| Rice Blast caused by Magnaporthe oryzae is an important fungal disease of crops.The occurrence and epidemic of this disease limit the yield of rice and threaten the global food security.To explore the molecular mechanism of the pathogenicity of M.oryzae and to develop a new control technology on this basis is an important direction for the prevention and control of Rice Blast in the future.The infection process of M.oryzae is precisely regulated by intracellular MAPK signaling pathways.Among them,Mps1 cascades mediate the penetration of appressorium of M.oryzae to the host surface,which is the key step to determine whether the infection is successful or not.At present,there have been a large number of reports about the function of Mps1 pathway,but it is mainly focused on several genes,which is not enough to fully reveal the role of Mps1 signal transduction pathway in the process of infection.Therefore,the identification of new factors related to the Mps1 pathway will expand our understanding of the regulatory mode of this pathway.Suppressor is an important mean to study the relationship between proteins.Fusarium graminearum has a unique advantage in studying the phenomenon and mechanism of suppressors because of its few repetitive sequences and high genome integrity.Therefore,basing on the suppressors of the mgv1(homologous gene of MPS1)deletion mutant in F.graminearum,we identified the survival factor Svf1,and confirmed the genetic interaction between Svf1 and Mgv1.Furthermore,the relationship between Svf1 and Mps1 signaling pathways was studied in M.oryzae.It was found that deletion of Svf1 could partially recover a variety of defects of mps1 mutant,including vegetative growth,conidiation and appressorium penetration.In addition,the recovery of cell wall integrity of mps1 svf1 double mutant compared with mps1 mutant could be found by mycelia lysis and cell wall stress treatment.Further q PCR of cell wall synthesis genes showed that the expression of Mo CHS2,Mo CHS3 and Mo CHS4 in mps1 svf1 double knockout mutant was significantly higher than that in mps1 mutant,even returned to the level of wild type.Since the mycelium development and host penetration of pathogenic fungi are related to the cell wall,we infer that the recovery of mps1 mutant defects depends on the regulation of cell wall integrity by Svf1.It is believed that apoptosis plays an important role in the infection of pathogenic fungi,and the Svf1 in yeast is also related to apoptosis.However,through the detection of the expression of apoptosis-related genes,we did not find the direct evidence of the relation among apoptosis,Svf1 and Mps1 signal pathway.As a survival factor,Svf1 is a new interaction factor in Mps1 signaling pathway.However,the function of M.oryzae Svf1 is not clear.In this study,the phylogeny of Svf1 was analyzed,and it was found that Svf1 was highly conserved in fungi.Through gene knockout and phenotypic observation of the mutant,it was found that the growth rate of the svf1 mutant was attenuate and the mycelium morphology was abnormal,but the conidiation of the mutant was slightly higher than that of the wild type.The results showed that Svf1 positively regulated the vegetative growth of M.oryzae and negatively regulated the development of spores.There were no visible defects in appressorium formation and pathogenicity of svf1 mutants,indicating that the function of Svf1 in the process of infection should be based on the loss of Mps1 signaling pathway.Fluorescence microscopic observation showed that Svf1 protein was inhomogeneously distributed in the whole cell.To further improve the interaction regulatory network of Svf1,we identified Svf1 interaction proteins by Pull Down-MS and found several proteins related to intracellular signal transduction and apoptosis.The analysis of the function of these proteins is helpful to further reveal the regulation and action mode of Svf1 and lay an important foundation for elucidating the infection mechanism of M.oryzae. |
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