Spontaneous and radical-induced plasma membrane lipid peroxidation in differently oxidant-sensitive yeast species and its suppression by antioxidants

Formation of thiobarbituric acid-reactive substances (TBRS; nmol/mg lipids) indicative of lipid peroxidation was measured in whole cells and in isolated plasma membrane lipids from three yeast species differing in oxidant sensitivity (Schizosaccharomyces pombe, Saccharomyces cerevisiae andRhodotorula glutinis) after exposure to the Fenton reagent, Fe^II, H₂O₂,tert-butyl hydroperoxide (TBHP) and azo compounds (AAPH, ACHN). In whole cells, spontaneous TBRS formation rose in the sequenceS. pombe<S. cerevisiae<R. glutinis (1:∼5:∼7). Oxidants increased the TBRS production 13–18 fold in the sequence Fe^II∼TBHP>AAPH∼ACHN∼Fe-Fenton>H₂O₂. This increase need not be solely due to increased lipid peroxidation. In isolated plasma membrane lipids from all three species, the spontaneous TBRS production referred to 1 mg lipids was 9–13-fold higher than in whole cells. InS. pombe lipids, only TBHP increased the TBRS production. In lipids fromS. cerevisiae andR. glutinis, all added oxidants increased the spontaneous TBRS production 2–3 times in the sequence TBHP>ACHN>AAPH>Fe^II>Fe-Fenton>H₂O₂. Oxidant-induced TBRS production in both whole cells and isolated membrane lipids was partially suppressed by the lipid peroxidation inhibitors 2,6-di-tert-butyl-4-methylphenol (“butylated hydroxytoluene”; BHT) and the newly synthesized PYA12 compound. Both agents were more effective in isolated lipids than in whole cells and against OH-producing than against ROO-or RO-producing oxidants. Yeast membrane lipids, which are generally poor in polyunsaturated fatty acids, are thus subject to perceptible lipid peroxidation.     

New phenolic antioxidants of PYA and PYE class increase the resistanceS. cerevisiae strain SP4, its SOD- and catalase-deficient mutants to lipophilic oxidants

Was demonstrate the protection ability against reactive oxygen species afforded toS. cerevisiae (wild-type strain SP4 and its mutants deficient in major antioxidant enzymes—catalase T and A, CuZnSOD) by PYA and PYE, new groups of phenolic antioxidants (quaternary ammonium salts of dihydrocinnamic acid amino esters with different alkyl chains; synthesized in this laboratory). The survival of strains exposed to the lipophilic oxidation inducerstert-butyl hydroperoxide (TBHP) and 1,1′-azobis(4-cyclohexane carbonitrile) (ACCN) with or without antioxidant pretreatment was determined by platingS. cerevisiae mutant deficient in SOD was found to be hypersensitive to TBHP and ACCN while the sensitivity of the strain deficient in catalase T and A was about the same as in the wild-type strain. A 1-h preincubation of cells of both the wild-type and the mutant strains with the phenolic antioxidants prior to exposure to TBHP or ACCN substantially increased the cell survival. The magnitude of protection depended on the strain and the length of the alkyl chain of the antioxidant; the best average protection against TBHP was provided by PYE and PYA compounds with 12-and 16-membered alkyl chains whereas PYE-8 and PYA-12 derivatives, afforded the best average protection against ACCN.     

Relationship between cadmium sensitivity and degree of plasma membrane fatty acid unsaturation in Saccharomyces cerevisiae

