title: Cytosolic ascorbate peroxidase 1 is a central component of the reactive oxygen gene network of Arabidopsis.
abstract: Reactive oxygen species (ROS), such as O2- and H2O2, play a key role in plant metabolism, cellular signaling, and defense. In leaf cells, the chloroplast is considered to be a focal point of ROS metabolism. It is a major producer of O2- and H2O2 during photosynthesis, and it contains a large array of ROS-scavenging mechanisms that have been extensively studied. By contrast, the function of the cytosolic ROS-scavenging mechanisms of leaf cells is largely unknown. In this study, we demonstrate that in the absence of the cytosolic H2O2-scavenging enzyme ascorbate peroxidase 1 (APX1), the entire chloroplastic H2O2-scavenging system of Arabidopsis thaliana collapses, H2O2 levels increase, and protein oxidation occurs. We further identify specific proteins oxidized in APX1-deficient plants and characterize the signaling events that ensue in knockout-Apx1 plants in response to a moderate level of light stress. Using a dominant-negative approach, we demonstrate that heat shock transcription factors play a central role in the early sensing of H2O2 stress in plants. Using knockout plants for the NADPH oxidase D protein (knockout-RbohD), we demonstrate that RbohD might be required for ROS signal amplification during light stress. Our study points to a key role for the cytosol in protecting the chloroplast during light stress and provides evidence for cross-compartment protection of thylakoid and stromal/mitochondrial APXs by cytosolic APX1.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA.
authors.forename: Sholpan
authors.initials: S
authors.lastname: Davletova
authors.forename: Ludmila
authors.initials: L
authors.lastname: Rizhsky
authors.forename: Hongjian
authors.initials: H
authors.lastname: Liang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Shengqiang
authors.forename: David J
authors.initials: DJ
authors.lastname: Oliver
authors.forename: Jesse
authors.initials: J
authors.lastname: Coutu
authors.forename: Vladimir
authors.initials: V
authors.lastname: Shulaev
authors.forename: Karen
authors.initials: K
authors.lastname: Schlauch
authors.forename: Ron
authors.initials: R
authors.lastname: Mittler
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060387:Ascorbate Peroxidases; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics; D003600:Cytosol / Q000201:enzymology*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D010775:Photic Stimulation; D018515:Plant Leaves / Q000201:enzymology* / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020524:Thylakoids / Q000201:enzymology / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D010544:Peroxidases; C555297:APXS protein, Arabidopsis; D060387:Ascorbate Peroxidases; D019255:NADPH Oxidases