Triacylglycerols in oilseed rape during seed development

Norton, G.; Harris, John F.

doi:10.1016/s0031-9422(00)97676-3

Cited by 42 publications

(20 citation statements)

References 7 publications

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“…Although VLCFAs, and erucoyl moieties in particular, do not accumulate in the endogenous LPA/PA and PC pools of developing MD embryos of B. napus cv Reston (28), the present data suggest that, rather than being excluded from polar lipid intermediates of the currently accepted TAG bioassembly pathway (24), newly synthesized VLCFAs may be channeled very rapidly from G-3-P through LPA, PA, DAG 20 LPA / PA (and, through interconversion with DAG pools, PC [24,28]) and accumulate only in the end product, TAG. The incorporation of 14C-VLCFAs into LPA/PA, DAG, PC/LPC, and TAGs was severely reduced when G-3-P was omitted from the reaction mixtures and newly synthesized VLCFAs accumulated in the acyl-CoA and FFA pools (Fig.…”

Section: Radio-hplc Analysismentioning

confidence: 56%

“…The result is that, for the first time, all (13,14). (28) and zygotic embryos (7,9,20,28). Furthermore, the in vitro results confirm that the LPA acyltransferase (EC 2.3.1.5 1) in B. napus is incapable of inserting newly synthesized erucoyl moieties at the sn-2 position on the glycerol backbone (25,26 CONCLUSIONS The present data are the first evidence to support strongly the Kennedy pathway as the mechanism for incorporation of VLCFAs, and erucoyl moieties in particular, into both the sn-1 and sn-3 positions of TAGs in developing MD and zygotic embryos of B. napus.…”

Section: Stereospecific Analyses Of '4c-labeled Tagsmentioning

confidence: 96%

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Biosynthesis of Acyl Lipids Containing Very-Long Chain Fatty Acids in Microspore-Derived and Zygotic Embryos of Brassica napus L. cv Reston

Taylor

Barton²,

Rioux³

et al. 1992

Plant Physiol.

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Biosynthesis of very long chain (>C18) fatty acids (VLCFAs) and the pathway for their incorporation into acyl liipids was studied in microspore-derived (MD) inantly at the sn-3 position, but were also found at the sn-1 position.[14C120:1, but not [14C]22:1, was detected at the sn-2 position. Similar patterns of 14C-labeled VLCFA distribution were obtained in experiments conducted using a 15,000g pellet fraction from 18-day MD embryos. All trends observed in the formation of TAGs containing VLCFAs in the Reston MD embryo system were also confirmed in studies of zygotic embryos of the same cultivar. The data support the biosynthesis of 20:1 and then 22:1 via successive condensations of malonyl-coenzyme A with oleoyl-coenzyme A and, for the first time in B. napus, demonstrate the incorporation of newly synthesized VLCFAs into TAGs via the Kennedy pathway.

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Section: Radio-hplc Analysismentioning

confidence: 56%

Section: Stereospecific Analyses Of '4c-labeled Tagsmentioning

confidence: 96%

Biosynthesis of Acyl Lipids Containing Very-Long Chain Fatty Acids in Microspore-Derived and Zygotic Embryos of Brassica napus L. cv Reston

Taylor

Barton²,

Rioux³

et al. 1992

Plant Physiol.

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“…Expression of the transgene was therefore surprisingly successful in light of the comparatively weak activity reported for the CaMV 35S promoter in seeds (Eccleston and Ohlrogge, 1998). Positional analysis of TAG showed that VLCPUFAs were largely excluded from the sn-2 position in both wild-type and transgenic plants, similar to the absence of VLCFAs from the sn-2 position of TAG in rapeseed oil (Brassica napus; Mattson and Volpenhein, 1961;Norton and Harris, 1983). In vitro assays using microsomal membranes from developing rapeseed embryos also showed that lysophosphate acid acyltransferase did not utilize erucoyl-CoA (Sun et al, 1988;Bernerth and Frentzen, 1990;Cao et al, 1990).…”

Section: Discussionmentioning

confidence: 95%

Expression of the Isochrysis C18-Δ9 Polyunsaturated Fatty Acid Specific Elongase Component Alters Arabidopsis Glycerolipid Profiles

