Characteristics of Synthesis of Very-Long-Chain Saturated and Tetraenoic Fatty Acids in Swine Cerebral Microsomes

The elongation of arachidoyl-CoA (20:0-CoA) yielded 22:0 and 24:0 concomitantly, whereas the elongation of behenoyl-CoA (22:0-CoA) yielded only a negligible amount of 24:0 in adult swine cerebral microsomes. The dependence on time, pH, and the substrate concentrations were examined for the synthesis of 22:0 and 24:0 from 20:0-CoA. A microcomputer-aided simulation study suggested that there were two parallel pathways in the elongation of 20:0-CoA to 22:0 and 24:0. The elongation of 22:0-CoA could not be observed in adult swine cerebral microsomes; however, it was observed clearly in newborn swine and rat brain microsomes. A dilution experiment with the addition of cold 22:0-CoA in the reaction of elongation of 20:0-CoA confirmed the above suggestion that no intermediate 22:0 appeared during the synthesis of 24:0 from 20:0-CoA. The elongation of endogenous 20:4-CoA to 22:4 and 24:4 was examined in newborn swine cerebral microsomes, and the presence of two parallel pathways in the elongation of 20:4-CoA to 22:4 and 24:4 similar to those involved in the elongation of 20:0-CoA to 22:0 and 24:0 was suggested.     

Incorporation of Very-Long-Chain Fatty Acids into Sphingolipids of Cultured Neural Cells

We examined effects of exogenous very-long-chain fatty acids on lipids of cultured chick neurons and astrocytes. When chick neurons were incubated in chemically defined medium containing 10 microM nervonic acid (C24:1) for 7 days, it was found that a major fatty acid moiety of gangliosides and sphingomyelin was nervonic acid itself, which was not normally detected in the sphingolipid fraction. This alteration in the fatty acid composition apparently occurred in each ganglioside species. Under these experimental conditions, nervonic acid was not found in the glycerophospholipid fraction, and the amounts of triacylglycerol and free nervonic acid increased. Addition of behenic acid (C22:0) or erucic acid (C22:1) also induced changes in the fatty acid composition of gangliosides. When chick astrocytes were incubated in the presence of 10 microM nervonic acid for 7 days, no significant change was observed in the fatty acid composition of gangliosides. These studies indicate that the manipulation of the fatty acid moiety of sphingolipids in cultured neurons is possible.     

In Vitro Activation of Rat Brain Protein Kinase C by Polyenoic Very-Long-Chain Fatty Acids

Abstract: A variety of fatty acids including the cis -polyunsaturated very-long-chain fatty acids (VLCFA) (>22 carbon atoms) common in retina, spermatozoa, and brain were examined for their ability to activate protein kinase C (PKC) purified from rat brain. Arachidonic [20:4(n-6)], eicosapentaenoic [20:5(n-3)], and docosahexaenoic [22:6(n- 3)] acids as well as the VLCFA dotriacontatetraenoic [32:4(n-6)] and tetratriacontahexaenoic [34:6(n-3)] were equally capable of activating PKC in vitro with maximal activity being between 25 and 50 μ M. The phorbol ester 12- O -tetradecanoylphorbol 13-acetate further enhanced the in vitro activation of PKC when added to the protein kinase assay system with the fatty acids. The fully saturated arachidic acid (20:0) was inactive in both assay systems. The potential significance of the in vitro activation of PKC by the VLCFA is discussed.     

Fatty Acids as Inhibitors of Microbial Cell Wall Synthesis

The Maillard reaction of DNA with ketoses was investigated. Several days of incubation of d-fructose 6-phosphate with deoxyribonucleotides or with polymer DNA in an aqueous buffer resulted in the formation of chromophores and fluorophores. Aminoguanidine and sodium cvanoborohydride inhibited the formation of fluorophores. Transition metal ions such as Cu²⁺, Fe³⁺, Fe²⁺, or Mn^{2 +} promoted the formation of chromophores and fluorophores. Metal-chelating agents such as DETAPAC, citrate, and Desferal inhibited the formation of fluorophores. Superoxide dismutase and catalase also inhibited the formation of fluorophores. The transition metal ion-catalyzed autoxidation of d-fructose 6-phosphate or of the Heyns rearrangement products were to be partially involved in the glycation of DNA and subsequent formation of chromophores and of fluorophores.     

