Main Phospholipids Research Articles

A CD study of uncoupling protein-1 and its transmembrane and matrix-loop domains

Conformations of the prototypic UCP-1 (uncoupling protein-1) and its TM (transmembrane) and ML (matrix-loop) domains were studied by CD spectroscopy. Recombinant, untagged mouse UCP-1 and a hexahistidine-tagged version of the protein were obtained in high purity following their overexpression in Escherichia coli. The TM and ML domains of hamster UCP-1 were chemically synthesized. Conformations of both recombinant UCP-1 proteins were dominantly helical (40-50%) in digitonin micelles. Binding of the purine nucleotides GDP and GTP to UCP-1, detected in the near-UV CD region, supported the existence of the functional form of the protein in digitonin micelles. All individual TM and ML peptides, except the third ML domain, adopted helical structures in aqueous trifluoroethanol, which implies that, in addition to six TM segments, at least two of the ML domains of the UCP-1 can form helical structures in membrane interface regions. TM and ML domains interacted with vesicles composed of the main phospholipids of the inner membrane of mitochondria, phosphatidylcholine, phosphatidylethanolamine and cardiolipin, to adopt dominantly beta- and/or unordered conformations. Mixtures of UCP-1 peptide domains spontaneously associated in aqueous, phospholipid vesicles and digitonin micelle environments to form ordered conformations, which exhibited common features with the conformations of the full-length proteins. Thermal denaturations of UCP-1 and its nine-peptide-domain assembly in digitonin were co-operative but not reversible. Assembly of six TM domains in lipid bilayers formed ion-conducting units with possible helical bundle conformations. Consequently, covalent connection between peptide domains, tight domain interactions and TM potential are essential for the formation of the functional conformation of UCP-1.

エーテル型リン脂質のTLCデンシトメトリーによる定量

A quantification method for analysis of individual ether-type phospholipids is important in studies of the regulation of membrane lipid biosynthesis in Archaea. For ester-type lipid of Bacteria and Eucarya, a densitometric method has been established for simultaneous quantification of individual phospholipids visualized with molybdenum blue reagent on a TLC plate. In this study, we developed a TLC densitometric method for rapid quantitative determination of 6 kinds of main ether-type phospholipids in a methanogenic archaeon and an extremely halophilic archaeon. It has been reported previously that on densitometric quantification the values of molar absorptivities are approximately the same among most ester-type phospholipids. On the other hand, we found significant disparity in the molar absorptivity of archaeal ether-type lipids and serine-containing ester-type lipid. Therefore, analysis should be accomplished by use of each standard mixture. Compared with a previous method (preparative TLC method) that is measurement of inorganic phosphate of silica gel powder scraped off from spots of phospholipids on a TLC plate, the TLC densitometry is accomplished at one tenth the sample size in a short time.

Lipids of marine cold-water fishes

The study deals with the lipid and fatty acid compositions of the muscles, gills and liver of marine fishes inhabiting cold waters (0.5–6°C) and caught in Peter the Great Bay (3 species) and Vostok Bay (2 species), as well as with the fatty acid compositions of the main phospholipids in the muscle tissues of fish from Olyutorskii Bay (4 species). The average content of phosphatidylcholine was about 60% in muscles and in the liver and 53.8% of the sum of all phospholipids in gills. The phosphatidylethanolamine content was on the average 24.3, 25.1 and 22.3% in muscles, liver and gills, respectively. Increased contents of phosphatidylserine and sphingomyeline were recorded in the gills. The mean (S.D.) molar ratios of cholesterol/phospholipids were 0.20, 0.32, and 0.58 in the muscles, liver, and gills, respectively. It was established that phosphatidylcholine has a higher content of saturated fatty acids, whereas phosphatidylethanolamine was richer in monoenic acids and docosahexaenoic acid (DHA). It was noted that the level of polyenic fatty acids was increasing and the level of monoenic and saturated acids was decreasing in the series from gills-liver-muscles. The species with a more active mode of life were distinguished by an increased content of docosahexaenoic acid.

