A MAP kinase of the vascular wilt fungus Fusarium oxysporum is essential for root penetration and pathogenesis

Abstract

The soil‐borne vascular wilt fungus Fusarium oxysporum infects a wide variety of plant species by directly penetrating roots, invading the cortex and colonizing the vascular tissue. We have identified fmk1, encoding a mitogen‐activated protein kinase (MAPK) of F. oxysporum that belongs to the yeast and fungal extracellular signal‐regulated kinase (YERK1) subfamily. Targeted mutants of F. oxysporum f. sp. lycopersici carrying an inactivated copy of fmk1 have lost pathogenicity on tomato plants but show normal vegetative growth and conidiation in culture. Colonies of the fmk1 mutants are easily wettable, and hyphae are impaired in breaching the liquid–air interface, suggesting defects in surface hydrophobicity. Fmk1 mutants also show reduced invasive growth on tomato fruit tissue and drastically reduced transcript levels of pl1 encoding the cell wall‐degrading enzyme pectate lyase. Conidia of the mutants germinating in the tomato rhizosphere fail to differentiate penetration hyphae, resulting in greatly impaired root attachment. The orthologous MAPK gene Pmk1 from the rice leaf pathogen Magnaporthe grisea complements invasive growth and partially restores surface hydrophobicity, root attachment and pathogenicity in an fmk1 mutant. These results demonstrate that FMK1 controls several key steps in the pathogenesis of F. oxysporum and suggest a fundamentally conserved role for the corresponding MAPK pathway in soil‐borne and foliar plant pathogens.

The Secreted Peptide PIP1 Amplifies Immunity through Receptor-Like Kinase 7

“…Foc 699- GFP strain was obtained by cotransformation of the F. oxysporum f. sp. conglutinans strain 699 with the sGFP coding region driven the Aspergillus nidulans gpdA promoter and the trpC terminator, and the hygromycin resistance cassette, as described previously [62], [63]. Foc 699- GFP was grown in half strength potato dextrose broth at 28°C for 2 to 3 days.…”

Host-induced silencing ofFusarium culmorumgenes protects wheat from infection

“…Secondly, knock-out mutation of the myosin motor domain-containing chitin synthase V (Fc ChsV ) gene in the maize anthracnose fungus Colletotrichum graminicola strongly impaired vegetative growth as well as plant infection (Werner et al , 2007). The third target gene corresponds to the Fc Fmk1 gene whose product, a mitogen-activated protein (MAP) kinase, a member of the yeast and fungal extracellular signal-regulated kinase subfamily, is an essential factor for pathogenicity of F. oxysporum and F. verticilloides attacking tomato and maize, respectively (Di Pietro et al , 2001; Zhang et al , 2011). The essential function of the Fmk1 protein appears to be restricted to in vivo interactions because vegetative growth and in vitro conidiospore formation of fmk1 null mutants of F. oxysporum were normal (Di Pietro et al , 2001).…”

Fungal model systems and the elucidation of pathogenicity determinants

“…2E and F) are performed by injecting a microconidial suspension into tomato fruits or apple slices and evaluating invasive growth and maceration of the surrounding fruit tissue (Di Pietro et al, 2001). The in vitro cellophane penetration assay has been shown to correlate significantly with in vivo pathogenicity on tomato plants.…”

“…The F. oxysporum MAPK Fmk1, an orthologue of the yeast Fus3/Kss1 MAPKs, was found to be essential for virulence on tomato plants (Di Pietro et al, 2001). Infection-related processes such as invasive growth, vegetative hyphal fusion and root adhesion (Di Pietro et al, 2001; Prados Rosales and Di Pietro, 2008) absolutely require Fmk1 and are negatively controlled by the nitrogen source ammonium (Lopez-Berges et al, 2010).…”