The sensitivity of Saccharomyces cerevisiae to the redox-active metal copper has recently been found to be influenced by cellular fatty acid composition. This study sought to investigate whether fatty acid composition affected plasma membrane permeabilisation and whole-cell toxicity induced by the redox-inactive metal cadmium. S. cerevisiae NCYC 1383 was enriched with the polyunsaturated fatty acids linoleate (18:2) and linolenate (18:3) by growth in 18:2- or 18:3-supplemented medium. Incorporation of the exogenous fatty acids resulted in them comprising more than 65% of the total fatty acids in plasma membrane lipids. Inhibition of cell division in the presence of Cd(NO₃)₂ was accentuated by growth in the presence of a polyunsaturated fatty acid. Furthermore, susceptibility to Cd²⁺-induced plasma membrane permeabilisation increased with the degree of fatty acid unsaturation. Thus, during exposure to Cd²⁺, K⁺ efflux from 18:2- and 18:3-enriched cells was up to 2.5-fold or 3-fold greater, respectively than that from unsupplemented cells. In addition, reductions in cell viability during exposure to Cd²⁺ were most marked in polyunsaturated-fatty-acid-supplemented cells. At certain times, unsupplemented Cd²⁺-exposed cells displayed up to 7-fold greater viability than supplemented Cd²⁺-exposed cells. The study demonstrates that the toxicity of the redox-inactive metal Cd²⁺ towards S. cerevisiae becomes markedly amplified with increased cellular and plasma membrane fatty acid unsaturation. Received: 14 March 1997 / Received revision: 4 June 1997 / Accepted: 7 June 1997     

Improvement of polyunsaturated fatty acids synthesis by the coexpression of CYB5 with desaturase genes in Saccharomyces cerevisiae

Since Saccharomyces cerevisiae contains Δ9 fatty acid desaturase (OLE1) as a sole fatty acid desaturase, it produces saturated and monounsaturated fatty acids of 16- and 18-carbon compounds. We showed earlier that Kluyveromyces lactis Δ12 (KlFAD2) and ω3 (KlFAD3) fatty acid desaturase genes enabled S. cerevisiae to make also polyunsaturated fatty acids (PUFAs), linoleic (18:2n-6), and α-linolenic (18:3n-3) acids. Unlike Δ9 fatty acid desaturase Ole1p, the two added fatty acid desaturases (KlFAD2and KlFAD3) do not contain a cytochrome b5 domain, and we now report on effects of the overexpression of K. lactis and S. cerevisiae cytochrome b5 (CYB5) genes as well as temperature effects on PUFA synthesis. Without extra cytochrome b5, while PUFA synthesis is significant at low temperature (20 °C), it was marginal at 30 °C. Overexpression of cytochrome b5 at 20 °C did not affect the fatty acid synthesis so much, but it significantly enhanced the synthesis of PUFA at 30 °C.     

Effects of zinc deficiency on the fatty acid composition and metabolism in rats fed a fat-free diet

The effects of dietary zinc deficiency (ZD) on the composition and metabolism of the fatty acyl chains of phospholipids in rat liver were investigated with a fat-free diet. The levels of (n−9) fatty acids such as 18∶1 and 20∶3(n−9) in liver phospholipids (PL) were significantly lower in ZD-rats (19.4% and 5.4%, respectively) than in PF-rats (25.2 and 8.3%). On the other hand, the level of (n−6) acids such as 18∶2 and 20∶4 were higher in ZD-rats (3.3 and 19.1%, respectively) than in PF-rats (2.1 and 14.9%). In order to study the metabolism of fatty acids in vivo,¹⁴C-18∶0 or¹⁴C-18∶2 was intravenously injected, and then the conversion to the respective metabolite was examined. After the injection of¹⁴C-18∶0, the radioactivity was found in 18∶0 (49.3% of the total), 18∶1 (33.2%), and 20∶3 (n−9) (9.1%) in liver PL in PF-rats at 24h. In ZD-rats, the radioactivity was dramatically lower in 18∶1 (23.5%) and 20∶ (n−9) (3.6%), suggesting that the conversion of 18∶0 to 18∶1 and 20∶3 (n−9) was strongly inhibited in ZD-rats. When¹⁴C-18∶2 was injected, the radioactivity was mainly found in 18∶2, 20∶3(n−6), and 20∶4. The radioactivity in 20∶4 in ZD-rats was slightly higher than that in control rats. These results indicate that zinc deficiency affects the fatty acid metabolism in liver, in particular, it causes a reduction in δ9 desaturase activity, when rats are fed a fat-free diet.     

Correlations between gametophytic (pollen) and sporophytic (seed) generations for polyunsaturated fatty acids in oilseed rape Brassica napus L.

