| 1. |
- Arnqvist, Lisa, 1970-, et al.
(författare)
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Overexpression of CYP710A1 and CYP710A4 in transgenic Arabidopsis plants increases the level of stigmasterol at the expense of sitosterol
- 2008
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 227:2, s. 309-317
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Tidskriftsartikel (refereegranskat)abstract
- Sitosterol and stigmasterol are major sterols in vascular plants. An altered stigmasterol:sitosterol ratio has been proposed to influence the properties of cell membranes, particularly in relation to various stresses, but biosynthesis of stigmasterol is poorly understood. Recently, however, Morikawa et al. (Plant Cell 18:1008–1022, 2006) showed in Arabidopsis thaliana that synthesis of stigmasterol and brassicasterol is catalyzed by two separate sterol C-22 desaturases, encoded by the genes CYP710A1 and CYP710A2, respectively. The proteins belong to a small cytochrome P450 subfamily having four members, denoted by CYP710A1-A4, and are related to the yeast sterol C-22 desaturase Erg5p acting in ergosterol synthesis. Here, we report on our parallel investigation of the Arabidopsis CYP710A family. To elucidate the function of CYP710A proteins, transgenic Arabidopsis plants were generated overexpressing CYP710A1 and CYP710A4. Compared to wild-type plants, both types of transformant displayed a normal phenotype, but contained increased levels of free stigmasterol and a concomitant decrease in the level of free sitosterol. CYP710A1 transformants also displayed higher levels of esterified forms of stigmasterol, cholesterol, 24-methylcholesterol and isofucosterol. The results confirm the findings of Morikawa et al. (Plant Cell 18:1008–1022, 2006) regarding the function of CYP710A1 in stigmasterol synthesis, and show that CYP710A4 also has this capacity. Furthermore, our results suggest that an increased stigmasterol level alone is sufficient to stimulate esterification of other major sterols.
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| 2. |
- Aslan, Selcuk, et al.
(författare)
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Increased production of wax esters in transgenic tobacco plants by expression of a fatty acid reductase:wax synthase gene fusion
- 2015
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Ingår i: Transgenic Research. - : Springer Science and Business Media LLC. - 0962-8819 .- 1573-9368. ; 24, s. 945-953
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Tidskriftsartikel (refereegranskat)abstract
- Wax esters are hydrophobic lipids consisting of a fatty acid moiety linked to a fatty alcohol with an ester bond. Plant-derived wax esters are today of particular concern for their potential as cost-effective and sustainable sources of lubricants. However, this aspect is hampered by the fact that the level of wax esters in plants generally is too low to allow commercial exploitation. To investigate whether wax ester biosynthesis can be increased in plants using transgenic approaches, we have here exploited a fusion between two bacterial genes together encoding a single wax ester-forming enzyme, and targeted the resulting protein to chloroplasts in stably transformed tobacco (Nicotiana benthamiana) plants. Compared to wild-type controls, transgenic plants showed both in leaves and stems a significant increase in the total level of wax esters, being eight-fold at the whole plant level. The profiles of fatty acid methyl ester and fatty alcohol in wax esters were related, and C16 and C18 molecules constituted predominant forms. Strong transformants displayed certain developmental aberrations, such as stunted growth and chlorotic leaves and stems. These negative effects were associated with an accumulation of fatty alcohols, suggesting that an adequate balance between formation and esterification of fatty alcohols is crucial for a high wax ester production. The results show that wax ester engineering in transgenic plants is feasible, and suggest that higher yields may become achieved in the near future.
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| 3. |
- Aslan, Selcuk, et al.
(författare)
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Transient silencing of the KASII genes is feasible in Nicotiana benthamiana for metabolic engineering of wax ester composition
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The beta-ketoacyl-ACP synthase II (KASII) is an enzyme in fatty acid biosynthesis, catalyzing the elongation of 16:0-acyl carrier protein (ACP) to 18:0-ACP in plastids. Mutations in KASII genes in higher plants can lead to lethality, which makes it difficult to utilize the gene for lipid metabolic engineering. We demonstrated previously that transient expression of plastid-directed fatty acyl reductases and wax ester synthases could result in different compositions of wax esters. We hypothesized that changing the ratio between C16 (palmitoyl-compounds) and C18 (stearoyl-compounds) in the plastidic acyl-ACP pool by inhibition of KASII expression would change the yield and composition of wax esters via substrate preference of the introduced enzymes. Here, we report that transient inhibition of KASII expression by three different RNAi constructs in leaves of N. benthamiana results in almost complete inhibition of KASII expression. The transient RNAi approach led to a shift of carbon flux from a pool of C18 fatty acids to C16, which significantly increased wax ester production in AtFAR6-containing combinations. The results demonstrate that transient inhibition of KASII in vegetative tissues of higher plants enables metabolic studies towards industrial production of lipids such as wax esters with specific quality and composition.
