title: Genetic elucidation of nitric oxide signaling in incompatible plant-pathogen interactions.
abstract: Recent experiments indicate that nitric oxide (NO) plays a pivotal role in disease resistance and several other physiological processes in plants. However, most of the current information about the function of NO in plants is based on pharmacological studies, and additional approaches are therefore required to ascertain the role of NO as an important signaling molecule in plants. We have expressed a bacterial nitric oxide dioxygenase (NOD) in Arabidopsis plants and/or avirulent Pseudomonas syringae pv tomato to study incompatible plant-pathogen interactions impaired in NO signaling. NOD expression in transgenic Arabidopsis resulted in decreased NO levels in planta and attenuated a pathogen-induced NO burst. Moreover, NOD expression in plant cells had very similar effects on plant defenses compared to NOD expression in avirulent Pseudomonas. The defense responses most affected by NO reduction during the incompatible interaction were decreased H(2)O(2) levels during the oxidative burst and a blockage of Phe ammonia lyase expression, the key enzyme in the general phenylpropanoid pathway. Expression of the NOD furthermore blocked UV light-induced Phe ammonia lyase and chalcone synthase gene expression, indicating a general signaling function of NO in the activation of the phenylpropanoid pathway. NO possibly functions in incompatible plant-pathogen interactions by inhibiting the plant antioxidative machinery, and thereby ensuring locally prolonged H(2)O(2) levels. Additionally, albeit to a lesser extent, we observed decreases in salicylic acid production, a diminished development of hypersensitive cell death, and a delay in pathogenesis-related protein 1 expression during these NO-deficient plant-pathogen interactions. Therefore, this genetic approach confirms that NO is an important regulatory component in the signaling network of plant defense responses.
authors.affiliation: John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom. zeier@botanik.uni-wuerzburg.de
authors.forename: Jürgen
authors.initials: J
authors.lastname: Zeier
authors.forename: Massimo
authors.initials: M
authors.lastname: Delledonne
authors.forename: Tatiana
authors.initials: T
authors.lastname: Mishina
authors.forename: Emmanuele
authors.initials: E
authors.lastname: Severi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Sonoda
authors.forename: Chris
authors.initials: C
authors.lastname: Lamb
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism* / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D016923:Cell Death; D004269:DNA, Bacterial / Q000235:genetics; D004274:DNA, Recombinant / Q000235:genetics; D016974:Dickeya chrysanthemi / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D017343:Genes, Plant; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism*; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D044224:Pseudomonas syringae / Q000472:pathogenicity; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016897:Respiratory Burst; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004274:DNA, Recombinant; D006420:Hemeproteins; D011994:Recombinant Proteins; C094007:hmpX protein, Bacteria; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D010105:Oxygenases; C114415:nitric oxide dioxygenase; D020156:Salicylic Acid