2006). The emergence of these specific but nonetheless rather diverse effects of DGDG deficiency might be correlated with the multiplicity of DGDG-binding sites. However, as shown by Hendrickson et al. (2006) cold acclimation of the dgd1 mutant, while not affecting the lipid composition, led to the recovery of PSII and PSI photochemistry as well as the CO2 GW-572016 supplier uptake capacity, and even the pigment composition became equivalent to that of WT. Based on these results, it was suggested that DGDG deficiency affected

the global physical properties of the membranes, which in turn exerted specific effects in a temperature-dependent fashion. As discussed by Hendrickson et al. (2006) and can be inferred from literature data (e.g., Williams 1998; Harwood 1998; Garab et al. 2000) temperature-dependent modifications in the global properties can arise from the altered ratio of the bilayer to non-bilayer lipid click here contents. The physical state of the lipid membrane, can influence a number of different global parameters of the thylakoid membrane, such as the macro-organization of the complexes, the packing of lipids, energy migration and trapping, the energization and permeability of

membranes—parameters which have not been studied in this mutant. In this study, we focused our attention on the role of DGDG for the overall structural organization of the thylakoid membrane and its thermal stability. Taking into account that DGDG participates in both the lipid matrix and in the protein structures, we investigate DGDG’s effects on the properties of these two environments separately. Our results reveal significant alterations in the overall organization of the thylakoid membranes in dgd1 and decreased thermal stability of the chirally organized LHCII-containing protein ADP ribosylation factor macroaggregates and also of the PSI supercomplexes. These changes are accompanied by changes in the fluorescence lifetimes of chlorophyll a. Furthermore, the

lipid packing in the thylakoid membrane appears to be different for the WT and dgd1, especially at elevated temperatures, where the energization of dgd1 membranes is hampered by an increased permeability. Materials and methods Plant material Both the WT Arabidopsis thaliana (Arabidopsis) ecotype Columbia and the dgd1 mutant were grown under 16-h-light/8-h-dark cycle at 20/18°C (day/night), light intensity of 200–250 W m−2 at about 70% humidity. The plants used in the experiments were 28–35 days old. Isolation of thylakoid membranes Dark-adapted leaves were homogenized in a medium containing 50 mM Tricine (pH 7.5), 400 mM sorbitol, 5 mM MgCl2 and 5 mM KCl; the suspension was filtered through four layers of cheese cloth and centrifuged for 4 min at 4,000×g. The chloroplasts were osmotically shocked in a hypotonic medium containing 50 mM Tricine (pH 7.