Fatty Acids In Phosphatidylglycerol Research Articles

The unsaturation of phosphatidylglycerol in thylakoid membrane alleviates PSII photoinhibition under chilling stress

Over-expression of chloroplast glycerol-3-phosphate acyltransferase gene (LeGPAT) in tomato increased cis-unsaturated fatty acid content in phosphatidylglycerol (PG) of the thylakoid membrane. Under chilling stress, the oxygen evolving activity, the maximal photochemical efficiency of PSII (F (v)/F (m)), and superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities decreased less in sense lines than in antisense lines compared to wild-type (WT) plants. Consistently, the relative electric conductivity, O⁻₂and H(2)O(2) contents in sense lines were lower than those of WT and antisense lines. The antisense lines with low level of unsaturated fatty acids in PG were extremely susceptible to photoinhibition of PSII and had a significant reduction in the D1 protein content of PSII reaction center under chilling stress. However, in the presence of streptomycin (SM), the degradation of D1 protein was faster in sense lines than in WT and antisense plants. These results suggested that, under chilling stress conditions, increasing cis-unsaturated fatty acids in PG through over-expression of LeGPAT can alleviate PSII photoinhibition by accelerating the repair of D1 protein and improving the activities of antioxidant enzymes in chloroplasts.

The increase in unsaturation of fatty acids of phosphatidylglycerol in thylakoid membrane enhanced salt tolerance in tomato

Overexpression of chloroplastic glycerol-3-phosphate acyltransferase gene (LeGPAT) in tomato increased cis-unsaturated fatty acid content in phosphatidylglycerol (PG) of thylakoid membrane. By contrast, suppressing the expression of LeGPAT decreased the content of cis-unsaturated fatty acid in PG. Under salt stress, sense transgenic plants exhibited higher activities of chloroplastic antioxidant enzymes, lower content of reactive oxygen species (ROS) and less ion leakage compared with the wild type (WT) plants. The net photosynthetic rate (P N) and the maximal photochemical efficiency (Fv/Fm) of photosystem II (PSII) decreased more slightly in sense lines but more markedly in the antisense ones, compared to WT. D1 protein, located in the reactive center of the PSII, is the primary target of photodamage and has the highest turnover rate in the chloroplast. Under salt stress, compared with WT, the content of D1 protein decreased slightly in sense lines and significantly in the antisense ones. In the presence of streptomycin (SM), the net degradation of the damaged D1 protein was faster in sense lines than in other plants. These results suggested that, under salt-stress conditions, increasing cis-unsaturated fatty acids in PG by overexpression of LeGPAT can alleviate PSII photoinhibition by accelerating the repair of D1 protein and improving the activity of antioxidant enzymes in chloroplasts.

Response of xanthophyll cycle and chloroplastic antioxidant enzymes to chilling stress in tomato over-expressing glycerol-3-phosphate acyltransferase gene

Over-expression of chloroplastic glycerol-3-phosphate acyltransferase gene (LeGPAT) increased unsaturated fatty acid contents in phosphatidylglycerol (PG) of thylakoid membrane in tomato. The effect of this increase on the xanthophyll cycle and chloroplast antioxidant enzymes was examined by comparing wild type (WT) tomato with the transgenic (TG) lines at chilling temperature (4 °C) under low irradiance (100 µmol m−2 s−1). Net photosynthetic rate and the maximal photochemical efficiency of photosystem (PS) 2 (Fv/Fm) in TG plants decreased more slowly during chilling stress and Fv/Fm recovered faster than that in WT plants under optimal conditions. The oxidizable P700 in both WT and TG plants decreased during chilling stress under low irradiance, but recovered faster in TG plants than in the WT ones. During chilling stress, non-photochemical quenching (NPQ) and the de-epoxidized ratio of xanthophyll cycle in WT plants were lower than those of TG tomatoes. The higher activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in TG plants resulted in the reduction of O2 −· and H2O2 contents during chilling stress. Hence the increase in content of unsaturated fatty acids in PG by the over-expression of LeGPAT could alleviate photoinhibition of PS2 and PS1 by improving the de-epoxidized ratio of xanthophyll cycle and activities of SOD and APX in chloroplast.

