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

• Published in: Planta 2011-03, Vol.233 (3), p.507-521
• Main Authors: Valenzuela-Soto, José Humberto, Iruegas-Bocardo, Fernanda, Martínez-Gallardo, Norma Angélica, Molina-Torres, Jorge, Gómez-Lim, Miguel Ángel, Délano-Frier, John Paul
• Format: Article
• Language: English
• Subjects: Acyl-CoA Oxidase; Agriculture; Animals; Ascorbate Peroxidases; Bacterial plant pathogens; Biological and medical sciences; Biomarkers - metabolism; Biomedical and Life Sciences; Catalase - metabolism; Cyclopentanes - analysis; Disease Susceptibility; Ecology; Forestry; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Hydrogen; Hydrogen peroxide; Hydrogen Peroxide - analysis; Infections; Leaves; Life Sciences; Nicotiana - genetics; Nicotiana - metabolism; Nicotiana - microbiology; Original Article; Oxidoreductases - metabolism; Oxylipins - analysis; Pathogens; Peroxidases - metabolism; Peroxisome proliferation; Peroxisome proliferation-associated receptor; Peroxisomes; Peroxisomes - metabolism; Phytopathology. Animal pests. Plant and forest protection; Plant cells; Plant Diseases - genetics; Plant Diseases - immunology; Plant Diseases - microbiology; Plant Immunity; Plant interaction; Plant Leaves - metabolism; Plant Leaves - microbiology; Plant Sciences; Plants; Plants, Genetically Modified - metabolism; Plants, Genetically Modified - microbiology; PPAR alpha - genetics; PPAR alpha - metabolism; Pseudomonas syringae; Pseudomonas syringae - pathogenicity; Reactive oxygen species; salicylic acid; Salicylic Acid - analysis; Superoxide Dismutase - metabolism; Time Factors; Tobacco; Xenopus Proteins - genetics; Xenopus Proteins - metabolism
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-010-1314-7

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 H₂O₂ and salicylic acid (SA) levels observed within the first 24 h of bacterial contact. Decreased H₂O₂ 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.