VIEW ARTICLE

Physiology and Biochemistry

O₂^–-Initiated Lipid Peroxidation in a Bacteria-Induced Hypersensitive Reaction in Tobacco Cell Suspensions. L. Dale Keppler, Microbiology and Plant Pathology Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705; C. Jacyn Baker, Microbiology and Plant Pathology Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705. Phytopathology 79:555-562. Accepted for publication 10 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/Phyto-79-555.

O₂^–-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 tobacco, were used as controls. Transient increases in lipid peroxidation and O₂^– 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^– scavengers added with P. s. syringae inhibited initial transient O₂^– production and lipid peroxidation and increased recovery of bacteria. O₂^–-Initiated lipid peroxidation seems to be involved in the hypersensitive reaction, and O₂^– radicals may be involved in reduced recovery of bacteria during the reaction.