Composition and positional distribution of fatty acids in polar lipids from Chlorella ellipsoidea differing in chilling susceptibility and frost hardiness

The composition and positional distribution of fatty acids in the polar lipids from 4 strains of Chlorella differing in chilling susceptibility and frost hardiness were analyzed by enzymatic hydrolysis and gas-liquid chromatography. Analysis of the polar lipids from chilling-sensitive, chilling-resistant and chilling-sensitive revertant strains of Chlorella ellipsoidea IAM C-102 showed that the sum of palmitic and trans -3-hexadecenoic acid in phosphatidylglycerol (PG) is about 60% for the sensitive strains and 53% for the resistant strain. The sum of dipalmitoyl and 1-palmitoyl-2-( trans -3-hexadecenoyl) PG as estimated from the positional distribution of their fatty acids, is about 10% in the case of each of the three strains. The contents of unsaturated fatty acids in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were higher in the resistant than in the sensitive strain. This suggests that unsaturation of fatty acids in not only PG but also PC and PE is involved in chilling sensitivity of Chlorella . On the other hand, lipid changes during the development of frost hardiness of C. ellipsoidea IAM C-27, a frost hardy strain, were examined. The results showed that fatty acids in most lipid classes are unsaturated in the hardening process but their degree of unsaturation is not greatly different from that of the chilling-resistant strain, suggesting that not only unsaturation of fatty acids in lipids but also other factors are necessary for the development of frost hardiness.     

渗透调节对冷敏感大豆[Glycine max(L.)Merr.]种子膜类脂组成和脂肪酸含量的影响

选用冷敏感的大豆[Gzycine max（L.）Merr．]品种“中黄22”为试材,运用薄层层析法和气相色谱法研究了渗控增强大豆种子活力过程中膜类脂的组成及变化规律,揭示生物膜类脂在抗吸胀冷害中的作用。结果表明,用33％（W／V）的PEG6000处理种子,随着渗控时间的延长,种子的发芽指数、活力指数和根干重都逐渐增加,在渗控72h时,大豆种子中不饱和磷脂如PC、PE的比例增加,各极性脂的脂肪酸组成也发生了变化,PC、PE和PI中饱和脂肪酸16：0的含量显著下降,而不饱和脂肪酸18：2明显上升,使它们的不饱和指数大大提高,并与渗控时间呈正相关。由以上结果可证明,经PEG渗控处理后,提高了冷敏感大豆膜的流动性,为防止吸胀冷害,保持膜系统的完整性和生物膜正常的代谢提供了前提条件。     

冷害对贮藏油桃膜脂脂肪酸及相关酶活性的影响

以秦光2号油桃为试材,研究了1℃和5℃贮藏温度下油桃果实的膜脂脂肪酸及相关酶活性的变化.结果表明:油桃果实的SOD、CAT和APX活性在冷害发生后迅速下降;冷害果实的相对膜透性和MDA含量显著高于对照;冷害促使油桃果实LOX活性的增强,使棕榈酸相对含量高于对照,油酸、亚麻酸相对含量低于对照,降低了膜脂脂肪酸的不饱和指数.     

Introduction of the cDNA for shape Arabidopsis glycerol-3-phosphate acyltransferase (GPAT) confers unsaturation of fatty acids and chilling tolerance of photosynthesis on rice

The chilling sensitivity of several plant species is closely correlated with the levels of unsaturation of fatty acids in the phosphatidylglycerol (PG) of chloroplast membranes. Plants with a high proportion of unsaturated fatty acids, such as Arabidopsis thaliana, are resistant to chilling, whereas species like squash with only a low proportion are rather sensitive to chilling. The glycerol-3-phosphate O-acyltransferase (GPAT) enzyme of chloroplasts plays an important role in determining the levels of PG fatty acid desaturation.A cDNA for oleate-selective GPAT of Arabidopsis under the control of a maize Ubiquitin promoter was introduced into rice (Oryza sativa L.) using the Agrobacterium-mediated gene transfer method. The levels of unsaturated fatty acids in the phosphatidylglycerol of transformed rice leaves were found to be 28% higher than that of untransformed controls. The net photosynthetic rate of leaves of transformed rice plants was 20% higher than that of the wild type at 17°C. Thus, introduction of cDNA for the Arabidopsis GPAT causes greater unsaturation of fatty acids and confers chilling tolerance of photosynthesis on rice.     

