Accumulation of gentisic acid as associated with systemic infections but not with the hypersensitive response in plant-pathogen interactions

• Published in: Planta Vol. 223; no. 3; pp. 500 - 511
• Main Authors: Belles, J.M, Garro, R, Pallas, V, Fayos, J, Rodrigo, I, Conejero, V
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.02.2006; Springer; Springer Nature B.V
• Subjects: Acids; Asteraceae - drug effects; Asteraceae - metabolism; Asteraceae - microbiology; benzoic acids; Biological and medical sciences; catechol oxidase; Catechol Oxidase - metabolism; Cotyledons; Cucumbers; Cucumis sativus; Cucumis sativus - metabolism; Cucumis sativus - microbiology; Cucumis sativus - virology; enzyme activity; Enzymes; Fundamental and applied biological sciences. Psychology; Generalities. Disease free stocks; Gentisates - metabolism; Gentisates - pharmacology; gentisic acid; Gibberellins - metabolism; Gynura aurantiaca; host-pathogen relationships; hypersensitive response; Infections; Inoculation; Ionization; Leaves; Liquid chromatography; Mass spectrometry; Oxidases; pathogenesis-related proteins; Pathogens; peroxidase; phenolic compounds; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - microbiology; Plant Diseases - virology; Plant Leaves - metabolism; Plant Leaves - microbiology; Plant Leaves - virology; plant pathogenic bacteria; Plant Proteins - metabolism; plant viruses; Plant Viruses - physiology; Polyphenols; Prunus necrotic ringspot virus; Pseudomonas syringae pv. tomato; salicylates; salicylic acid; Signal Transduction; Tomatoes; Vegetables; Viroids; Viroids - physiology; Viruses; Cucumis; Plant pathogen; Rosaceae; Catechol oxidase; Gynura; Phenolics; Gentisic acid; Dicotyledones; Angiospermae; Lycopersicon esculentum; Prunus; Peroxidase; Solanaceae; Salicylic acid; Pathogenesis-related proteins; Enzyme; Hypersensitivity; Cucurbitaceae; Glucoside; Cucumis sativus; Pathogenesis related protein; Peroxidases; Spermatophyta; Oxidoreductases; Compatible interactions; Polyphenol oxidase
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-005-0109-8

In the present work we have studied the accumulation of gentisic acid (2,5-dihydroxybenzoic acid, a metabolic derivative of salicylic acid, SA) in the plant-pathogen systems, Cucumis sativus and Gynura aurantiaca, infected with either prunus necrotic ringspot virus (PNRSV) or the exocortis viroid (CEVd), respectively. Both pathogens produced systemic infections and accumulated large amounts of the intermediary signal molecule gentisic acid as ascertained by electrospray ionization mass spectrometry (ESI-MS) coupled on line with high performance liquid chromatography (HPLC). The compound was found mostly in a conjugated (β-glucoside) form. Gentisic acid has also been found to accumulate (although at lower levels) in cucumber inoculated with low doses of Pseudomonas syringae pv. tomato, producing a nonnecrotic reaction. In contrast, when cucumber was inoculated with high doses of this pathogen, a hypersensitive reaction occurred, but no gentisic-acid signal was induced. This is consistent with our results supporting the idea that gentisic-acid signaling may be restricted to nonnecrotizing reactions of the host plant (Bellés et al. in Mol Plant-Microbe Interact 12:227-235, 1999). In cucumber and Gynura plants, the activity of gentisic acid as inducing signal was different to that of SA, thus confirming the data found for tomato. Exogenously supplied gentisic acid was able to induce peroxidase activity in both Gynura and cucumber plants in a similar way as SA or pathogens. However, gentisic-acid treatments strongly induced polyphenol oxidase activity in cucumber, whereas pathogen infection or SA treatment resulted in a lower induction of this enzyme. Nevertheless, gentisic acid did not induce other defensive proteins which are induced by SA in these plants. This indicates that gentisic acid could act as an additional signal to SA for the activation of plant defenses in cucumber and Gynura plants.