Comparative Biochemistry of the Oxidative Burst Produced by Rose and French Bean Cells Reveals Two Distinct Mechanisms

Cultured cells of rose (Rosa damascena) treated with an elicitor derived from Phytophthora spp. and suspension-cultured cells of French bean (Phaseolus vulgaris) treated with an elicitor derived from the cell walls of Colletotrichum lindemuthianum both produced H(2)O(2). It has been hypothesized that in rose cells H(2)O(2) is produced by a plasma membrane NAD(P)H oxidase (superoxide synthase), whereas in bean cells H(2)O(2) is derived directly from cell wall peroxidases following extracellular alkalinization and the appearance of a reductant. In the rose/Phytophthora spp. system treated with N,N-diethyldithiocarbamate, superoxide was detected by a N,N′-dimethyl-9,9′-biacridium dinitrate-dependent chemiluminescence; in contrast, in the bean/C. lindemuthianum system, no superoxide was detected, with or without N,N-diethyldithiocarbamate. When rose cells were washed free of medium (containing cell wall peroxidase) and then treated with Phytophthora spp. elicitor, they accumulated a higher maximum concentration of H(2)O(2) than when treated without the washing procedure. In contrast, a washing treatment reduced the H(2)O(2) accumulated by French bean cells treated with C. lindemuthianum elicitor. Rose cells produced reductant capable of stimulating horseradish (Armoracia lapathifolia) peroxidase to form H(2)O(2) but did not have a peroxidase capable of forming H(2)O(2) in the presence of reductant. Rose and French bean cells thus appear to be responding by different mechanisms to generate the oxidative burst.