title: Uncoupling of reactive oxygen species accumulation and defence signalling in the metal hyperaccumulator plant Noccaea caerulescens.
abstract: The metal hyperaccumulator plant Noccaea caerulescens is protected from disease by the accumulation of high concentrations of metals in its aerial tissues, which are toxic to many pathogens. As these metals can lead to the production of damaging reactive oxygen species (ROS), metal hyperaccumulator plants have developed highly effective ROS tolerance mechanisms, which might quench ROS-based signals. We therefore investigated whether metal accumulation alters defence signalling via ROS in this plant. We studied the effect of zinc (Zn) accumulation by N. caerulescens on pathogen-induced ROS production, salicylic acid accumulation and downstream defence responses, such as callose deposition and pathogenesis-related (PR) gene expression, to the bacterial pathogen Pseudomonas syringae pv. maculicola. The accumulation of Zn caused increased superoxide production in N. caerulescens, but inoculation with P. syringae did not elicit the defensive oxidative burst typical of most plants. Defences dependent on signalling through ROS (callose and PR gene expression) were also modified or absent in N. caerulescens, whereas salicylic acid production in response to infection was retained. These observations suggest that metal hyperaccumulation is incompatible with defence signalling through ROS and that, as metal hyperaccumulation became effective as a form of elemental defence, normal defence responses became progressively uncoupled from ROS signalling in N. caerulescens.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Helen N
authors.initials: HN
authors.lastname: Fones
authors.affiliation: Department of Chemistry, The Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Eyles
authors.affiliation: Biology Division, Imperial College London, Exhibition Road, London, SW7 2AZ, UK.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Bennett
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: J Andrew C
authors.initials: JAC
authors.lastname: Smith
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Gail M
authors.initials: GM
authors.lastname: Preston
mesh_terms: D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D005936:Glucans / Q000378:metabolism; D008670:Metals / Q000378:metabolism*; D008954:Models, Biological; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016897:Respiratory Burst; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D031227:Thlaspi / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology
chemical_list: D005936:Glucans; D008670:Metals; D010940:Plant Proteins; D017382:Reactive Oxygen Species; C048306:callose; D020156:Salicylic Acid
keywords: Noccaea caerulescens; Pseudomonas syringae; metal hyperaccumulation; oxidative burst; plant defence; reactive oxygen species (ROS); signalling