title: Biogenesis of a specialized plant-fungal interface during host cell internalization of Golovinomyces orontii haustoria.
abstract: Powdery mildew fungi are biotrophic pathogens that require living plant cells for their growth and reproduction. Elaboration of a specialized cell called a haustorium is essential for their pathogenesis, providing a portal into host cells for nutrient uptake and delivery of virulence effectors. Haustoria are enveloped by a modified plant plasma membrane, the extrahaustorial membrane (EHM), and an extrahaustorial matrix (EHMx), across which molecular exchange must occur, but the origin and composition of this interfacial zone remains obscure. Here we present a method for isolating Golovinomyces orontii haustoria from Arabidopsis leaves and an ultrastructural characterization of the haustorial interface. Haustoria were progressively encased by deposits of plant cell wall polymers, delivered by secretory vesicles and multivesicular bodies (MVBs) that ultimately become entrapped within the encasement. The EHM and EHMx were not labelled by antibodies recognizing eight plant cell wall and plasma membrane antigens. However, plant resistance protein RPW8.2 was specifically recruited to the EHMs of mature haustoria. Fungal cell wall-associated molecular patterns such as chitin and β-1,3-glucans were exposed at the surface of haustoria. Fungal MVBs were abundant in haustoria and putative exosome vesicles were detected in the paramural space and EHMx, suggesting the existence of an exosome-mediated secretion pathway.
authors.affiliation: Department of Plant-Microbe Interactions, Max-Planck-Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 29 Köln, Germany.
authors.forename: Cristina O
authors.initials: CO
authors.lastname: Micali
authors.forename: Ulla
authors.initials: U
authors.lastname: Neumann
authors.forename: Dorit
authors.initials: D
authors.lastname: Grunewald
authors.forename: Ralph
authors.initials: R
authors.lastname: Panstruga
authors.forename: Richard
authors.initials: R
authors.lastname: O'Connell
mesh_terms: D017360:Arabidopsis / Q000737:chemistry / Q000382:microbiology*; D001203:Ascomycota / Q000737:chemistry / Q000472:pathogenicity*; D005656:Fungal Proteins / Q000032:analysis; D005936:Glucans / Q000032:analysis; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000737:chemistry / Q000382:microbiology; D010940:Plant Proteins / Q000032:analysis
chemical_list: D005656:Fungal Proteins; D005936:Glucans; D010940:Plant Proteins