S-RNases from self-incompatible and -compatible apple cultivars: purification,cloning, enzymic properties,and pollen tube growth inhibitory activity

Four S-RNases (RNase associated with self-incompatibility) were purified from the styles of two apple cultivars (Malus domestica), a self-incompatible cv., Starking Delicious (SD), and a self-compatible cv., Megumi (MG). Each cultivar produced two S-RNases and their enzymatic properties such as specific activity, pH optimum, thermal stability, and molecular mass, were characterized. The four S-RNases inhibited the tube growth of apple pollen in an in vitro bioassay at 25 microg/ml (1.0 microM), but did not distinguish self from non-self pollen. The cDNAs of four S-RNases were cloned, and the nucleotide and deduced amino acid sequences were analyzed. The nucleotide sequence of SD-Se RNase was a new one and the other was identical to that of Sc-RNase of cv. Fuji. In MG one was identical to the sequence of SD-Sc RNase and the other to that of Sa-RNase of cv. Golden Delicious except for one base. From results of the isolation amounts and the Western blot analysis for stylar crude extracts the amount of S-RNases in MG was apparently less than that in SD.     

Rat Brain Phosphatidyl-N,N-Dimethylethanolamine Is Rich in Polyunsaturated Fatty Acids

Phosphatidyl-N,N-dimethylethanolamine (PDME), an intermediate in the formation of phosphatidylcholine (PC) by the sequential methylation of phosphatidylethanolamine (PE), was purified from rat brain and its fatty acid (FA) composition compared with those of brain PC and PE. The proportion of polyunsaturated fatty acids (PUFAs) in the PDME (29.8%) was similar to that of PE (27.7%) and much greater than in PC (2.8%). Like the PUFAs of PE, the major PUFAs found in PDME were arachidonic acid (20:4) and docosahexaenoic acid (22:6). An isotopic method was developed to quantify the PDME purified from brain; a tritiated methyl group from CH3I was transferred to the PDME in the presence of cyclohexylamine to form [3H]PC, and the radioactivity of the PC was then counted. The concentration of rat brain PDME obtained using this method (33.0 +/- 1.8 micrograms/g brain) was very similar to that obtained using quantitative GLC analysis of its FAs (36.9 +/- 1.8 micrograms/g). The FAs in the PE and PC of rat brain synaptosomes were also analyzed; too little PDME was present in synaptosomes to permit similar analysis. The percentage of unsaturated FAs insynaptosomal PE was even higher (43.4 vs. 27.7) than that in PE prepared from whole brain. Since synaptosomes have a very high activity of phosphatidyl-N-methyltransferase, the enzyme complex that methylates PE to form PC, this enzyme may serve, in nerve endings, to produce a particular pool of PC, rich in PUFAs, which may have a distinct physiological function.     

Effects of Cadmium on Polar Lipid Composition and Unsaturation in Maize （Zea mays） in Hydroponic Culture

