title: Endocytosis is essential for pathogenic development in the corn smut fungus Ustilago maydis.
abstract: It is well established that polarized exocytosis is essential for fungal virulence. By contrast, the contribution of endocytosis is unknown. We made use of a temperature-sensitive mutant in the endosomal target soluble N-ethylmaleimide-sensitive factor attachment protein receptor Yup1 and demonstrate that endocytosis in Ustilago maydis is essential for the initial steps of pathogenic development, including pheromone perception and cell-cell fusion. Furthermore, spore formation and germination were drastically reduced, whereas colonization of the plant was only slightly inhibited. The function of endocytosis in the recognition of mating pheromone through the G protein-coupled pheromone receptor Pra1 was analyzed in greater detail. Biologically active Pra1-green fluorescent protein localizes to the plasma membrane and is constitutively endocytosed. Yup1(ts) mutants that are blocked in the fusion of endocytic transport vesicles with early endosomes are impaired in pheromone perception and conjugation hyphae formation. This is attributable to an accumulation of Pra1-carrying endocytic vesicles in the cytoplasm and the depletion of the receptor from the membrane. Consistently, strong Pra1 expression rescues the signaling defects in endocytosis mutants, but subsequent cell fusion is still impaired. Thus, we conclude that endocytosis is essential for recognition of the partner at the beginning of the pathogenic program but has additional roles in mating as well as spore formation and germination.
authors.affiliation: Max-Planck-Institut für Terrestrische Mikrobiologie, D-35043 Marburg, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Fuchs
authors.forename: Gerd
authors.initials: G
authors.lastname: Hause
authors.forename: Isabel
authors.initials: I
authors.lastname: Schuchardt
authors.forename: Gero
authors.initials: G
authors.lastname: Steinberg
mesh_terms: D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000032:analysis; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D043563:Receptors, Pheromone / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000032:analysis; D015398:Signal Transduction; D014588:Ustilago / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D003313:Zea mays / Q000033:anatomy & histology / Q000382:microbiology*; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D008565:Membrane Proteins; D043563:Receptors, Pheromone; D011993:Recombinant Fusion Proteins; C409262:Yup1 protein, Ustilago maydis; D049452:Green Fluorescent Proteins; D020696:rab5 GTP-Binding Proteins