The Respiratory Burst and Electrolyte Leakage Induced by Sulfhydryl Blockers in Egeria densa Leaves Are Associated with H₂O₂ Production and Are Dependent on Ca²⁺ Influx

• Published in: Plant physiology (Bethesda) 1998-12, Vol.118 (4), p.1379-1387
• Main Authors: Marre, MT, Amicucci, E, Zingarelli, L, Albergoni, F, Marre, E
• Format: Article
• Language: English
• Subjects: Cell Biology and Signal Transduction; Cell membranes; Depolarization; Electrolyte leakage; Electrolytes; Guard cells; Hydrogen peroxide; Hypersensitive response; Leaves; Oxidases; Plant cells; Plants; Reagents
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.118.4.1379

In leaves of Egeria densa Planchon, N-ethylmaleimide (NEM) and other sulfhydryl-binding reagents induce a temporary increase in nonmitochondrial respiration ($\Delta \text{QO}_{2}$) that is inhibited by diphenylene iodonium and quinacrine, two known inhibitors of the plasma membrane NADPH oxidase, and are associated with a relevant increase in electrolyte leakage (M. Bellando, S. Sacco, F. Albergoni, P. Rocco, M. T. Marré [1997] Bot Acta 110: 388-394). In this paper we report data indicating further analogies between the oxidative burst induced by sulfhydryl blockers in E. densa and that induced by pathogen-derived elicitors in animal and plant cells: (a) NEM- and $\text{Ag}^{+}$-induced $\Delta \text{QO}_{2}$ was associated with H2O2 production and both effects depended on the presence of external Ca2+; (b) Ca2+ influx was markedly increased by treatment with NEM; (c) the Ca2+ channel blocker LaCl3 inhibited $\Delta \text{QO}_{2}$, electrolyte release, and membrane depolarization induced by the sulfhydryl reagents; and (d) LaCl3 also inhibited electrolyte leakage induced by the direct infiltration of the leaves with H2O2. These results suggest a model in which the interaction of sulfhydryl blockers with sulfhydryl groups of cell components would primarily induce an increase in the Ca2+ cytosolic concentration, followed by membrane depolarization and activation of a plasma membrane NADPH oxidase. This latter effect, producing active oxygen species, might further influence plasma membrane permeability, leading to the massive release of electrolytes from the tissue.