This study aimed to evaluate the effect of Cd exposure （100 μmol/L） on polar lipid composition, and to examine the level of fatty acid unsaturation in maize （Zea mays L.）. In roots, the level of 16：0 and monounsaturated fatty acids （16：1 ＋ 18：1） decreased in phosphatidylcholine （PC） and phosphatidylethanolamine （PE）. In contrast, the proportion of unsaturated 18-C fatty acid species showed an opposite response to Cd. The content, on the other hand, of PC, PE, digalactosyldiacylglycerol （DGDG）, and steryl lipids increased in roots （2.9-, 1.6-, 5.3-, and 1.7-fold increase, respectively）. These results suggest that a more unsaturated fatty acid composition than found in control plants with a concomitant increase in polar lipids may favor seedling growth during Cd exposure. However, the observed increase in the steryl lipid （SL） ： phospholipid （PL） ratio （twofold）, the decrease in monogalactosyldiacylglycerol （MGDG） ： DGDG ratio, as well as the induction of lipid peroxidation in roots may represent symptoms of membrane injury. In shoots, the unsaturation level was markedly decreased in PC and phosphatidylglycerol （PG） after Cd exposure, but showed a significant increase in sulfoquinovosyldiacylglycerol （SQDG）, MGDG and DGDG. The content of PG and MGDG was decreased by about 65%, while PC accumulated to higher levels （4.4-fold increase）. Taken together, these changes in the polar lipid unsaturation and composition are likely to be due to alterations in the glycerolipid pathway. These results also support the idea that the increase in overall unsaturation plays some role in enabling the plant to withstand the metal exposure.     

Age-related changes in mitochondrial membrane composition of rainbow trout (Oncorhynchus mykiss) heart and brain

Membrane composition, particularly of mitochondria, could be a critical factor by determining the propagation of reactions involved in mitochondrial function during periods of high oxidative stress such as rapid growth and aging. Considering that phospholipids not only contribute to the structural and physical properties of biological membranes, but also participate actively in cell signaling and apoptosis, changes affecting either class or fatty acid compositions could affect phospholipid properties and, thus, alter mitochondrial function and cell viability. In the present study, heart and brain mitochondrial membrane phospholipid compositions were analyzed in rainbow trout during the four first years of life, a period characterized by rapid growth and a sustained high metabolic rate. Specifically, farmed fish of three ages (1-, 2- and 4-years) were studied, and phospholipid class compositions of heart and brain mitochondria, and fatty acid compositions of individual phospholipid classes were determined. Rainbow trout heart and brain mitochondria showed different phospholipid compositions (class and fatty acid), likely related to tissue-specific functions. Furthermore, changes in phospholipid class and fatty acid compositions with age were also tissue-dependent. Heart mitochondria had lower proportions of cardiolipin (CL), phosphatidylserine (PS) and phosphatidylinositol, and higher levels of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) with age. Heart mitochondrial membranes became more unsaturated with age, with a significative increase of peroxidation index in CL, PS and sphingomyelin (SM). Therefore, heart mitochondria became more susceptible to oxidative damage with age. In contrast, brain mitochondrial PC and PS content decreased in 4-year-old animals while there was an increase in the proportion of SM. The three main phospholipid classes in brain (PC, PE and PS) showed decreased n-3 polyunsaturated fatty acids, docosahexaenoic acid and peroxidation index, which indicate a different response of brain mitochondrial lipids to rapid growth and maturation.     

Homeoviscous adaptation under pressure. III. The fatty acid composition of liver mitochondrial phospholipids of deep-sea fish

Homeoviscous adaptation of biological membranes to high hydrostatic pressure has been investigated by determining the differences in lipid composition of membranes from fish obtained from depths between 200 and 4000 m. The fatty acid composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine/inositol and cardiolipin from a liver mitochondrial fraction was analysed by capillary gas-liquid chromatography. The ratio of saturated to unsaturated fatty acids significantly and negatively related to depth in PC and PE as predicted by homeoviscous adaptation to pressure. Thus, deep sea species possess greater proportions of unsaturated fatty acids than shallow species. Cardiolipin showed the opposite trend. An unsaturation index was not significantly related to depth in any phospholipid fraction.     