Very-Long-Chain Fatty Acids Are Involved in Polar Auxin Transport and Developmental Patterning in Arabidopsis

Very-long-chain fatty acids (VLCFAs) are essential for many aspects of plant development and necessary for the synthesis of seed storage triacylglycerols, epicuticular waxes, and sphingolipids. Identification of the acetyl-CoA carboxylase PASTICCINO3 and the 3-hydroxy acyl-CoA dehydratase PASTICCINO2 revealed that VLCFAs are important for cell proliferation and tissue patterning. Here, we show that the immunophilin PASTICCINO1 (PAS1) is also required for VLCFA synthesis. Impairment of PAS1 function results in reduction of VLCFA levels that particularly affects the composition of sphingolipids, known to be important for cell polarity in animals. Moreover, PAS1 associates with several enzymes of the VLCFA elongase complex in the endoplasmic reticulum. The pas1 mutants are deficient in lateral root formation and are characterized by an abnormal patterning of the embryo apex, which leads to defective cotyledon organogenesis. Our data indicate that in both tissues, defective organogenesis is associated with the mistargeting of the auxin efflux carrier PIN FORMED1 in specific cells, resulting in local alteration of polar auxin distribution. Furthermore, we show that exogenous VLCFAs rescue lateral root organogenesis and polar auxin distribution, indicating their direct involvement in these processes. Based on these data, we propose that PAS1 acts as a molecular scaffold for the fatty acid elongase complex in the endoplasmic reticulum and that the resulting VLCFAs are required for polar auxin transport and tissue patterning during plant development.     

植物不饱和脂肪酸的生物合成及调控

不饱和脂肪酸是植物细胞中的一类重要代谢物质,是组成细胞膜的主要成分,对调节细胞的生理功能起着重要作用。不饱和脂肪酸也是人类必须的一类营养物质,对健康发挥着重要作用。因此,研究植物不饱和脂肪酸的合成和调控机制具有着重要的理论和现实意义。不饱和脂肪酸的合成主要发生在质体和内质网,由一系列编码基因控制,并受到外在环境胁迫及发育的调控。本研究综述了近年来不饱和脂肪酸合成和调控机制相关的一些研究进展,解析了不饱和脂肪酸合成的一些关键基因,以期为将来利用相关基因进行种质创新,从而实现改良食用油品质或提升植物的抗性育种提供思路和实践。     

微生物合成奇数链脂肪酸研究进展*

奇数链脂肪酸(odd-chain fatty acids,OCFA)在自然界分布广泛但含量低,在食品、医药健康和工业等领域有着巨大的应用潜力。目前获取OCFA的方法主要为提取法和化学合成法,但成本高、效率低,而通过微生物发酵有望实现OCFA大规模工业生产。总结OCFA的应用范围和天然合成OCFA的微生物种类,详述微生物合成OCFA的代谢途径,并从基因工程策略和发酵调控策略两方面综述目前提升OCFA产量的研究现状,旨在为利用合成生物学策略改造和提升微生物合成OCFA的能力提供较为系统的理论依据。     

龟板脂肪酸调控鼠骨髓间质干细胞增殖作用

为了解龟板浸膏中对鼠骨髓间质干细胞体外增殖起促进作用的化学成分,用石油醚提取促进鼠骨髓间充质干细胞增殖的龟板有效部位,用MTT比色法及流式细胞仪研究了提取物调控鼠骨髓间充质干细胞活性,采用GC-MS技术研究了石油醚提取物的化学成分。初步结果表明,石油醚提取物能明显促进干细胞增殖,其主要成分是脂肪酸、甾醇和甾酮,且十八烷酸、十六烷酸和甾酮能起调控鼠骨髓间充质干细胞活性。龟板浸膏中,脂肪酸起调控鼠骨髓间充质干细胞增殖作用,这为龟板浸膏促进鼠骨髓间充质干细胞增殖又不引起干细胞过度生长的分子机制提供实验依据,也为中医药调控干细胞的研究提供重要的参考。     

龟板脂肪酸调控鼠骨髓间质干细胞增殖作用

为了解龟板浸膏中对鼠骨髓间质干细胞体外增殖起促进作用的化学成分,用石油醚提取促进鼠骨髓间充质干细胞增殖的龟板有效部位,用MTT比色法及流式细胞仪研究了提取物调控鼠骨髓间充质干细胞活性,采用GC-MS技术研究了石油醚提取物的化学成分。初步结果表明,石油醚提取物能明显促进干细胞增殖,其主要成分是脂肪酸、甾醇和甾酮,且十八烷酸、十六烷酸和甾酮能起调控鼠骨髓间充质干细胞活性。龟板浸膏中,脂肪酸起调控鼠骨髓间充质干细胞增殖作用,这为龟板浸膏促进鼠骨髓间充质干细胞增殖又不引起干细胞过度生长的分子机制提供实验依据,也为中医药调控干细胞的研究提供重要的参考。     

