title: Control of Ascorbate Peroxidase 2 expression by hydrogen peroxide and leaf water status during excess light stress reveals a functional organisation of Arabidopsis leaves.
abstract: In Arabidopsis leaves, high light stress induces rapid expression of a gene encoding a cytosolic ascorbate peroxidase (APX2), whose expression is restricted to bundle sheath cells of the vascular tissue. Imaging of chlorophyll fluorescence and the production of reactive oxygen species (ROS) indicated that APX2 expression followed a localised increase in hydrogen peroxide (H2O2) resulting from photosynthetic electron transport in the bundle sheath cells. Furthermore, leaf transpiration rate also increased prior to APX2 expression, suggesting that water status may also be involved in the signalling pathway. Abscisic acid stimulated APX2 expression. Exposure of ABA-insensitive mutants (abi1-1, abi2-1) to excess light resulted in reduced levels of APX2 expression and confirmed a role for ABA in the signalling pathway. ABA appears to augment the role of H2O2 in initiating APX2 expression. This regulation of APX2 may reflect a functional organisation of the leaf to resolve two conflicting physiological requirements of protecting the sites of primary photosynthesis from ROS and, at the same time, stimulating ROS accumulation to signal responses to changes in the light environment.
authors.affiliation: Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Fryer
authors.forename: Louise
authors.initials: L
authors.lastname: Ball
authors.forename: Kevin
authors.initials: K
authors.lastname: Oxborough
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Karpinski
authors.forename: Philip M
authors.initials: PM
authors.lastname: Mullineaux
authors.forename: Neil R
authors.initials: NR
authors.lastname: Baker
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects / Q000528:radiation effects; D029681:Arabidopsis Proteins; D060387:Ascorbate Peroxidases; D019069:Cell Respiration / Q000187:drug effects / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008027:Light; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D010937:Plant Growth Regulators / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D018526:Plant Transpiration / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014867:Water / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; D017382:Reactive Oxygen Species; D014867:Water; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; D010544:Peroxidases; C555293:APX2 protein, Arabidopsis; D060387:Ascorbate Peroxidases; D008156:Luciferases