Isolation and identification of 1(3),2-diacylglyceryl-(3)-O-4'-(N,N,N-trimethyl)homoserine from the soil amoeba, Acanthamoeba castellanii

A polar lipid accounting for 12.5% of the total lipid nitrogen has been isolated from the protozoan Acanthamoeba castellanii. On the basis of thin-layer chromatography and mass spectral analysis, the lipid has been identified as diacylglyceryltrimethylhomoserine (DGTS). Fast atom bombardment (FAB) mass spectra of DGTS are reported for the first time and are compared to the FAB mass spectra of phosphatidylcholines and the electron ionization (EI) and field desorption (FD) mass spectra of DGTS. Gas-liquid chromatographic-mass spectrometric (GLC-MS) analysis of the acyl chain composition of this lipid has shown that 87.5% consists of cis-9-octadecenoic acid. Plasma membrane isolated from this organism has shown that labeled DGTS appears in the plasma membrane but is not enriched in this fraction. DGTS has been isolated previously only from a limited number of green plants and one species of fungus. Identification of this lipid in Acanthamoeba indicates that this lipid is distributed among a diverse group of lower eucaryotes.     

Biosynthesis of diacylglyceryl-N,N,N-trimethylhomoserine in Rhodobacter sphaeroides and evidence for lipid-linked N methylation.

Rhodobacter sphaeroides, which produces diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) under phosphate-limiting conditions, was incubated with L-[1-14C]- and L-[methyl-14C]methionine in pulse and pulse-chase experiments. The label was incorporated specifically into the polar part of DGTS and of three other compounds. One of them (compound 3) could be identified as diacylglyceryl-N,N-dimethylhomoserine by cochromatography with a reference obtained semisynthetically from DGTS. It was labelled when using L-[1-14C]- as well as L-[methyl-14C]methionine as a precursor and was converted to DGTS when incubated with the DGTS-forming eukaryotic alga Ochromonas danica (Chrysophyceae). Of the other two compounds labelled with L-[1-14C]methionine, compound 2 was also labelled with L-[methyl-14C]methionine whereas compound 1 was not, suggesting that these two intermediates are the corresponding N-methyl and nonmethylated lipids, respectively. The methyltransferase inhibitor 3'-deazaadenosine enhanced the amounts of compounds 1 to 3 but decreased the amount of DGTS. It is concluded that in R. sphaeroides, DGTS is synthesized by the same pathway as in eukaryotic organisms and that the N methylation is the terminal step in this process and occurs on the preformed lipid. Since the phosphatidylcholine-deficient mutant CHB20, lacking the phosphatidylcholine-forming N-methyltransferase was able to synthesize DGTS, one or several separate N-methyltransferases are suggested to be responsible for the synthesis of DGTS.     

工业用油料植物播娘蒿引种初报

在四川采集到若干亚麻酸含量高的十字花科油料植物,这些植物种子的脂肪酸分析结果表明,涩荠(Malcolmia africana(L.)R.Br)和硬毛南芥(Arabis hirsuta(L.)Scop.)具有较高的亚麻酸含量,分别为57.37％和51.38％,但引种较难。播娘蒿(Decurainia sophia(L.)Webb ex Prantl)的种子含油量高,特别是红原采集的样本,其含油量达44.17％;亚麻酸含量也较高,达40.9％;引种的种子产量较高,达1264.5kg/hm~2。作者认为,这种油料植物可引种用于工业。     

Membrane lipid biosynthesis in Chlamydomonas reinhardtii. In vitro biosynthesis of diacylglyceryltrimethylhomoserine

Diacylglyceryltrimethylhomo-Ser (DGTS) is an abundant lipid in the membranes of many algae, lower plants, and fungi. It commonly has an inverse concentration relationship with phosphatidylcholine, thus seemingly capable of replacing this phospholipid in these organisms. In some places this replacement is complete; Chlamydomonas reinhardtii is such an organism, and was used for these investigations. We have assayed headgroup incorporation to form DGTS in vitro. The precursor for both the homo-Ser moiety and the methyl groups was found to be S-adenosyl-L-Met. DGTS formation was associated with microsomal fractions and is not in plastids. By analogy with phosphatidylcholine and phosphatidylethanolamine biosynthesis in higher plants, the microsomal activity probably is associated with the endoplasmic reticulum. The pH optimum for the total reaction was between 7.5 and 8.0, and the best temperature was 30 degrees C. The apparent K(m) and V(max) for S-adenosyl-L-Met in the overall reaction were 74 and 250 microM, respectively.     

