Changes in Phospholipid Composition of a Winter Wheat Cultivar during Germination at 2 C and 24 C

Abstract

Evaluation of various solvent systems for lipid extraction of wheat Triticum aestivum L. cv. Rideau seeds showed that boiling 2-propanol followed by the Bligh-Dyer procedure was the most efficient method, with respect to lipid yield and ability to inactivate lipolytic enzymes. Ten phospholipids were identified in dry seeds; the major components being phosphatidyleholine, lysophosphatidylcholine, N-acyl lysophosphatidylethanolamine, N-acylphosphatidylethanolamine, and phosphatidylethanolamine. After growth for 1 week (2 C) or 31 hours (24 C), the proportions of phosphatidylethanolamine + lysophosphatidic acid and phosphatidic acid increased, lysophosphatidylcholine decreased, and the remaining phospholipids showed little change. At 5 weeks (2 C) or 72 hours (24 C), the seedlings showed 5-fold increases in the proportion of phosphatidic acid largely at the expense of phosphatidylcholine, small decreases in N-acyl lysophosphatidylethanolamine and N-acylphosphatidylethanolamine, and significant increases in lysophosphatidylcholine. The changes in phosphatidic acid and phosphatidylcholine are interpreted as being partially due to increasing phospholipase D activity during germination. In general, the phospholipid composition was similar in morphologically equivalent seedlings grown at 2 C or 24 C. The increased membrane content in seedlings grown at 2 C does not reflect any preferential synthesis of individual phospholipids.In a previous study (8) seedlings of Triticum aestivum L. cv.Rideau grown at 2 C were found to be more resistant to freezing temperature than their morphological equivalents germinated at 24 C. This resistance was correlated with increased synthesis and unsaturation of cell membrane phospholipids at the lower temperature. Knowledge of the changes in amounts of individual phospholipids in wheat seedlings during germination at both temperatures is required to clarify further the biochemical mechanisms underlying cold-hardiness.The phospholipid composition of wheat seeds has not pre- III. Petroleum ether (b.p. 30-60 C); three 1-hr extractions each with 10 ml of solvent at room temperature (3).IV. Chloroform-methanol-water (1:2:0.8); by the BlighDyer procedure (8). V. Boiling 2-propanol; two extractions each with 5 ml of solvent followed by a Bligh-Dyer extraction (8) of the meal residue; the extracts were combined.VI. Chloroform-methanol (2: 1); four 1-hr extractions with 10 ml of solvent followed by gel filtration on Sephadex G-25 (29).All total lipid extracts were brought to dryness under N2, and the residues were dried in a vacuum desiccator to constant weight, dissolved in 5 ml of chloroform, and aliquots were taken for phosphorus and fatty acid analysis (8).Phospholipid Composition of Seeds. Seeds were imbibed for 5 hr at 24 C, incubated at either 24 C for 31 and 72 hr or at 2 C for 1 and 5 weeks as described elsewhere (8); 2-g lots of seeds were macerated with 0.5 g of silica gel in a mortar with pestle, and total lipids were extracted separately by the methods IV and V. An aliquot of t...

Structural and Functional Responses of Wheat Mitochondrial Membranes to Growth at Low Temperatures

“…Over half of the label migrates to the exterior of the bound phospholipid domain under these conditions. 3 Lipids from mitochondrial wash after centrifugation. 4 Experiment numbers refer to runs which were completed in a single day.…”

“…Four varieties of wheat (Triticum aestivum L.) were grown in the dark on moist filter paper at 2 and 24 C as described previously (3,4). Seedlings of two cold hardy winter wheat varieties (Rideau and Kharkov), an unhardy winter wheat (Cappelle-Desprez), and a spring wheat (Marquis) were grown for 2 to 2.5 days at 24 C and from 4 to 5 weeks at 2 C. It has been previously reported (3) that the cellular morphology and composition of the shoots, while dependent on growth time and temperature, are comparable when growth conditions are carefully controlled at these two temperatures.…”

N-Acylphosphatidylethanolamine in Dry and Imbibing Cottonseeds (Amounts, Molecular Species, and Enzymatic Synthesis)

“…After 1 min of cooling in ice, 1 part chloroform and 0.3 parts water (v/v) were added to the mixture and lipids were extracted at 4°C overnight. Isopropanol was substituted for methanol in lipid extractions as a precaution to avoid potential artifacts generated by phospholipases (DeLaRoche et al, 1973). Insoluble material was sedimented by centrifugation at 2000 rpm for 5 min.…”

Stimulation of Phospholipid Biosynthesis during Frost Hardening of Winter Wheat

“…Increased phospholipid synthesis does not seem to be a prerequisite to hardening in winter wheat. However, a high rate of phospholipid synthesis may be required to maintain frost resistance.An increase in phospholipids has generally been observed during hardening of plants (4,5,7,8,11,12, 14). It is not known whether this increase is a result of low temperature or whether it is part of the frost-hardening process.…”