Changes in plasma-membrane lipid composition: a strategy for acclimation to copper stress

Wheat seedlings were grown hydroponically in the presence of 50 muM Cu2+. T he copper stress resulted in plasma-membrane (PM) changes of the root cells as altered lipid composition, a decreased phosphatidylcholine (PC)/phospha tidylethanolamine (PE) ratio from 0.7 to 0.3, a decreased fatty acyl unsatu ration and a decrease in the lipid/protein ratio. Membrane vesicles made fr om total lipid extracts of isolated PMs of wheat grown under copper excess showed a remarkably low permeability to polar molecules like glucose, as co mpared with the control, and no difference in proton permeability. Permeabi lity studies of vesicles of plasma-membrane lipids, which were selectively modified by addition of specific lipids such as PC and PE, were also perfor med. The results are discussed with emphasis on the role of the increased P E proportion.