Membrane phospholipids and sterols in microfiltered milk fat globules

AbstractNative milk fat globules of various mean diameters, ranging from d43 = 2.3 µm to 8.0 µm, were obtained using microfiltration of raw whole milk. After milk fat globule washing, the milk fat globule membrane (MFGM) was separated by manual churning. After total lipid extraction and separation of polar lipids, their phospholipid (PL) and sterol composition was measured using thin‐layer chromatography, methyl ester analyses by gas chromatography, and gas chromatography coupled to mass spectrometry. The main PL species were phosphatidylethanolamine, phosphatidylcholine and sphingomyelin. The respective fatty acid composition of each PL species was measured. Many different minor bioactive sterols were detected in the MFGM, e.g. lanosterol, lathosterol, desmosterol, stigmasterol and β‐sitosterol. No significant differences in the PL and sterol profile were found between MFGM extracted from small and large milk fat globule fractions.

Short-term high fat-feeding results in morphological and metabolic adaptations in the skeletal muscle of C57BL/6J mice

The prevalence of the metabolic syndrome (MS) is rapidly increasing all over the world. Consequently, there is an urgent need for more effective intervention strategies. Both animal and human studies indicate that lipid oversupply to skeletal muscle can result in insulin resistance, which is one of the characteristics of the MS. C57BL/6J mice were fed a low-fat (10 kcal%) palm oil diet or a high-fat (45 kcal%; HF) palm oil diet for 3 or 28 days. By combining transcriptomics with protein and lipid analyses we aimed to better understand the molecular events underlying the early onset of the MS. Short-term HF feeding led to altered expression levels of genes involved in a variety of biological processes including morphogenesis, energy metabolism, lipogenesis, and immune function. Protein analysis showed increased levels of the myosin heavy chain, slow fiber type protein, and the complexes I, II, III, IV, and V of the oxidative phosphorylation. Furthermore, we observed that the main mitochondrial membrane phospholipids, phosphatidylcholine and phosphatidylethanolamine, contained more saturated fatty acids. Altogether, these results point to a morphological as well as a metabolic adaptation by promoting a more oxidative fiber type. We hypothesize that after this early positive adaptation, a continued transcriptional downregulation of genes involved in oxidative phosphorylation will result in decreased oxidative capacity at a later stage. Together with increased saturation of phospholipids of the mitochondrial membrane this can result in decreased mitochondrial function, which is a hallmark observed in insulin resistance and Type 2 diabetes.

Lysophosphatidylcholine upregulates LOX-1, chemokine receptors, and activation-related transcription factors in human T-cell line Jurkat

In arteriosclerosis, activated T cells infiltrating the atherosclerotic lesions are directly involved in the pathogenesis of these vascular disorders. Infiltration and accumulation of T cells into the vascular wall occur at the earliest stage of atherosclerosis. The atherosclerotic lesion also sees the accumulation of modified lipids such as lysophosphatidylcholine (lysoPC), the main phospholipid component of oxidized low-density lipoprotein. However, it remains less clear how lysoPC affects CD4 T cells. Therefore, we assessed the effect of lysoPC on various mRNA expressions in human T cells using real-time quantitative Reverse Transcription-PCR. Exposure of Jurkat cells (a human CD4 T-cell line) to lysoPC resulted in upregulation of CXCR4 and CCR5 chemokine receptors, receptor for oxidized low-density lipoprotein (LOX-1), the transcription factors, nuclear factor-kappa beta (NF-kB) and Yin Yang 1, and target molecules of NF-kB, A1/Bfl1/BCL2A1 and c-IAP1/BIRC2, in a dose-dependent manner. These data indicate that lysoPC is a positive regulator of the inflammatory response in human CD4 T cells. Further, it suggested that lysoPC and CD4 T cells accumulating in atherosclerotic lesions contribute to the development of arteriosclerosis.

Tocopherol Content and Fatty Acid Distribution of Peas (Pisum sativum L.)

