Immunity In Aphis Citricolavander

Aphids are one of the important agricultural pests.Among them,the damage of apple yellow aphids(Aphis citricolavander)had caused great losses to the apple production industry.However,the main control of Aphis citricolavander is currently based on chemical pesticides.The heavy use of chemical pesticides has caused serious "3R" problems and affected apple quality and output.Therefore,the development of environmentally pesticides is imminent.Destruxin is a secondary metabolite secreted by the entomogenous fungus Metarhizium anisopliae and has a broad spectrum of insecticidal activity.Compared with the Bt toxic protein that has dominated the market in recent years,destruxin is less prone to drug resistance and has a highly effective insecticidal activity.As a brand-new green pesticide with a mechanism of action,destruxin has a better prospect in agricultural pest control.However,due to the current high cost of producing destructive hormones,it is difficult to apply them to agricultural production practices,so research on its mechanism of action is helpful for the development and application of new pesticides.Studies have shown that destruxin affects the innate immune system of insects,but the effect mechanism is not clear.In this paper,Aphis citricolavander is taken as the research object,and the transcriptome database of Aphis citricolavander before and after destruxin treatment is determined to screen the potential genes of scavenger receptor scavenger receptor class B(SR-B).The molecular biological characteristics of SR-B were analyzed;the function of SR-B in the innate immunity of Aphis citricolavander was studied by expressing the recombinant protein SR-B and using of RNAi technology;elucidating the mechanism of action of destruxin on the immune response mediated by Aphis citricolavander.1.The transcriptome sequencing technology was used to compare the differentially expressed genes of Aphis citricolavander after destruxin treatment 6 hours.The results showed that 735 differentially expressed genes were identified after 6 hours of destruxin treatment,of which 305 genes were up-regulated and 430 genes were down-regulated.The scavenger receptors class B of aphid immune-related genes regulated by destruxin were screened out.2.Cloning the scavenger receptor class B(SR-B)of Aphis citricolavander is in response to destruxin,and obtained the full-length cDNA,which was successfully uploaded to the GenBank database with accession number MN840488,it contains a typical CD36 domain.The similarity between Aphis citricolavander SR-B and Aphis gossypii SR-B was 93%.RT-qPCR results showed that SR-B was specifically and highly expressed in adults and winged aphids,and the expression level in the abdomen was the highest among different tissues.3.The expression of Aphis citricolavander SR-B increased after 6h induced by the microorganism.Compared with E.coli,the expression of SR-B decreased significantly after 12 h of infection with Metarhizium anisopliae,and the expression of SR-B after the destruxin treatment appeared the trend of increasing first and then decreasing indicates that destruxin inhibits the expression of SR-B in Aphis citricolavander.A prokaryotic expression vector of AcSR-B was constructed,and the immune activity of recombinant protein rAcSR-B was analyzed.The results showed that r AcSR-B had agglutinating activity against both E.coli and Metarhizium anisopliae spores,which indicated that AcSR-B had a recognition function for microorganisms and played an important role in the immune response.4.The technology of RNA interference was applied to Aphis citricolavander by feeding method.After feeding different concentrations of dsAcSR-B to interfere with gene expression,it was found that as the concentration of dsRNA increased,the mortality of Aphis citricolavander gradually increased.Interfering SR-B with dsRNA at a concentration of 500 ng /?l has a significant synergistic effect on the virulence of destruxin.Interfering Aphis citricolavander SR-B also inhibited the activity of phenol oxidase and melanization reaction of aphids.Destruxin also inhibits the activity of phenol oxidase of Aphis citricolavander,and then affects the melanization reaction.In summary,SR-B is a potential target for destruxin,and destruxin inhibits the expression of SR-B,thereby affecting the melanin immune response of Aphis citricolavander.This study reveals the target of Aphis citricolavander innate immunity against destruxin,and further elucidates the mechanism by which destruxin inhibits the immune response of Aphis citricolavander through SR-B.The research provide target genes and new strategies for pest control,it relied on the technology of RNAi based on the action of destructin as a template,which is of great significance to the sustainable development of green agriculture.