Temporary hypoxia suppresses the oxidative burst and subsequent hypersensitive cell death in cells of tobacco and soybean challenged with zoospores of incompatible isolates of Phytophthora species

摘要

We studied the effect of temporary hypoxia on responses associated with disease resistance in cell suspensions of tobacco and soybean challenged with zoospores of compatible and incompatible races of Phytophthora nicotianae and Phytophthora sojae, respectively. Under normal atmospheric conditions both hosts respond to incompatible challenge with a burst of superoxide (O-2(-)) release beginning 6 h after inoculation, followed within 2 h by the onset of cell death. NBT staining reveals that O-2(-) is released around the point of contact between the pathogen and cell in both hosts. Hypoxia, imposed by incubating challenged cells under an atmosphere of nitrogen between 4 and 9 h after inoculation, abolishes the O-2(-) burst and cell death in both tobacco and soybean cells. Under these conditions normally incompatible pathogen races infect and colonize host cells, indicating a failure of resistance expression. Compatible interactions, and the viability of uninoculated cells of tobacco and soybean, are not affected by temporary hypoxia. These results strongly implicate a requirement for oxygen, O-2(-) release and hypersensitive cell death in the resistance of tobacco and soybean to incompatible pathogen races.