Functional Analysis Of Three LXAR Effectors In Magnaporthe Oryzae

Effectors are required for the colonization of pathogens.Magnaporthe oryzae,causing destructive disease of rice,is one of important model organisms in studying interactions between the host and pathogenic fungi.Studying the function of blast effectors could not only improve our understanding of the pathogenic mechnism of fugal pathogens,but also facilitate the management of blat fungus.In oomycet,the RXLR motif plays important role in the transmembrane trafficking of cytoplasmic effectors.Though there are a lot of putative secreted proteins contained the LXAR motif,termed as M.oryzae LXAR-like effectors(MoLLEs).However,the function of these MoLLE proteins and the LXAR motif remain elusive.To explore the fuction of these MoLLE proteins,we previously screen these MoLLE proteins for effectors that could induce cell death or inhibit BAX-induced cell death when transiently expressed in N.benthamiana.We have successfully screened three candidates:MoLLE1,MoLLE2 and MoLLE3.Among them,MoLLE1 without the signal peptide(MoLLE1-NS)can suppress the hypersensitive response(HR)induced by mouse pro-apoptosis protein BAX in N.benthamiana.On the contrary,MoLLE2-NS can induce HR in N.benthamiana,while MoLLE2-FL can suppress the BAX-induced hypersensitive response;MoLLE3-NS can inhibit HR induced by BAX.We further generated the knockout mutants of the ?Mollel and ?Molle3 using the gene-targeted replacement technology.To functionally study these MoLLE candidates,we performed the complementation assay of ? Mollel and ? Molle 3 mutant and generated the MoLLE2-RNAi knock-down mutant.These mutants were used for further study to clarify the possible roles of these MoLLE proteins.When grown on SYM(starch and yeast culture medium),all the three mutants displayed no significant reduced growth rate than that of wild type,including the ?Mollel,?Molle3 mutants and the MoLLE2-RNAi mutants.However,the deletion mutants of MoLLE1 showed cell wall defects.And all the three mutants slightly reduced in conidiation.It is possible that MoLLE genes participate in the process of spore production in rice blast fungus.In addition,the pathogenicity of ?Molle1 and ?Molle3 was attenuated,which suggesting that MoLLE1 and MoLE3 may play important role in infectious process of rice blast.However,further studies are required to illustrate the mechanisms of MoLLEs in conidiation and other physiological processes.