A putative MAP kinase kinase kinase, MCK1, is required for cell wall integrity and pathogenicity of the rice blast fungus, Magnaporthe oryzae.
Insertional mutagenesis of Magnaporthe oryzae led to the identification of MCK1, a pathogenicity gene predicted to encode mitogen-activated protein kinase kinase kinase (MAPKKK) homologous to BCK1 in Saccharomyces cerevisiae. Targeted disruption of MCK1 resulted in the fungus undergoing autolysis and showing hypersensitivity to cell-wall-degrading enzyme. The mck1 produced significantly reduced numbers of conidia and developed appressoria in a slightly retarded manner compared with the wild type. Appressorium of the mck1 mutant was unable to penetrate into plant tissues, thereby rendering the mutant nonpathogenic. Cytorrhysis assay and monitoring of lipid mobilization suggested that the appressorial wall was altered, presumably affecting the level of turgor pressure within appressorium. Furthermore, the mck1 mutant failed to grow inside plant tissue. Complementation of the mutated gene restored its ability to cause disease symptoms, demonstrating that MCK1 is required for fungal pathogenicity. Taken together, our results suggest that MCK1 is an MAPKKK involved in maintaining cell wall integrity of M. oryzae, and that remodeling of the cell wall in response to host environments is essential for fungal pathogenesis.
Jeon
Junhyun
J
Department of Agricultural Biotechnology, Center for Fungal Genetic Resources, Seoul National University, Seoul 151-921, Korea.
Goh
Jaeduk
J
Yoo
Sungyong
S
Chi
Myoung-Hwan
MH
Choi
Jaehyuk
J
Rho
Hee-Sool
HS
Park
Jongsun
J
Han
Seong-Sook
SS
Kim
Byeong Ryun
BR
Park
Sook-Young
SY
Kim
Soonok
S
Lee
Yong-Hwan
YH
D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D020082:Magnaporthe / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D008855:Microscopy, Electron, Scanning; D009154:Mutation; D012275:Oryza / Q000382:microbiology*; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods; D014774:Virulence / Q000235:genetics
D005656:Fungal Proteins; D020930:MAP Kinase Kinase Kinases