Summary Lipids were extracted from the diploid seed and haploid pollen of Brassica napus L. Two fractions of pollen lipids, namely the diploid-specified pollen-coat and the haploid-specified internal cytoplasmic lipids were obtained. Significant correlations exist between pollen and seed generations for linoleic (182) and linolenic (183) acids. In pollen internal storage lipids, the level of 183 is positively correlated and the level of 182 is negatively correlated with the level of 183 in seed lipids. Evidence is presented that strongly supports the hypothesis that lipid biosynthesis occurs within the pollen and that synthesis is specified by haploid genes. These data support the concept of pollen selection, so that selecting among living pollen grains for superior individuals has potential as a new plant breeding tool for improving seed oil quality.     

Effects of dietary lead,fish oil,and ethoxyquin on hepatic fatty acid composition in chicks

Three experiments were conducted with day-old broiler chicks reared to 18 or 19 d of age. The objective was to examine the effects of dietary oil (cottonseed oil vs fish oil), dietary antioxidant (0 vs 75 ppm ethoxyquin), and dietary lead (0 vs 1000 ppm Pb as lead acetate trihydrate) on hepatic fatty acid composition. A 2×2 factorial arrangement was used in all experiments. In Experiment 1, the factors were oil (4% of each) and Pb. In Experiments 2 and 3, the factors were ethoxyquin and Pb in diets containing 3.5% cottonseed oil (Experiment 2) or 3.5% fish oil (Experiment 3). Hepatic fatty acid profiles were measured by gas-liquid chromatography in 10 chicks/treatment (Experiment 1) or 4 chicks/treatment (Experiments 2 and 3). Dietary oils altered the profiles, with cottonseed oil producing the higher values for linoleic acid (18∶2) and arachidonic acid (20∶4). With fish oil, in addition to the lower levels of 18∶2 and 20∶4, there were significant levels of eicosapentaenoic acid (20∶5) and docosahexaenoic acid (22∶6). Pb enhanced the levels of 20∶4, but the effect was greater with cottonseed oil diets compared with fish oil diets. The enhanced 20∶4 levels resulted in lower ratios of 18∶2/20∶4. Ethoxyquin enhanced the level of 18∶2 with the cottonseed oil diet, and of 20∶5 and 22∶6 with the fish oil diet. Ethoxyquin decreased the level of hepatic 20∶4 when fish oil was fed. The results clearly show that all three factors (oil type, Pb level, and ethoxyquin level) after hepatic fatty acid composition. Both oil source and Pb level appeared to exert an effect on the metabolic conversion of 18∶2 and 20∶4. The primary effect of ethoxyquin was to enhance the levels of polyunsaturated fatty acids in liver. The data do not allow the partitioning of possible ethoxyquin effects to protection of polyunsaturated acids in feed vs protection of polyunsaturated acids in liver tissue. Use of trade names implies neither approval by the North Carolina Agricultural Research Service of products named nor criticism of products not named.     

Cloning and identification of a novel C18-Δ9 polyunsaturated fatty acid specific elongase gene from DHA-producing <Emphasis Type="Italic">Isochrysis galbana</Emphasis> H29

Isochrysis galbana, a marine prymnesiophyte microalga, is able to produce a high level of long chain polyunsaturated fatty acids such as docosahexaenoic acid (DHA, C22:6n-3). In this article, a novel gene (IgASE2) that encoded a C18-Δ9 polyunsaturase fatty acids specific (C18-Δ9-PUFAs-specific) elongase was isolated and characterized from DHA-rich microalga, I. galbana H29. A full-length cDNA of 1653 bp was cloned by rapidamplification of cDNA ends (RACE) PCR techniques. The IgASE2 contained a 786 bp ORF encoding a protein of 261 amino acids that shared 87% identity with the reported Δ9-elongase IgASE1, a 44 bp 5′ untranslated region and an 823 bp 3′ untranslated region. The function of IgASE2 was demonstrated by its heterologous expression in Saccharomyces cerevisiae. In S. cerevisiae, IgASE2 elongated linoleic acid (LA, C18:2n-6), α-linolenic (ALA, C18:3n-3) to eicosadienoic acid (EDA, C20:2n-6) and eicosatrienoic acid (ETrA, C20:3n-3). The conversion ratios of LA to EDA and ALA to ETrA were 60.47 and 58.36%, respectively. However, IgASE2 could not catalyze the elongation reactions of oleic acid (OA, C18:1n-9) and other fatty acids. These results confirmed that IgASE2 had C18-Δ9-PUFAs-specific elongase activity.     

