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Eukaryot Cell. 2015 Sep;14(9):846-57. doi: 10.1128/EC.00022-15. Epub 2015 May 1.

Chitinases Are Essential for Cell Separation in Ustilago maydis.

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Heinrich-Heine University Düsseldorf, Institute for Microbiology, Düsseldorf, Germany.
Westfälische Wilhelms-Universität Münster, Institute of Plant Biology and Biotechnology, Münster, Germany.
Department of Energy Great Lakes Bioenergy Research Center and DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, USA.
Heinrich-Heine University Düsseldorf, Institute for Microbiology, Düsseldorf, Germany Cluster of Excellence in Plant Sciences, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany


Chitin is an essential component of the fungal cell wall, providing rigidity and stability. Its degradation is mediated by chitinases and supposedly ensures the dynamic plasticity of the cell wall during growth and morphogenesis. Hence, chitinases should be particularly important for fungi with dramatic morphological changes, such as Ustilago maydis. This smut fungus switches from yeast to filamentous growth for plant infection, proliferates as a mycelium in planta, and forms teliospores for spreading. Here, we investigate the contribution of its four chitinolytic enzymes to the different morphological changes during the complete life cycle in a comprehensive study of deletion strains combined with biochemical and cell biological approaches. Interestingly, two chitinases act redundantly in cell separation during yeast growth. They mediate the degradation of remnant chitin in the fragmentation zone between mother and daughter cell. In contrast, even the complete lack of chitinolytic activity does not affect formation of the infectious filament, infection, biotrophic growth, or teliospore germination. Thus, unexpectedly we can exclude a major role for chitinolytic enzymes in morphogenesis or pathogenicity of U. maydis. Nevertheless, redundant activity of even two chitinases is essential for cell separation during saprophytic growth, possibly to improve nutrient access or spreading of yeast cells by wind or rain.

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