Journal Article

Localized changes in peroxidase activity accompany hydrogen peroxide generation during the development of a nonhost hypersensitive reaction in lettuce

Bestwick, C.S. (University of London, Kent, UK.), Brown, I.R, Mansfield, J.W

1998

Overview

Peroxidase activity was characterized in lettuce (Lactuca sativa L.) leaf tissue. Changes in the activity and distribution of the enzyme were examined during the development of a nonhost hypersensitive reaction (HR) induced by Pseudomonas syringae (P.s.) pv phaseolicola and in response to an hrp mutant of the bacterium. Assays of activity in tissue extracts revealed pH optima of 4.5, 6.0, 5.5 to 6.0, and 6.0 to 6.5 for the substrates tetramethylbenzidine, guaiacol, caffeic acid, and chlorogenic acid, respectively. Inoculation with water or with wild-type or hip mutant strains of P. s. pv phaseolicola caused an initial decline in total peroxidase activity; subsequent increases depended on the hydrogen donor used in the assay. Guaiacol peroxidase recovered more rapidly in tissues undergoing the HR, whereas changes in tetramethylbenzidine peroxidase were generally similar in the two interactions. In contrast, increases in chlorogenic acid peroxidase were significantly higher in tissues inoculated with the hrp mutant. During the HR, increased levels of Mn2+/2,4-dichlorophenol-stimulated NADH and NADPH oxidase activities, characteristic of certain peroxidases, were found in intercellular fluids and closely matched the accumulation of H2O2 in the apoplast. Histochemical analysis of peroxidase distribution by electron microscopy revealed a striking, highly localized increase in activity within the endomembrane system and cell wall at the sites of bacterial attachment. However, no clear differences in peroxidase location were observed in tissue challenged by the wild-type strain or the hrp mutant. Our results highlight the significance of the subcellular control of oxidative reactions leading to the generation of reactive oxygen species, cell wall alterations, and the HR

• Publisher: American Society of Plant Physiologists
• Subject: ACIDE CAFEIQUE / ACIDE CHLOROGENIQUE / ACIDO CAFEICO / ACIDO CLOROGENICO / ACTIVIDAD ENZIMATICA / ACTIVITE ENZYMATIQUE / Bacterial plant pathogens / Biological and medical sciences / CAFFEIC ACID / CELL STRUCTURE / Cell walls / CHLOROGENIC ACID / COMPOSE PHENOLIQUE / COMPUESTOS FENOLICOS / DESINTOXICACION / DETOXIFICATION / DISEASE RESISTANCE / enzyme activity / Enzymes / ENZYMIC ACTIVITY / ESTRUCTURA CELULAR / FEUILLE / Fundamental and applied biological sciences. Psychology / GUAIACOL / HOJAS / HYDROGEN PEROXIDE / Hypersensitive response / HYPERSENSITIVITY / INDUCTION / Inoculation / LACTUCA SATIVA / LEAVES / Lettuce / LOCALIZATION / Mesophyll cells / nonhost hypersensitive reaction / OXIDACION / Oxidases / OXIDATION / OXYDATION / PATHOGENICITY / Pathology. Damages, economic importance / PATOGENICIDAD / PEROXIDASAS / peroxidase / PEROXIDASES / PEROXIDO DE HIDROGENO / PEROXYDASE / PEROXYDE D'HYDROGENE / phenol / PHENOLIC COMPOUNDS / Phytopathology. Animal pests. Plant and forest protection / Plant cells / Plant-Microbe and Plant-Insect Interactions / Plants / POUVOIR PATHOGENE / PSEUDOMONAS SYRINGAE / PSEUDOMONAS SYRINGAE PV. PHASEOLICOLA / REACCIONES ALERGICAS / REACTION ALLERGIQUE / RESISTANCE AUX MALADIES / RESISTENCIA A LA ENFERMEDAD / STRUCTURE CELLULAIRE / SUBSTRATES / TETRAMETHYLBENZIDINE / ULTRAESTRUCTURA / ULTRASTRUCTURE / VIRULENCE