title: The Neurospora crassa exocyst complex tethers Spitzenkörper vesicles to the apical plasma membrane during polarized growth.
abstract: Fungal hyphae are among the most highly polarized cells. Hyphal polarized growth is supported by tip-directed transport of secretory vesicles, which accumulate temporarily in a stratified manner in an apical vesicle cluster, the Spitzenkörper. The exocyst complex is required for tethering of secretory vesicles to the apical plasma membrane. We determined that the presence of an octameric exocyst complex is required for the formation of a functional Spitzenkörper and maintenance of regular hyphal growth in Neurospora crassa. Two distinct localization patterns of exocyst subunits at the hyphal tip suggest the dynamic formation of two assemblies. The EXO-70/EXO-84 subunits are found at the peripheral part of the Spitzenkörper, which partially coincides with the outer macrovesicular layer, whereas exocyst components SEC-5, -6, -8, and -15 form a delimited crescent at the apical plasma membrane. Localization of SEC-6 and EXO-70 to the plasma membrane and the Spitzenkörper, respectively, depends on actin and microtubule cytoskeletons. The apical region of exocyst-mediated vesicle fusion, elucidated by the plasma membrane-associated exocyst subunits, indicates the presence of an exocytotic gradient with a tip-high maximum that dissipates gradually toward the subapex, confirming the earlier predictions of the vesicle supply center model for hyphal morphogenesis.
authors: Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada, Ensenada, BC 22860, Mexico Department of Biochemistry and Biophysics, Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331 School of Life Sciences, Arizona State University, Tempe, AZ 85287 Department of Molecular Plant Physiology, Institute for Biologie II, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093.
authors: Meritxell
authors: M
authors: Riquelme
authors: Erin L
authors: EL
authors: Bredeweg
authors: Olga
authors: O
authors: Callejas-Negrete
authors: Robert W
authors: RW
authors: Roberson
authors: Sarah
authors: S
authors: Ludwig
authors: Alejandro
authors: A
authors: Beltrán-Aguilar
authors: Stephan
authors: S
authors: Seiler
authors: Peter
authors: P
authors: Novick
authors: Michael
authors: M
authors: Freitag
mesh_terms: D008841:Actin Cytoskeleton; D002462:Cell Membrane; D016764:Cell Polarity; D005089:Exocytosis; D005656:Fungal Proteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D025301:Hyphae / Q000254:growth & development* / Q000378:metabolism; D008870:Microtubules; D009492:Neurospora crassa / Q000254:growth & development*; D017434:Protein Structure, Tertiary; D022142:Secretory Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins