Stearidonic acid (18:4ω3) in Primula florindae

Stearidonic acid (18:4ω3), which is reported to be of rare occurrence in the plant kingdom and which is of considerable dietary and pharmaceutical interest has been found in three closely related Primula species. It occurs, together with γ-linolenic acid (3–4% of the seed oil total fatty acids), in significant percentages in Primula florindae (11%), P. sikkimensis (14%) and P. alpicola (14%). 18:4(ω3 may also be of chemotaxonomic interest in the genus Primula, as high levels may be typical for section Sikkimensis. The only commercial plant source of stearidonic acid known so far is the seed oil of Ribes nigrum.     

The regulation of the fatty-acid composition of the triacylglycerols in microsomal preparations from avocado mesocarp and the developing cotyledons of safflower

The utilisation of [¹⁴C]glycerol 3-phosphate and [¹⁴C]linoleoyl-CoA in the synthesis of triacylglycerol has been studied in the microsomal preparations of developing cotyledons of safflower seed. The results confirm that the glycerol backbone, which flows towards triacylglycerol from phosphatidic acid through the Kennedy pathway, can enter phosphatidylcholine from diacylglycerol. The equilibration between diacylglycerol and phosphatidylcholine offers a mechanism for the return of oleate to phosphatidylcholine for desaturation to linoleate. We have established that the oleate entering position 1 of sn-phosphatidylcholine from diacylglycerol is desaturated in situ to linoleate. The results indicate that the diacylglycerol phosphatidylcholine interconvertion coupled to the acyl exchange between acyl-CoA and position 2 of sn-phosphatidylcholine brings about the continuous enrichment of the glycerol backbone with C₁₈-polyunsaturated fatty acids and hence these enzymes are of major importance in regulating the acyl quality of the accumulating triacylglycerols. Microsomal preparations from avocado mesocarp, however, did not have detectable acyl exchange between acyl-CoA and phosphatidylcholine or diacylglycerol phosphatidylcholine interconversion despite the high activity of the enzymes of the Kennedy pathway. A scheme is presented which incorporates many of the observations on triacylglycerol synthesis and provides a working model for the regulation of acyl quality in linoleate-rich vegetable oils.Abbreviation BSA bovine serum albumin     

OCCURRENCE OF AN ISOPRENOID C25 DIUNASATURATED ALKENE AND HIGH NEUTRAL LIPID CONTENT IN ANTRACTIC SEA-ICE DIATOM COMMUNITIES1

The lipid and hydrocarbon composition of natural populations of diatom communities collected during the austral spring bloom of 1985 in the sea-ice at McMurdo Sound, Antartica was analyzed by TLC-FID, GC and GC-MS. Sea-ice diatom communities were dominated by Amphiprora sp., Nitzschia stellata Manguin and Berkeleya sp. at Cape Armitage; N. stellata, Amphiprora, Pleurosigma, N. kerguelensis (O'Meara) Hasle and some small centric diatoms adjacent to the Erebus Ice Tongue; and Porosira pseudodenticulata (Hustedt) Jouse at Wohlschlag Bay. Lipid distributions of the sea ice diatom communities from the Cape Armitage and Ereus sites were characterized by high concentrations of tracylaglecycerol (triacylglycerolplar lipid = 1.0 to 1.5). The hydrocarbon n-C_21:6, common in temperate diatoms, and an isoprenoid C₂₅ diunsaturated alkene were the dominant hydrocarons detected at these two sites. Hydrogenation of the C₂₅ diene produced the known alkane 2, 6, 10, 14-tetramethyl-7- (3-methylpentyl)-pentadecane. The C₂₅ diene is one of several structurally related hydrocarbons reported in many estuarine, coastal and ocean ic sediments. We propose that certain species of diatoms are a likely source of these alkenes in sediments. The first reported biological occurrence of the C₂₅ diene in the green seaweed Enteromorpha prolifera may have been due to the presence of epiphytic microalgae in the field sample analysed.     

Incorporation of free fatty acids into acylthioesters and lipids of developing sunflower seeds

The synthesis of lipids from radioactive fatty acids in developing sunflower seeds has been examined. Lauric, palmitic, stearic and oleic acids were us     

Lipidome and proteome of lipid droplets from the methylotrophic yeast Pichia pastoris

Lipid droplets (LD) are the main depot of non-polar lipids in all eukaryotic cells. In the present study we describe isolation and characterization of LD from the industrial yeast Pichia pastoris. We designed and adapted an isolation procedure which allowed us to obtain this subcellular fraction at high purity as judged by quality control using appropriate marker proteins. Components of P. pastoris LD were characterized by conventional biochemical methods of lipid and protein analysis, but also by a lipidome and proteome approach. Our results show several distinct features of LD from P. pastoris especially in comparison to Saccharomyces cerevisiae. P. pastoris LD are characterized by their high preponderance of triacylglycerols over steryl esters in the core of the organelle, the high degree of fatty acid (poly)unsaturation and the high amount of ergosterol precursors. The high phosphatidylinositol to phosphatidylserine of ~ 7.5 ratio on the surface membrane of LD is noteworthy. Proteome analysis revealed equipment of the organelle with a small but typical set of proteins which includes enzymes of sterol biosynthesis, fatty acid activation, phosphatidic acid synthesis and non-polar lipid hydrolysis. These results are the basis for a better understanding of P. pastoris lipid metabolism and lipid storage and may be helpful for manipulating cell biological and/or biotechnological processes in this yeast.     

