Plasma membrane lipids in the resurrection plant Ramonda serbica following dehydration and rehydration

Plants of Ramonda serbica were dehydrated to 3.6% relative water content (RWC) by withholding water for 3 weeks, afterwards the plants were rehydrated for 1 week to 93.8% RWC. Plasma membranes were isolated from leaves using a two-phase aqueous polymer partition system. Compared with well-hydrated (control) leaves, dehydrated leaves suffered a reduction of about 75% in their plasma membrane lipid content, which returned to the control level following rewatering. Also the lipid to protein ratio decreased after dehydration, almost regaining the initial value after rehydration. Lipids extracted from the plasma membrane of fully-hydrated leaves were characterized by a high level of free sterols and a much lower level of phospholipids. Smaller amounts of cerebrosides, acylated steryl glycosides and steryl glycosides were also detected. The main phospholipids of control leaves were phosphatidylcholine and phosphatidylethanolamine, whereas sitosterol was the free sterol present in the highest amount. Following dehydration, leaf plasma membrane lipids showed a constant level of free sterols and a reduction in phospholipids compared with the well-hydrated leaves. Both phosphatidylcholine and phosphatidylethanolamine decreased following dehydration, their molar ratio remaining unchanged. Among free sterols, the remarkably high cholesterol level present in the control leaves (about 14 mol%) increased 2-fold as a result of dehydration. Dehydration caused a general decrease in the unsaturation level of individual phospholipids and total lipids as well. Upon rehydration the lipid composition of leaf plasma membranes restored very quickly approaching the levels of well-hydrated leaves.     

Lipids of plasma membranes prepared from oat root cells : effects of induced water-deficit tolerance

Plasma membranes were isolated from oat (Avena sativa) roots by the phase-partitioning method. The membranes were exposed to repeated periods of moderate water-deficit stress, and a water-deficit tolerance was induced (acclimated plants). The plasma membranes of the controls (nonacclimated plants) were characterized by a high phospholipid content, 79% of total lipids, cerebrosides (9%) containing hydroxy fatty acids (>90% 24:1-OH) and free sterols, acylated sterylglucosides, sterylglucosides, and steryl esters, together amounting to 12%. Major phospholipids were phosphatidylcholine and phosphatidylethanolamine with lesser amounts of phosphatidylglycerol, phosphatidylinositol, and phosphatidic acid. After the membranes were acclimated to dehydration, the lipid to protein ratio decreased from 1.3 to 0.7 micromoles per milligram. Furthermore, the cerebrosides decreased to 5% and free sterols increased from 9% (nonacclimated plants) to 14%. Because the total phospholipids did not change significantly, the free sterol to phospholipid ratio increased from 0.12 to 0.19. There was no change in the relative distribution of sterols after acclimation. The ratio of phosphatidylcholine to phosphatidylethanolamine changed from 1.1 in the nonacclimated plants to 0.69 in the acclimated plants. The results show that acclimation to dehydration implies substantial alterations in the lipid composition of the plasma membrane.     

LIPID COMPOSITION OF THE BROWN ALGA FUCUS VESICULOSUS1,2

The lipids of the brown alga Fucus vesiculosus consist of approximately 3.6% hydrocarbons (including carotenes) and sterol esters, 11.8% triglycerides, 4.2% free fatty acids, 10.6% sterols, 15.1% chlorophylls and xanthophylls, 29.9% glycolipids, and 6.5% phospholipids. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylinositol appear to be present and phosphatidylcholine is absent.     

The dispersion of cholesterol with phospholipids and glycolipids

Of the polar lipids studied (phospholipids and glycolipids), only phosphatidylcholine and sphingomyelin can disperse in water with up to 2 mol cholesterol/mol polar lipid. However, mixtures of phosphatidylethanolamine with small amounts of phosphatidylcholine and mixed lipids from mitochondria and myelin will also form sterol-rich dispersions. Steroids in which the 3β-OH group is replaced by an oxo function do not form such steroid-rich dispersions. Electron microscopy and optical rotatory dispersion (ORD) show that sterols disperse with cerebrosides and gangliosides to form cylindrical structures with the regions around C atoms 3 and 7 of the sterol in less polar environments than those they occupy in phospholipid liposomes.

It is proposed that choline-containing phospholipids facilitate entry of sterol molecules into the outer leaflet of cell surface membranes but that the phospholipid composition itself will not give rise to an asymmetric distribution of sterol in membranes with a high cholesterol content.     