Occurrence of diacylglyceryltrimethylhomoserines and major phospholipids in some plants

Over 40 higher plant species were examined for the contents of total lipids, phospholipids, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) by using micro-HPTLC. The results showed a wider range of plants containing betaine lipids. So, DGTS was found in some higher plant species, not studied earlier, belonging to Equisetophyta, Polypodiophyta; the lipid composition of many other species from Spermatophyta was also studied. It was demonstrated that more primitive plant species contained, as a rule, the betaine lipid DGTS. The quantitative data for the distribution of the main phospholipid classes PC, PE, and PG in various plant species and their tissues are given in this paper.     

Some radiobiological effects in higher plants growing on the territory of the East Ural Radioactive Trace

The spontaneous level of cytogenetic damage in three plant species (Achyrophorus maculatus (Scop.) L.; Plantago lanceolata L.; and Plantago media L.) growing on the territory of the East Ural Radioactive Trace is studied. The radiation resistance of plants from radioactive and control nonpolluted sites is determined. The effects of additional fractionated irradiation at different doses and the role of antioxidant systems in the formation of the radioprotector effect are examined. It is shown that the level of the mutation process in the plant population growing at the radiation polluted sites is increased compared to the control populations from nonpolluted territories. Additional acute γ irradiation of seeds collected from polluted and nonpolluted territories demonstrates improved radiation resistance of the plants from the polluted territory. In the control population of A. maculatus in the versions with a one-hour interval between fractions, the radiation effect follows the additivity principle; at the same time, at a one-day interval between fractions, a highly significant radioprotective effect is manifested clearly in the experimental population. For higher plants, the enhanced effectiveness of the functioning of the antioxidant systems in plants growing on territories contaminated with radiation is shown for the first time. Thus, the radioprotector mechanisms of low-dose chronic and preliminary irradiation are similar and one of these mechanisms is activation of the antioxidant systems in plants growing under conditions of chronic low-intensity irradiation for long periods of time.     

Distribution of a Betaine Lipid O-(1,2-Diacylglycero)-4′-(N,N,N-Trimethyl)homoserine in Tissues of Some Lycopodiophyta Species

The distribution of O-(1,2-diacylglycero)-4-(N,N,N-trimethyl)homoserine (DGTS), a betaine lipid, in ten samples of plants belonging to the division Lycopodiophyta collected in various habitats was studied. Homogeneous plant tissues (vegetative shoots and spikelets) and mixed tissues (shoots with spikelets) were analyzed. A particular attention was paid to the DGTS-synthesizing ability of various club mosses, various tissue types forming an organ in a single plant species, as well as the ratio between DGTS and other glycerolipid classes.     

Distribution of a betaine lipid O-(1,2-diacylglycero)-N,N,N-trimethylhomoserine in tissues of some Lycopodiophyta species

The distribution of O-(1,2-diacylglycero)-4'-(N,N,N-trimethyl)homoserine (DGTS), a betaine lipid, in ten samples of plants belonging to the division Lycopodiophyta collected in various habitats was studied. Homogeneous plant tissues (vegetative shoots and spikelets) and mixed tissues (shoots with spikelets) were analyzed. Particular attention was paid to the DGTS-synthesizing ability of various club mosses and to various tissue types forming an organ in a single plant species, as well as the ratio between DGTS and other glycerolipid classes. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 6; see also http://www.maik.ru.     

