title: Nitric oxide modulates ozone-induced cell death, hormone biosynthesis and gene expression in Arabidopsis thaliana.
abstract: Nitric oxide (NO) is involved together with reactive oxygen species (ROS) in the activation of various stress responses in plants. We have used ozone (O₃) as a tool to elicit ROS-activated stress responses, and to activate cell death in plant leaves. Here, we have investigated the roles and interactions of ROS and NO in the induction and regulation of O₃-induced cell death. Treatment with O₃ induced a rapid accumulation of NO, which started from guard cells, spread to adjacent epidermal cells and eventually moved to mesophyll cells. During the later time points, NO production coincided with the formation of hypersensitive response (HR)-like lesions. The NO donor sodium nitroprusside (SNP) and O₃ individually induced a large set of defence-related genes; however, in a combined treatment SNP attenuated the O₃ induction of salicylic acid (SA) biosynthesis and other defence-related genes. Consistent with this, SNP treatment also decreased O₃-induced SA accumulation. The O₃-sensitive mutant rcd1 was found to be an NO overproducer; in contrast, Atnoa1/rif1 (Arabidopsis nitric oxide associated 1/resistant to inhibition by FSM1), a mutant with decreased production of NO, was also O₃ sensitive. This, together with experiments combining O₃ and the NO donor SNP suggested that NO can modify signalling, hormone biosynthesis and gene expression in plants during O₃ exposure, and that a functional NO production is needed for a proper O₃ response. In summary, NO is an important signalling molecule in the response to O₃.
authors.affiliation: Plant Biology, Department of Biological and Environmental Sciences, University of Helsinki, PO Box 65 (Viikinkaari 1), FI-00014 Helsinki, Finland             Institute of Technology, University of Tartu, Nooruse 1, Tartu 50411, Estonia.
authors.forename: Reetta
authors.initials: R
authors.lastname: Ahlfors
authors.forename: Mikael
authors.initials: M
authors.lastname: Brosché
authors.forename: Hannes
authors.initials: H
authors.lastname: Kollist
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kangasjärvi
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D016923:Cell Death; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D058503:Mesophyll Cells / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D010126:Ozone / Q000494:pharmacology*; D019441:Plant Epidermis / Q000378:metabolism; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; C492758:RCD1 protein, Arabidopsis; D017382:Reactive Oxygen Species; D009599:Nitroprusside; D009569:Nitric Oxide; D010126:Ozone; C521947:NOA1 protein, Arabidopsis; D019001:Nitric Oxide Synthase; D020156:Salicylic Acid