AbstractThe positional distribution of fatty acids (FA) of triacylglycerols (TAG) and major phospholipids (PL) prepared from four cultivars of peas (Pisum sativum L.) were investigated as well as their tocopherol contents. The lipids extracted from these peas were separated by thin‐layer chromatography (TLC) into seven fractions. The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while the other components were also present in minor proportions (5.6–9.2%). γ‐Tocopherol was present in the highest concentration, and α‐ and δ‐tocopherols were very small amounts. The main PL components isolated from the four cultivars were phosphatidylcholine (42.3–49.2%), followed by phosphatidylinositol (23.3–25.2%) and then phosphatidylethanolamine (17.7–20.5%). Small but significant differences (P < 0.05) in FA distribution existed when different pea cultivars were determined. However, the principal characteristics of the FA distribution in the TAG and the three PL were evident among the four cultivars; unsaturated FA were predominantly located in the sn‐2 position, and saturated FA primary occupied the sn‐1 or sn‐3 position in the oils of the peas. These results suggest that the regional distribution of tocopherols and fatty acids in peas is not dependent on the climatic conditions and the soil characteristics of the cultivation areas during the growing season.

Biochemical aspects of basidiospore maturation in Agaricus bisporus at various temperatures

Phosphatidylethanolamine is the main phospholipid of Agaricus bisporus basidiospores obtained under sterile conditions from young basidiomes with closed partial veils. Storing the basidiospores for five months at room temperature resulted in a complete loss of their germinating capacity. Conversely, storing them at a low temperature increased their germination rate by 15-20%. At both temperature levels, the phosphatidylcholine ratio significantly increased during storage to the level found in mature basidiospores. In addition, a drastic (8-10-fold) decrease in trehalose content occurred after two months of storage at room temperature. The trehalose content decreased only 1.5-fold at low temperatures. The involvement of trehalose and lipids in the retention of spore viability is discussed.

Distribution of fatty acids in triacylglycerols and phospholipids from peas (Pisum sativum L.)

The fatty acid distribution of triacylglycerols (TAG) and major phospholipids (PL) obtained from four varieties of peas (Pisum sativum) was investigated. The total lipids extracted from the peas were separated by thin layer chromatography into seven fractions. The major lipid components were PL (52.2-61.3%) and TAG (31.2-40.3%), while hydrocarbons, steryl esters, free fatty acids and diacylglycerols (sn-1,3 and sn-1,2) were also present in minor proportions (5.6-9.2%). The main PL components isolated from the four varieties were phosphatidylcholine (42.3-49.2%), phosphatidylinositol (23.3-25.2%) and phosphatidylethanolamine (17.7-20.5%). Significant differences (P < 0.05) in fatty acid distribution were found for different pea varieties. Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. However, the principal characteristics of the fatty acid distribution in the TAG and three PL were evident among the four varieties: unsaturated fatty acids were predominantly located in the sn-2 position while saturated fatty acids primarily occupied the sn-1 or sn-3 position in the oils of the peas. These results should be useful to both producers and consumers for the manufacture of pea foods in Japan. Copyright © 2007 Society of Chemical Industry.

REGIONAL DISTRIBUTION IN THE FATTY ACIDS OF TRIACYLGLYCEROLS AND PHOSPHOLIPIDS OF SESAME SEEDS (SESAMUM INDICUM)

ABSTRACT The fatty acid distribution of triacylglycerols (TAGs) and major phospholipids (PLs) in sesame (Sesamum indicum) seeds was investigated in relation to the endogenous antioxidants. γ‐Tocopherol was present in the highest concentration, and δ‐ and α‐tocopherols were found in very small amounts. Sesamin and sesamolin were the main lignan components. The lipids extracted from three cultivars were separated by thin‐layer chromatography. The major lipid components were TAGs and PLs, while steryl esters, free fatty acids and sn‐1,3‐ and sn‐1,2‐diacylglycerols were also present in minor proportions. Significant differences (P &lt; 0.05) in fatty acid distribution existed when different sesame seed cultivars were examined. However, the principal characteristics of the fatty acid distribution in the TAGs, as well as the major PLs, were evident among the three cultivars; unsaturated fatty acids were predominantly concentrated in the sn‐2‐position, and saturated fatty acids primarily occupied the sn‐1‐ or sn‐3‐position. These results suggest that there are no essential differences (P &gt; 0.05) in the oil components among three cultivars.PRACTICAL APPLICATIONSThis paper describes the fatty acid compositions of glycerides, particularly the positional distribution of the fatty acids of triacylglycerols along with those of the main PL in sesame seeds in relation to the endogenous antioxidants. These results were similar to the positional fatty acid distributions in the lipid classes of peanut, corn and soybeans among the plants seeds in the literature, and suggest that there are no essential differences (P &gt; 0.05) in the oil components among the three cultivars. The data obtained would be contributed to both producers and consumers to investigate the functional properties of sesame seed oil.

