Functional Analysis Of A Putative GEF MoDock1 And Its Partner MoElmo1 In Magnaporthe Oryzae

Conidial adhesion and appressorium formation of Magnaporthe oryzae on the rice surface are important early events in the infection process.Firm adhesion of fungal plant pathogens to their hosts is critical at several stages in the host-pathogen interaction.Here we show that MoDock1 and MoElmo1,proteins with homology to Dock180/Elmo1 complex,which form an evolutionarily conserved bibasil guanine nucleotide exchange factor controlling Rac GTPase signaling during cell migration,phagocytosis,and myoblast fusion,are necessary for conidial adhesion and accurate appressorium differentiation.Homologous recombination resulting in targeted deletion of MoDockl or MoElmol have no effect on vegetative growth,conidiation,cell wall integrity and sexual reproduction,but exhibited a reduced ability to infect susceptible rice leaves.In the current work,the MoELMO1 and MoDOCK1 deletion mutants exhibited a reduced attachment and they were delayed in appressorium formation.The germ tube were long and straight,appressoria formed by MoElmo1 and MoDock1 deletion mutants were fully melanized but smaller than wild-type and a part of it were defective in penetrating plant cells.Besides,septum appeared in the germ tube of Modock1 and Moelmo1 4h after incubate on the hydrophobic surface,while the wild-type ?ku80 form septum at the convergence of mature appressorium and germ tube,these may indicate MoDockl and MoElmol are involved in septum formation during appressorium development.The presence of cAMP and IBMX restored the delayed appressorium formation of the mutants to the level of wild-type,they also restored the abnormal germ tube and disordered septation.This may suggest that MoDock1 and MoElmo1 are involved in cAMP signalling of M.oryzae.Spray assay of MoDock1 and MoElmo1 deletion mutants indicated they are reduced in virulence,?Modock1 and ?Moelmo1 have less lesion number than?ku80.