Triacylglycerol synthesis and metabolism in germinating soybean cotyledons

Wilson, Richard F.; Kwanyuen, P.

doi:10.1016/0005-2760(86)90299-7

Cited by 23 publications

(20 citation statements)

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“…DGAT catalyzes the final step of the TAG biosynthesis pathway and presumably has the highest activity during seed development, although postembryonic activity of DGAT has been demonstrated or implicated by previous studies (Wilson and Kwanyuen, 1986;Hobbs et al, 1999;Zou et al, 1999). In an attempt to understand the effect of loss of DGAT1 activity on postembryonic development, we analyzed the previously isolated tag1 mutants in Arabidopsis (Katavic et al, 1995;Routaboul et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

“…However, several lines of evidence suggest that TAG synthesis and DGAT activity are not restricted to the embryo. Developing pollen grains accumulate a large amount of TAG (Piffanelli et al, 1997); DGAT activity was also found in germinating soybean (Glycine max) cotyledons (Wilson and Kwanyuen, 1986). TAG1 transcripts have been detected in many tissues in Arabidopsis, including developing siliques, flowers, germinating seeds, and young seedlings (Zou et al, 1999).…”

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confidence: 99%

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Arabidopsis Mutants Deficient in Diacylglycerol Acyltransferase Display Increased Sensitivity to Abscisic Acid, Sugars, and Osmotic Stress during Germination and Seedling Development

Hills

2002

Plant Physiology

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Arabidopsis seeds store triacylglycerol (TAG) as the major carbon reserve, which is used to support postgerminative seedling growth. Diacylglycerol acyltransferase (DGAT) catalyzes the final step in TAG synthesis, and two isoforms of DGAT have previously been identified in Arabidopsis. It has been shown that DGAT1 plays an important role in seed development because Arabidopsis with mutations at the TAG1 locus accumulate less seed oil. There is also evidence showing that DGAT1 is active after seed germination. The aim of this study is to investigate the effect of mutations of DGAT1 on postembryonic development in Arabidopsis. We carried out detailed analyses of two tag1 mutants in different ecotypic backgrounds of Arabidopsis. Results show that during germination and seedling growth, seed storage TAG degradation was not affected in the tag1 mutants. However, sugar content of the mutant seedlings is altered, and activities of the hexokinases are significantly increased in the tag1 mutant seedlings. The tag1 mutants are also more sensitive to abscisic acid, glucose, and osmotic strength of the medium in germination and seedling growth.Germination and seedling development are critical phases in the life cycle of seed plants, during which seedlings must adapt their developmental and metabolic programs to the prevailing environmental conditions (Holdsworth et al., 1999). Seed reserves serve as an initial carbon and energy source for seedling growth (Bradbeer, 1988). Many seeds store oil, in the form of triacylglycerol (TAG), as the major reserve (Bewley and Black, 1994). The biosynthesis of TAG has been proposed to take place in the endoplasmic reticulum by the action of the acyltransferases of the Kennedy pathway (Gurr, 1980;Ohlrogge and Browse, 1995). Diacylglycerol lies at the branch point between membrane phospholipid synthesis via sn-1,2-diacylglycerol (DAG):cholinephosphotransferase and storage TAG synthesis catalyzed by diacylglycerol acyltransferase (DGAT). DGAT catalyzes the acylation of position 3 of DAG, the final step of TAG synthesis (Ohlrogge and Browse, 1995). Two sequence-unrelated genes coding for DGAT have been cloned (Hobbs et al., 1999;Lardizabal et al., 2001). Arabidopsis mutants with mutations at the TAG1 locus encoding the DGAT1 enzyme can only accumulate about 55% to 75% (w/w) of seed triacylglycerols of the wild type (Katavic et al., 1995;Routaboul et al., 1999). Therefore, TAG1 plays an important role in TAG biosynthesis in developing seeds. The fact that the seeds can still synthesize more than one-half of their normal complement of TAG suggests that the DGAT2 gene or other mechanisms for TAG synthesis are also at work (Dahlqvist et al., 2000;Lardizabal et al., 2001).TAG synthesis mainly occurs during the seed maturation phase before the seed enters the period of desiccation (Mansfield and Briarty, 1991). However, several lines of evidence suggest that TAG synthesis and DGAT activity are not restricted to the embryo. Developing pollen grains accumulate a large amount of TAG (Piffanelli et a...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Arabidopsis Mutants Deficient in Diacylglycerol Acyltransferase Display Increased Sensitivity to Abscisic Acid, Sugars, and Osmotic Stress during Germination and Seedling Development

Hills

2002

Plant Physiology

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“…In each case the studies have utilized seeds harvested throughout a limited range of seed development (Ichihara andNoda, 1981b, 1982;Cao andHuang, 1986, 1987;Bemerth and Frentzen, 1990). Similar studies have also been conducted with germinating oilseeds (Kwanyuen and Wilson, 1986), which have been shown to synthesize TG (Ichihara and Noda, 1981a;Wilson and Kwanyuen, 1986).…”

