title: Identification and characterization of secreted and pathogenesis-related proteins in Ustilago maydis.
abstract: Interactions between plants and fungal pathogens require a complex interplay at the plant-fungus interface. Extracellular effector proteins are thought to play a crucial role in establishing a successful infection. To identify pathogenesis-related proteins in Ustilago maydis we combined the isolation of secreted proteins using a signal sequence trap approach with bioinformatic analyses and the subsequent characterization of knock-out mutants. We identified 29 secreted proteins including hydrophobins and proteins with a repetitive structure similar to the repellent protein Rep1. Hum3, a protein containing both, a hydrophobin domain and a repetitive Rep1-like region, is shown to be processed during passage through the secretory pathway. While single knock-outs of hydrophobin or repellent-like genes did not affect pathogenicity, we found a strong effect of a double knock-out of hum3 and the repetitive rsp1. Yeast-like growth, mating, aerial hyphae formation and surface hydrophobicity were unaffected in this double mutant. However, pathogenic development in planta stops early after penetration leading to a complete loss of pathogenicity. This indicates that Hum3 and Rsp1 are pathogenicity proteins that share an essential function in early stages of the infection. Our results demonstrate that focusing on secreted proteins is a promising way to discover novel pathogenicity proteins that might be broadly applied to a variety of fungal pathogens.
authors.affiliation: Max Planck Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829, Koeln, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Müller
authors.forename: Peter H
authors.initials: PH
authors.lastname: Schreier
authors.forename: Joachim F
authors.initials: JF
authors.lastname: Uhrig
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal; D054884:Host-Pathogen Interactions; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014588:Ustilago / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics; D003313:Zea mays / Q000382:microbiology
chemical_list: D017931:DNA Primers; D004271:DNA, Fungal; D005656:Fungal Proteins; D011994:Recombinant Proteins