Mitogen-activated protein kinase pathways and fungal pathogenesis
In eukaryotic cells, a family of serine/threonine protein kinases known as mitogen-activated protein (MAP) kinases (MAPKs) is involved in the transduction of a variety of extracellular signals and the regulation of different developmental processes. The MAPK is activated by dual phosphorylation of the TXY motif by MAPK kinase (MEK or MAPKK), which is activated in turn by MEK kinase (MEKK or MAPKKK). The sequential activation of the MAPK cascade eventually results in the activation of transcription factors and the expression of specific sets of genes in response to environmental stimuli. In the budding yeast Saccharomyces cerevisiae, five MAPK pathways are known to regulate mating, invasive growth, cell wall integrity, hyperosmoregulation, and ascospore formation (50). In the past decade, MAPKs in various plant and human pathogenic fungi have been characterized. In this review, we will compare their functions in different fungal pathogens with a focus on infection-related morphogenesis and virulence.