An Electrostatic/Hydrogen Bond Switch as the Basis for the Specific Interaction of Phosphatidic Acid with Proteins

Phosphatidic acid (PA) is a minor but important phospholipid that, through specific interactions with proteins, plays a central role in several key cellular processes. The simple yet unique structure of PA, carrying just a phosphomonoester head group, suggests an important role for interactions with the positively charged essential residues in these proteins. We analyzed by solid-state magic angle spinning 31P NMR and molecular dynamics simulations the interaction of low concentrations of PA in model membranes with positively charged side chains of membrane-interacting peptides. Surprisingly, lysine and arginine residues increase the charge of PA, predominantly by forming hydrogen bonds with the phosphate of PA, thereby stabilizing the protein-lipid interaction. Our results demonstrate that this electrostatic/hydrogen bond switch turns the phosphate of PA into an effective and preferred docking site for lysine and arginine residues. In combination with the special packing properties of PA, PA may well be nature's preferred membrane lipid for interfacial insertion of positively charged membrane protein domains.

AMP-Activated Protein Kinase α2 Deficiency Affects Cardiac Cardiolipin Homeostasis and Mitochondrial Function

AMP-activated protein kinase (AMPK) plays an important role in controlling energy homeostasis and is envisioned as a promising target to treat metabolic disorders. In the heart, AMPK is involved in short-term regulation and in transcriptional control of proteins involved in energy metabolism. Here, we investigated whether deletion of AMPKalpha2, the main cardiac catalytic isoform, alters mitochondrial function and biogenesis. Body weight, heart weight, and AMPKalpha1 expression were similar in control littermate and AMPKalpha2(-/-) mice. Despite normal oxygen consumption in perfused hearts, maximal oxidative capacity, measured using saponin permeabilized cardiac fibers, was approximately 30% lower in AMPKalpha2(-/-) mice with octanoate, pyruvate, or glutamate plus malate but not with succinate as substrates, showing an impairment at complex I of the respiratory chain. This effect was associated with a 25% decrease in mitochondrial cardiolipin content, the main mitochondrial membrane phospholipid that is crucial for complex I activity, and with a 13% decrease in mitochondrial content of linoleic acid, the main fatty acid of cardiolipins. The decrease in cardiolipin content could be explained by mRNA downregulation of rate-limiting enzymes of both cardiolipin synthesis (CTP:PA cytidylyltransferase) and remodeling (acyl-CoA:lysocardiolipin acyltransferase 1). These data reveal a new role for AMPKalpha2 subunit in the regulation of cardiac muscle oxidative capacity via cardiolipin homeostasis.

The Influence of Plant Hormones on Phospholipid Monolayer Stability

The influence of hormones in water subphase on the stability of monolayers built of phospholipid mixtures extracted from embryogenic (PLE) and nonembryogenic (PLNE) wheat calli was examined. Additionally, experiments on individual lipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidic acid (DPPA), were performed. DPPC was chosen because it was the main phospholipid present in both calli. Negatively charged DPPA could mimic a negatively charged natural mixture of lipids. As hormones, auxins (IAA and 2,4-D), cytokinins (zeatin and kinetin) and zearalenone were chosen. The time of monolayer stability for PLNE calli was much longer than for PLE calli. Kinetics of monolayer stability of PLNE was similar to DPPA, whereas that of PLE was similar to DPPC. Generally, hormones increased the time after which the monolayer stability was reached and decreased the surface pressure. The greatest effect was observed for auxins (especially IAA), whereas cytokinins affected the monolayer stability to a lesser degree.

