Mechanisms Of Chitin Synthesis On Pathogenesis In Metarhizium Acridum

Metarhizium acridum of entomopathogenic fungus was widely studied and it is necessary to elucidate the molecular mechanism of infection.Chitin is an important component of the fungal cell wall and essential for life and virulence.Chitin is synthesized by chitin synthase.However,systematic characterization of virulence mechanism by chitin synthase genes has not yet been reported in entomopathogenic fungi.The main results in this article are as follows:1.MaChsIII,MaChsV and MaChsVII genes are important for virulence.MaChsI,MaChsII,MaChsIV and MaChsVI are not essential for virulence.However,MaChsIII and MaChsV mutants exhibited reduced virulence by topical inoculation.Interestingly,disruption of MaChsV increased fungal virulence by hemocoel injection.Unlike the other Machs mutants,the MaChsVII mutant was non-pathogenic by topical inoculation and drasticly reduced in virulence by intrahaemocoel injection.2.?MaChsIII,?MaChsV,?MaChsVII have defects in the attachment of insect surface.The conidia surface hydrophobicity of MaChsIII,MaChsV and MaChsVII mutants were decreased and found that the conidia of three mutants can not disperse in paraffin oil which was used for preparation of spore suspension.3.?MaChsIII,?MaChsV,?MaChsVII have defects in the penetration of insect surface.The conidia germination of ?MaChsV accelerated while ?MaChsIII and ?MaChsVII delaied on locust hind wings.Those date showed that MaChsIII,MaChsV and MaChsVII mutants have defects in appressorium development on locust wings compared to WT.For the MaChsIII,MaChsV and MaChsVII mutants ~51 %,~63 % and ~15% of germinated conidia differentiated into appressoria,which were significantly lower than the rate of WT(~72 %).The appressorium of three mutants also displayed a characteristic phenotype compared with WT.4.The locusts enhanced immune response to ?MaChsIII,?MaChsV,?MaChsVII mutants.5.The MaChsIII,MaChsV and MaChVII are contribute to the cell wall interity of M.acridum and cell wall become fragile after inactivation of three genes.6.Cell wall components of M.Acridumm affected by the Chitin Synthase family isoforms.The MaChsI,MaChsII and MaChsIV mutants did not have significantly changed in cell wall composition,while drastic altered were observed in other mutants.Chitin levels were reduced by 37% in MaChsVI mutant compared with WT,which differed significantly.The chitin content and ?-1,3-glucans in MaChsV and MaChsVII mutants cell walls were significantly higher than that of the wild-type cells.The mannoprotein content was reduced approximately 10% in the MaChsV mutant but increased approximately 20% in the MaChsIII mutant.In this study,the MaChsIII,MaChsV and MaChsVII mutants had significant defects in virulence.First,the MaChsIII,MaChsV and MaChsVII mutants have defects in the formation of appressorium,which regard as one of most important steps for infection.Second,The locusts enhanced immune response to ?MaChsIII,?MaChsV,?MaChsVII mutants.Third,deletion of MaChsIII,MaChsV and MaChsVII lead to the cell wall of M.acridumm become fragile,once article report that weakened cell wall leads to reduced virulence.