title: Cytosolic calcium rises and related events in ergosterol-treated Nicotiana cells.
abstract: The typical fungal membrane component ergosterol was previously shown to trigger defence responses and protect plants against pathogens. Most of the elicitors mobilize the second messenger calcium, to trigger plant defences. We checked the involvement of calcium in response to ergosterol using Nicotiana plumbaginifolia and Nicotiana tabacum cv Xanthi cells expressing apoaequorin in the cytosol. First, it was verified if ergosterol was efficient in these cells inducing modifications of proton fluxes and increased expression of defence-related genes. Then, it was shown that ergosterol induced a rapid and transient biphasic increase of free [Ca²⁺](cyt) which intensity depends on ergosterol concentration in the range 0.002-10 μM. Among sterols, this calcium mobilization was specific for ergosterol and, ergosterol-induced pH and [Ca²⁺](cyt) changes were specifically desensitized after two subsequent applications of ergosterol. Specific modulators allowed elucidating some events in the signalling pathway triggered by ergosterol. The action of BAPTA, LaCl₃, nifedipine, verapamil, neomycin, U73122 and ruthenium red suggested that the first phase was linked to calcium influx from external medium which subsequently triggered the second phase linked to calcium release from internal stores. The calcium influx and the [Ca²⁺](cyt) increase depended on upstream protein phosphorylation. The extracellular alkalinization and ROS production depended on calcium influx but, the ergosterol-induced MAPK activation was calcium-independent. ROS were not involved in cytosolic calcium rise as described in other models, indicating that ROS do not systematically participate in the amplification of calcium signalling. Interestingly, ergosterol-induced ROS production is not linked to cell death and ergosterol does not induce any calcium elevation in the nucleus.
authors.affiliation: UMR CNRS/INRA/Université de Bourgogne, Plante-Microbe-Environnement, 17 Rue de Sully, BP 86510, 21065 Dijon Cedex, France.
authors.forename: Parul
authors.initials: P
authors.lastname: Vatsa
authors.forename: Annick
authors.initials: A
authors.lastname: Chiltz
authors.forename: Estelle
authors.initials: E
authors.lastname: Luini
authors.forename: Elodie
authors.initials: E
authors.lastname: Vandelle
authors.forename: Alain
authors.initials: A
authors.lastname: Pugin
authors.forename: Gabriel
authors.initials: G
authors.lastname: Roblin
mesh_terms: D000331:Aequorin / Q000235:genetics / Q000378:metabolism*; D001059:Apoproteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002470:Cell Survival; D003600:Cytosol / Q000378:metabolism; D004875:Ergosterol / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D030821:Plants, Genetically Modified; D011522:Protons; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology*; D015398:Signal Transduction; D013997:Time Factors; D014026:Nicotiana / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
chemical_list: D001059:Apoproteins; D011522:Protons; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; C060014:apoaequorin; D000331:Aequorin; D006861:Hydrogen Peroxide; D020929:Mitogen-Activated Protein Kinase Kinases; D002118:Calcium; D004875:Ergosterol