title: Antifungal mechanisms of a plant defensin MtDef4 are not conserved between the ascomycete fungi Neurospora crassa and Fusarium graminearum.
abstract: Defensins play an important role in plant defense against fungal pathogens. The plant defensin, MtDef4, inhibits growth of the ascomycete fungi, Neurospora crassa and Fusarium graminearum, at micromolar concentrations. We have reported that MtDef4 is transported into the cytoplasm of these fungi and exerts its antifungal activity on intracellular targets. Here, we have investigated whether the antifungal mechanisms of MtDef4 are conserved in these fungi. We show that N. crassa and F. graminearum respond differently to MtDef4 challenge. Membrane permeabilization is required for the antifungal activity of MtDef4 against F. graminearum but not against N. crassa. We find that MtDef4 is targeted to different subcellular compartments in each fungus. Internalization of MtDef4 in N. crassa is energy-dependent and involves endocytosis. By contrast, MtDef4 appears to translocate into F. graminearum autonomously using a partially energy-dependent pathway. MtDef4 has been shown to bind to the phospholipid phosphatidic acid (PA). We provide evidence that the plasma membrane localized phospholipase D, involved in the biosynthesis of PA, is needed for entry of this defensin in N. crassa, but not in F. graminearum. To our knowledge, this is the first example of a defensin which inhibits the growth of two ascomycete fungi via different mechanisms.
authors.affiliation: Donald Danforth Plant Science Center, St Louis, MO, 63132, USA.
authors.forename: Kaoutar
authors.initials: K
authors.lastname: El-Mounadi
authors.affiliation: Donald Danforth Plant Science Center, St Louis, MO, 63132, USA.
authors.forename: Kazi T
authors.initials: KT
authors.lastname: Islam
authors.affiliation: Manchester Fungal Infection Group, Institution of Inflammation and Repair, University of Manchester, Manchester, M13 9NT, UK.
authors.forename: Patricia
authors.initials: P
authors.lastname: Hernández-Ortiz
authors.affiliation: Manchester Fungal Infection Group, Institution of Inflammation and Repair, University of Manchester, Manchester, M13 9NT, UK.
authors.forename: Nick D
authors.initials: ND
authors.lastname: Read
authors.affiliation: Donald Danforth Plant Science Center, St Louis, MO, 63132, USA.
authors.forename: Dilip M
authors.initials: DM
authors.lastname: Shah
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D020126:Brefeldin A / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000502:physiology; D023082:Defensins / Q000378:metabolism*; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D005372:Filipin / Q000494:pharmacology; D005670:Fusarium / Q000254:growth & development*; D009492:Neurospora crassa / Q000254:growth & development*; D010712:Phosphatidic Acids / Q000737:chemistry; D010739:Phospholipase D / Q000737:chemistry / Q000235:genetics; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000382:microbiology; D013172:Spores, Fungal / Q000187:drug effects / Q000254:growth & development
chemical_list: D000935:Antifungal Agents; D023082:Defensins; D010712:Phosphatidic Acids; D010940:Plant Proteins; D020126:Brefeldin A; D005372:Filipin; D010739:Phospholipase D; C106801:phospholipase D1