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Growth in excess copper induces changes in the lipid composition and fluidity of PSII‐enriched membranes in wheat
Author(s) -
Quartacci Mike F.,
Pinzino Calogero,
Sgherri Cristina L. M.,
Dalla Vecchia Francesca,
NavariIzzo Flavia
Publication year - 2000
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2000.108001087.x
Subject(s) - thylakoid , electron paramagnetic resonance , membrane , membrane fluidity , chemistry , chloroplast , spin probe , biochemistry , phospholipid , biophysics , biology , nuclear magnetic resonance , physics , gene
Changes in the lipid composition and fluidity of PSII‐enriched thylakoids were studied in seedlings of wheat ( Triticum durum Desf. cv. Adamello) grown in nutrient solution supplemented with CuSO 4 to achieve a final concentration of 10 and 50 μ M Cu. Metal content increased in the chloroplasts of the 50 μ M Cu‐grown plants. PSII isolated from wheat supplied with 10 μ M Cu did not show any alteration in the lipid composition or in the lipid and protein levels of the membranes, nor was any change in the ultrastructure of the membranes detected. The 50 μ M Cu‐grown plants showed thylakoid swelling, particularly in the stroma and terminal grana thylakoids. Furthermore, an alteration in the lipid composition of PSII preparations was observed together with a decrease in the lipid content, which resulted in a reduction in the lipid to protein ratio. The monogalactosyldiacylglycerol (MGDG) to digalactosyldiacylglycerol (DGDG) molar ratio decreased, whereas the degradation of the polar lipids caused an accumulation of free fatty acids (FFA). The total amount of unsaturated lipids associated with the PSII‐enriched membranes of wheat was not affected by excess copper supplies, even though changes in the individual fatty acids occurred. The effect of copper on the fluidity of PSII membranes was evaluated by electron paramagnetic resonance (EPR) measurements, using spin‐probed fatty acids as probes. The PSII membranes, spin probed by means of 5‐ and 16‐doxylstearic acids, showed that only the fluidity of the surface region of the bilayer close to the polar head group was reduced following the 50 μ M Cu supply. In contrast, the fluidity of the inner membrane region of the bilayer did not show any change. The implications of changes in the lipid composition and lipid‐protein interactions on the fluidity of specific transversal membrane regions are discussed.