Effect Of Surface Hydrophobin Of Spores Of Entomopathogenic Fungi On Host Immune Response

It is generally believed that insects lack of acquired immune system,while insects form a complex innate immune system during their long evolution history.Therefore,insects will activate their innate immune system to resist when invaded by foreign pathogenic microorganisms.During the interaction between insect and pathogenic fungi,hydrophobins on the spores are very important for the pathogenic fungi to enter the host insect.Recent research has found that humoral immune response occurs before the fungal spores germinate after attached to the insect body wall,indicating that the host insect has a rapid immune response to the fungal spores.Hydrophobins are the outermost layer on the surface of fungal spores and may play a role in host immune response.A hydrophobin of richoderma asperellum can promotes the salicylic acid and jasmonic acid genes up-regulated expression in poplar and reduce the resistence to fungi.The removal of hydrophobin from spores of Aspergillus fumigatus can activate host immune response,so its role is considered to protect pathogenic fungi from host immune response.However,the role of hydrophobin on the spores of entomogenous fungi in host immune response has not been reported.Locusta migratoria manilensis is an important pest of agriculture.Metarhizium acridum,a specific pathogenic fungus to L.migratory,has been widely used in locust control.L.migratory and M.acridum is an ideal model for studying the co-evolution of insects and pathogenic fungi.In order to elucidate the role of hydrophobins on the spore surface of pathogenic fungi on different host in the early immune response of insects.In this study,the specific strain M.acridum CQMa102 and the broad-spectrum M.anisopliae strain CQMa421 and B.basiana strain ZJU435 were used as materials to extract the hydrophobins on the surface,respectively,and test the immune response of the L.migratory,Spodoptera frugiperda and Galleria mellonella to hydrophobins.Further analyzed and confirmed the role of hydrophobins of spores in early innate immune response of host.Compared with the control groups,the resistance of L.migratory to M.acridum or M.anisopliae was significantly improved after topical or injection of Mac HYD3.There was no effect on resistance of Spodoptera frugiperda and Galleria mellonella against the infection after topical application with Mac HYD3 from M.acridum.And significantly more nodules were formed in the inner body walls of locust dorsal at 12-h after injection Mac HYD3 and inoculation of M.acridum compared with untreated with Mac HYD3.The cellular and humoral immune responses of L.migratory were activated 1 hour after the spores of M.acridum were added to the body surface of the fifth instar locust,indicating that M.acridum spores could rapidly activate the immune response of locusts.In this study,the cellular and humoral immune responses of L.migratory were activated when topical application with Mac HYD3,the hemocytes were significantly decreased with higher phagocyte rate,the Toll-pathway genes in fat body were up-regulated,and PO activity in hemolymph was increased compared to control groups.r Mac HYD3 decreased the number of hemocytes and improved PO activity in hemolymph.while there was no significant changes in the number of hemocytes and the activity of peroxidase after topical application with hydrophobins from M.anisopliae or B.bassiana.The main conclusions are as follows:1 The number of hemocytes decreased rapidly with a higher phagocytes rate in hemolymph,the activity of phenol oxidase in hemolymph increased,and the expression level of immune-related genes in locust fat body was up-regulated when L.Migratory topical application with M.acridum;2 The number of hemocytes decreased rapidly with a higher phagocytes rate in hemolymph,the activity of phenol oxidase in hemolymph increased,and the expression level of immune-related genes in locust fat body was up-regulated when L.Migratory topical application with Mac HYD3,while hydrophobins extracted from M.anisopliae and B.bassiana had no effect on L.Migratory;3 Mac HYD3 of M.acridum improved the resisance of locust to M.acridum or M.anisopliae,but had no effects on the fungal resistance of other insects including S.frugiperda and G.mellonella when Mac HYD3 was topical application on the cuticle of insects;4 L.Migratory with significantly more nodules in the inner body walls of dorsal at12-h after injection Mac HYD3 and inoculation of M.acridum compared with untreated with Mac HYD3.