title: Transformed tobacco (Nicotiana tabacum) plants over-expressing a peroxisome proliferator-activated receptor gene from Xenopus laevis (xPPARα) show increased susceptibility to infection by virulent Pseudomonas syringae pathogens.
abstract: Transgenic tobacco plants capable of over-expressing Xenopus PPARα (xPPARα), a transcription factor known to be required for peroxisome proliferation in animals, were recently generated. These plants (herewith referred to as PPAR-OE) were found to have increased peroxisome abundance, higher peroxisomal acyl-CoA oxidase and catalase activity and modified fatty acid metabolism. Further characterization of PPAR-OE plants revealed a higher susceptibility to virulent and a partial loss of resistance to avirulent Pseudomonas syringae pathogens, whereas the basal resistance response remained unaffected. Biochemical- and defense-related gene expression analyses showed that increased susceptibility to bacterial invasion coincided with the generalized reduction in H(2)O(2) and salicylic acid (SA) levels observed within the first 24 h of bacterial contact. Decreased H(2)O(2) levels were correlated with modified activity levels of catalase and other antioxidant enzymes. A correspondence between a rapid (within 1-24 hpi; ACCO and AOC) and sustained increase (up to 6 days pi; ACCO) in the expression levels of ethylene (ACCO) and jasmonic acid (AOC) biosynthetic genes and a higher susceptibility to virulent bacterial invasion was also observed in PPAR-OE plants. Conversely, no apparent differences in the short- and/or long-term expression levels of markers for the hypersensitive-response, oxidative burst and systemic-acquired resistance were observed between wild type and PPAR-OE plants. The results suggest that peroxisome proliferation could lead to increased susceptibility to bacterial pathogens in tobacco by altering the redox balance of the plant and the expression pattern of key defense signaling pathway genes.
authors.affiliation: Unidad de Biotecnología e Ingeniería Genética de Plantas, (Cinvestav-Unidad Irapuato), Km 9.6 del Libramiento Norte Carretera Irapuato-León, Apartado Postal 629, C.P. 36821, Irapuato, Gto., Mexico.
authors.forename: José Humberto
authors.initials: JH
authors.lastname: Valenzuela-Soto
authors.forename: Fernanda
authors.initials: F
authors.lastname: Iruegas-Bocardo
authors.forename: Norma Angélica
authors.initials: NA
authors.lastname: Martínez-Gallardo
authors.forename: Jorge
authors.initials: J
authors.lastname: Molina-Torres
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Gómez-Lim
authors.forename: John Paul
authors.initials: JP
authors.lastname: Délano-Frier
mesh_terms: D042962:Acyl-CoA Oxidase; D000818:Animals; D060387:Ascorbate Peroxidases; D015415:Biomarkers / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D003517:Cyclopentanes / Q000032:analysis; D004198:Disease Susceptibility; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000032:analysis; D010088:Oxidoreductases / Q000378:metabolism; D054883:Oxylipins / Q000032:analysis; D047493:PPAR alpha / Q000235:genetics / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism*; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000378:metabolism / Q000382:microbiology; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D020156:Salicylic Acid / Q000032:analysis; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015415:Biomarkers; D003517:Cyclopentanes; D054883:Oxylipins; D047493:PPAR alpha; D029867:Xenopus Proteins; C011006:jasmonic acid; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; C107176:peroxisomal acyl-CoA oxidase; D042962:Acyl-CoA Oxidase; D020156:Salicylic Acid