title: Identification of a hydrogen peroxide signalling pathway in the control of light-dependent germination in Arabidopsis.
abstract: Germination is controlled by external factors, such as temperature, water, light and by hormone balance. Recently, reactive oxygen species (ROS) have been shown to act as messengers during plant development, stress responses and programmed cell death. We analyzed the role of ROS during germination and demonstrated that ROS in addition to their role as cell wall loosening factor are essential signalling molecules in this process. Indeed, we showed that ROS are released prior to endosperm rupture, that their production is required for germination, and that class III peroxidases, as ROS level regulators, colocalized with ROS production. Among ROS, H2O2 modifies, during germination early steps, the expression of genes encoding for enzymes regulating ROS levels. This pointing out a regulatory feedback loop for ROS production. Measurements of endogenous levels of ROS following application of GA and ABA suggested that ABA inhibits germination by repressing ROS accumulation, and that, conversely, GA triggers germination by promoting an increase of ROS levels. We followed the early visible steps of germination (testa and endosperm rupture) in Arabidopsis seeds treated by specific ROS scavengers and as the light quality perception is necessary for a regular germination, we examined the germination in presence of exogenous H2O2 in different light qualities. H2O2 either promoted germination or repressed germination depending on the light wavelengths, showing that H2O2 acts as a signal molecule regulating germination in a light-dependent manner. Using photoreceptors null-mutants and GA-deficient mutants, we showed that H2O2-dependent promotion of germination relies on phytochrome signalling, but not on cryptochrome signalling, and that ROS signalling requires GA signalling.
authors.affiliation: Laboratory of Molecular Biology of Higher Plants, University of Geneva, Quai Ernest-Ansermet 30, Geneva 4, Switzerland.
authors.forename: Patricia
authors.initials: P
authors.lastname: Lariguet
authors.forename: Philippe
authors.initials: P
authors.lastname: Ranocha
authors.forename: Mireille
authors.initials: M
authors.lastname: De Meyer
authors.forename: Odile
authors.initials: O
authors.lastname: Barbier
authors.forename: Claude
authors.initials: C
authors.lastname: Penel
authors.forename: Christophe
authors.initials: C
authors.lastname: Dunand
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D056625:Endosperm / Q000187:drug effects / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant; D018525:Germination; D006861:Hydrogen Peroxide / Q000032:analysis / Q000378:metabolism; D008027:Light; D008954:Models, Biological; D009154:Mutation; D009928:Organ Specificity; D010544:Peroxidases / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; D017382:Reactive Oxygen Species; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; D010544:Peroxidases