Use of an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae to modify the lipid composition and function of mitochondrial membranes

KD115 (ol1), an unsaturated fatty acid auxotroph of S. cerevisiae, was grown in a semi-synthetic medium supplemented with 3.3 x 10(-4) M palmitoleic (cis 16:1) or palmitelaidic (trans 16:1) acids. The parent strain S288C was studied as a control. The lipid composition (fatty acids, neutral lipids, and phospholipids), respiratory activity (O2 consumption), and ultrastructure were compared in mutant yeast grown with each unsaturated fatty acid supplement. The fatty acid supplement represented 70-80% of the yeast fatty acids. Yeast grown in trans 16:1 contained more squalene, a higher ratio of phosphatidylethanolamine (PE) to phosphatidylcholine (PC), and had 10-20% of the respiratory activity compared to the same yeast grown in cis 16:1. The mitochondrial morphology of yeast in each growth supplement was notably different. The use of mixtures of cis and trans 16:1 in different proportions revealed that the PE/PC ratio, the squalene content, the respiratory defect, and the mitochondrial morphology were all similarly dependent on the fraction of trans 16:1 in the mixtures. As little as 10-20% of cis 16:1 in the mixture was sufficient to abrogate the physiological effects of trans 16:1 on each of the parameters noted above. The combined effects of high content of trans unsaturated fatty acid and the altered phospholipid composition seem to account for the decrease in lipid fluidity, the defective structure and function of the mitochondrial membrane.     

Protein synthesis and phospholipids in soybean axes in response to imbibitional chilling

The responses of two cultivars of soybean (Merr.) to a chilling treatment (4 C for first hour of imbibition) were compared. The germination of cv. Biloxi was unaffected by the treatment, while the germination of cv. Fiskeby was reduced. The phospholipid fatty acids of dry axes of the two cultivars were very similar, and, thus, could not be correlated with their responses to chilling. The fatty acid composition of chilling-tolerant Biloxi did not change over a subsequent 23-hour warm incubation, but there was a marked reduction in the unsaturated fatty acids of chilling-sensitive Fiskeby after 12 hours, which may be a symptom of deterioration. Protein synthesis in both cultivars was reduced by the chilling treatment. Redrying of Biloxi axes up to 18 hours after the onset of imbibition had no effect on their germination upon rehydration. Germination of Fiskeby axes was reduced by redrying after 8 hours of imbibition. After 7 months of dry storage of intact seeds, the sensitivity of the axes to chilling was retested. Biloxi axes had become chilling-sensitive, while the germination of Fiskeby axes was reduced to zero by the chilling treatment. A hypothesis is presented that imbibitional chilling sensitivity is an indication of reduced vigor, axes with a high vigor can tolerate the stress, while those without cannot.     

Laboratory tests carried out onMicrothrix inconspicuella [Lep.: Pyralidae], a biological control agent forEmex australis in Australia

Host specificity tests of the moth,Microthrix inconspicuella Ragonot in Australia, indicated that larvae could feed and develop on young apple leaves. Additional tests in South Africa on leaves and fruit of the 4 apple varieties, Jonathan, Starking (Red Delicious), Granny Smith and Golden Delicious, showed that apples were not a preferred food. Little feeding occurred and pupation happened infrequently. No 2^nd generation resulted whenM. inconspicuella colonies were confined on apple fruit or leaves.      

Incidence of ripening and chilling injury on the oxidative activities and Fatty Acid compositions of the mitochondria from mango fruits

The succinate oxidation capacities of mitochondria isolated from mango fruits (Mangifera indica L.) stored at 4, 8, 12, and 20 C were investigated during storage. In normally ripening fruits (at 12 and 20 C) the oxidative capacities increased during the first 10 days and then decreased slowly. At lower temperatures (4 and 8 C), the fruits showed chilling injury symptoms, after about 10 days of storage and the succinate oxidation capacities of mitochondria decreased progressively. Plots of succinate oxidation capacities as against storage temperature showed a marked discontinuity between 12 and 8 C, only when chilling injury was observed on fruits stored at low temperature.

The variations of mitochondrial fatty acid composition during the storage of fruits at different temperatures were also investigated. A marked decrease of the molar ratio palmitoleic acid/palmitic acid, the predominant fatty acids in mitochondrial lipids, was observed to accompany both the succinate oxidation decrease and the induction of chilling injury.