Two unusual glycerophospholipids from a filamentous fungus, Absidia corymbifera

The chloroform-methanol extractable lipids of the soil filamentous fungus Absidia corymbifera VKMF-965 account for about 20% by weight of dry cells and are composed of low-polarity constituents (about 75% of the total lipids), such as triacylglycerols (mainly), diacylglycerols, sterols and free fatty acids, as well as of glycolipids (about 3%) and phospholipids. The last consist largely of components common to the fungal lipids, namely, phosphatidylethanolamine (38% of the total phospholipids), phosphatidyl-myo-inositol (16%), diphosphatidylglycerol (12%), phosphatidylcholine (7%), phosphatidic acid (6%) and phosphatidylglycerol (3%), and two unusual phospholipids, PL1 (6%) and PL2 (9%). Based on the infrared (IR), (1)H-nuclear magnetic resonance (NMR), (13)C-NMR and mass spectra along with the results of degradation experiment, these two phospholipids have been established to be 1,2-diacyl-sn-glycero-3-phospho(N-acetylethanolamine), or N-acetyl phosphatidylethanolamine, and 1,2-diacyl-sn-glycero-3-phospho(N-ethoxycarbonyl-ethanolamine), respectively. These structures have been confirmed by preparing similar phospholipids from the phosphatidylethanolamine isolated from the same fungus and correlating their chromatographic behaviour, IR and (1)H-NMR spectra with those of PL1 and PL2. So far N-acetyl phosphatidylethanolamine has been detected only in cattle and human brains and a human placenta but its structure was not rigorously proved. PL2 is a novel lipid; to our knowledge no natural phospholipid with an urethane group has yet been found. The main fatty acids of both the phospholipids are n-hexadecanoic, octadecanoic and octadecadienoic ones; PL2 contains in addition a considerable amount of octadecatrienoic acid with its greater portion located at the sn-1 position.     

Evidence for a Composite State of an F′his,gnd Element and a Cryptic Plasmid in a Derivative of Salmonella typhimurium LT2

The zoospores of Blastocladiella emersonii, when derived from cultures grown on solid media, contain about 11% total lipid. This lipid was separated chromatographically on silicic acid into neutral lipid (46.6%), glycolipid (15.8%), and phospholipid (37.6%). Each class was fractionated further on columns of silicic acid, Florisil, or diethylaminoethyl-cellulose, and monitored by thin-layer chromatography. Triglycerides were the major neutral lipids, mono- and diglycosyldiglycerides were the major glycolipids, and phosphatidylcholine and phosphatidylethanolamine were the major phospholipids. Other neutral lipids and phospholipids detected were: hydrocarbons, free fatty acids, free sterols, sterol esters, diglycerides, monoglycerides, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidic acid, phosphatidylserine, and phosphatidylinositol. Palmitic, palmitoleic, stearic, oleic, gamma-linolenic, and arachidonic acids were the most frequently occurring fatty acids. When B. emersonii was grown in (14)C-labeled liquid media, lipid again accounted for 11% of both mature plants and zoospores released from them. The composition of the lipid extracted from such plants and spores was also the same; however, it differed markedly from that of the lipid in spores harvested from solid media, consisting of 28.3% neutral lipid, 12.0% glycolipid, and 59.7% phospholipid. The major lipids were again triglycerides for neutral lipids, mono- and diglycosyldiglycerides for glycolipids, and phosphatidyl choline and phosphatidylethanolamine for phospholipids.     

Reversal of dietary-induced hyperlipidemia in Biomphalaria glabrata (Gastropoda).

1. To determine if dietary induced hyperlipidemia in snails could be reversed, thin-layer chromatography studies were done on lipids in the digestive gland-gonad (DGG) complex of Biomphalaria glabrata fed either hen's egg yolk for 2 weeks (Group A), yolk for 1 week followed by leaf lettuce for 1 week (Group B), or lettuce for 2 weeks (Group C). 2. The major lipid fractions in Group A were triacylglycerols, phosphatidylethanolamine, and phosphatidylcholine, along with lesser amounts of sterol esters, methyl esters, free fatty acids, free sterols and unidentified phospholipids. 3. Groups B and C had about one-half the amount of triacylglycerols than Group A and did not show sterol esters or methyl esters. 4. The triacylglycerol increase of the DGG resulting from the hen's egg diet could be reversed by returning the snails to the lettuce diet.     

