Involvement of protein kinases and calcium in the NO-signalling cascade for defence-gene induction in ozonated tobacco plants.
This study analyses the signalling pathways triggered by nitric oxide (NO) in response to ozone (O(3)) fumigation of tobacco plants, with particular attention to protein kinase cascades and free cytosolic Ca(2+) in defence-gene activation. NO was visualized with the NO probe DAF-FM. Using a pharmacological approach, the effects of different inhibitors on the expression profiles of NO-dependent defence genes were monitored using RT-PCR. The assay of the kinase activity of the immunoprecipitates complexes shows that O(3) stimulates a 48 kDa salicylic acid (SA)-induced protein kinase (SIPK) in an NO-dependent manner. The O(3)-induced alternative oxidase 1a (AOX1a) and phenylalanine ammonia lyase a (PALa) genes are modulated by phosphorylation by protein kinases, and SIPK might have a role in this up-regulation. By contrast, protein dephosphorylation mediates pathogenesis-related protein 1a (PR1a) expression in O(3)-treated tobacco plants. Ca(2+) is essential, but not sufficient, to promote NO accumulation in ozonated tobacco plants. Intracellular Ca(2+) transients are also essential for PALa up-regulation and cGMP-induced PR1a expression. Partial dependence on intracellular Ca(2+) suggests two different pathways of SA accumulation and PR1a induction. A model summarizing the signalling networks involving NO, SA, and the cellular messengers in this O(3)-induced defence gene activation is proposed.
Department of Applied Biology, University of Perugia, Borgo XX Giugno, 74, I-06121 Perugia, Italy. spas@unipg.it
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Pasqualini
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Reale
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Calderini
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Pagiotti
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Ederli
D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival; D006152:Cyclic GMP / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010126:Ozone / Q000494:pharmacology*; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D000099188:Alternative Oxidase
D002118:Calcium; D006152:Cyclic GMP; D024101:Mitochondrial Proteins; D009569:Nitric Oxide; D010088:Oxidoreductases; D010126:Ozone; D010650:Phenylalanine Ammonia-Lyase; D010940:Plant Proteins; D011494:Protein Kinases; D020156:Salicylic Acid; D000099188:Alternative Oxidase; C053376:pathogenesis-related proteins, plant