Adaptations for an amphibious life: changes in leaf morphology, growth rate, carbon and nitrogen investment, and reproduction during adjustment to emersion by the freshwater macrophyte Littorella uniflora

Littorella uniflora (L.) Ascherson is a small, perennial, amphibious rhizophyte of rosette life-form which is common along the margins of lakes, tarns and reservoirs where water-level fluctuations are often rapid and unpredictable. The majority of plants are continuously submersed and reproduce vegetatively, but a small proportion become completely emersed for variable lengths of time, when flowering and seed set occur. To find out how L. uniflora adjusts to sudden emersion we studied the plants at a reservoir where water level falls each spring and remains low throughout the summer; L. uniflora adjusted very quickly showing a degree of phenotypic plasticity not expected in a 'stress tolerator', including the production of a new set of terrestrial leaves with reduced lacunal volume and increased stomatal density, a rapid increase in leaf growth rate, and flowering within 3–4 wk. Comparison of terrestrial L. uniflora with aquatic plants growing permanently submersed in lake and tarn habitats showed that three to fourfold more carbon (C) and nitrogen (N) was incorporated into above-ground biomass by emersed plants. However, ramet production in the aquatic environment appeared to be more costly, in terms of C and N invested, than terrestrial flower and seed production. The combination of continuous, submersed vegetative spread with the capacity for a high degree of phenotypic plasticity allowing some flower and seed production to occur during brief periods of emersion seems to account for the success of this plant in the amphibious niche.     

Seasonal variability of lipids and fatty acids in the tree-growing lichen Xanthoria parientina L.

The composition of lipids, PLs and FAs in the treegrowing lichenXanthoria parientina, collected during the period from Marchto May, was studied. The major polar lipids found, includingphospholipids, were DGTS, PC, PE, and PG. Polar and PL contentswere also identified, and certain trends in the changing proportionsof PC (increasing from 17.8 to 50.1%) and DGTS (decreasing from27.1 to 12.6%) were determined. The fatty acid composition wasexamined using capillary GC-MS in the neutral, glyco- and PLfractions. Hydroxy acids were detected only in the glycolipidfraction; their seasonal dynamics were also studied. The seasonalchanges occurring in lipid composition due to the temperaturefactor were identified. It was found that X. parientina hada characteristic temperature-based lipid pattern, increasingin its neutral lipid content from 40.6% in March to 52.7% inMay but decreasing in glycolipid from 39.0% in March to 27.0%in May. Key words: Xanthoria, lipids, DGTS, fatty acids, lichen     

The regulator gene phoB mediates phosphate stress-controlled synthesis of the membrane lipid diacylglyceryl-N,N,N-trimethylhomoserine in Rhizobium (Sinorhizobium) meliloti

Bacteria react to phosphate starvation by activating genes involved in the transport and assimilation of phosphate as well as other phosphorous compounds. Some soil bacteria have evolved an additional mechanism for saving phosphorous. Under phosphate-limiting conditions, they replace their membrane phospholipids by lipids not containing phosphorus. Here, we show that the membrane lipid pattern of the free-living microsymbiotic bacterium Rhizobium (Sinorhizobium) meliloti is altered at low phosphate concentrations. When phosphate is growth limiting, an increase in sulpholipids, ornithine lipids and the de novo synthesis of diacylglyceryl trimethylhomoserine (DGTS) lipids is observed. Rhizobium meliloti phoCDET mutants, deficient in phosphate uptake, synthesize DGTS constitutively at low or high medium phosphate concentrations, suggesting that reduced transport of phosphorus sources to the cytoplasm causes induction of DGTS biosynthesis. Rhizobium meliloti phoU or phoB mutants are unable to form DGTS at low or high phosphate concentrations. However, the functional complementation of phoU or phoB mutants with the phoB gene demonstrates that, of the two genes, only intact phoB is required for the biosynthesis of the membrane lipid DGTS.     