Plant Morphological and Biochemical Responses to Field Water Deficits : II. Responses of Leaf Glycerolipid Composition in Cotton

The effects of water deficits on leaf glycerolipid composition were analyzed in two photoperiodic strains of field grown cotton (Gossypium kirsutum L.) that differ in sensitivity to drought. Leaves from plants grown under dryland conditions exhibited increased dry weight and specific leaf weight. The average midday leaf water potential in the dryland treatment decreased to −1.9 and −2.4 megapascals, respectively, for the T25 and T185 genotypes. Total leaf lipid content of plants exposed to dryland conditions was 5.9 and 7.5% of leaf dry weight for strain T25 and T185, respectively. The difference in leaf lipid content between these genotypes was caused by water deficits and was attributed to loss of both phospholipids and glycolipids in strain T25. There was no apparent loss of phospholipids due to water deficits in the T185 genotype; however, a significant loss of glycolipids was partially compensated by a 2-fold increase in triacylglycerol. No change in triacylglycerol was found between treatments in T25 leaves. Water deficit caused a significant decline in the relative degree of acylunsaturation in phospholipids and glycolipids from both genotypes; however, the double bond index for triacylglycerol increased in both genotypes. It is believed that the observed responses of leaf lipid composition to dryland conditions may be an additional criterion for characterization and selection of new drought-tolerant cotton genotypes.     

Composition of lipids in roots, stalks, leaves and flowers of Eichhornia crassipes (Mart.) Solms

The lipid contents of the roots, leaf stalks, leaves and flowers of Eichhornia crassipes (Mart.) Solms (water-hyacinth) were 1.6, 0.9, 14.9 and 5.7%, respectively, on a dry-weight basis. Non-polar lipids were half the total, while glycolipids and phospholipids in approximately equal proportions constituted the remainder, except in leaf stalks, where glycolipids were a larger fraction. Among the non-polar lipids, triacyglycerols predominated, except for pigments in the leaves. Monogalactosyldiglycerides and digalactosyldiglycerides were the major glycolipids. The main phospholipids were phosphatidylcholine in the roots, phosphatidylglycerol in the leaf stalks and leaves, and phosphatidylethanolamine in the flowers. The major fatty acids were palmitic and linoleic in the roots, linoleic in the leaf stalks, palmitic in the leaves, and linolenic and linoleic in the flowers.     

The Effect of Seasonal Shifts in Temperature on the Lipid Composition of Marine Macrophytes

The comparative study of lipid composition was carried out in four species of marine algae, Ahnfeltia tobuchiensis, Laminaria japonica, Sargassum pallidum, and Ulva fenestrata, as well as a higher plant grass wrack (Zostera marina). Plants were collected in the Japan Sea in spring at 2.9 and 5.5°C and in summer at 23°C. The main lipid components of membranes were determined, and the general patterns of the ratio of phospholipids (PL), glycolipids (GL), betaine (BL), and neutral (NL) lipids were discerned. The relative content of NL in all species (except A. tobuchiensis) was higher in summer. The level of triacylglycerols was as high as 18–37%. The content of individual classes of PL and GL varied between the spring and summer samples, the relative content of PL being higher in spring. In most species, the ratio of PL to GL decreased in summer. The content of free sterols did not depend on the season. The molar ratios of phosphatidylcholine and diacylglycerol-o-(hydroxymethyl)-(N,N,N-trimethyl)homoserine to free sterols varied from 0.9 to 1.7. The seasonal changes of lipid composition were apparently related to macrophyte adaptation to water temperature and to biology of their development.     

Effects of moderately enhanced levels of ozone on the acyl lipid composition and dynamical properties of plasma membranes isolated from garden pea (Pisum sativum)

Plasma membranes were isolated from leaves of 16-day-old garden pea, Pisum sativum L., that had been grown in the absence or presence of 65 nl l⁻¹ ozone for 4 days prior to membrane isolation. Plasma membranes from ozone-fumigated plants contained significantly more acyl lipids per protein than those from leaves of plants grown in filtered air on a molar/weight ratio. The ratio between the major acyl lipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC), also increased due to the ozone fumigation, while the fatty acid unsaturation level was unaltered in total plasma membrane acyl lipids, as well as in PC and PE. The amount of free sterols per protein was unaltered, but the percentage of campesterol increased, concomitant with a decrease in stigmasterol. The dynamical properties of the isolated plasma membranes were assessed using Laurdan fluorescence spectroscopy, which monitors water penetration and mobility at the hydrophilic-hydrophobic interface of the membrane. At 0°C, the molecular mobility was slightly lower in plasma membranes from ozone-fumigated plants than in plasma membranes from control plants, possibly reflecting the increased PE/PC, campesterol/stigmasterol and lipid/protein ratios, and suggesting that ozone-fumigated pea plants may be more susceptible to freezing injuries.     