Separation of protein and fatty acids from tuna viscera using supercritical carbon dioxide

Supercritical carbon dioxide extraction was investigated as a method for removing lipids and bad flavor from tuna viscera. To find the optimum conditions, different experimental variables, such as pressure, temperature, flow rate of solvent and sample size, were evaluated for the effective removal of lipids and the undesirable smell. Ethanol was used as the entrainer, with a 3% by vol CO₂ flow rate. By increasing the pressure at constant temperature, the efficiency of the lipid removal was improved and the protein was concentrated without denaturalization. The main fatty acids extracted from the tuna viscera were palmitic acid (16∶0), heptadecanoic acid (17∶1), oleic acid (18∶1) and docosahexaenoic acid (22∶6). The major amino acids in the tuna viscera treated by supercritical carbon dioxide were glutamic acid, leucine and lysine, and the free amino acids werel-proline, taurine andl-α-aminoadipic acid.     

Lead-induced tissue fatty acid alterations and lipid peroxidation

Previous work showed that dietary lead (Pb) increases the relative concentration of arachidonic acid (20∶4) as a percentage of total fatty acids, and decreases the relative proportion of linoleic acid (18∶2) to arachidonic acid (18∶2/20∶4) in chick liver, serum, and erythrocyte membranes. The present investigation was undertaken to examine the time-course and magnitude of the fatty acid alterations with increasing dietary Pb levels. We also examined the effects of Pb on the fatty acid composition and lipid peroxide content of hepatic subcellular organelles. In Exp. 1, chicks were fed diets containing 0, 62.5, 125, 250, 500, or 1000 ppm added Pb (as Pb acetate trihydrate) from 1 to 21 d of age. After 21 d, no growth effects were observed; however, Pb lowered the 18∶2/20∶4 ratio and increased 20∶4 concentration in total liver and serum lipids, and in total hepatic phospholipids in a dose-dependent manner. Hepatic mitochondrial membrane fatty acids were not altered, nor was there any increase in hepatic lipid peroxidation. In Exp. 2, chicks were fed diets containing 0, 500, 1000, or 2000 ppm added Pb from 1 to 21 or 22 d of age. Pb depressed growth in a dose-dependent manner. In addition, Pb lowered the 18∶2/20∶4 ratio and increased 20∶4 concentration in total liver lipids and in hepatic mitochondrial and microsomal membranes in a dose-dependent manner. Total hepatic lipid peroxidation was increased over control values by 1000 ppm Pb, and hepatic microsomal lipid peroxidation was increased by dietary Pb levels of 1000 and 2000 ppm. In Exp. 3, body weight, hepatic microsomal lipid peroxidation, and fatty acid composition were determined in 4-, 9-, 14-, 18-, and 23-d-old chicks fed 0 or 1500 ppm added Pb. Body weights of Pb-treated chicks were significantly lower than those of control chicks by day 18. Microsomal 20∶4 concentration and peroxidation increased, and the 18∶2/20∶4 ratio decreased with age in both groups, but the changes were of greater magnitude in the Pb-treated chicks. The results suggest that some of the manifestations of Pb toxicity may be a reflection of increased concentration of 20∶4 in specific membranes. Further, since the Pb-induced alterations in fatty acid composition were noted in the absence of any growth depression, we propose that fatty acid composition is more sensitive than growth rate to the presence of lead in the diet.     

