title: Multiple exocytotic markers accumulate at the sites of perifungal membrane biogenesis in arbuscular mycorrhizas.
abstract: Arbuscular mycorrhizas (AMs) are symbiotic interactions established within the roots of most plants by soil fungi belonging to the Glomeromycota. The extensive accommodation of the fungus in the root tissues largely takes place intracellularly, within a specialized interface compartment surrounded by the so-called perifungal membrane, an extension of the host plasmalemma. By combining live confocal imaging of green fluorescent protein (GFP)-tagged proteins and transmission electron microscopy (TEM), we have investigated the mechanisms leading to the biogenesis of this membrane. Our results show that pre-penetration responses and symbiotic interface construction are associated with extensive membrane dynamics. They involve the main components of the exocytotic machinery, with a major participation of the Golgi apparatus, as revealed by both TEM and in vivo GFP imaging. The labeling of known exocytosis markers, such as v-SNARE proteins of the VAMP72 family and the EXO84b subunit of the exocyst complex, allowed live imaging of the cell components involved in perifungal membrane construction, clarifying how this takes place ahead of the growing intracellular hypha. Lastly, our novel data are used to illustrate a model of membrane dynamics within the pre-penetration apparatus during AM fungal penetration.
authors.affiliation: Department of Plant Biology, University of Turin, Torino, Italy. andrea.genre@unito.it
authors.forename: A
authors.initials: A
authors.lastname: Genre
authors.forename: S
authors.initials: S
authors.lastname: Ivanov
authors.forename: M
authors.initials: M
authors.lastname: Fendrych
authors.forename: A
authors.initials: A
authors.lastname: Faccio
authors.forename: V
authors.initials: V
authors.lastname: Zársky
authors.forename: T
authors.initials: T
authors.lastname: Bisseling
authors.forename: P
authors.initials: P
authors.lastname: Bonfante
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D018552:Daucus carota / Q000166:cytology / Q000378:metabolism / Q000382:microbiology / Q000648:ultrastructure; D005089:Exocytosis; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D049452:Green Fluorescent Proteins / Q000378:metabolism; D046913:Medicago truncatula / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D008954:Models, Biological; D038821:Mycorrhizae / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D010940:Plant Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D015415:Biomarkers; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins