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Updated: Jun 11, 2026

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions
11:42

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

Published on: September 30, 2016

Sho1 and Msb2-related proteins regulate appressorium development in the smut fungus Ustilago maydis

Daniel Lanver1, Artemio Mendoza-Mendoza, Andreas Brachmann

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

The Plant Cell
|July 1, 2010
PubMed

Insights

In Ustilago maydis, Sho1 (synthetic high osmolarity sensitive) and Msb2 proteins are crucial for sensing the plant surface and initiating infection structure development. These proteins regulate key signaling pathways involved in fungal differentiation.

Area of Science:

  • Mycology
  • Plant Pathology
  • Molecular Biology

Background:

  • Ustilago maydis is a dimorphic fungus that transitions between budding and hyphal growth.
  • Appressorium formation is a critical step for U. maydis to infect host plants, triggered by environmental cues like hydrophobicity and hydroxy fatty acids.
  • In other fungi, Sho1 (synthetic high osmolarity sensitive) and Msb2 regulate stress responses and pseudohyphal growth.

Purpose of the Study:

  • To investigate the roles of Sho1 and Msb2-like proteins in appressorium differentiation in Ustilago maydis.
  • To elucidate the signaling pathways involving Sho1, Msb2, and mitogen-activated protein (MAP) kinases during U. maydis infection structure development.

Main Methods:

  • Two-hybrid screening to identify interaction partners of MAP kinase Kpp6.
  • Epistasis analysis to determine the genetic order of sho1, msb2, kpp2, and kpp6.
  • Biochemical assays to assess the interaction between Sho1 and Kpp6.
  • Phenotypic analysis of sho1 msb2 mutants under different induction conditions.

Main Results:

  • Sho1 interacts with MAP kinase Kpp6 and acts upstream of MAP kinases Kpp2 and Kpp6.
  • Sho1 destabilizes Kpp6 via direct interaction, suggesting a role in fine-tuning Kpp6 activity.
  • sho1 msb2 mutants exhibit significantly reduced differentiation on hydrophobic surfaces but are unaffected by hydroxy fatty acids.

Conclusions:

  • Sho1 and Msb2 are essential for sensing the plant surface hydrophobicity in U. maydis.
  • These proteins play a key role in regulating appressorium differentiation, a critical step in fungal pathogenesis.
  • The findings highlight a novel function for Sho1 and Msb2 in fungal-plant surface interactions.

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