Sense Of Metarhizium Acridum Cell Wall Polysaccharides By The Host Insect Locusta Migratoria Manilensis

Since fungal cell wall is putative initial sensed by the host immune system. Whatcomponents of fungal cell wall recognized by the host and induce anti-fungal reactionsis crucial to investigate the mechanism. Here we explored the analogues of3primaryfungal cell wall polysaccharides: mannan, β-1,3-glucans and chitin, whether they couldinduce anti-fungal defense like Toll activity in host insect locusta migratoria manilensis（L. migratoria）. We found that laminarin and chitosan could induce Toll in fatbody,and further determined the polysaccharides of laminarin and low molecular chitosaninfiltrated into locust hemolymph by FITC-labeled. High molecular weight chitosan wasfound to bind locust suface protein by chromatography.To further investigate the interaction between host locust and chitosan in hemocytelevel, we applied chitosan specific stain Eosin Y and detected chitosan was the cell wallcomponent of Metarhizium acridum (M. acridum). Then we extracted chitosan andcharacterized and compared to commercial chitosan by Fourier Transform InfraredSpectroscopy (FI-IR), X-ray Diffraction (XRD) and Nuclear Magnitic Resonance(NMR). From these results, M. acridum derived chitosan has higher degree ofdeacetylation (DDA) than commercial chitosan. Next we found host response ofReactive oxygen species (ROS) and phenoloxidase (PO) production by induce of eitherextracted chitosan or commercial chitosan. With Eosin Y we found possible cellcytophagy towards chitosan. Interestingly, co-injection with chitosan and sporessuspension of M. acridum showed improvement of M. acridum virulence. One possibleexplanation for this result maybe the cytophagy towards chitosan leads to the lowdefense towards M. acridum.The main results are as follows:①Laminarin and chitosan in different molecular weight could induce of host Tollactivity of fatbody in L. migratoria during the early stage of M. acridum infection;②Polysaccharides of low molecular weight could infiltrated into locust hemolymph,while polysaccharides of high molecular weight may interact with surface protein oflocust cuticle;③Chitosan was the cell wall component and could be extracted fromemtomopathogenic fungus M. acridum, M. acridum derived chitosan has higher degreeof deacetylation than commercial chitosan; ④Both M. acridum derived and commercial chitosan could induce of host defenseof ROS and PO production in hemolymph of locust significantly;⑤Co-injection of chitosan and spores suspension of M. acridum could significantlyimprove of M. acridum virulence.