Consequence of O 2·− generation during a bacterially induced hypersensitive reaction in tobacco: deterioration of membrane lipids

Abstract

Changes in the lipid composition of host cell membranes were characterized during the hypersensitive reaction (HR) induced by Pseudomonas syringae pv. syringae in plants of Nicotiana tabacum cv. Burley 21. Before the appearance of symptoms of the HR, and before the decrease in the amounts of phospholipids and galactolipids, increased O 2 ·− generation and lipid peroxidation were detected as well as reductions in the degree of unsaturation of polar acyl lipids and in the free sterol pool. Inoculation with a Tn 5 transposon mutant of Pseudomonas syringae pv. phaseolicola, which had lost the ability to induce an HR did not result in these changes. Application of different types of free radical scavengers, such as ascorbic acid, reduced glutathione, α-tocopherol-acetate and bovine serum albumin, delayed the development of the HR. These results are consistent with the hypothesis that membrane deterioration during bacterially induced HR is caused by various forms of activated oxygen.