Different mechanisms of the biochemical adaptation of mycelial fungi to temperature stress: Changes in the lipid composition

A comparative study was conducted concerning the effect of temperature stress on the lipid composition of representatives of the subkingdomsEomycota andNeomycota. Changes in the composition of lipid acyl chains (such as saturation and desaturation, isomerization, and changes in the length of fatty acid carbon chains), in the phospholipid composition, and in the contents of sterols and other neutral lipids were revealed. Hyperthermia resulted in (i) an increase in the phosphatidylcholine level, (ii) a decrease in the phosphatidylethanolamine level, (iii) a rise in the content of reserve lipids (triacylglycerols), and (iv) a decline in the free fatty acid level in the neutral lipids. An inverse pattern occurred under hypothermic conditions. The peculiarities in the patterns of the temperature adaptation-related changes in the lipid bilayer composition are considered in terms of the systematic position of the fungi.     

Interaction of furosemide with lipid membranes

Summary The interaction of furosemide with different phospholipids was investigated. Its influence on the lipid structure was inferred from its effect on the phase transition properties of lipids and on the conductance of planar bilayer membranes. The thermotropic properties of dipalmitoyl phosphatidylcholine, phosphatidylethanolamine (natural), dipalmitoyl phosphatidylethanolamine, brain sphingomyelin, brain cerebrosides and phosphatidylserine in the presence and absence of furosemide were investigated by differential scanning calorimetry,. The modifying effect of furosemide seems to be strongest on phosphatidylethanolamine (natural) and sphingomyelin bilayers. The propensity of furosemide to decrease the electrical resistance of planar lipid membranes was also studied and it is shown that the drug facilitates the transport of ions. Partition coefficients of furosemide between lipid bilayers and water were measured.Abbreviations DSC differential scanning calorimetry - PLM planar lipid membranes - DPPC dipalmitoyl phosphatidylcholine - DMPC dimyristoyl phosphatidylcholine - PE phosphatidyl ethanol     

Plasma membrane lipid alterations induced by NaCl in winter wheat roots

A highly enriched plasma membrane traction was isolated by two phase partitioning from wheat roots ( Triticum aestivum L. cv. Vivant) grown with and without 100 m M NaCl. The lipids of the plasma membrane fraction were extracted and characterised. Phosphatidylcholine and phosphatidylethanolamine were the major phospholipids with lesser amounts of phosphandylinositol, phosphatidylglycerol, diphosphalidylglycerol, phosphatidic acid and phosphatidylseriae. NaCl decreased the total phospholipids and the phosphatidylcholine portion of the plasma membranes. Salt treatment had no effect on total sterols and glycolipids. but the relative abundance of the tree sterols was altered: cholesterol, stigma sterol and brassicasterol were significantly increased. Salt treatment resulted in an increase of the more planar/less planar ratio of the free sterols and in introduction of a double bond in the C₂₂ position in the side chain of stigma sterol and brassicasterol. The degree of fatty acid saturation of total phospholipids, phospha-tidylcholine and phosphatidylethanolamine was increased after salt treatment. These lipid changes are discussed in relation to the salt tolerance mechanism.     

Different modes of ozone-induced lipid oxidation in Candida utilis yeast cells and isolated membrane preparations

Significant differences in the development of ozonolysis of lipids in membrane preparations and intact cells of the Candida utilis yeast were revealed. First, unlike isolated membranes, in which lipid modifications can be initiated by low ozone doses (< 0.5 micromol O3/mg protein) and develop proportionally to the treatment dose, in intact yeast cells, even the most ozone-sensitive sterols and nitrogen-containing phospholipids (phosphatidylcholine and phosphatidylethanolamine) did not undergo oxidative destruction at doses up to 6.0 micromol O3/mg protein. Second, the peculiarity of the ozone-initiated lipid modification in intact cells was that different classes of lipids exhibited different sensitivity to ozone. With an increase in the ozone dose, neutral lipids (sterols) and nitrogen-containing phospholipids (phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin) were modified to a greater extent. Third, the accumulation of lipid peroxidation products upon ozone treatment of cells, in contrast to the isolated membranes, was absent at low ozone doses and was recorded only after the lethal damage. It is suggested that these differences are related to both the function of antioxidative enzymes (catalase, superoxide dismutase, peroxidase, etc.) and the difference between the structural states (i.e., stability and accessibility to oxidation) of lipids in the isolated membranes and the intact cells.     

