A Contrast of the Plasma Membrane Lipid Composition of Oat and Rye Leaves in Relation to Freezing Tolerance

Abstract

l h e lipid composition of the plasma membrane isolated from leaves of spring oat (Avena safiva 1. cv Ogle) was vastly different from that of winter rye (Secale cereale 1. cv Puma). l h e plasma membrane of spring oat contained large proportions of phospholipids (28.8 mol% of the total lipids), cerebrosides (27.2 mol%), and acylated sterylglucosides (27.3 mol%) with lesser proportions of free sterols (8.4 mol%) and sterylglucosides (5.6 mol%). In contrast, the plasma membrane of winter rye contained a greater proportion of phospholipids (36.6 mol%), and there was a lower proportion of cerebrosides (16.4 mol%); free sterols (38.1 mol%) were the predominant sterols, with lesser proportions of sterylglucosides (5.6 mol%) and acylated sterylglucosides (2.9 mol%). Although the relative proportions of individual phospholipids, primarily phosphatidylcholine and phosphatidylethanolamine, and the molecular species of these two phospholipids were similar in oat and rye, the relative proportions of di-unsaturated species of these two phospholipids were substantially lower in oat than in rye. l h e relative proportions of sterol species in oat were different from those in rye; the molecular species of cerebrosides were similar in oat and rye, with only slight differences in the proportions of the individual species. After 4 weeks of cold acclimation, the proportion of phospholipids increased significantly in both oat (from 28.8 to 36.8 mol%) and rye (from 36.6 to 43.3 mol%) as a result of increases in the proportions of phosphatidylcholine and phosphatidylethanolamine. For both oat and rye, the relative proportions of di-unsaturated species increased after cold acclimation, but the increase was greater in rye than in oat. In both oat and rye, this increase occurred largely during the first week of cold acclimation. During the 4 weeks of cold acclimation, there was a progressive decrease in the proportion of cerebrosides in the plasma membrane of rye (from 16.4 to 10.5 mol%), but there was only a small decrease in oat (from 27.2 to 24.2 mol%). In both oat and rye, there were only small changes in the proportions of free sterols and sterol derivatives during cold acclimation. Consequently, the proportions of both acylated sterylglucosides and cerebrosides remained substantially higher in oat than in rye after cold acclimation. l h e relationship between these differences in the plasma membrane lipid composition of oat and rye and their freezing tolerance is presented.

Differential Effect of Plant Lipids on Membrane Organization

“…Interestingly, the proportions of SG and ASG in PM differ greatly depending on the plant species and the growth conditions, varying from 8% SG plus ASG in Arabidopsis thaliana leaves to 6% SG and 27% ASG in spring oat (Avena sativa) leaf (102,103). The similar ability of conjugated and free forms of phytosterols alone to order membrane evidenced in this study (Fig.…”

Advances in physiological and molecular aspects of plant cold tolerance

“…Through the cold acclimation process, reprogramming of gene expression and various modifications in the metabolism take place (Chinnusamy et al 2010). Acclimation also causes an increase in the production of antioxidants, abscisic acid (ABA) and compatible osmolytes such as soluble sugars and proline (Lynch & Steponkus 1987;Koster & Lynch 1992;Chen et al 1993;Kishitani et al 1994;Uemura & Steponkus 1994;Murelli et al 1995;Nomura et al 1995;Dörffling et al 1997;Tao et al 1998). Denesik (2007) reported that cold treatment affects membrane fluidity resulting in an increase in the membrane rigidity.…”

Current Issues in Plant Cryopreservation

“…Cold acclimation of winter rye (Secale cereale) seedlings showed an increase in free sterol content, with β-sitosterol having the largest increase (Lynch & Steponkus, 1987). Uemura and Steponkus (1994) also found an increase of β-sitosterol with cold acclimation in winter rye; however, these results were not mimicked in spring oats (Avena sativa L. cv Ogle), where there was no significant change in β-sitosterol, but the stigmasterol proportion increased, whilst cholesterol decreased.…”

“…Changes in phospholipid and sterol composition were found in Arabidopsis thaliana after cold acclimation at 2°C for one week, which increased its freezing tolerance from -2°C down to -10°C (Uemura et al, 1995). Cell membrane phospholipid changes were also observed in oat leaves (Uemura & Steponkus, 1994). These changes may be related to improved membrane stability in these plants.…”

“…Cell membrane phospholipids and sterols have been observed to increase in proportion upon cold acclimation in winter rye, with a particular increase in di-unsaturated PC and -sitosterol (Uemura & Steponkus, 1994). Changes in phospholipid and sterol composition were found in Arabidopsis thaliana after cold acclimation at 2°C for one week, which increased its freezing tolerance from -2°C down to -10°C (Uemura et al, 1995).…”