Fraser

Elhussein

et al. 2004

Plant Physiology

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A cDNA isolated from the prymnesiophyte micro-alga Isochrysis galbana, designated IgASE1, encodes a fatty acid elongating component that is specific for linoleic acid (C18:2n-6) and a-linolenic acid (C18:3n-3). Constitutive expression of IgASE1 in Arabidopsis resulted in the accumulation of eicosadienoic acid (EDA; C20:2n-6) and eicosatrienoic acid (ETrA; C20:3n-3) in all tissues examined, with no visible effects on plant morphology. Positional analysis of the various lipid classes indicated that these novel fatty acids were largely excluded from the sn-2 position of chloroplast galactolipids and seed triacylglycerol, whereas they were enriched in the same position in phosphatidylcholine. EDA and ETrA are precursors of arachidonic acid (C20:4n-6), eicosapentaenoic acid (C20:5n-3), and docosahexaenoic acid (C22:6n-3) synthesized via the so-called v6 D8 desaturase and v3 D8 desaturase biosynthetic pathways, respectively. The synthesis of significant quantities of EDA and ETrA in a higher plant is therefore a key step in the production of very long chain polyunsaturated fatty acid in oil-seed species. The results are further discussed in terms of prokaryotic and eukaryotic pathways of lipid synthesis in plants.The very long chain polyunsaturated fatty acids (VLCPUFAs), arachidonic acid (AA; C20:4n-6), docosahexaenoic acid (DHA; C22:6n-3), and eicosapentaenoic acid (EPA; C20:5n-3) are considered to have profound effects on cell function and development. The reduction in nonfatal and fatal cardiovascular events that is associated with the consumption of EPA and DHA may be due to the stabilization of atherosclerotic plaques (Thies et al., 2003). AA and DHA are considered to be important in pre-and postnatal development (Crawford, 2000; for review, see Lauritzen et al., 2001). Such VLCPUFAs are also precursors of the physiologically active prostaglandins, thromboxanes, and leukotrienes. No higher plants contain these fatty acids and hence it is considered desirable to genetically engineer the capacity to synthesize them in oilseed species and so provide an important source for the nutraceutical/pharmaceutical industries.Isochrysis galbana is a marine microalga that is rich in DHA and EPA (Lopez et al., 1994). Recently we isolated and characterized a cDNA from I. galbana, which encodes a novel fatty acid elongase component designated IgASE1 (Qi et al., 2002(Qi et al., , 2003. Transgenic yeastexpressing IgASE1 converted linoleic acid (LA; C18:2n-6) and a-linolenic acid (ALA; C18:3n-3) to eicosadienoic acid (EDA; C20:2n-6) and eicosatrienoic acid (ETrA; C20:3n-3), respectively (Qi et al., 2002). The substrate specificity of IgASE1 is consistent with it catalyzing the condensation reaction of fatty acid elongation (Qi et al., 2003). We have further suggested (Qi et al., 2002(Qi et al., , 2003 that the IgASE1 elongating activity is the first committed step in VLCPUFA synthesis and hence AA, EPA, and DHA formation via the so-called v3 D8 and v6 D8 pathways, respectively ( Fig. 1; Nichols and Appleby, 1969).Here we report the...

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“…Rapeseed amasses 22:l and 20:l to make up to 65% of its oil composition (Stefansson, 1983). VLCFAs are found in the sn-1 and sn-3 positions of the TAGs but are excluded from the sn-2 position (Mattson and Volpenhein, 1961;Norton and Harris, 1983). This sn-2 exclusion limits the 22:l content of rapeseed oil and prevents the synthesis of trierucin.…”

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confidence: 99%

Lysophosphatidic Acid Acyltransferase from Meadowfoam Mediates Insertion of Erucic Acid at the sn-2 Position of Triacylglycerol in Transgenic Rapeseed Oil

Lassner¹,

Levering²,

Davies³

et al. 1995

Plant Physiol.

142

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Lysophosphatidic acid acyltransferase acylates the sn-2 hydroxyl group of lysophosphatidic acid to form phosphatidic acid, a precursor to triacylglycerol. A cDNA encoding lysophosphatidic acid acyltransferase was isolated from developing seeds of meadowfoam (Limnanthes alba alba). The cDNA encodes a 281-amino acid protein with a molecular m a s of 32 kD. The cDNA was expressed in developing seeds of transgenic high-erucic-acid rapeseed (Brassica napus) using a napin expression cassette. Erucic acid was present at the sn-2 position of triacylglycerols from transgenic plants but was absent from that position of seed oil extracted from control plants. Trierucin was present in the transgenic oil. Alteration of the sn-2 erucic acid composition did not affect the total erucic acid content. These experiments demonstrate the feasibility of using acyltransferases to alter the stereochemical composition of transgenic seed oils and also representa necessary step toward increasing the erucic acid content of rapeseed oil.

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Triacylglycerols in oilseed rape during seed development

Cited by 42 publications

References 7 publications

Biosynthesis of Acyl Lipids Containing Very-Long Chain Fatty Acids in Microspore-Derived and Zygotic Embryos of Brassica napus L. cv Reston

Biosynthesis of Acyl Lipids Containing Very-Long Chain Fatty Acids in Microspore-Derived and Zygotic Embryos of Brassica napus L. cv Reston

Expression of the Isochrysis C18-Δ9 Polyunsaturated Fatty Acid Specific Elongase Component Alters Arabidopsis Glycerolipid Profiles

Lysophosphatidic Acid Acyltransferase from Meadowfoam Mediates Insertion of Erucic Acid at the sn-2 Position of Triacylglycerol in Transgenic Rapeseed Oil

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