The MAP kinase kpp2 regulates mating and pathogenic development in Ustilago maydis.
In the phytopathogenic fungus Ustilago maydis, fusion of compatible haploid cells is a prerequisite for infection. This process is genetically controlled by the biallelic a locus, encoding pheromone precursors and receptors. These are presumed to be coupled to a heterotrimeric G protein and a MAP kinase cascade, leading to activation of the HMG domain transcription factor Prf1. Here, we have demonstrated that putative MAP kinase sites in Prf1 are required for its activity during mating. In addition, we have identified a gene, kpp2, which encodes a putative MAP kinase related to Pmk1 of Magnaporthe grisea and Fus3p of Saccharomyces cerevisiae. kpp2 deletion mutants are attenuated in several steps of development: cell fusion, induction of pheromone-responsive genes and pathogenicity. Epistasis analysis shows that kpp2 does not affect pheromone gene expression through the cAMP signalling cascade. Pathogenicity of kpp2 mutants can be partially restored by overexpressing the b genes, indicating a regulation of Prf1 by Kpp2. These data support the hypothesis that the MAP kinase Kpp2 transmits the pheromone signal.
Müller
P
P
Institut für Genetik und Mikrobiologie, Maria-Ward-Str. 1a, D-80638 München, Germany.
Aichinger
C
C
Feldbrügge
M
M
Kahmann
R
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004843:Epistasis, Genetic; D036781:Fimbriae Proteins; D005656:Fungal Proteins; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010675:Pheromones / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins; D016415:Sequence Alignment; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014588:Ustilago / Q000472:pathogenicity / Q000502:physiology*
D001426:Bacterial Proteins; D005656:Fungal Proteins; D006609:High Mobility Group Proteins; D010675:Pheromones; D010940:Plant Proteins; D014157:Transcription Factors; C403708:fap1 protein, Streptococcus; C121065:pheromone response factor 1, Ustilago maydis; D036781:Fimbriae Proteins; D000242:Cyclic AMP; D020928:Mitogen-Activated Protein Kinases; C403707:kpp2 protein, Ustilago maydis