Identification of O-mannosylated Virulence Factors in Ustilago maydis

PLoS Pathogens

José I. Ibeas¹  Alfonso Fernández-Álvarez¹  Alberto Elías-Villalobos¹  Antonio J. Pérez-Pulido¹  Miriam Marín-Menguiano¹  Alberto Jiménez-Martín¹  Daniel Lanver²  Regine Kahmann² 

[1] Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide, Consejo Superior de Investigaciones Científicas, Sevilla, Spain;Department of Organismic Interactions, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany

关键词: Appressoria;    Ustilago maydis;    Plant fungal pathogens;    Membrane proteins;    Fungi;    Saccharomyces cerevisiae;    Glycosylation;    Maize;   

DOI  :  10.1371/journal.ppat.1002563

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

The O-mannosyltransferase Pmt4 has emerged as crucial for fungal virulence in the animal pathogens Candida albicans or Cryptococcus neoformans as well as in the phytopathogenic fungus Ustilago maydis. Pmt4 O-mannosylates specific target proteins at the Endoplasmic Reticulum. Therefore a deficient O-mannosylation of these target proteins must be responsible for the loss of pathogenicity in pmt4 mutants. Taking advantage of the characteristics described for Pmt4 substrates in Saccharomyces cerevisiae, we performed a proteome-wide bioinformatic approach to identify putative Pmt4 targets in the corn smut fungus U. maydis and validated Pmt4-mediated glycosylation of candidate proteins by electrophoretic mobility shift assays. We found that the signalling mucin Msb2, which regulates appressorium differentiation upstream of the pathogenicity-related MAP kinase cascade, is O-mannosylated by Pmt4. The epistatic relationship of pmt4 and msb2 showed that both are likely to act in the same pathway. Furthermore, constitutive activation of the MAP kinase cascade restored appressorium development in pmt4 mutants, suggesting that during the initial phase of infection the failure to O-mannosylate Msb2 is responsible for the virulence defect of pmt4 mutants. On the other hand we demonstrate that during later stages of pathogenic development Pmt4 affects virulence independently of Msb2, probably by modifying secreted effector proteins. Pit1, a protein required for fungal spreading inside the infected leaf, was also identified as a Pmt4 target. Thus, O-mannosylation of different target proteins affects various stages of pathogenic development in U. maydis.

【 授权许可】

CC BY