In Vivo Low Temperature-Induced Decrease in 3-Transhexadecenoic Acid Influences Oligomerization of LHCII

Abstract

Winter rye (Secale cereale L cv Puma) is dependent on low growth temperature in order to develop a photosynthetic apparatus capable of efficient processing of light energy and reduction of CO₂ to carbohydrates (1). Functionally, Puma rye leaves developed at 5°C exhibit a 70% greater capacity to utilize CO₂ at low temperature than rye leaves developed at 20°C (2). This was correlated with light-saturated rates of whole chain electron transport (H₂O ----> MV) which were 40% higher in thylakoids isolated from 5°C leaves than those isolated from 20°C leaves (3). In addition, 77°K fluorescence emission spectra and room temperature fluorescence induction measurements in the presence of DCMU indicated that the energy distribution between LHCII and PSII reaction centres and between PSI and PSII reaction centres had been altered upon growth and developement at low temperature (4). Griffith et al (5) concluded that development of rye leaves at low temperature results in an alteration in protein-protein interactions associated with LHCII. This is consistent with an earlier report which indicated that 5°C thlakoids exhibited a decrease in particle size on the EF fracture face (6). However, Huner and co-workers (6, 7) have reported that no significant differences between 5°C and 20°C thylakoids exist with respect to pigment or polypeptide composition. In this report we present preliminary evidence which indicates that low temperature developemnt results in a specific alteration in the fatty composition of thylakoid phosphatidylgycerol which, in turn, affects the structural organization of LHCII.