ChMob2 binds to ChCbk1 and promotes virulence and conidiation of the fungal pathogen Colletotrichum higginsianum

Background: Mob family proteins are conserved between animals, plants and fungi and are essential for the activation of NDR kinases that control crucial cellular processes like cytokinesis, proliferation and morphology. Results: We identified a hypomorphic allele of ChMOB2 in a random insertional mutant (vir-88) of the hemibiotrophic ascomycete fungus Colletotrichum higginsianum. The mutant is impaired in conidiation, host penetration and virulence on Arabidopsis thaliana. ChMob2 binds to and co-localizes with the NDR/LATS kinase homolog ChCbk1. Mutants in the two potential ChCbk1 downstream targets ChSSD1 and ChACE2 show defects in pathogenicity. The genome of C. higginsianum encodes two more Mob proteins. While we could not detect any effect on pathogenicity in Delta Chmob3 mutants, ChMob1 is involved in conidiation, septae formation and virulence. Conclusion: This study shows that ChMob2 binds to the conserved NDR/LATS Kinase ChCbk1 and plays an important role in pathogenicity of Colletotrichum higginsianum on Arabidopsis thaliana.