O2(1-)-initiated lipid peroxidation in a bacteria-induced hypersensitive reaction in tobacco cell suspensions

O2(1-)-Initiated lipid peroxidation was observed in a hypersensitive reaction induced in an incompatible plant/bacterium combination of tobacco cell suspension and the phytopathogenic bacterium Pseudomonas syringae pv. syringae. The earliest symptoms of this hypersensitive reaction are increases in extracellular pH and K+ . A Tn5 insertion mutant of P. s. syringae, which does not induce the hypersensitive reaction, and Pseudomonas syringae pv. tabaci, a pathogen of tabacco, were used as controls. Transient increases in lipid peroxidation and O2(1-) production which preceded the initial increases in extracellular pH and K+ were observed. Recovery of P. s. syringae was lower from cell suspensions undergoing a hypersensitive reaction than from those treated with bacteria that did not induce a hypersensitive reaction. O2(1-) scavengers added with P. s. syringae inhibited initial transient O2(1-) production and lipid peroxidation and increased recovery of bacteria. O2(1-)-Initiated lipid peroxidation seems to be involved in the hypersensitive reaction, and O2(1-) radicals may be involved in reduced recovery of bacteria during the reaction