Functional Analysis Of Adenylate-forming Reductase In Metarhizium Acridum

BACKGROUND: Entomopathogenic fungi have been developed as environmentally friendly alternatives to chemical pesticides to controlling agricultural pests.However,poor efficacy has blocked their large-scale application.The genetic manipulation was an important way to enhancing fungal virulence against crop pests on the basis of the pathogenic mechanisms.Previous study in our laboratory showed that Metarhizium acridum Adenylate-forming reductase(MaAfr)might negatively regulate the pathogenicity of strains against Locusta migratoria manilensis.Exploring the role of MaAfr in infection will further reveal the pathogenic mechanism,and then mine new virulence candidate for mycoinsecticides.RESULTS: Expression of MaAfr was induced on wings of L.migratoria manilensis.In the topical inoculation test,the lack of MaAfr increased the virulence(median lethal time,LT50)of M.acridum against L.migratoria anilensis with a 25.2% reduction than the wild type strains(WT).Consistently,DNA of MaAfr-disruption transformant(?MaAfr)in hemolymph was detected 1 day earlier than WT.However there is no difference for the virulence and concentration in the injection test.Furthermore,the lack of MaAfr caused the conidia germinating earlier and more the appressoria,in which the expression of Pr1 and turgor pressure was higher,on the wings.Similarly,more lipids and glycerol leading to turgor pressure were observed.But difference was not checked in the expression of immune genes in Toll pathway and activity of the polyphenol oxidase of locusts infected by ?MaAfr and WT.In addition,a further significant finding was that the conidiation on dead locusts infected ?MaAfr strain was blocked.CONCLUSION: Lack of MaAfr increased the virulence of M.acridum against L.migratoria manilensis by promoting the insect cuticle invasion without changing the immune response of locusts to M.acridum,and blocked the conidia formation in the carcasses.This study showed that MaAfr was a new pathogenic virulence gene,and can be used as a safe resource for genetically enhancing entomopathogenic fungi.