Influence of silybin on biophysical properties of phospholipid bilayers

Silybin (silibinin) is major biologically active flavonolignan extracted from milk thistle (Sylibum marianum). Its biological activities include hepato-protection, anticancer properties, and antioxidant- and membrane-stabilizing functions. Although membranes are postulated to be one of the cellular targets for silybin, little is known about its interaction with phospholipid bilayers. In the present work, the interactions of silybin with phosphatidylcholine bilayers were studied in detail using fluorescence spectroscopy, microcalorimetry and electron spin resonance techniques. The results showed that silybin interacted with the surface of lipid bilayers. It affected the generalized polarization of the fluorescent probe Prodan, while not influencing the more deeply located Laurdan. Silybin lowered the main phospholipid phase transition temperature as judged by microcalorimetry, and caused the immobilization of spin probe Tempo-palmitate located on the surface of membranes. The mobility of spin probes 5- and 16-doxyl stearic acid was not affected by silybin. Silybin-induced quenching of 1,6-diphenyl-1,3,5-hexatriene fluorescence indicated that some flavonoid molecules partitioned into the hydrophobic region of membranes, which did not change significantly the biophysical properties of the deeper membrane regions. Such a behavior of silybin in membranes is in accordance with its postulated biological functions and neglectable side effects of therapies using silybin.

Diet Alters the Fatty Acid Composition of Individual Phospholipid Classes in Beef Muscle

The objective of this study was to investigate the effect of diet on the distribution of phospholipid classes and fatty acid profiles of individual phospholipid classes in longissimus muscle of beef. An experiment was established to examine the effect of pasture-based versus concentrate diet offered to two different breeds (German Holstein and German Simmental bulls) to enhance the content of beneficial fatty acids in beef and improve the meat quality for the consumer. High-performance thin-layer chromatography was utilized to separate the phospholipid classes. The fatty acid composition of the individual phospholipid classes was determined by gas chromatography. The main phospholipid classes in the muscle were phosphatidylethanolamine and phosphatidylcholine, representing approximately 60% of the total phospholipids, followed by phosphatidylinositol ranging between 11.8 and 14.8%. The results have shown that the fatty acid profiles in the detected seven phospholipid classes can be affected by different feeding systems. Pasture-based feeding resulted in an enrichment of total and individual n-3 fatty acids in all phospholipid classes of muscle lipids of bulls compared with those fed on concentrate. In contrast, pasture-based diet significantly decreased the proportion of total and individual n-6 fatty acids in phospholipid classes, except in the sphingomyelin fraction. The total saturated fatty acid proportions in the phospholipid classes were different and ranged between 4.5% in the cardiolipin fraction and 50.5% in the sphingomyelin fraction of muscle lipids of bulls. Furthermore, the diet effects on the saturated fatty acid proportion in the different phospholipid classes differ widely. The results have shown that the C18:1 trans and CLA profiles in the detected seven phospholipid classes can be affected by different feeding systems.

Docosahexaenoic acid (22:6n‐3) enrichment of membrane phospholipids increases gap junction coupling capacity in cultured astrocytes

Although it is agreed that n-3 polyunsaturated fatty acids (PUFAs) are important for brain function, it has yet to be demonstrated how they are involved in precise cellular mechanisms. We investigated the role of enhanced n-3 PUFA in astrocyte membranes on the gap junction capacity of these cells. Astrocytes isolated from newborn rat cortices were grown in medium supplemented with docosahexaenoic acid (DHA), the main n-3 PUFA in cell membranes, or arachidonic acid (AA), the main n-6 PUFA, plus an antioxidant (alpha-tocopherol or N-acetyl-cystein) to prevent peroxidation. The resulting three populations of astrocytes differed markedly in their n-3:n-6 PUFA ratios in phosphatidylethanolamine and phosphatidylcholine, the main phospholipids in membranes. DHA-supplemented cells had a physiological high n-3:n-6 ratio (1.58), unsupplemented cells had a low n-3:n-6 ratio (0.66) and AA-supplemented cells had a very low n-3:n-6 ratio (0.36), with excess n-6 PUFA. DHA-supplemented astrocytes had a greater gap junction capacity than unsupplemented cells or AA-supplemented cells. The enhanced gap junction coupling of DHA-enriched cells was associated with a more functional distribution of connexin 43 at cell interfaces (shown by immunocytochemistry) and more of the main phosphorylated isoform of connexin 43. These findings suggest that the high n-3:n-6 PUFA ratio that occurs naturally in astrocyte membranes is needed for optimal gap junction coupling in these cells.