Characterisation of the Escherichia coli membrane structure and function during fedbatch cultivation

BackgroundImportant parameters during recombinant protein production in Escherichia coli, such as productivity and protein activity, are affected by the growth rate. This includes the translocation of protein over the membrane to gain better folding capacity or reduced proteolysis. To vary the growth rate two techniques are available: fedbatch and continuous cultivation, both controlled by the ingoing feed rate.ResultsDuring fedbatch cultivation, E. coli contains phosphatidylethanolamine, phosphatidylglycerol, cardiolipin and saturated fatty acids in amounts which are stable with growth rate. However, the levels of cardiolipin are very high compared to continuous cultivation. The reason for fedbatch triggering of this metabolism is not known but hypothesised to result from an additional need for carbon and energy. The reason could be the dynamic and sometimes rapid changes in growth rate to which the fedbatch cell has at all times to adjust. The membrane flexibility, essential for translocation of various components, is however to some degree sustained by production of increased amounts of unsaturated fatty acids in phosphatidylglycerol. The result is a functionally stiff membrane which generally promotes low cell lysis and is constant with respect to protein leakage to the medium. At comparatively high growth rates, when the further stabilising effect of cyclic fatty acids is gone, the high level of unsaturated fatty acids results in a pronounced effect upon sonication. This is very much in contrast to the membrane function in continuous cultivation which shows very specific characteristics as a function of growth rate.ConclusionsThe stiff and unchanging fedbatch membrane should promote a stable behaviour during downstream processing and is less dependent on the time of harvest. However, optimisation of protein leakage can only be achieved in the continuously cultivated cell where leakage is twice as high compared to the constant leakage level in fedbatch. If leakage is undesired, continuous cultivation is also preferred since it can be designed to lead to the lowest values detected. Induction at low growth rate (<0.2 h-1) should be avoided with respect to productivity, in any system, since the specific and total protein production shows their lowest values at this point.

An increase in unsaturation of fatty acids in phosphatidylglycerol from leaves improves the rates of photosynthesis and growth at low temperatures in transgenic rice seedlings.

The level of cis-unsaturated fatty acids in phosphatidylglycerol (PG) from rice leaves was genetically altered from 19.3% in the wild-type to 29.4 and 32.0% in T1 plants segregated with cDNAs for glycerol-3-phosphate acyltransferase of chloroplasts (GPAT; EC 2.3.1.15) from Arabidopsis (+AGPAT plant) and spinach (+SGPAT plant), respectively; and to 21.4% in a non-transformant segregated from +SGPAT plants (-SGPAT plant). In all these plants, O2 evolution from leaves was similar at 25 degrees C and was impaired to a similar extent at 5 and 11 degrees C. However, in parallel with the levels of cis-unsaturated fatty acids in PG, +AGPAT and +SGPAT plants showed less impaired rates of O(2) evolution from leaves than the wild-type and -SGPAT plants at 14 and 17 degrees C. In agreement with this, the fresh weight of 14-day-old seedlings increased to 571 + or - 18, 591 + or - 23, 687 + or - 32 and 705 + or - 31 mg in the wild-type, -SGPAT, +AGPAT and +SGPAT plants, respectively, after 6 weeks at 17/14 degrees C (day/night). These results demonstrate the practical importance of the present technology with GPAT in improvement of the chilling sensitivity of crops.

Effect of Non-Chilling Temperature and Light Intensity during Growth of Squash Cotyledons on the Composition of Thylakoid Membrane Lipids and Fatty Acids

The lipid composition, in particular the content of fatty acids in phosphatidylglycerol (PG), is believed to be crucial for the understanding of the chilling injury mechanism occurring in the thylakoid membrane (TM) of higher plants. In this investigation, we have studied the effect of growth conditions (e.g. temperature and light) on the composition of glycerolipid classes and their respective fatty acids during the maturation period of squash cotyledons. We have found that the changes in the lipid fatty acid composition of TM which are induced by different temperature and light growth conditions occurred only during the development of cotyledons but not when these latter had reached their maturity. The major changes were an increase of 18:3 and a decrease of 16:0 in galacto- and sulfolipids, and an increase of 16:1(3t) and 18:3 with a concomitant decrease of 16:0 and 18:1 in PG, when the temperature was low (20°C compared to 30°C). We conclude that low temperature conditions of growth induced an increase of the end acyl products [18:3 and/or 16:1(3t)] in PG and galactolipids. The possible mechanism is discussed in terms of the relative temperature dependence of fatty acid synthesis and desaturation processes. The light intensity of growth affected only the fatty acid composition of PG, i.e. when it was high (350 compare to 100 μmol m−2 s−1), an increase of 16:1(3t) at the expense of 16:0 was observed. Whatever the growth conditions, the level of 16:1(3t) increased during the maturation of cotyledons and was characterized by an increasing linear correlation (r=0.99) with the fresh weight. In contrast, a decreasing linear relationship (r=–0.99) was found between the fresh weight and 16:0. Thus, we propose that a constant level of 16:1(3t) is a good criterion for defining the chloroplast maturity and that it is highly advisable to study the effect of temperature and light on the lipid composition when the cotyledons have reached their maturity. Under these conditions, these effects can be considered regardless of developmental factors.