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| 4. |
- Aslan, Selcuk, et al.
(författare)
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Wax esters of different compositions produced via engineering of leaf chloroplast metabolism in Nicotiana benthamiana
- 2014
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Ingår i: Metabolic Engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; 25, s. 103-112
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Tidskriftsartikel (refereegranskat)abstract
- In a future bin based economy, renewable sources for lipid compounds at attractive cost are needed for applications where today petrochemical derivatives are dominating. Wax esters and fatty alcohols provide diverse industrial uses, such as in lubricant and surfactant production. In this study, chloroplast metabolism was engineered to divert intermediates from de nova fatty acid biosynthesis to wax ester synthesis. To accomplish this, chloroplast targeted fatty acyl recluctases (EAR) and wax ester synthases (WS) were transiently expressed in Nic"onana benthamiuna loaves. Wax esters of different qualities and quantities were produced providing insights to the properties and interaction of the individual enzymes used. In particular, a phytyl ester synthase was found to be a premium candidate for medium chain wax ester synthesis. Catalytic activities of FAR and WS were also expressed as a fusion protein and determined functionally equivalent to the expression of individual enzymes for wax ester synthesis in chloroplasts. (C) 2014 The Authors. Published by Elsevier Inc. On behalf of International Metabolic Engineering Society.
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| 5. |
- Azadmard-Damirchi, Sodeif, et al.
(författare)
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A single step solid-phase extraction method for complete separation of sterol oxidation products in food lipids
- 2009
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1216, s. 36-42
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Tidskriftsartikel (refereegranskat)abstract
- One of the crucial steps in determination of sterol oxidation products (SOPs) in foods is their enrichment and purifications by various preparative methods for further analysis by GC and GC-MS. Among the preparative methods, SPE of various adsorbents and solvent systems, are being used most widely. At present, no single step SPE method is suitable to completely separate the SOPs. In this study, a SPE (I g silica) method, suitable for both transesterified and cold saponified oil samples. was developed to separate completely SOPs from other lipid components. This method resulted in high recovery from rapeseed oil of added 5 beta,6 beta-epoxycholestan-3 beta-ol (94-96%), cholest-5-en-3 beta-ol-7-one(94%), cholestane-3 beta,5 alpha,6 beta-triol (88-91%), cholest-5-en-3 beta,7 alpha-diol and 5 alpha,6 alpha-epoxycholestan-3 beta-ol (88-90%). The method has a high sample capacity of up to I g transesterified or cold-saponified oil sample. The method was tested and applied to different vegetable oils and to monitor the effects of refining processes on POPs in hazelnut oil. (C) 2008 Elsevier B.V. All rights reserved.
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| 6. |
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| 7. |
- Beste, Lisa, et al.
(författare)
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Synthesis of Hydroxylated Sterols in Transgenic Arabidopsis Plants Alters Growth and Steroid Metabolism
- 2011
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 157:1, s. 426-440
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Tidskriftsartikel (refereegranskat)abstract
- To explore mechanisms in plant sterol homeostasis, we have here increased the turnover of sterols in Arabidopsis (Arabidopsis thaliana) and potato (Solanum tuberosum) plants by overexpressing four mouse cDNA encoding cholesterol hydroxylases (CHs), hydroxylating cholesterol at the C-7, C-24, C-25, or C-27 positions. Compared to the wild type, the four types of Arabidopsis transformant showed varying degrees of phenotypic alteration, the strongest one being in CH25 lines, which were dark-green dwarfs resembling brassinosteroid-related mutants. Gas chromatography-mass spectrometry analysis of extracts from wild-type Arabidopsis plants revealed trace levels of alpha and beta forms of 7-hydroxycholesterol, 7-hydroxycampesterol, and 7-hydroxysitosterol. The expected hydroxycholesterol metabolites in CH7-, CH24-, and CH25 transformants were identified and quantified using gas chromatography-mass spectrometry. Additional hydroxysterol forms were also observed, particularly in CH25 plants. In CH24 and CH25 lines, but not in CH7 ones, the presence of hydroxysterols was correlated with a considerable alteration of the sterol profile and an increased sterol methyltransferase activity in microsomes. Moreover, CH25 lines contained clearly reduced levels of brassinosteroids, and displayed an enhanced drought tolerance. Equivalent transformations of potato plants with the CH25 construct increased hydroxysterol levels, but without the concomitant alteration of growth and sterol profiles observed in Arabidopsis. The results suggest that an increased hydroxylation of cholesterol and/or other sterols in Arabidopsis triggers compensatory processes, acting to maintain sterols at adequate levels.
