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A Rapid and Efficient Method for Assessing Pathogenicity of Ustilago maydis on Maize and Teosinte Lines
07:09

A Rapid and Efficient Method for Assessing Pathogenicity of Ustilago maydis on Maize and Teosinte Lines

Published on: January 4, 2014

Mating and pathogenic development of the Smut fungus Ustilago maydis are regulated by one mitogen-activated protein

Philip Müller1, Gerhard Weinzierl, Andreas Brachmann

  • 1Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany.

Eukaryotic Cell
|December 11, 2003
PubMed

Insights

In Ustilago maydis, a pheromone signaling pathway involving Kpp4, Fuz7, and Kpp2 is crucial for fungal development and pathogenesis. Disrupting this mitogen-activated protein kinase (MAPK) cascade impairs infection and tumor formation.

Area of Science:

  • * Molecular Mycology
  • * Plant Pathology
  • * Signal Transduction

Background:

  • * Pheromone-mediated cell fusion is essential for initiating infection by the phytopathogenic fungus Ustilago maydis.
  • * Cyclic AMP and mitogen-activated protein kinase (MAPK) signaling pathways regulate this process.
  • * A MAPK cascade involving Ubc4 (MAP3K), Fuz7 (MAP2K), and Ubc3/Kpp2 (MAPK) is hypothesized to be involved.

Purpose of the Study:

  • * To investigate the roles of Kpp4, Fuz7, and Kpp2 in Ustilago maydis pheromone signaling and pathogenesis.
  • * To elucidate the components and function of the MAPK cascade in fungal development and infection.

Main Methods:

  • * Gene isolation and allelism tests (kpp4).
  • * Epistasis analyses using constitutively active alleles.
  • * In vitro interaction and activation assays (Fuz7 and Kpp2).
  • * Analysis of gene deletion and mutant strains (kpp4, fuz7, kpp2, kpp2(T182A/Y184F)).

Main Results:

  • * Kpp4 is allelic to ubc4, and Kpp4, Fuz7, and Kpp2 function within the same MAPK module.
  • * Fuz7 activates Kpp2, and they interact in vitro.
  • * The MAPK cascade regulates pheromone-responsive gene expression (via Prf1) and conjugation tube formation (Prf1-independent).
  • * Deletion mutants of kpp4 and fuz7 are nonpathogenic; kpp2 mutants show reduced virulence.
  • * A non-phosphorylatable Kpp2 mutant exhibits severe defects in tumor induction and early infection differentiation.

Conclusions:

  • * The Kpp4-Fuz7-Kpp2 MAPK cascade is a critical regulator of Ustilago maydis virulence.
  • * This cascade controls distinct developmental processes, including pheromone gene expression and conjugation tube formation.
  • * Phosphorylation of Kpp2 is essential for Ustilago maydis pathogenesis and infection-related differentiation.

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