Functional Analysis Of The Exocytosis Associated Gene MoSec4 In Magnaporthe Oryzae

Including endocytosis and exocytosis pathways,macromolecular transportation is a specific protein transport in all eukaryotic cells.Act as transporters,Rab GTPases play a significant role in regulating the vesicular formation and transport.Sec4 is one of the Rab GTPases in yeast,in tethering the secretory vesicles from Golgi complex to plasma membrane,prior to vesicles fusion then let the proteins outside.During the plant-pathogen interaction,to successfully infect plant,fungi must secrete effector proteins into host tissues to support its colonization and these effectors may play a vital role in plant pathogenesis.It is important to analysis of the yeast sec4 homologue gene in Magnapoythe oryzae.In this study,we analyzed the function of MoSec4 in the growth,development and pathogenicity of Magnapoythe oryzae via biochemical and molecular biological,cell biological and plant pathological methods.The results showed that disruption of MoSec4 lead to defects in vegetative growth and conidial morphology,the conidial were elongated,and became more sensitive to the cell wall stress chemicals like CR,SDS,H2O2 and so on.In addition,MoSec4 was required for full virulence on compatible rice variety for its role in appressorium turgor establishment and the following colonization.Moreover,we demonstrated that loss of MoSec4 gene made the fungus more susceptible to ER stress and reduced the secretion of extracellular hydrolases as fructosidase,amylolytic enzyme,CMCase and laccase.MoSec4 deletion mutants were defective in the induction of the Pid3,Pi9 and Pib resistance gene-mediated hypersensitive response,while rice plants were infected by MoSec4 deletion mutants for 48h to 72h.ROS accumulation in plant cell was weak,defense-related gene OsPRla,OsPAL,OsPBZl were transcribed at a higher level in the plants.The cytoplasmic effector AvrPizt-mcherry and apoplastic effector BAS4-GFP were transferred into MoSec4 deletion mutant respectively.The results showed that no BICs(biotrophic interfacial complex)were observed in infection hyphal during ?MoSec4-AvrPizt-mcherry strain infecting plant and a little fluorescence signal could be obseved around the hyphal membrane,but little accumulated inside the hyphal in ?MoSec4-BAS4-GFP infecting plant.These results clearly showed that,as a key component of exocyst pathway,MoSec4 was critical for the secretion of cytoplasmic effector AvrPiz-t and apoplastic effector BAS4.Besides,the MoSec4 downstream gene Spa2 was also affected by loss of MoSec4,The Spa2 subcellular localization,signal could not be observed in the hypal and germinal tube tip.In conclusion,MoSec4 is one of the important proteins involved in the secretion pathway in Magnapoythe oryzae,acted as a key part in regulating the intracellular proteins transport like enzymes and effectors that necessary for fungal growth,development and pathogenesis.MoSec4 also mediated PTI and ETI reactions.It is valuable for further understanding the secretion and pathogenesis mechanism in Magnapoythe oryzae.