     

Fatty acid composition of rat liver mitochondrial phospholipids during ethanol inhalation

Male Sprague-Dawley rats were exposed to increasing concentrations (15-22 mg/l) of ethanol vapor over a 4-day period. Phospholipids were analyzed in liver mitochondria isolated from ethanol-treated and pair-weighted control animals. After a 2-day inhalation period, the proportion of monoenoic acids in total phospholipids increased, whereas that of arachidonic acid decreased. These changes were more striking in phosphatidylcholine (PC) than in phosphatidylethanolamine (PE). The decrease in 20:4 may be related to increased lipid peroxidation. After a 4-day inhalation period, quite different changes in phospholipid fatty acids were found. They consisted in a trend towards a more unsaturated system, the proportion of 20:4 being increased in PC and that of 22:6 in PE. This increase in polyunsaturated acids might be related to a direct ethanol effect on lipid structure and/or metabolism that would be linked to the high blood alcohol level present at this stage of ethanol intoxication.     

Lipids and fatty acids of the southwestern corn borer,Diatraea grandiosella

The lipids of the adults and of several immature stages of the southwestern corn borer, Diatraea grandiosella, were studied after they were fed natural corn stalks or artificial diets. Linoleic acid (18:2) was the major fatty acid of the neutral lipids in both the natural and the artificial diets, but aleic acid (18:1) was the principal neutral lipid in all insect stages. Also, linoleic acid and oleic acid were the principal acids in the insect phospholipids of all stages. The content of linoleic acid in the natural diet was also high, but that in the artificial diet appeared to be much too low for insect requirements. Phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were the major phospholipids in all growth stages. Thus, in larvae diapausing in the field, the unsaturated fatty acid content of PC was 59·3 per cent, primarily 16:1 and 18:1, and PE was 87·4 per cent, primarily 18:1, 18:2, and 18:3, and the fatty acids in the number 1- and 2-positions of PC were 53·6 and 97·2 per cent unsaturated, respectively. The haemolymph of diapausing southwestern corn borer larvae contained primarily glycerides but also had some PC and PE. Fat body from diapausing larvae contained primarily 16:0, 16:1, and 18:1 in a ratio of 1 : 1 : 2. Thus lipids of the southwestern corn borer do not reflect dietary lipids as closely as do other insects studied.     

低温强光下籼粳稻紫黄质脱环氧化酶活性和类囊体膜脂不饱和度的变化

为了阐明籼稻(Oryza sativa L.spp.indica)、粳稻(O.sativa L.spp.japonica)对低温强光敏感件的差异,着重研究了低温强光下水稻类囊体膜脂不饱和度与叶黄素循环的变化。随着低温强光处理时间的延长,类囊体膜脂不饱和脂肪酸含量降低,饱和脂肪酸含量增加,因而膜脂不饱和指数(IUFA)下降。同时,叶黄素循环的关键酶——紫黄质脱环氧化酶(VDE)活性降低,叶黄素循环组分中紫黄质(V)含量增加,而单环氧玉米黄质(A)和玉米黄质(Z)的含量减少,表现为(A Z)／(A Z V)比值下降。Arrhenius分析证明,VDE对低温和膜脂不饱和度都敏感。相关分析表明,类囊体IUFA分别与VDE活性、(A Z)／(A Z V)和D1蛋白量呈显著的正相关。与粳稻9516相比,籼稻汕优63类囊体膜的IUFA较低,低温下类囊体膜脂流动性和稳定性较筹,VDE活性和(A Z)／(A Z V)比值较低。     

Effects of ethanol on the incorporation of free fatty acids into cerebral membrane phospholipids