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| 8. |
- Dutta, Paresh
(författare)
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Analytical Methods for Quantification of Modified Fatty Acids and Sterols Formed as a Result of Processing
- 2009
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Ingår i: Food Analytical Methods. - : Springer Science and Business Media LLC. - 1936-9751 .- 1936-976X. ; 2, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- Fats and oils are often submitted to technological treatments before being consumed. Some treatments like refining, hydrogenation, and frying often lead to the formation of modified fatty acids such as cyclic fatty acid monomers (CFAM), geometrical fatty acid isomers, and/or oxidized fatty acids and sterols (cholesterol and phytosterols). Both cholesterol oxidation products (COP) and phytosterol oxidation products (POP), may be present in foods. As some of the newly formed components may present some adverse effects upon consumption, methods have been developed to analyze these compounds in food products and biological samples. Gas liquid chromatography (GC) on long polar columns (100m) is a good choice to quantify trans mono- and poly-unsaturated fatty acids. In some cases a pre-fractionation step using silver nitrate thin layer chromatography (AgNO3-TLC) may be necessary to avoid GC overlapping of cis and trans isomers. Analysis of CFAM usually involves transformation of the sample in fatty acid methyl esters (FAME) which after addition of an internal standard (IS) are further hydrogenated. An enrichment step using reverse phase high performance liquid chromatography (RP-HPLC) permits to obtain a fraction which consists of a mixture of CFAM and the IS. This fraction is further analyzed by GC on a polar column. The analysis of oxidized triacylglycerol monomers (oxTG) as a group was feasible by a combination of adsorption and size-exclusion chromatography. Quantification in used frying fats and oils around the limit of rejection for human consumption (25% polar compounds) has shown that the amount of oxTG range 5.9-9.4% expressed on fat or oil weight. In foods and biological tissues, the level of oxidized sterols (SOP) is often a very small fraction of their unoxidized forms. Analysis of SOP involved extraction of lipids, saponification or transesterification, enrichment, and subsequent qualitative and quantitative determination by GC and GC-MS, or HPLC and HPLC-MS. In addition, enrichment of SOP requires complete separation from the unoxidized sterols in order to separate these compounds even by high resolution GC capillary columns.
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| 9. |
- Dutta, Paresh
(författare)
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Cholesterol and lipid oxidation in raw and pan-fried minced beef stored under aerobic packaging
- 2010
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 0022-5142 .- 1097-0010. ; 90, s. 1050-1055
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The type of packaging atmosphere has been reported as a technological factor that consistently affects the quality of lipid fraction in meat. Oxidation of cholesterol and lipids was evaluated before and after pan frying in commercial refrigerated minced beef stored under aerobic atmosphere for 1 and 8 days.RESULTS: In raw beef, cholesterol and lipid oxidation developed at a slow rate. Cholesterol oxidation products (COPs) did not significantly vary (similar to 8 mu g COPs g(-1) of fat) over 8 days, while in the same period thiobarbituric acid reactive substances (TBARS) less than doubled (from 0.7 to 1.2 malondialdehyde equivalents kg(-1) of muscle). Pan frying did not influence the oxidative degree in the fresh product but consistently catalyzed cholesterol oxidation in stored beef. A significant increase was assessed in beef at the end of storage: from 8.6 to 30.0 mu g COPs g(-1) of fat in raw and cooked beef, respectively.CONCLUSION: Aerobic packaging did not appear as a pro-oxidant factor in fresh minced beef with a good oxidative quality during a short period of refrigerated storage. (C) 2010 Society of Chemical Industry
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| 10. |
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