Endemic infection reduces transmission potential of an epidemic parasite during co-infection

Endemic, low-virulence parasitic infections are common in nature. Such infections may deplete host resources, which in turn could affect the reproduction of other parasites during co-infection. We aimed to determine whether the reproduction, and therefore transmission potential, of an epidemic parasite was limited by energy costs imposed on the host by an endemic infection. Total lipids, triacylglycerols (TAG) and polar lipids were measured in cockroaches (Blattella germanica) that were fed ad libitum, starved or infected with an endemic parasite, Gregarina blattarum. Reproductive output of an epidemic parasite, Steinernema carpocapsae, was then assessed by counting the number of infective stages emerging from these three host groups. We found both starvation and gregarine infection reduced cockroach lipids, mainly through depletion of TAG. Further, both starvation and G. blattarum infection resulted in reduced emergence of nematode transmission stages. This is, to our knowledge, the first study to demonstrate directly that host resource depletion caused by endemic infection could affect epidemic disease transmission. In view of the ubiquity of endemic infections in nature, future studies of epidemic transmission should take greater account of endemic co-infections.     

Wheat leaf lipids during heat stress: I. High day and night temperatures result in major lipid alterations

Understanding how wheat (Triticum aestivum L.) plants under high temperature (HT) regulate lipid composition is critical to developing climate‐resilient varieties. We measured 165 glycerolipids and sterol derivatives under optimum and high day and night temperatures in wheat leaves using electrospray ionization‐tandem mass spectrometry. Levels of polar lipid fatty acyl chain unsaturation were lower in both heat‐tolerant genotype Ventnor and susceptible genotype Karl 92 under HT, compared with optimum temperature. The lower unsaturation was predominantly because of lower levels of 18:3 acyl chains and higher levels of 18:1 and 16:0 acyl chains. Levels of 18:3‐containing triacylglycerols increased threefold/more under HT, consistent with their possible role in sequestering fatty acids during membrane lipid remodelling. Phospholipids containing odd‐numbered or oxidized acyl chains accumulated in leaves under HT. Sterol glycosides (SG) and 16:0‐acylated sterol glycosides (ASG) were higher under HT than optimum temperatures. Ventnor had lower amounts of phospholipids with oxidized acyl chains under HT and higher amounts of SG and 16:0‐ASG than Karl 92. Taken together, the data demonstrate that wheat leaf lipid composition is altered by HT, in which some lipids are particularly responsive to HT, and that two wheat genotypes, chosen for their differing physiological responses to HT, differ in lipid profile under HT.     

The fatty acid compositions of predator Piocoris luridus （Heteroptera： Lygaeidae） and its host Monosteria unicostata （Heteroptera： Tingidae） reared on almond

The changes in fatty acid compositions during nutritional interaction among almond Amygdalus communis Linnaeus （Rosales： Rosaceae） （host plant）, lacebug Monosteria unicostata （Mulsant and Rey） （Heteroptera： Tingidae） and its predator Piocoris luridus Fieber （Heteroptera： Lygaeidae） were determined by gas chromatography and gas chromatography-mass spectrometry analyses. The fatty acid profiles of phospholipids and triacylglycerols were substantially different. Unlike the general observations for virtually most terrestrial insects, arachidonic and eicosapentaenoic acids were detected in high proportions of phospholipid fractions in both insects, especially in P. luridus. Also the almond tissues provide very little oleic acid to the herbivore diet, yet both insect species developed high proportions of this component. Our data reveals instances of specific accumulation of fatty acid biosynthesis, elongation/desaturation, and not incorporating selected fatty acids into cellular lipids.     

Production of fuels and chemicals from renewable resources using engineered Escherichia coli

Biotechnological production of fuels and chemicals from renewable resources is an appealing way to move from the current petroleum-based economy to a biomass-based green economy. Recently, the feedstocks that can be used for bioconversion or fermentation have been expanded to plant biomass, microbial biomass, and industrial waste. Several microbes have been engineered to produce chemicals from renewable resources, among which Escherichia coli is one of the best studied. Much effort has been made to engineer E. coli to produce fuels and chemicals from different renewable resources. In this paper, we focused on E. coli and systematically reviewed a range of fuels and chemicals that can be produced from renewable resources by engineered E. coli. Moreover, we proposed how can we further improve the efficiency for utilizing renewable resources by engineered E. coli, and how can we engineer E. coli for utilizing alternative renewable feedstocks. e.g. C1 gases and methanol. This review will help the readers better understand the current progress in this field and provide insights for further metabolic engineering efforts in E. coli.