Relationship between growth temperature and the levels of phosphatidylglycerol (PG) molecular species in thylakoid membranes of squash and spinach cotyledons

Abstract

Lipid unsaturation, the major factor to maintain thylakoid membrane fluidity, is affected by temperature. In this study, we investigated the effect of temperature on PG molecular species in thylakoid membranes. Spinach (Spinacia oleracea), a chilling-resistant plant, and squash (Cucurbita pepo), a chilling-sensitive plant, were grown at different temperatures and PG molecular species isolated from developing cotyledons were analyzed by HPLC. The most abundant molecular species in spinach was those containing linolenic acid and that in squash was those containing palmitic acid at the sn-1 position of glycerol backbone. Temperature affected greatly the levels of these two types of molecular species in both plants. Lowering temperature induced an increase in the former at the expense of the latter. The levels of both types of molecular species were linearly correlated with growth temperatures. Our results indicate that the levels of these two molecular species can be regulated to adapt changes in growth temperature in spinach and squash. In addition, the molecular species containing trans-D 3-hexadecenoic acid rapidly decreased when spinach plants were grown at 30° C. It has been reported that these molecular species play a crucial role in the biogenesis and the trimerization of LHCII. Our results suggest that the process could be affected by high levels of linolenic acid containing molecular species at a relatively high temperature.