Lipids in Cryptomonas CR-1. II. Biosynthesis of Betaine Lipids and Galactolipids

The biosynthesis of lipids in Cryptomonas strain CR-1 was studiedusing radioactive tracers. For studies of general aspects ofthe biosynthesis of lipids, the cells were labelled with [¹⁴C]NaHCO₃or with [l,3-¹⁴]glycerol. In both cases, monogalactosyl diacylglycerol(MGDG) was the most heavily labelled lipid. Phosphatidylcholineand the alanine lipid DGTA were not labelled to specific activitiescomparable to those of MGDG and DGDG. It is improbable thatthe so-called "eukaryotic pathway", which has been suggestedas the pathway for the synthesis of " eukaryotic" molecularspecies of MGDG from PC in higher plants, is operative in Cryptomonascells which contain typical "eukaryotic" MGDG. The homoserinelipid DGTS was labelled to a significant level only in its polargroup. The C-3 and C-4 atoms of methionine, as well as the methylcarbon of methionine, were incorporated into both DGTS and DGTA,whereas the C-l carbon of methionine was incorporated uniquelyinto DGTS. Results of pulse-chase experiments with [3,4-¹⁴C]methionineand [methyl.-^l4C]methionine suggest the conversion of DGTS toDGTA. (Received April 22, 1991; Accepted June 12, 1991)     

Mitochondrial Activity and Ethanol Accumulation in Ice-encased Winter Cereal Seedlings

Cold-hardened dark-grown seedlings of winter wheat (Triticum aestivum L.) and winter rye (Secale cereale L.) are killed during total encasement in ice at −1 C at a rate related to the initial cold hardiness of the cultivars. Few plants remain alive after 7 days of encasement. Nonhardened seedlings are rapidly killed in ice. The respiratory properties of mitochondria isolated from plants after increasing periods of ice encasement decline slowly, and activity is little impaired when intact plants are about 50% killed. Electron microscopy indicates that mitochondrial structure is not disrupted until 3 weeks of ice encasement. Ethanol accumulates in hardened and nonhardened plants in ice, but at levels which are not toxic to the plants.     

Phytoextraction of trace elements and physiological changes in Indian mustard plants (Brassica nigra L.) grown in post methanated distillery effluent (PMDE) irrigated soil

The metal accumulation potential and its physiological effects in Indian mustard plants (Brassica nigra L.) grown in soil irrigated with post methanated distillery effluent (25%, 50%, 75%, 100%, v/v) were studied after 30, 60 and 90 days after sowing. An increase in the chlorophyll and protein contents was recorded at the lower concentrations of post methanated distillery effluent (PMDE) at initial exposure periods followed by a decrease at higher concentrations of PMDE compared to their respective controls. An enhanced lipid peroxidation in tested plants was observed, which was evidenced by the increased malondialdehyde content in shoot, leaves and seeds at all the concentrations of PMDE and exposure periods compared to their respective controls. This study revealed that Indian mustard plants (B. nigra L.) are well adopted to tolerate and accumulate high quantities of trace elements due to increased level of antioxidants (cysteine and ascorbic acid) in root, shoot and leaves of the treated plants at all the concentrations and exposure periods except at 90 days, whereas a decrease was observed at 100% PMDE as compared to their respective controls.     

Seasonal changes in polar lipids in fronds of the ferns Dryopteris filix-mas and Matteuccia struthiopteris

The distribution pattern of total lipids, glyco- and phospholipids, and one betaine lipid (DGTS) in the fronds of the ferns Dryopteris filix-mas and Matteuccia struthiopteris was studied. The lipid composition of the embryo leaflets forming a bud, or treble clef, and that of fully opened leaves changed throughout the growth season. The maximum amount of DGTS in clefs and mature leaves was detected at the beginning of the season. By midsummer, the DGTS content decreased, dropping to zero in the fully opened leaves, and then increased again. The amount of DGTS in the clefs collected in October versus those collected in May was somewhat higher in the case of Dryopteris filix-mas and almost twofold lower in the case of Matteuccia struthiopteris. The ratio between polar lipids contained in the clefs and mature leaves throughout the growth season was determined.     