Simultaneous analysis of glycolipids and phospholids molecular species in avocado ( Persea americana Mill) fruit

The molecular species of phospholipids (PLs) and glycolipids (GLs) were simultaneously characterized in the pulp and almond of the avocado fruit ( Persea americana Mill) of four varieties by means of high performance liquid chromatography–electrospray ionisation ion-trap tandem mass spectrometry. In the pulp, the predominant species of monoglycosyldiglycerides (MGD) were m/ z 796.6 (oleic/linolenic and linoleic/linoleic acids) and m/ z 800.4 (stearic/linoleic and oleic/oleic acids). One of the main diglycosyldiglycerides (DGD) both in the pulp and almond was m/ z 958.5 (oleic/linolenic); however, the pulp was also rich of m/ z 962.4 (oleic/oleic), whereas in the almond, m/ z 934.5 (palmitic/linoleic and palmitoleic/oleic) and m/ z 960.5 (oleic/linoleic and stearic/linolenic) were more abundant. In the almond, the main PL classes (phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI)) contained always palmitic/linoleic acids. α-Linolenic acid was contained as MGD (linolenic/linolenic) and DGD (linolenic/linolenic), more present in the pulp than in the almond. The major molecular species of glycocerebrosides (GCer) in the pulp and almond carried hydroxy-palmitic acid (C 16h:0)/4,8-sphyngadienine (d 18:2).

Multivariate toxicity screening of liposomal formulations on a human buccal cell line

The influence of various formulation factors on the in vitro cellular toxicity of liposomes on human buccal cells (TR146), were studied by using the concept of statistical experimental design and multivariate evaluation. The factors investigated were the type of main phospholipid (egg-PC, DMPC, DPPC), lipid concentration, the type of charge, liposome size, and amount and nature of the charged component (diacyl-PA, diacyl-PG, diacyl-PS, stearylamine (SA), diacyl-TAP) in the liposomes. Both full factorial design and D-optimal designs were created. Several significant main factors and interactions were revealed. Positively charged liposomes were shown to be toxic. The toxicity of negatively charged liposomes was relatively low. Diacyl-TAP was less toxic than SA, and DPPC was less toxic than DMPC. Low level of positively charged component was favourable and essential when using egg-PC as the main lipid. The amount of negatively charged component, the liposome size, and the total lipid concentration did not affect the toxicity within the experimental room. DPPC appeared to be a good candidate when formulating both positively and negatively charged liposomes with low cellular toxicity. The concept of statistical experimental design and multivariate evaluation was shown to be a useful approach in cell toxicity screening studies.

Comparison of the phospholipid classes in human milk in Japanese mothers of term and preterm infants

Phospholipids (PLs) play an essential role in the growth and brain development of infants. To investigate PL composition in human milk (HM), including lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine (PC) and sphingomyelin (SM), from healthy Japanese mothers. Analyses were performed on colostrum, transitional milk and mature milk from mothers of preterm and term infants. HM samples were collected from mothers of 15 term infants (term group) and of 19 preterm infants (preterm group). PL composition was determined by two-dimensional thin-layer chromatography in conjunction with phosphorus analysis. In both groups, the PL content (% of total lipid) of mature milk was significantly lower than in colostrum. SM and PC were the main PLs in HM, but in the preterm group, the percentage of SM in mature milk was significantly higher and PC in mature milk was significantly lower than in the term group. The transition from colostrum to mature milk leads to an increase in SM and a decrease in PC in the HM of preterm infants, along with a decrease in PL content. This is the first report to demonstrate the differences in PL composition in HM between mothers of preterm and term infants.

Phospholipid molecular profiles in the seed kernel from different sunflower (Helianthus annuus) mutants

Phospholipids are essential components of plant cell membranes whose acyl composition appears to be influenced by oil composition in the sunflower. In the current study, we have determined the diacylglycerol profile of the main phospholipids using phospholipase C degradation and separation of the diacylglycerols by HPLC and GLC. The main polar lipid molecular species were defined in different classes of sunflower kernel: PC, PE, and PI. The proportions of each were determined at different stages of development in order to define the point at which the mutations carried by each sunflower line affected the phospholipid composition of the seeds. The results indicated that modifications to intraplastidial de novo FA synthesis affected the seed phospholipid profile during the whole period of the seed formation, including accumulation and maturation, whereas the influence of mutations in the endoplasmic reticulum desaturases were more readily detected at later stages of development. These results are discussed in terms of the pathways involved in glycerolipid synthesis and phospholipid conversion in sunflower seeds.