Mitogen-activated protein kinase signaling in plant pathogenic fungi

Like in other eukaryotic organisms, mitogen-activated protein (MAP) kinase cascades play important roles in response to host and environmental signals in fungal pathogens. In general, mitogen-activated protein kinase (MAPK) is activated by phosphorylation at the well-conserved threonine-x-tyrosine (TXY) motif by mitogen-activated protein kinase (MEK), which is in turn activated by mitogen-activated protein kinase (MEKK). The budding yeast Saccharomyces cerevisiae has five MAPK pathways that regulate mating, invasive growth, cell wall integrity, osmoregulation, and ascospore formation. Except for ascosporogenesis-specific MAPK sporulation-specific mitogen-activated protein kinase (Smk1), other yeast MAPKs are conserved in plant-pathogenic ascomycetes to regulate different infection and developmental processes, which is the focus of this review. In phytopathogenic basidiomycetes, MAPKs have only been well characterized in Ustilago maydis.