Focus on Ethylene: Ethylene Biosynthesis Is Promoted by Very-Long-Chain Fatty Acids during Lysigenous Aerenchyma Formation in Rice Roots

In rice (Oryza sativa) roots, lysigenous aerenchyma, which is created by programmed cell death and lysis of cortical cells, is constitutively formed under aerobic conditions, and its formation is further induced under oxygen-deficient conditions. Ethylene is involved in the induction of aerenchyma formation. reduced culm number1 (rcn1) is a rice mutant in which the gene encoding the ATP-binding cassette transporter RCN1/OsABCG5 is defective. Here, we report that the induction of aerenchyma formation was reduced in roots of rcn1 grown in stagnant deoxygenated nutrient solution (i.e. under stagnant conditions, which mimic oxygen-deficient conditions in waterlogged soils). 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a key enzyme in ethylene biosynthesis. Stagnant conditions hardly induced the expression of ACS1 in rcn1 roots, resulting in low ethylene production in the roots. Accumulation of saturated very-long-chain fatty acids (VLCFAs) of 24, 26, and 28 carbons was reduced in rcn1 roots. Exogenously supplied VLCFA (26 carbons) increased the expression level of ACS1 and induced aerenchyma formation in rcn1 roots. Moreover, in rice lines in which the gene encoding a fatty acid elongase, CUT1-LIKE (CUT1L; a homolog of the gene encoding Arabidopsis CUT1, which is required for cuticular wax production), was silenced, both ACS1 expression and aerenchyma formation were reduced. Interestingly, the expression of ACS1, CUT1L, and RCN1/OsABCG5 was induced predominantly in the outer part of roots under stagnant conditions. These results suggest that, in rice under oxygen-deficient conditions, VLCFAs increase ethylene production by promoting 1-aminocyclopropane-1-carboxylic acid biosynthesis in the outer part of roots, which, in turn, induces aerenchyma formation in the root cortex.Aerenchyma formation is a morphological adaptation of plants to complete submergence and waterlogging of the soil, and facilitates internal gas diffusion (Armstrong, 1979; Jackson and Armstrong, 1999; Colmer, 2003; Voesenek et al., 2006; Bailey-Serres and Voesenek, 2008; Licausi and Perata, 2009; Sauter, 2013; Voesenek and Bailey-Serres, 2015). To adapt to waterlogging in soil, rice (Oryza sativa) develops lysigenous aerenchyma in shoots (Matsukura et al., 2000; Colmer and Pedersen, 2008; Steffens et al., 2011) and roots (Jackson et al., 1985b; Justin and Armstrong, 1991; Kawai et al., 1998), which is formed by programmed cell death and subsequent lysis of some cortical cells (Jackson and Armstrong, 1999; Evans, 2004; Yamauchi et al., 2013). In rice roots, lysigenous aerenchyma is constitutively formed under aerobic conditions (Jackson et al., 1985b), and its formation is further induced under oxygen-deficient conditions (Colmer et al., 2006; Shiono et al., 2011). The former and latter are designated constitutive and inducible lysigenous aerenchyma formation, respectively (Colmer and Voesenek, 2009). The gaseous plant hormone ethylene regulates adaptive growth responses of plants to submergence (Voesenek and Blom, 1989; Voesenek et al., 1993; Visser et al., 1996a,b; Lorbiecke and Sauter, 1999; Hattori et al., 2009; Steffens and Sauter, 2009; van Veen et al., 2013). Ethylene also induces lysigenous aerenchyma formation in roots of some gramineous plants (Drew et al., 2000; Shiono et al., 2008). The treatment of roots with ethylene or its precursor (1-aminocyclopropane-1-carboxylic acid [ACC]) stimulates aerenchyma formation in rice (Justin and Armstrong, 1991; Colmer et al., 2006; Yukiyoshi and Karahara, 2014), maize (Zea mays; Drew et al., 1981; Jackson et al., 1985a; Takahashi et al., 2015), and wheat (Triticum aestivum; Yamauchi et al., 2014a,b). Moreover, treatment of roots with inhibitors of ethylene action or ethylene biosynthesis effectively blocks aerenchyma formation under hypoxic conditions in maize (Drew et al., 1981; Konings, 1982; Jackson et al., 1985a; Rajhi et al., 2011).Ethylene biosynthesis is accomplished by two main successive enzymatic reactions: conversion of S-adenosyl-Met to ACC by 1-aminocyclopropane-1-carboxylic acid synthase (ACS), and conversion of ACC to ethylene by 1-aminocyclopropane-1-carboxylic acid oxidase (ACO; Yang and Hoffman, 1984). The activities of both enzymes are enhanced during aerenchyma formation