Changes in tobacco cell membrane composition and structure caused by cercosporin

Cercosporin, a toxin produced by Cercospora species, rapidly kills plant cells in the light. Previous work has shown that cercosporin treatment causes products of lipid peroxidation to be released. We have found that the unsaturated acyl chains of lipids in tobacco (Nicotiana tabacum) cell membranes are destroyed when cells are treated with cercosporin. Concomitant with this change in composition is a change in structure of the membranes as detected by two different fatty acid spin labels, 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl (denoted I12,3]) and 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl (denoted I1,14]). Cercosporin causes the membranes to become more rigid at all temperatures tested and increases the membrane phase transformation temperature from 12.7°C to 20.8°C.