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The MAP kinase kpp2 regulates mating and pathogenic development in Ustilago maydis
P Müller1, C Aichinger, M Feldbrügge
1Institut für Genetik und Mikrobiologie, Maria-Ward-Str. 1a, D-80638 München, Germany.
Molecular Microbiology
|December 14, 1999
Summary
The study identifies Kpp2, a MAP kinase essential for Ustilago maydis development and pathogenicity. Kpp2 transmits pheromone signals, regulating cell fusion and gene expression during mating.
Area of Science:
- Molecular Mycology
- Signal Transduction in Fungi
Background:
- Cell fusion in Ustilago maydis is crucial for infection and controlled by the 'a' locus.
- This process involves pheromone signaling, a G protein, and a MAP kinase cascade activating transcription factor Prf1.
Purpose of the Study:
- To investigate the role of MAP kinase sites in Prf1 activity during mating.
- To identify and characterize novel components of the pheromone signaling pathway in Ustilago maydis.
Main Methods:
- Site-directed mutagenesis of Prf1 to assess MAP kinase site function.
- Gene deletion of the putative MAP kinase gene kpp2.
- Epistasis analysis to determine the position of Kpp2 in the signaling pathway.
- Complementation studies by overexpressing 'b' genes in kpp2 mutants.
Main Results:
- Putative MAP kinase sites on Prf1 are necessary for its mating activity.
- Deletion of kpp2 impairs cell fusion, pheromone gene induction, and pathogenicity.
- Kpp2 acts independently of the cAMP signaling cascade.
- Overexpression of 'b' genes partially restores pathogenicity in kpp2 mutants, suggesting Kpp2 regulates Prf1.
Conclusions:
- The MAP kinase Kpp2 is a key component in transmitting pheromone signals in Ustilago maydis.
- Kpp2 plays a critical role in fungal development, including cell fusion and pathogenicity.
- These findings elucidate a novel signaling mechanism regulating fungal mating and infection.