Chronic ethanol exposure is known to affect deacylation-reacylation of membrane phospholipids (PL). In our earlier studies we have demonstrated that chronic exposure to ethanol (EtOH) leads to a progressive increase in membrane phospholipase A2 (PLA2) activity. In the current study, we investigated the effects of chronic EtOH exposure on the incorporation of different free fatty acids (FFAs) into membrane PL. The results suggest that the incorporation of fatty acids into four major PL varied from 9.6 fmol/min/mg protein for docosahexaenoic acid (DHA) into phosphatidylinositol (PI) to 795.8 fmol/min/mg protein for linoleic acid (LA) into phosphatidylcholine (PC). These results also suggest a preferential incorporation of DHA into PC; arachidonic acid (AA) into PI; oleic acid into phosphatidylethanolamine (PE) and PC; LA into PC and stearic acid into PE. Chronic EtOH exposure affected the incorporation of unsaturated fatty acid into PI, phosphatidylserine (PS) and PC. However, EtOH did not affect significantly the incorporation of any of the fatty acids (FA) studied into PE. No significant differences were observed with the stearic acid. It is suggested that acyltransferases may play an important role in the membrane adaptation to the injurious effects of EtOH.     

Phospholipid Biosynthesis and Fatty Acid Content in Relation to Chilling Injury during Germination of Seeds

The proportion of labeled ¹⁴C-glycerol incorporated into phospholipids and the fatty acid composition of three phospholipids in germinating seeds and seedlings of chilling-sensitive lima beans (Phaseolus lunatus L.) and chilling-resistant broad beans (Vicia faba L.) and peas (Pisum sativum L.) at 10 and 25 C were determined. During the imbibition of seeds (first 24 hours), lima beans were sensitive to chilling injury at 10 C and a higher proportion of label was incorporated into phosphatidylethanolamine and phosphatidylglycerol than in broad beans and peas. Broad beans and peas incorporated a higher proportion of label into phosphatidylcholine. The oleic acid content of phosphatidylcholine was higher and linolenic acid content was lower in peas and broad beans than in lima beans at 10 and 25 C. The unsaturated to saturated fatty acid ratio was much higher for the chilling-resistant seeds than for the chilling-sensitive ones. In the seedling stage, the proportion of label incorporated into the four major phospholipids was similar in the three species regardless of temperature treatment. The fatty acid content of the phospholipids examined was not different in the three species in the seedling stage.     

Nuclear Deoxyribonucleic Acid Metabolism and Membrane Fatty Acid Content Related to Chilling Resistance in Germinating Cotton (Gossypium barbadense)

Chilling damage was examined in the chilling-sensitive plant Gossypium barbadense. Between 30 and 36 h of germination at 34°C, the seedlings are extremely sensitive to temperatures below 10°C. The initiation of chilling damage by exposure to 2°C for 5 h during the sensitive period resulted in a large reduction in DNA synthesis. The reduction was correlated with a reduced efficiency of nuclear DNA polymerase activity. Comparing a more chilling resistant genotype to a more sensitive variety indicated that the resistant genotype nuclear DNA polymerase activity is more efficient when exposed to a chilling stress. Resistance was also correlated with a higher degree of unsaturated fatty acid content in the nuclear membranes of the resistant variety.     

Seasonal changes of phospholipids in last instar larvae of rice stem borer Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Phospholipids of the cell membrane have been studied from the viewpoint of how overwintering insects inhabiting temperate zones adapt to low temperature. The transition of cell membrane phospholipids from a liquid crystalline phase to a gel phase is a crucial cause of cold or freezing injuries. We determined the qualitative and quantitative changes of phospholipids in the last instar larvae of the rice stem borer in summer and winter. We found that the total amount of their phospholipids did not change significantly between summer and winter and that the sum of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) comprised about 85% of their total phospholipids. In summer, the ratio of their PE to PC was almost one, while from autumn to mid‐winter it increased and reached three in February. The fatty acid compositions of PC hardly changed, and the percentage of unsaturated fatty acids did not exceed 50%. In contrast, the percentage of unsaturated fatty acids of PE in overwintering larvae increased up to 80% as ambient temperatures fell and oleic acid mainly contributed to the high percentage of unsaturation. In the present study, the relationship between the quantitative and qualitative changes of phospholipids and adaptation of the rice stem borer to cold winter climate are discussed.