Plasma Membrane Redox Enzyme Is Involved in the Synthesis of O2- and H2O2 by Phytophthora Elicitor-Stimulated Rose Cells.
An elicitor prepared from the autoclaved cell walls of Phytophthora sp. induced O2- generation and H2O2 accumulation by cultured cells of Rosa damascena Mill. cv Gloire de Guilan. N,N-Diethyldithiocarbamate, a superoxide dismutase inhibitior, blocked H2O2 accumulation and caused a dramatic accumulation of O2- by elicitor-treated rose cells. In the absence of N,N-diethyldithiocarbamate no detectable O2- was accumulated. Diphenyleneiodonium, quinacrine, pyridine, and imidazole, inhibitors of the mammalian neutrophil NADPH oxidase responsible for the generation of O2- during phagocytosis, inhibited O2- generation by elicitor-treated rose cells. Diphenyleneiodonium also inhibited NADH-dependent O2- production by plasma membranes isolated from rose cells. None of the four compounds inhibited the peroxidase activity in the cell-suspension medium. These results demonstrate that elicitor-stimulated accumulation of H2O2 comes only from superoxide dismutase-catalyzed dismutation of O2-. The data are inconsistent with the hypothesis that the synthesis of O2- is catalyzed by extracellular peroxidase and suggest that the enzyme responsible for the synthesis of O2- by elicitor-treated rose cells might be similar to the mammalian neutrophil NADPH oxidase.
Auh
C. K.
CK
Section of Plant Biology, Division of Biological Sciences, University of California, Davis, California 95616.
Murphy
T. M.
TM