title: Effects of modifying alternative respiration on nitric oxide-induced virus resistance and PR1 protein accumulation.
abstract: Nitric oxide (NO) is an important defensive signal in plants but its effects on virus infection are not well understood. Administration of NO-releasing compounds immediately before inoculation of tobacco leaves with potato virus X and tobacco mosaic virus decreased the accumulation of virus, indicating that NO can induce resistance rapidly. Resistance induction was inhibited by co-administration with an NO-scavenging compound or when experiments were done in transgenic tobacco plants expressing increased alternative respiratory pathway capacity due to constitutive expression of the plant mitochondrial enzyme, alternative oxidase (AOX). These results indicate that NO, which inhibits electron transport chain activity, is triggering defensive signalling by inducing changes in mitochondrial reactive oxygen species levels that are in turn regulated by AOX. Experiments using nahG-transgenic plants, which cannot accumulate the defensive plant hormone salicylic acid (SA) showed that NO rapidly induces resistance to virus infection independently of SA. However, this initial state of resistance may be transient. Subsequently, by 5 days post-treatment, NO had caused an increase in pathogenesis-related protein 1 (PR1) expression (a proxy for increased SA biosynthesis), which correlated with a longer-term state of resistance to virus infection. The induction by NO of PR1 accumulation was modified in AOX-transgenic plants. This indicates that the influence of NO on defensive gene expression is in part mediated through its effects on mitochondria.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.affiliation: Institute of Biotechnology, College of Agriculture and Biotechnology, Zijingang Campus, Zhejiang University, Hangzhou 310058, PR China.|Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Wu-Sheng
authors.initials: WS
authors.lastname: Liang
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: John P
authors.initials: JP
authors.lastname: Carr
mesh_terms: D036022:Capsid Proteins; D019069:Cell Respiration / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000096:biosynthesis; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009569:Nitric Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000096:biosynthesis; D010935:Plant Diseases; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D017863:Potexvirus / Q000235:genetics; D020156:Salicylic Acid / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D014027:Tobacco Mosaic Virus / Q000235:genetics*; D000099188:Alternative Oxidase
chemical_list: D036022:Capsid Proteins; D024101:Mitochondrial Proteins; D006899:Mixed Function Oxygenases; D009569:Nitric Oxide; D010088:Oxidoreductases; D010940:Plant Proteins; D020156:Salicylic Acid; D000099188:Alternative Oxidase; C009496:H protein, Tobacco mosaic virus; C053376:pathogenesis-related proteins, plant