The Avoidance Mechanism Of Fungal Pathogens In The Locusta Migratoria

Locust,which is an important pest all over the world,have a negative impact on our food security.In the last few years,the flood and drought disasters occur alternately and frequently due to the uneven spread of rainfall and the global climate changed,which causes result in the serious damage for the environment.These changes have created favorable conditions for the locust plagues.Chemical insecticides are the most common and effective way to control pests,but they also have a hugely negative impact,which can damage the ecological environment seriously and threaten the survival safety for a lot of animals and even human beings.Entomopathogenic fungi have been developed as promising environmentally friendly mycoinsecticides,but it is a barrier to large-scale production and application due to their slow killing speed.The immune system is important for defensing the pathogens in insects,which is mainly divided into humoral immunity and cellular immunity.The behavioral immunity is less studied,but it may be the most effective defense against the pathogens.Metarhizium acridum and Metarhizium anisopliae can effectively control locusts.In our experiment,found locusts can exhibit the behavioral avoidance of pathogens by dual-choice of locust nymphs in the camber.Antennae is a vital sensory organ in insect.we cutted off the antennae of locusts,found it is essential to avoid entomopathogenic fungi by dual-choice experiments.There are 3109 proteins were identified from the antennal proteome in Locusta.migratoria.It was found that 149 proteins were more abundant in the antennae of male and 111 in the antennae of female.Olfactory related proteins are the most important in the antennae.They can detect the chemical signals in the environment,which are an essential way to maintain life and trigger a series of important behavioral responses.Nine odorant binding proteins(OBPs),twenty-seven chemosensory proteins(CSPs),thirty-one odorant receptors(ORS)and eight ionotropic receptor(IRS)proteins were identified.And two new chemosensory proteins(CSPs)were found in the locust antennal database.Furthermore,we found that 194 differential expression proteins(DEPs)identified between the uninfected and infected males,among which 104 proteins were up-regulated.Comparative analyses of antennal proteomes identified 218 DEPs between the uninfected and infected females,128 of which were highly expressed in the antennae of the infected females.By comparing proteomics and fluorescence quantitative PCR,we found that three CSPs(Lmig CSP1,Lmig CSP20 and Lmig CSP60)and one OBP(Lmig OBP1)were highly expressed in the infected male and female antennae.Then we only found that the 5th instar locust nymphs did not show the behavioral avoidance of pathogenic fungi after si Lmig CSP60 interference,which indicated that Lmig CSP60 played a significant role in the avoidance behavior in locusts.In order to study the effect of the volatile compounds of M.anisopliae on the avoidance behavior in locusts,we discovered that the epoxypropyl methacrylate,methoxyacetyl chloride,dimethyl ether,1-methylindole and benzylcarbil can induce the avoidance behavior in locusts,among which dimethyl ether,1-methylindole and benzylcarbil were more effective.Lmig CSP60 have ability to bind to 1-methylindole across the fluorescence competitive binding experiment.The result is suggested that the chemical compound of 1-methylindole can be transmitted by Lmig CSP60.By RNA interference experiments,found that locusts did not showed avoidance behavior for1-methylindole.The results indicated that 1-methylindole,which identified from M.anisopliae,is an important volatile compound for the perception of pathogens and the behavioral avoidance of pathogens in locusts.In order to find out the possible downstream genes of Lmig CSP60,a total of 12 gustatory receptors(GRs)were identified,but their expression of RNA levels were not significantly increased after inoculated with M.anisopliae.Finally,it was found that the5 th instar locust nymphs did not avoid entomopathogenic fungi after si Lmig OR16 interference,which indicated that Lmig OR16 played an essential role in the behavioral avoidance of pathogens.The project has studied the immune behavior and the mechanism of pathogen perception in L.migratoria.The detailed knowledge of chemosensory in locusts at the molecular level will help understanding the diversity of molecular mechanism of organism as well as designing novel repellents and attractants for pest control.