Lipid composition of the yeast

Summary The lipids of two strains of Lipomyces kononenkoae, grown in batch culture, were extracted and analysed. The major lipids present were phospholipids, free sterols, esterified sterols, and triacylglycerols. Phospholipid analysis indicated that phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol were the major ones. The fatty-acyl residues were C₁₂-C₁₈ and contained 67–74% unsaturated residues. Polyunsaturated residues accounted for 15% and 30% in L. kononenkoae CBS 2514 and L. kononenkoae CBS 5608, respectively. Analysis of the fatty-acyl residues of a low-density vesicle fraction obtained from sphaeroplasts of L. kononenkoae CBS 2514 was carried out and the results are discussed in relation to plasma membrane synthesis. The suitability of L. kononenkoae for production of single-cell protein is also discussed.     

Studies on furan fatty acids of salmon roe phospholipids

Mature salmon roe lipids were found to consist of triacylglycerols (63%), phospholipids (30%), sterols (4.2%), steryl esters (0.7%), and other minor components. In the steryl esters and phospholipids, furan fatty acids were detected instead of the triacylglycerols of the testes lipids in male fish. The representative 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid (F6) amounted to 3.8% and 0.6% of the total fatty acids in each fraction, respectively. However, the absolute amount of the acid in the phospholipid was much more than that contained in the steryl esters. The characteristic distribution of the furan acids found in the phospholipids was common to the steryl esters in the liver. Large amounts of furan acids were contained in phosphatidylcholine (PC) rather than in phosphatidylethanolamine. For positional analysis of furan fatty acids in PC, furan-containing species in the molecule were concentrated fourteenfold by using selective hydrogenation and repeated silica gel column chromatography. A series of furan fatty acids in PC was found to be exclusively linked to the sn-1 position. The amount of the acids in the roe exclusively linked to the sn-1 position. The amount of the acids in the roe phospholipids was comparable with that in the testes triacylglycerols. The physiological roles of furan fatty acids are discussed.     

The effects of temperature acclimation on membrane sterols and phospholipids of Neurospora crassa

Experiments were conducted to examine the effects of temperature acclimation on sterol and phospholipid biosynthesis in Neurospora crassa. Cultures grown at high (37 degrees C) and low (15 degrees C) temperatures show significant differences in free and total sterol content, sterol/phospholipid ratios and distribution of major phospholipid species in total lipids and two functionally distinct membrane fractions. The ratio of free sterols to phospholipids in total cellular lipids from 15 degrees C cultures was found to be about one-half that found at 37 degrees C, whereas sterol/phospholipid ratios of mitochondrial and microsomal membranes were found to be higher at the low growth temperature. Total sterol and phospholipid biosynthetic rates showed parallel reductions in cultures acclimating to a shift from 37 to 15 degrees C growth conditions. Distribution of [14C]acetate label into free sterols was significantly lower under these conditions, however; indicating an increase in the conversion rate of sterols to sterol esters at the lower temperature. Mitochondrial and microsomal membrane fractions showed distinct phospholipid distributions which also differed from total lipid distributions at the two growth temperatures. In each case there was a consistent decrease in phosphatidylcholine and a corresponding increase in phosphatidylethanolamine as growth temperatures were lowered.     

The effect of radish plant rotation around a vertical axis on leaf morphology and lipid composition

The effects of radish (Raphanus sativus L. var. radicula D.C., cv. Rozovo-krasnyi s belym konchikom) plant clockwise rotation (2 rpm) around the vertical axis during their growth on growth parameters and also on the composition and content of polar lipids (PL) and neutral lipids (NL) in plant leaves and fatty acids included in them were studied. Rotation in the plane of the Earth’s magnetic field horizontal component did not affect the number of leaves but declined their total mass by 25%. However, a reduction of the root mass was observed only at elevated temperature. Rotation reduced the ratio of PL to NL by 1.5–2.0 times as compared with control, decreasing the content of such PL as glycoand phospholipids and increasing the content of NL, triacylglycerols and free sterols. Among glycolipids, the content of monogalactosyldiacylglycerols and digalactosyldiacylglycerols was reduced in comparison with stationary control, and among phospholipids the content of phosphatidylcholin was reduced by ∼50%. The ratio of phospholipids to sterols was reduced more than by 30%, indirectly indicating the decreased fluidity of the lipid bilayer of membranes; the ratio PL/NL was reduced as well, indicating an acceleration of age-dependent changes in the rotated plants. Rotation increased the content of linolenic acid and reduced the contents of oleic and erucic acids, thus increasing the index of fatty acid desaturation. We concluded that radish plant clockwise rotation around the vertical axis is an unfavorable factor inducing the appearance of the signs of premature senescence.