Phosphatidylglycerol Content and Composition Influence in Vitro Oligomerization of Purified Lhcii From Winter Rye

Abstract

Williams and co-workers (1) reported that growth and development of winter rye at low, cold-hardening temperatures (5°C) resulted in a specific 72% decrease in the transhexadecenoic acid (trans-16;l) level of PG although the general thylakoid lipid content was not significantly different. The microenvironment of the thylakoid buyer was not significantly altered as indicated by the rotational correlation times of the spin probe, 16-doxyl stearic acid but differential scanning calorimetry (DSC) indicated that both the number of endotherms resolved and their respective transition temperatures were generally reduced in thylakoid membranes developed at 5°C compared to the temperature transitions in thylakoids developed at 20°C. Specifically, the transitions at 60°C and 73°C were not resolved in 5°C thylakoids and have been associated with PSII and LHCII organization respectively (Low, personnal communication). In addition, in situ results based on freeze fracture (2) and Chl fluorescence (3) are consistent with in vitro results (1) which indicated that the oligomeric form of LHCII predominates during development at 20°C whereas the monomeric or an intermediate form predominates upon development of rye at 5°C. Williams et al (1) concluded that low developmental temperature modulates the organization of LHCII by specifically affecting the fatty acid composition of PG.