under hypoxic conditions in maize root (He et al., 1996). Since the ACC content in roots of maize is increased by oxygen deficiency and is strongly correlated with ethylene production (Atwell et al., 1988), ACC biosynthesis is essential for ethylene production during aerenchyma formation in roots. In fact, exogenously supplied ACC induced ethylene production in roots of maize (Drew et al., 1979; Konings, 1982; Atwell et al., 1988) and wheat (Yamauchi et al., 2014b), even under aerobic conditions. Ethylene production in plants is inversely related to oxygen concentration (Yang and Hoffman, 1984). Under anoxic conditions, the oxidation of ACC to ethylene by ACO, which requires oxygen, is almost completely repressed (Yip et al., 1988; Tonutti and Ramina, 1991). Indeed, anoxic conditions stimulate neither ethylene production nor aerenchyma formation in maize adventitious roots (Drew et al., 1979). Therefore, it is unlikely that the root tissues forming inducible aerenchyma are anoxic, and that the ACO-mediated step is repressed. Moreover, aerenchyma is constitutively formed in rice roots even under aerobic conditions (Jackson et al., 1985b), and thus, after the onset of waterlogging, oxygen can be immediately supplied to the apical regions of roots through the constitutively formed aerenchyma.Very-long-chain fatty acids (VLCFAs; ≥20 carbons) are major constituents of sphingolipids, cuticular waxes, and suberin in plants (Franke and Schreiber, 2007; Kunst and Samuels, 2009). In addition to their structural functions, VLCFAs directly or indirectly participate in several physiological processes (Zheng et al., 2005; Reina-Pinto et al., 2009; Roudier et al., 2010; Ito et al., 2011; Nobusawa et al., 2013; Tsuda et al., 2013), including the regulation of ethylene biosynthesis (Qin et al., 2007). During fiber cell elongation in cotton ovules, ethylene biosynthesis is enhanced by treatment with saturated VLCFAs, especially 24-carbon fatty acids, and is suppressed by an inhibitor of VLCFA biosynthesis (Qin et al., 2007). The first rate-limiting step in VLCFA biosynthesis is condensation of acyl-CoA with malonyl-CoA by β-ketoacyl-CoA synthase (KCS; Joubès et al., 2008). KCS enzymes are thought to determine the substrate and tissue specificities of fatty acid elongation (Joubès et al., 2008). The Arabidopsis (Arabidopsis thaliana) genome has 21 KCS genes (Joubès et al., 2008). In the Arabidopsis cut1 mutant, which has a defect in the gene encoding CUT1 that is required for cuticular wax production (i.e. one of the KCS genes), the expression of AtACO genes and growth of root cells were reduced when compared with the wild type (Qin et al., 2007). Furthermore, expression of the AtACO genes was rescued by exogenously supplied saturated VLCFAs (Qin et al., 2007). These observations imply that VLCFAs or their derivatives work as regulatory factors for gene expression during some physiological processes in plants.reduced culm number1 (rcn1) was first identified as a rice mutant with a low tillering rate in a paddy field (Takamure and Kinoshita, 1985; Yasuno et al., 2007). The rcn1 (rcn1-2) mutant has a single nucleotide substitution in the gene encoding a member of the ATP-binding cassette (ABC) transporter subfamily G, RCN1/OsABCG5, causing an Ala-684Pro substitution (Yasuno et al., 2009). The mutation results in several mutant phenotypes, although the substrates of RCN1/OsABCG5 have not been determined (Ureshi et al., 2012; Funabiki et al., 2013; Matsuda et al., 2014). We previously found that the rcn1 mutant has abnormal root morphology, such as shorter root length and brownish appearance of roots, under stagnant (deoxygenated) conditions (which mimics oxygen-deficient conditions in waterlogged soils). We also found that the rcn1 mutant accumulates less of the major suberin monomers originating from VLCFAs in the outer part of adventitious roots, and this results in a reduction of a functional apoplastic barrier in the root hypodermis (Shiono et al., 2014a).The objective of this study was to elucidate the molecular basis of inducible aerenchyma formation. To this end, we examined lysigenous aerenchyma formation and ACC, ethylene, and VLCFA accumulation and their biosyntheses in rcn1 roots. Based on the results of these studies, we propose that VLCFAs are involved in inducible aerenchyma formation through the enhancement of ethylene biosynthesis in rice roots.     

