Functional Analysis Of Casein Kinase?in Magnaporthe Oryzae

Rice blast is a major disease of rice that seriously threatens rice production and human food security.The pathogen is the filamentous fungus Magnaporthe oryzae.It has become a model pathogen for studying the interaction between pathogenic fungi and host plants,and has been extensively studied.Understanding the biological functions of genes involved in the pathogenicity of M.oryzae is of great significance for explaining the pathogenic mechanism of M.oryzae and developing environmentally friendly fungicides.This study identified casein kinase I and systematically analyzed its involvement in the growth,development and pathogenicity of M.oryzae.Casein kinases I are serine / threonine protein kinases that are evolutionarily conserved in yeast and humans,and are involved in a series of important cellular processes.However,the biological functions of casein kinases in M.oryzae have not been identified in previous studies.In this study,two casein kinases I,MoYCK1 and MoHRR25,were identified and targeted for replacement in M.oryzae,but only MoYCK1 was further characterized because of the possible nonviability of the MoHRR25 deletion mutant.Disruption of MoYck1 will lead to pleiotropic defects such as growth,conidia formation and morphogenesis,conidia germination,and appressorium formation and penetration,resulting in reduced pathogenicity on rice seedlings and barley leaves.It is worth noting that compared with the wild type,under nitrogen starvation conditions,the deletion of MoYCK1 caused rapid lipidation of MoAtg8 and degradation of the autophagy marker protein GFP-MoAtg8,indicating that autophagy activity was negatively regulated by MoYck1.In addition,we found that MoVps41,a subunit of the HOPS complex(regulating vacuolar fusion and protein sorting),has been identified as a substrate for MoYck1 in yeast,colocalizes with MoAtg8 in cells,and positively regulates the lipidation of MoAtg8 and degradation of GFP-MoAtg8.Furthermore,MoYck1 also participates in the response to ion hypertonicity and heavy metal cation stress.Interaction between MoHrr25 and MoFrq,a core protein of the circadian clock,was verified by yeast two-hybrid assay,which partially confirmed that its important role in regulating the circadian rhythm in M.oryzae.In conclusion,the results of this study reveal the key roles of casein kinases I in regulating the growth and development,cell autophagy,circadian rhythm,and pathogenicity in M.oryzae.