Arachidonic and oleic acids stimulate zygote formation in the presence of mating pheromone in the yeast,Saccharomyces cerevisiae

Effect of exogenous fatty acids on zygote formation in Saccharomyces cerevisiae was studied. Arachidonic and oleic acids considerably stimulated zygote formation, but other fatty acids tested, linoleic, linolenic, stearic and palmitic acids, did not. Pretreatment experiments with arachidonic acid showed that the stimulation of zygote formation by the fatty acid required the presence of mating pheromone.Abbreviations YPD yeast-peptone-dextrose medium - A₅₃₀ absorbance at 530 nm     

Isolation of biochemical mutants using haploid mesophyll protosplasts of Hyoscyamus muticus

The question of whether membrane expansion, which is caused by anesthetics in animal systems, alters the lipid composition of plant cell membranes was investigated. We have measured the effects of several anesthetics on the relative amounts of the principal fatty acids from the polar lipids of barley (Hordeum vulgare L.) root membranes. Procaine, dibucaine, tetracaine, chloroform and, to a lesser degree, methanol increased the proportions of palmitic, stearic and oleic acids and decreased the proportions of linoleic and linolenic acids. Ethanol had no significant effect. Total amounts of the fatty acids from the polar lipids of roots in procaine solution decreased markedly so that all of the acids decreased in amount. The anesthetic was effective as soon as the roots were introduced to the solution and the changes progressed at constant rates for 6 h. Only the polar membrane lipids were altered; other lipids were not affected. Increased hydrostatic pressure of about 1.0 MPa largely prevented the anesthetic effects, including the decrease in the total amounts of the fatty acids. Hydrostatic pressure as high as 2 MPa had no effect per se on the membrane lipid composition. These results indicate that anesthetics cause expansion of the root membranes which results in the lipid changes. That a compositional change in the membrane lipids involves a conformational change such as expansion is an indication of the nature of the link between changes in the membrane lipids and changes in function of areas where hydrophilic ions permeate.Abbreviations 16:0 palmitic acid - 18:0 stearic acid - 18:1 oleic acid - 18:2 linoleic acid - 18:3 linolenic acid     

The Effects of Dietary Selenium and Vitamin E and their Combination on the Fatty Acids of Erythrocytes,Bone Marrow and Spleen Tissue Lipids of Lambs

The object was to determine the influence of dietary vitamin E, selenium and their combination on the fatty acid con-tent of erythrocytes, bone marrow and spleen lipids of Akkaraman lambs. After supplementation for 15 days, the amount of all fatty acids was slightly higher (p < 0·05) in the vitamin E as compared to the control group, whereas the amount of longer fatty acids was significantly higher (p < 0·01, p < 0·001) in the selenium and combination groups. On the thirtieth day, the amount of all fatty acids was slightly high (p < 0·5) in all the supplemented groups in comparison with the control group. In the bone marrow lipids, the amount of longer fatty acids was decreased (p < 0·05, p < 0·01, p < 0·001) in the vitamin E and combination groups as compared to the control. Although the amount of some fatty acids was high (p < 0·05, p < 0·01) in the selenium group compared to the control, linoleic (18:2), linolenic (18:3) and the polyunsaturated fatty acids (PUFA) were lower (p < 0·05, p < 0·001). In the spleen lipids, the amount of longer fatty acids was slightly decreased (p < 0·05) in the vitamin E group as compared with the control; however the amount of longer fatty acids was significantly higher (p < 0·05, p < 0·01) in the selenium and combination groups in comparison to the control group. Thus dietary supplementation with selenium was more effective than dietary vitamin E supplementation in altering the fatty acid content of the erythrocyte, bone marrow and spleen lipids. © 1997 John Wiley & Sons, Ltd.     

Fatty acids compositions of polar and non-polar lipid fractions of wheat leaves inoculated with three brown rust races during progressive pathogenesis

The fatty acids composition of the polar and non-polar lipid fractions of wheat leaves was affected due to progressive brown rust infection during early stages of pathogenesis,i.e. 0, 12, 24, 36, 48 and 72 h after inoculation. The three races ofPuccinia recondita differentially affected the composition of saturated and unsaturated fatty acids and their relative occurrence in wheat leaves. The infection of wheat by race 77 resulted in a relative decrease in fatty acid chain length as measured through C₁₆∶C₁₈ fatty acid ratio. An increase in the relative degree of unsaturation (18∶2/18∶3 acids ratio) was recorded in both lipid fractions. Such changes may be taken as one of the earliest characteristics of disease development.     