JAGGED Controls Growth Anisotropy and Coordination between Cell Size and Cell Cycle during Plant Organogenesis

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Highlights? JAGGED (JAG) is required for growth of initiating floral organs in Arabidopsis ? JAG decouples cell cycle from cell growth during organ emergence ? JAG promotes fast, anisotropic growth when floral organs emerge from the meristem ? JAG directly represses meristem identity genes     

Fatty Acids in Buckwheat are Growth Inhibitors

Four fatty acids, palmitic, stearic, arachidic and behenic acids,were identified (using gas chromatography-mass spectrometry)from buckwheat seedlings. These fatty acids at a concentrationof 250 ppm caused a slight but significant inhibition in growthof rice seedlings. Fagopyrum cymosum, fatty acid, growth inhibitor     

Biosynthesis of Cutin: Enzymatic Conversion of omega-Hydroxy Fatty Acids to Dicarboxylic Acids by Cell-free Extracts of Vicia Faba Epidermis

Long chain dicarboxylic acids are constituents of the protective biopolymers cutin and suberin of plants. Cell-free extracts from the excised epidermis of Vicia faba leaves catalyzed conversion of 16-hydroxy[G-(3)H]hexadecanoic acid to the corresponding dicarboxylic acid with nicotinamide-adenine dinucleotide phosphate as the preferred cofactor. This enzymatic activity, located largely in the 100,000g supernatant fraction, had a pH optimum near 8. This dehydrogenase showed an apparent Km of 1.25 x 10(-5)m and 3.6 x 10(-4)m for 16-hydroxyhexadecanoic acid and NADP, respectively. Modification of the substrate, either by esterification of the carboxyl group or by introduction of another hydroxyl group at C-10, resulted in a substantial (two-thirds) decrease in the rate of reaction, and hexadecanol was not a good substrate. The enzyme was inhibited by thiol reagents such as N-ethylmaleimide and p-chloromercuribenzoate. The aldehyde intermediate was trapped by the inclusion of dinitrophenyl hydrazine in the reaction mixture, and the 16-oxo compound was regenerated and identified. Furthermore, synthetic 16-oxo-[G-(3)H] hexadecanoic acid was readily converted to the dicarboxylic acid by the cell-free preparation. These results demonstrate that epidermis of Vicia faba contains an omega-hydroxyacid dehydrogenase and an omega-oxoacid dehydrogenase.     

Temperature-induced Changes in the Synthesis of Unsaturated Fatty Acids by Acanthamoeba castellanii

ABSTRACT. Major fatty acid components of Acanthamoeba castellanii lipids extracted after growth at 30°C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15°C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30°C to 15°C, increased lipid unsaturation occurred over a period of 24 h; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15°C to 30°C gave negligible alterations in fatty acid composition over a similar period. At 15°C organisms rapidly use [1-¹⁴C] acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30°C indicate only de novo synthesis and Δ9-desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1-¹⁴C] oleate at 30°C was not accompanied by metabolic conversion over two hours, whereas at 15°C n-6 desaturation to linoleate was observed. Temperature shift of organisms from 15°C to 30°C in the presence of [1-¹⁴C] acetate revealed that over half of the fatty acids in newly-synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 h. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n-6 desaturation in the low temperature adaptation of Acanthamoeba castellanii .     

Vitamin D Stimulates Cardiomyocyte Proliferation and Controls Organ Size and Regeneration in Zebrafish

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多不饱和脂肪酸合成途径研究进展

多不饱和脂肪酸在大多数生物体膜生物学和信号传递过程中起着至关重要的作用。最近研究发现,一些深海生物合成多不饱和脂肪酸并非由饱和脂肪酸的延长及脱饱和反应,而是由聚酮合酶途径(polyketide synthase,PKS)直接合成。介绍多不饱和脂肪酸的生物合成并总结近年来聚酮合酶这一新途径及其分子机制的研究进展。