Calcineurin is an antagonist to PKA protein phosphorylation required for postmating filamentation and virulence, while PP2A is required for viability in Ustilago maydis.
Ustilago maydis is a dimorphic basidiomycete and the causal agent of corn smut disease. It serves as a genetic model for understanding dimorphism, pathogenicity, and mating response in filamentous fungi. Previous studies indicated the importance of regulated cAMP-dependent protein kinase A (PKA) for filamentous growth and pathogenicity in U. maydis. The roles of two protein phosphatases that potentially act antagonistically to PKA were assessed. A reverse genetics approach to mutate the catalytic subunits of calcineurin (CN, protein phosphatase [PP]2B) and PP2A in U. maydis was employed. A mutation in the CN catalytic subunit ucn1 caused a dramatic multiple-budding phenotype and mating between two ucn1 mutants was severely reduced. The pathogenicity of ucn1 mutant strains was also severely reduced, even in a solopathogenic haploid strain. Importantly, mutations disrupting protein phosphorylation by PKA were epistatic to ucn1 mutation, indicating a major role of ucn1 as a PKA antagonistic phosphatase. Genetic and inhibitor studies indicated that the U. maydis PP2A catalytic subunit gene (upa2) was essential.
Egan
John D
JD
Department of Plant Pathology, University of Georgia, Athens, GA 30602-7274, USA.
García-Pedrajas
María D
MD
Andrews
David L
DL
Gold
Scott E
SE
D001483:Base Sequence; D019703:Calcineurin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005800:Genes, Fungal; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000502:physiology; D050296:Microbial Viability; D008954:Models, Biological; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D010935:Plant Diseases / Q000382:microbiology; D054648:Protein Phosphatase 2 / Q000378:metabolism; D021122:Protein Subunits; D014588:Ustilago / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D014774:Virulence / Q000235:genetics / Q000502:physiology; D003313:Zea mays / Q000382:microbiology
D017931:DNA Primers; D004271:DNA, Fungal; D021122:Protein Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D054648:Protein Phosphatase 2