MAP kinase signalling pathway components and targets conserved between the distantly related plant pathogenic fungi Mycosphaerella graminicola and Magnaporthe grisea.

Mycosphaerella graminicola is a dimorphic fungus which causes Septoria tritici leaf blotch. This report describes the examination of the role of several components of the Pmk1p/Fus3p mitogen-activated protein kinase (MAPK) signalling pathway in the development of this species. The genes encoding the MAPK kinase kinase MgSte11p and the MAPK kinase MgSte7p were found to be indispensible for pathogenicity while the deletion of the gene encoding the proposed scaffold protein MgSte50p led to a reduction in virulence. These phenotypes were attributed to a reduced ability to form filaments on the plant surface which prevented penetration. A delayed disease progression was observed on deletion of the gene MGSTE12. The MGSTE7, MGSTE50 and MGSTE12 genes were able to complement mutants of Magnaporthe grisea lacking the orthologous genes. Interactions between the My. graminicola signalling components were also investigated. Furthermore genes whose MgSte12p/Mst12p dependence is conserved between My. graminicola and Ma. grisea were identified.