title: Dihydrosphingosine-induced programmed cell death in tobacco BY-2 cells is independent of H₂O₂ production.
abstract: Sphinganine or dihydrosphingosine (d18:0, DHS), one of the most abundant free sphingoid Long Chain Base (LCB) in plants, has been recently shown to induce both cytosolic and nuclear calcium transient increases and a correlated Programmed Cell Death (PCD) in tobacco BY-2 cells. In this study, in order to get deeper insight into the LCB signaling pathway leading to cell death, the putative role of Reactive Oxygen Species (ROS) has been investigated. We show that DHS triggers a rapid dose-dependent production of H₂O₂ that is blocked by diphenyleniodonium (DPI), indicating the involvement of NADPH oxidase(s) in the process. In addition, while DPI does not block DHS-induced calcium increases, the ROS production is inhibited by the broad spectrum calcium channel blocker lanthanum (La³+). Therefore, ROS production occurs downstream of DHS-induced Ca²+ transients. Interestingly, DHS activates expression of defense-related genes that is inhibited by both La³+ and DPI. Since DPI does not prevent DHS-induced cell death, these results strongly indicate that DHS-induced H₂O₂ production is not implicated in PCD mechanisms but rather would be associated to basal cell defense mechanisms.
authors.affiliation: UPS, UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux, Université de Toulouse, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Lachaud
authors.forename: Daniel
authors.initials: D
authors.lastname: Da Silva
authors.forename: Nicolas
authors.initials: N
authors.lastname: Amelot
authors.forename: Chloé
authors.initials: C
authors.lastname: Béziat
authors.forename: Christian
authors.initials: C
authors.lastname: Brière
authors.forename: Valérie
authors.initials: V
authors.lastname: Cotelle
authors.forename: Annick
authors.initials: A
authors.lastname: Graziana
authors.forename: Sabine
authors.initials: S
authors.lastname: Grat
authors.forename: Christian
authors.initials: C
authors.lastname: Mazars
authors.forename: Patrice
authors.initials: P
authors.lastname: Thuleau
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014026:Nicotiana / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D017382:Reactive Oxygen Species; D007811:Lanthanum; D006861:Hydrogen Peroxide; D013110:Sphingosine; C005682:safingol