古尔班通古特沙漠四种草本植物不同生长期C、N、P化学计量比的动态变化分析

以古尔班通古特沙漠地区广泛分布的4种荒漠草本植物沙蓬（Agriophyllum squarrosum（L.） Moq.）、雾冰藜（Bassia dasyphylla（Fisch.et Mey.） O.Kuntze）、角果藜（Ceratocarpus arenarius L.）和碱蓬（Suaeda glauca（Bge.） Bge.）为对象,对他们在不同生长期的C、N、P含量及计量比的动态变化进行研究。结果显示：4种植物的C、N、P含量以及C：N、C：P、N：P在整个生长期的变化趋势不同,不同生长期各个指标的变异系数在物种间存在明显差异;4种植物的C、N、P含量及计量比的季节性变异分析结果表明,N、P含量及C：N、N：P的季节性变异幅度较大,相反,C含量和C：P的变异幅度较小;4种植物C含量和C：P由季节变化所引起的变异系数范围分别为2.43%~15.80%和6.77%~18.67%,而N、P含量和C：N、N：P的变异系数范围分别为21.26%~34.38%、11.18%~30.26%、18.52%~27.11%、14.90%~25.91%;整个生长季内,4种植物C、N、P含量及计量比的变异系数依次为：N（30.00%） > C：N（22.87%） > N：P （20.12%） > P（17.76%） > C：P（11.72%） > C（9.02%）。研究结果表明4种植物在不同生长周期的C、N、P含量及计量比的变化规律与他们的生长周期和植物种类存在显著相关性。     

The characterisation and cyclic production of a highly unsaturated homoserine lipid in Chlorella minutissima

The marine alga Chlorella minutissima contains DGTS (diacylglyceryl-N,N,N-trimethylhomoserine) as a major component (up to 44% of total lipids). This lipid is absent from other members of the Chlorococcales, except for C. fusca, which contains DGTS as 1.3% of total lipids. Contrary to expectation, the DGTS is accompanied by PC (phosphatidylcholine) as the major phospholipid. DGTS is normally highly saturated in the C-1 position of glycerol, but in C. minutissima, both C-1 and C-2 are acylated with EPA (eicosapentaenoic acid, 20:5) in the major molecular species (over 90% of total). The DGTS level shows a marked rhythmic fluctuation with time which is inversely correlated with the level of MGDG (monogalactosyldiacylglycerol), the other major lipid. Improved NMR data and the first electrospray MS data on this lipid are presented.     

三峡水库消落带外来植物组成及分布特征

[目的]探究三峡水库消落带外来植物的物种组成及分布特征,为库区外来植物管理防控、生物多样性保护和生态安全管理提供理论支持和数据参考。[方法]通过对库区消落带外来植物的实地调查,结合文献资料,研究外来植物的物种组成、原产地、引入途径、生活型及消落带外来植物的分布现状。[结果]三峡水库消落带存在66种外来植物,隶属于22个科50属,其中菊科、豆科、茄科和苋科是三峡水库消落带外来植物的优势科,共有40种,占总种数约60.6%,菊科的数目最多,达到21种;外来植物中来源于美洲的物种最多,达到66.7%;生活型以一年生草本植物居多;花果期多集中于5—10月份;外来植物中分布最为广泛的物种是大狼杷草、喜旱莲子草、鬼针草、钻叶紫菀、小蓬草和土荆芥;三峡水库内库首和库中区域消落带分布的外来植物较多。[结论]三峡水库消落带外来植物种类较多,分布广泛,在常年回水区外来植物入侵态势较为严重,入侵植物防控的形势不容乐观。建议结合消落带管理方法和消落带植物群落特征建立外来植物防治机制,积极采取相关措施,加强消落带外来植物扩散机制及其对本地生态系统影响的研究。     

Formation of diacylglyceryltrimethylhomoserines in the surface culture of the basidiomycete <Emphasis Type="Italic">Flammulina velutipes</Emphasis>

Betaine-type lipids—diacylglyceryltrimethylhomoserines (DGTS)—were revealed in the mycelium of the basidial fungus Flammulina velutipes obtained by surface cultivation on agarized malt extract. DGTS accumulation was shown to occur at the late stages of culture development under deficiency of a complex of nutrients, including nitrogen, phosphorus, potassium, and trace elements. Induction of the synthesis of betaine lipids in F. velutipes occurred against the background of a decreased rate of growth of the vegetative mycelium, formation of monilioid hyphae, and inhibition of fructification. The relationship between DGTS formation and the environmental factors (temperature, illumination) was studied. It was established that the most active DGTS accumulation occurred at 15°C in the dark.