Establishment of compatibility in the Ustilago maydis/maize pathosystem
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Updated: Jul 11, 2026
A Rapid and Efficient Method for Assessing Pathogenicity of Ustilago maydis on Maize and Teosinte Lines
Published on: January 3, 2014
Gunther Doehlemann1, Ramon Wahl, Miroslav Vranes
1Max-Planck-Institut für Terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany.
Abstract:
The fungus Ustilago maydis is a biotrophic pathogen parasitizing on maize. The most prominent symptoms of the disease are large tumors in which fungal proliferation and spore differentiation occur. In this study, we have analyzed early and late tumor stages by confocal microscopy. We show that fungal differentiation occurs both within plant cells as well as in cavities where huge aggregates of fungal mycelium develop. U. maydis is poorly equipped with plant CWDEs and we demonstrate by array analysis that the respective genes follow distinct expression profiles at early and late stages of tumor development. For the set of three genes coding for pectinolytic enzymes, deletion mutants were generated by gene replacement. Neither single nor triple mutants were affected in pathogenic development. Based on our studies, we consider it unlikely that U. maydis feeds on carbohydrates derived from the digestion of plant cell wall material, but uses its set of plant CWDEs for softening the cell wall structure as a prerequisite for in planta growth.
Insights
Ustilago maydis causes maize tumors by differentiating within plant cells and cavities. The fungus likely softens plant cell walls for growth rather than consuming carbohydrates.
Area of Science:
- Plant Pathology
- Mycology
- Molecular Biology
Background:
- Ustilago maydis is a biotrophic pathogen of maize, causing significant crop damage.
- Tumor formation is a key symptom, characterized by fungal proliferation and spore differentiation.
Purpose of the Study:
- To analyze the fungal differentiation and gene expression of Ustilago maydis during maize tumor development.
- To investigate the role of plant cell wall degrading enzymes (CWDEs) in the pathogenesis of U. maydis.
Main Methods:
- Confocal microscopy was used to examine early and late tumor stages.
- Gene expression analysis (array analysis) was performed for U. maydis CWDE genes.
- Deletion mutants for pectinolytic enzyme genes were created using gene replacement.
Main Results:
- Fungal differentiation was observed both within plant cells and in large mycelial aggregates in cavities.
- Expression profiles of CWDE genes varied significantly between early and late tumor stages.
- Single and triple deletion mutants of pectinolytic enzyme genes showed no impairment in pathogenic development.
Conclusions:
- Ustilago maydis likely softens maize cell walls for in planta growth rather than utilizing plant carbohydrates.
- The study provides insights into the mechanisms of fungal pathogenesis and host-pathogen interactions.