The influence of zinc and sulphur deficiency on oil-filling in peanut (Arachis hypogaea L.) kernels

In the developing peanut (Arachis hypogaea L.) kernels, the period between 15 and 35 days after podding (DAP) was identified as the active period of oil-filling. The period of active oil-filling was associated with a decrease in the starch, soluble sugars and proteins so as to make available the energy and carbon skeleton for the synthesis of oil. The oil content in the mature kernels decreased by 11, 12 and 25 per cent with Zn, S and Zn+S deficiency, respectively. In addition, proteins and starch content decreased significantly while that of soluble sugars increased slightly. The activity of malate dehydrogenase and glucose-6-phosphate dehydrogenase also decreased due to Zn as well as S deficiency. The deficiency treatments resulted in a decrease in phospholipids, free fatty acids and triacylglycerols in mature kernels. Further the proportion of 16∶0 and 18∶2 decreased while that of 18∶1 increased in developing kernels.     

Functional characterization of a delta 6-desaturase gene from the black seabream (<Emphasis Type="Italic">Acanthopagrus schlegeli</Emphasis>)

Delta 6-fatty acid desaturase (D6DES) is used in the synthesis of polyunsaturated fatty acids (PUFAs) from microorganisms to higher animals, including arachidonic acid (ARA) and eicosapentaenoic acid (EPA). A 1,338 bp full-length cDNA encoding D6DES was cloned from Acanthopagrus schlegeli (AsD6DES) through degenerate- and RACE-PCR methods. A recombinant vector expressing AsD6DES (pYES-AsD6DES) was subsequently constructed and transformed into Saccharomyces cerevisiae to test the enzymatic activity of AsD6DES towards the production of n-6 and n-3 fatty acids. The exogenously expressed AsD6DES produced γ-linolenic acid (18:3 n-6) and stearidonic acid (18:4n-3) at 26 and 36% from exogenous linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3), respectively, indicating that it is essentially a delta 6-fatty acid desaturase.     

Changes in the lipid and fatty acid composition of hemolymph and ovaries during the reproductive cycle of Labidura riparia

Lipid metabolism was investigated during the reproductive cycle of Labidura riparia (Pallas). The lipid classes and their constitutive fatty acids present in hemolymph and ovaries were measured using thin‐layer chromatography and gas‐liquid chromatography. In the hemolymph, total lipids increase steadily from the previtellogenic period to vitellogenic arrest. These lipids are predominantly diacylglycerols and phospholipids. In the ovaries, total lipids increase during vitellogenesis then decrease during the vitellogenesis arrest period. The major lipids are triacylglycerols, followed by phospholipids. In both hemolymph and ovaries, all lipid classes contained variable proportions of seven main fatty acids: the saturated fatty acids myristic acid (14:0), palmetic acid (16:0), and stearic acid (18:0); the monounsaturated fatty acids palmitoleic acid (16:1) and oleic acid (18:1); and the polyunsaturated fatty acids linoleic acid (18:2) and linolenic acid (18:3). Unsaturated fatty acids predominate throughout the reproductive cycle. The percentage compositions of total and triacylglycerol fatty acids do not change markedly during the reproductive cycle in hemolymph nor in ovaries, with 18:2, 18:1 and 16:0 fatty acids being the major components. However, for diacylglycerols and phospholipids, the proportions of fatty acids vary systematically. For phospholipids during the vitellogenesis period, 18:2 increases considerably whereas other fatty acids decrease; for diacylglycerols, these fatty acids vary in the reverse way.     

