Functional implications of the subcellular localization of ethylene-induced chitinase and beta-1,3-glucanase in bean leaves

• Published in: The Plant cell 1989-04, Vol.1 (4), p.447-457
• Main Authors: Mauch, F. (University of Colorado, Boulder, CO), Staehelin, L.A
• Format: Article
• Language: English
• Subjects: AGENT PATHOGENE; AGING; ANALISIS DE TEJIDOS; ANALYSE DE TISSUS; ANTIBODIES; ANTICORPS; ANTICUERPOS; BIOCHEMISTRY; BIOCHIMIE; BIOQUIMICA; Cell aggregates; Cell walls; CHEMISTRY; CHIMIE; CHITINASE; Cytochemistry; DISEASE RESISTANCE; ENVEJECIMIENTO; Enzymes; ETHYLENE; ETILENO; GLICOSIDASAS; GLYCOSIDASE; GLYCOSIDASES; IMMUNOLOGIE; IMMUNOLOGY; INMUNOLOGIA; Leaves; ORGANISMOS PATOGENOS; PATHOGENS; PHASEOLUS VULGARIS; Plant cells; Plants; Protoplasts; QUIMICA; QUITINASA; RESISTANCE AUX MALADIES; RESISTENCIA A LA ENFERMEDAD; TISSUE ANALYSIS; Vacuoles; VIEILLISSEMENT
• ISSN: 1040-4651; 1532-298X
• DOI: 10.2307/3869105

Plants respond to an attack by potentially pathogenic organisms and to the plant stress hormone ethylene with an increased synthesis of hydrolases such as chitinase and β-1,3-glucanase. We have studied the subcellular localization of these two enzymes in ethylene-treated bean leaves by immunogold cytochemistry and by biochemical fractionation techniques. Our micrographs indicate that chitinase and β-1,3-glucanase accumulate in the vacuole of ethylene-treated leaf cells. Within the vacuole label was found predominantly over ethylene-induced electron dense protein aggregates. A second, minor site of accumulation of β-1,3-glucanase was the cell wall, where label was present nearly exclusively over the middle lamella surrounding intercellular air spaces. Both kinds of antibodies labeled Golgi cisternae of ethylene-treated tissue, suggesting that the newly synthesized chitinase and β-1,3-glucanase are processed in the Golgi apparatus. Biochemical fractionation studies confirmed the accumulation in high concentrations of both chitinase and β-1,3-glucanase in isolated vacuoles, and demonstrated that only β-1,3-glucanase, but not chitinase, was present in intercellular washing fluids collected from ethylene-treated leaves. Based on these results and earlier studies, we propose a model in which the vacuole-localized chitinase and β-1,3-glucanase are used as a last line of defense to be released when the attacked host cells lyse. The cell wall-localized β-1,3-glucanase, on the other hand, would be involved in recognition processes, releasing defense activating signaling molecules from the walls of invading pathogens.