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Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions
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The chitin-binding Cladosporium fulvum effector protein Avr4 is a virulence factor

H Peter van Esse1, Melvin D Bolton, Ioannis Stergiopoulos

  • 1Laboratory of Phytopathology, Centre for Biosystems Genomics (CBSG), Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands.

Molecular Plant-Microbe Interactions : MPMI
|September 14, 2007
PubMed

Insights

The fungal protein Avr4 enhances pathogen virulence by protecting fungal cell walls from plant defenses. Silencing Avr4 reduces pathogen virulence, revealing its essential role in fungal infections.

Area of Science:

  • Plant Pathology
  • Molecular Plant-Microbe Interactions
  • Fungal Genetics

Background:

  • Cladosporium fulvum causes tomato leaf mold.
  • Avr4 is a secreted effector protein crucial for C. fulvum virulence.
  • Avr4 binds chitin in fungal cell walls, inhibiting plant chitinases.

Purpose of the Study:

  • To investigate the intrinsic function of the Avr4 protein.
  • To determine Avr4's role in pathogen virulence and plant defense.
  • To elucidate the mechanism of Avr4-mediated virulence.

Main Methods:

  • Heterologous expression of Avr4 in Arabidopsis and tomato.
  • Assessing pathogen virulence on plants with and without Avr4 expression.
  • Tomato GeneChip analysis to study gene expression changes.
  • Gene silencing of Avr4 in C. fulvum.

Main Results:

  • Avr4 expression increased virulence of chitin-possessing fungal pathogens in Arabidopsis.
  • Avr4 expression enhanced Fusarium oxysporum virulence in tomato.
  • Avr4 expression induced minimal gene expression changes in tomato.
  • Silencing Avr4 in C. fulvum significantly reduced its virulence on tomato.

Conclusions:

  • Avr4 possesses a counter-defensive activity essential for full fungal pathogen virulence.
  • Avr4's function is specific to pathogens with exposed chitin, highlighting a targeted virulence mechanism.
  • This study provides the first report on the intrinsic function of a fungal avirulence protein with counter-defensive activity.

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