Position and pairing of fatty acids in phosphatidylglycerol from pea leaf chloroplasts and mitochondria

Chloroplasts and mitochondria were isolated in pure form from pea leaves and used for a comparison of membrane lipids. Three phospholipids present in both organelles (i.e. phosphatidylcholine, -inositol and -glycerol) showed a lipid as well as an organelle-specific fatty acid profile. Phosphatidylglycerol was subjected to an analysis of positional distribution and pairing of fatty acids. The chloroplast phospholipid contained only molecules of procaryotic C 18/C 16 pairing type, whereas the lipid of mitochondrial origin was a mixture of C 18/C 16, C 16/C 18 and C 18/C 18 pairings in the approximate proportions of 43, 32 and 25%, respectively. The pool of C 18/C 18 pairings may represent a source for cardiolipin biosynthesis.

Chilling sensitivity in higher plants: the role of phosphatidylglycerol

Abstract A compilation of data on the level of high melting point fatly acids in the phosphalidylglycerol of leaves of higher plants suggests that the content of these acids is not directly related to the chilling sensitivity of the plant. Within a given plant family the level of high melting point fatty acids in phosphatidylglycerol appears to be relatively constant, although the individual species may differ widely in their susceptibility to low temperature. It seems possible that differences observed in the levels of high melting point fatty acids in the phosphatidylglycerols of chilling‐sensitive and chilling‐tolerant plants may be largely due to choice of experimental material.

Fatty-acid composition of polar lipids in fruit and leaf chloroplasts of ?16:3?- and ?18:3?-plant species

The fatty-acid composition of polar lipids from fruit and leaf chloroplasts was compared in five Solanaceous and two cucurbit species. The acylated fatty acids in monogalactosyl diglycerides (MGDG) from leaf chloroplasts of all five Solanaceous species included substantial amounts of Δ (7,10,13)-hexadecatrienoic acid (16:3). In contrast, the MGDG from fruit chloroplasts of the Solanaceae contained very little of this plastid-specific polyunsaturate, and instead included a proportionately greater percentage of linoleic acid (18:2). In MGDG from leaf chloroplasts of two cucurbits, α-linolenic acid (18:3) constituted 94-95% of the acylated fatty acids. Fruit-chloroplast galactolipids of the cucurbits had a greater abundance of 18:2, and hence a higher 18:2/18:3 ratio, than found in the corresponding leaf lipids. Among the phosphoglycerides, the unusual fatty acid Δ3-trans-hexadecenoate (trans-16:1) constituted from 15 to 24% of the acylated fatty acids in phosphatidyl glycerol (PG) from leaf chloroplasts (all species). In sharp contrast, trans-16:1 was virtually absent in PG from fruit chloroplasts of both Solanaceous and cucurbit species, and was replaced by a proportionate increase in the content of palmitate (16:0). The observed differences in the polar lipid fatty-acid composition of fruit and leaf chloroplasts are discussed in terms of the relative activity of several intrachloroplastic enzymes involved in lipid synthesis and fatty-acyl desaturation.

A simplified isolation of phosphatidylglycerol

A two-stage, thin-layer chromatographic technique for the unequivocal separation of phosphatidylglycerol (PG) from other leaf glycerolipids is described. The method takes advantage of the partitioning of PG into petroleum ether from acidified aquous methanol and of its high chromatographic mobility on acidified adsorbents. Although particularly suited to the analyses of fatty acids in PGs from diverse leaves, the technique may also be used preparatively. The high content of saturated fatty acids within the PG of C4, dicotyledenous plants but not of C4 grasses is confirmed. Hexadeca- trans-3-enoic acid was absent from the leaf PG of all of the orchid species analysed.

Compositions and Positional Distributions of Fatty Acids in Phospholipids from Leaves of Chilling-Sensitive and Chilling-Resistant Plants

The compositions and positional distributions of fatty acids in the major leafphospholipids of phosphatidylg lycerol, phosphatidylcholine and phosphatidylethanolamine were analyzed by gas-liquid chromatography and enzymic hydrolysis, and chilling-sensitive and chilling-resistant plants were compared with respect to the relative contents of palmitic and (ranj-jd3-hexadecenoic acids in the separated phospholipids. A distinct difference between these plants was found in the fatty acid compositions of phosphatidylglycerol, in which the sum of palmitic and trans-A 3-hexadecenoic acids ranged from 60 to 78% of the total fatty acids in 8 species of chilling-sensitive plants, and from 50 to 57% in 11 species of chilling-resistant plants. The only exception among the chillingsensitive plants in this respect was the tomato, in which the sum of palmitic and trans^]3-hexadecenoic acids in phosphatidylglycerol amounted to 54%. The fatty acid compositions and the positional distributions of fatty acids in phosphatidylg lycerol suggest that the occurrence of high proportions of dipalmitoyl and l-palmitoyl-2-((raRi-/J3hexadecenoyl) species in this lipid is correlated with the susceptibility to chilling of the leaves of higher plants. In the compositions and positional distributions of fatty acids in phosphatidylcholine and phosphatidylethanolamine, no difference was found between the chilling-sensitive and chilling-resistant plants.

