The cAMP Signaling and MAP Kinase Pathways in Plant Pathogenic Fungi

Abstract

All eukaryotic organisms must be able to sense and respond to extracellular signals for regulating various developmental and differentiation processes. The cyclic AMP (cAMP) signaling and mitogen-activated protein (MAP) kinase pathways are among the best studied signal transduction pathways in eukaryotes. The key components of the cAMP-PKA pathway include the adenylate cyclase (AC) and regulatory and catalytic subunits of protein kinase A (PKA). In Saccharomyces cerevisiae, both small GTPase Ras and trimeric G-protein Gpa2 Gα function upstream from the cAMP-PKA pathway. Adenylate cyclase is activated by Gα subunits in Schizosaccharomyces pombe and the model filamentous fungus Neurospora crassa (Kays et al. 2000). Although there are no experimental data to determine whether AC is activated by Ras or heterotrimeric G-proteins in most ascomycetous fungal pathogens, phenotype analyses of related mutants and pharmacological studies often suggest the involvement of Ga in the cAMP-PKA pathway (Gronover et al. 2001; Liu and Dean 1997).