title: Antifungal effects and mechanism of action of viscotoxin A3.
abstract: Viscotoxins are cationic proteins, isolated from different mistletoe species, that belong to the group of thionins, a group of basic cysteine-rich peptides of approximately 5 kDa. They have been shown to be cytotoxic to different types of cell, including animal, bacterial and fungal. The aim of this study was to obtain information on the cell targets and the mechanism of action of viscotoxin isoform A3 (VtA3). We describe a detailed study of viscotoxin interaction with fungal-derived model membranes, its location inside spores of Fusarium solani, as well as their induced spore death. We show that VtA3 induces the appearance of ion-channel-like activity, the generation of H2O2, and an increase in cytoplasmic free Ca2+. Moreover, we show that Ca2+ is involved in VtA3-induced spore death and increased H2O2 concentration. The data presented here strongly support the notion that the antifungal activity of VtA3 is due to membrane binding and channel formation, leading to destabilization and disruption of the plasma membrane, thereby supporting a direct role for viscotoxins in the plant defence mechanism.
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Alicante, Spain.
authors.forename: Marcela
authors.initials: M
authors.lastname: Giudici
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Poveda
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Molina
authors.forename: Laura
authors.initials: L
authors.lastname: de la Canal
authors.forename: José M
authors.initials: JM
authors.lastname: González-Ros
authors.forename: Karola
authors.initials: K
authors.lastname: Pfüller
authors.forename: Uwe
authors.initials: U
authors.lastname: Pfüller
authors.forename: José
authors.initials: J
authors.lastname: Villalaín
mesh_terms: D000595:Amino Acid Sequence; D016923:Cell Death / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D005658:Fungi / Q000187:drug effects*; D005670:Fusarium / Q000187:drug effects / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry; D018613:Microscopy, Confocal; D014784:Mistletoe / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000201:enzymology; D028321:Plant Preparations / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000378:metabolism / Q000494:pharmacology*; D018547:Plant Stems / Q000201:enzymology; D011485:Protein Binding / Q000187:drug effects; D013172:Spores, Fungal / Q000187:drug effects / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D028321:Plant Preparations; D010940:Plant Proteins; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; C488038:viscotoxin