Phosphatidylglycerol in lung surfactant II. Subcellular distribution and mechanism of biosynthesis in vitro

Lamellar inclusion bodies, apparent precursors for alveolar surfactant lining, have remarkably similar phospholipid composition to surfactant from alveolar lavage, but distinctly different from other fractions studied: mitochondria, microsomal fraction containing endoplasmic reticulum membranes, plasma membranes and nuclei. Surfactant contained (as % of total phospholipid phosphate): 75.5–77.0% lecithin, 11.0–11.2% phosphatidylglycerol, 4.2–4.6% phosphatidylethanolamine, 3.0–3.2% phosphatidylinositol, 1.5–1.7% bis(monoacylglycerol) phosphate, 1.2–1.9% phosphatidylserine, and 0.7–1.5% sphingomyelin. Fatty acids of phosphatidylglycerol from lamellar bodies were similar to those from microsomes but different from those in mitochondria. Lung homogenate in continuous sucrose density gradient displayed two major activity peaks of phosphatidylglycerol synthesis: the heavier from mitochondria; the lighter from endoplasmic reticulum. Studies on mechanism of phosphatidylglycerol synthesis in vitro revealed (in these two fractions) CDP-diglyceride and sn-glycerol phosphate precursors to phosphatidylglycerol phosphate, that hydrolysed to phosphatidylglycerol. In microsomes disaturated CDP-diglycerides were 1.6–1.9 times more active substrates than in mitochondria, whereas CDP-diglycerides from egg lecithin were almost equally active. In contrast to lung mitochondria no cardiolipin synthesis was detected in microsomes. The highest specific activities for phosphatidate cytidyltransferase, CDP-diglyceride-inositol phosphatidyltransferase, choline phosphotransferase, and phosphatidylethanolamine methyltransferase were all found in microsomes. The present in vitro studies and additional evidence (M. Hallman and L. Gluck (1975) Fed. Proc. 34, 274) support the hypothesis that de novo synthesis of surfactant lecithin phosphatidylinositol and phosphatidylglycerol takes place in the endoplasmic reticulum of alveolar cells.

The relationship between fatty acid structure and the positional distribution of esterified fatty acids in phosphatidyl glycerol from Mycoplasma laidlawii B

1. 1. The distribution of a number of fatty acids between the 1- and 2-positions of phosphatidyl glycerol from Mycoplasma laidlawii B has been investigated. The fatty acid composition of the phosphatidyl glycerol was systematically altered so that the positional distribution values determined here are accurate reflections of the relative positional affinities of the individual fatty acids examined. 2. 2. The positional distribution of any given fatty acid constituent was independent of the amount of that acid in the phosphatidyl glycerol, provided that the fatty acid in question was not present in sufficient quantity to saturate the preferred position. 3. 3. Within any single class of fatty acids, the positional specificity was markedly dependent on the chain length of the fatty acid. The smaller the total number of carbon atoms, the lesser was the affinity for the 1-position. 4. 4. Positional distribution was also dependent on the structural characteristics of the fatty acids. The following is the order of the fatty acid classes arranged according to a decreasing affinity for the 1-position: straight-chain saturated > branched-chain saturated > trans-monounsaturated > cis-monounsaturated > cyclopropane > cis-diunsaturated.

The path of carbon in photosynthesis of the lipids

The rates of C 11 incorporation into lipids and their components during steady-state photosynthesis in C 11O 2 by Chlorella pyrenoidosa reveal the metabolic importance of the galaclolipids and phosphatidyl glycerol. The most, rapidly labeled of the water-soluble deacylation products were galactosyl glycerol, digalactosyl glycerol, diglycerophosphate, sulfoglycosyl glycerol, and glycerophosphorylinositol. Labeling of the triglycerides proceeded more slowly than that of any of the surfactant lipids. Acid hydrolysis of the labeled galactolipids demonstrated active exchange of the galactose moieties with the intermediates of hexose photosynthesis and relatively slower labeling of the associated glycerol or fatty acids. However, the fatty acids of phosphatidylglycerol and the galactosyl diglycerides were more rapidly labeled than any other esterified fatty acids. Periodate oxidation of diglycerophosphate from phosphatidylglycerol indicated uniform labeling before 5 min. of steady-state photosynthesis. Possible metabolic sequences in the biosynthesis of the galactolipids and the phosphatides are discussed. The remarkable metabolic activity and high concentrations of phosphatidyl glycerol and the galactolipids in Chlorella attest to their importance in photosynthesis.