Transgenic expression of a Δ12-epoxygenase gene in Arabidopsis seeds inhibits accumulation of linoleic acid

The Crepis palaestina cDNA Cpal2 encodes a Δ12-epoxygenase that can catalyse the synthesis of 12,13-epoxy-cis-9-octadecenoic acid (18:1E) from linoleic acid (18:2). When the Cpal2 gene was expressed under the control of the napin seed-specific promoter in Arabidopsis thaliana (L.) Heynh., the seed lipids accumulated only low levels of 18:1E and also 12,13-epoxy-cis-9,15-octadec-2-enoic acid (18:2E). Despite the fact that the levels of these epoxy fatty acids comprised only up to 6.2% of the total fatty acids, there was a very marked increase in oleic acid (18:1) and decrease in linoleic (18:2) and α-linolenic (18:3) acids in these plants, indicating that endogenous Δ12-desaturation was greatly reduced in these plants. Significant between-line differences in the levels of Cpal2 mRNA were observed during seed development, but were not associated with any major variation in mRNA levels for the endogenous ArabidopsisΔ12-desaturase (Fad2). This suggests that if an unfavourable interaction occurs between the transgenic Δ12-epoxygenase and the endogenous Δ12-desaturase, which decreases the level of desaturation, it occurs at either the translational or post-translational level. We further show that the co-expression of a Δ12-desaturase gene from C. palaestina in Cpal2 transgenic Arabidopsis returns the relative proportions of the C18 seed fatty acids to normal levels and results in an almost twofold increase in total epoxy fatty acids. Received: 11 August 2000 / Accepted: 7 September 2000     

Lipids of the meristems of the main coniferous edificators from central siberia under low-temperature adaptation: 1. The characteristics of the fatty acid composition of phospholipids from winter meristems of Larix sibirica Ledeb., Picea obovata L., and Pinus sylvestris L.

Trienoic fatty acids (FAs) have been found to be the dominant group of unsaturated fatty acids in the composition of phospholipids (PLs) from Larix sibirica Ledeb., whereas dienoic FAs have been established to prevail in PLs from Picea obovata L. and Pinus sylvestris L. Bud swelling in spring is accompanied by a decrease in the content of unsaturated FAs by approximately 30%. The analysis of the change in the content of individual C₁₈ FAs in the PL structure upon the transition of the tree from winter dormancy to vegetation has revealed the important functional role of acyl-lipid ω₆ desaturase, which is responsible for the synthesis of linoleic acid (C_{18: 2}), in the formation of the cryoprotected state of meristem cell membranes of Larix sibirica Ledeb., Picea obovata L., and Pinus sylvestris L. In addition, the particular significance of acyl-lipid ω₃ desaturase for the cryoadaptation of meristem cells in Larix sibirica Ledeb., as it catalyzes the transformation of linoleic acid (C_{18: 2}) to linolenic acid (C_{18: 3}) in PLs of larch 1.5–3 times more intensively than in the case of spruce and pine, is shown.     

Identification and characterization of Δ12 and Δ12/Δ15 bifunctional fatty acid desaturases in the oleaginous yeast Lipomyces starkeyi

Fatty acid desaturases play vital roles in the synthesis of unsaturated fatty acids. In this study, Δ12 and Δ12/Δ15 fatty acid desaturases of the oleaginous yeast Lipomyces starkeyi, termed LsFad2 and LsFad3, respectively, were identified and characterized. Saccharomyces cerevisiae expressing LsFAD2 converted oleic acid (C18:1) to linoleic acid (C18:2), while a strain of LsFAD3-expressing S. cerevisiae converted oleic acid to linoleic acid, and linoleic acid to α-linolenic acid (C18:3), indicating that LsFad2 and LsFad3 were Δ12 and bifunctional Δ12/Δ15 fatty acid desaturases, respectively. The overexpression of LsFAD2 in L. starkeyi caused an accumulation of linoleic acid and a reduction in oleic acid levels. In contrast, overexpression of LsFAD3 induced the production of α-linolenic acid. Deletion of LsFAD2 and LsFAD3 induced the accumulation of oleic acid and linoleic acid, respectively. Our findings are significant for the commercial production of polyunsaturated fatty acids, such as ω-3 polyunsaturated fatty acids, in L. starkeyi.