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confidence: 83%

Developmental Profile of Diacylglycerol Acyltransferase in Maturing Seeds of Oilseed Rape and Safflower and Microspore-Derived Cultures of Oilseed Rape

et al. 1993

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Diacylglycerol acyltransferase (EC 2.3.1.20) activity was assayed during the maturation of seeds of oilseed rape (Brassica napus 1.) and safflower (Carthamus tinctorius 1.). Developmental studies were also conducted with microspore-derived embryos of oilseed rape (6. napus 1. cv Topas) and an embryogenic microsporederived cell-suspension culture of winter oilseed rape (B. napus 1.cv Jet Neuf), In the maturing seeds, diacylglycerol acyltransferase activity increased to a maximum during rapid accumulation of lipid and declined, thereafter, with seed maturity. In microspore-derived embryos of oilseed rape (cv Topas), high levels of diacylglycerol acyltransferase activity were found throughout the early torpedo to late cotyledonary developmental stages with maximum enzyme specific activity associated with the mid-cotyledonary developmental stage. The cell-suspension culture of winter oilseed rape (cv Jet Neuf) contained 3 to 4% triacylglycerol on a dry weight basis and represented about half of the total lipid. The fatty acid profile of total lipid and triacylglycerol in the cell-suspension culture was similar in samples taken during a 1-year period. The Jet Neuf culture contained diacylglycerol acyltransferase with specific activity similar to that of Topas microspore-derived embryos. Jet Neuf diacylglycerol acyltransferase also displayed an enhanced specificity for erucoyl-COA over oleoyl-COA when assayed with 14 p~ acyl-coenzyme A in the readion mixture. The specific activity of diacylglycerol acyltransferase in homogenates prepared from the Jet Neuf culture ranged from 5 to 15 pmol of triacylglycerol min-' mg-' of protein when assayed at intervals during a period of 1 year. Thus, the cell-suspension culture may represent an attractive tissue source for purification and characterization of triacylglycerol biosynthetic enzymes.The determination of the quantity and composition of storage lipid during seed maturation in various oilseed crops has been reported in numerous studies such as those of Sims ' Supported by the following grants to R

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“…Incorporation of [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]Acetate into TAG-E. coli cells (A 600 ϭ 0.6) were induced with isopropyl ␤-D-thiogalactopyranoside, incubated with […”

Section: Methodsmentioning

confidence: 99%

“…Several lines of evidence suggest that the TAG biosynthesis and DGAT activity are not restricted to the embryo and anthers. There are reports of having DGAT activity in leaves (8) and cotyledons of the germinating seeds (9). TAG is also formed in the plants via two different acyl-CoA-independent pathways, catalyzed by phospholipid: DAG acyltransferase (10) and DAG transacylase (11).…”

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confidence: 99%

Defective in Cuticular Ridges (DCR) of Arabidopsis thaliana, a Gene Associated with Surface Cutin Formation, Encodes a Soluble Diacylglycerol Acyltransferase

Sapa

Krishna

Saha

et al. 2010

Journal of Biological Chemistry

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A key step in the triacylglycerol (TAG) biosynthetic pathway is the final acylation of diacylglycerol (DAG) by DAG acyltransferase. In silico analysis has revealed that the DCR (defective in cuticular ridges) (At5g23940) gene has a typical HX 4 D acyltransferase motif at the N-terminal end and a lipid binding motif VX 2 GF at the middle of the sequence. To understand the biochemical function, the gene was overexpressed in Escherichia coli, and the purified recombinant protein was found to acylate DAG specifically in an acyl-CoA-dependent manner. Overexpression of At5g23940 in a Saccharomyces cerevisiae quadruple mutant deficient in DAG acyltransferases resulted in TAG accumulation. At5g23940 rescued the growth of this quadruple mutant in the oleate-containing medium, whereas empty vector control did not. Lipid particles were localized in the cytosol of At5g23940-transformed quadruple mutant cells, as observed by oil red O staining. There was an incorporation of 16-hydroxyhexadecanoic acid into TAG in At5g23940-transformed cells of quadruple mutant. Here we report a soluble acyl-CoA-dependent DAG acyltransferase from Arabidopsis thaliana. Taken together, these data suggest that a broad specific DAG acyltransferase may be involved in the cutin as well as in the TAG biosynthesis by supplying hydroxy fatty acid. Triacylglycerol (TAG),3 an acyl ester glycerol, is the most efficient storage form of energy in eukaryotic cells (1, 2). In plants, TAG is the major component of the seed oils and is mainly deposited during seed and fruit development. Plant oils have a tremendous socioeconomic value in the food industry as well as in the production of lubricants and biofuels. They are also becoming increasingly important raw materials in the petrochemical industry as a substitute for non-renewable crude oil reserves (3). Thus, numerous conventional and molecular genetic strategies have been explored in attempts to increase the TAG content and modify the fatty acid composition of the plant seed oils. Isolation of the genes involved in oil biosynthesis offer exciting opportunities for overexpressing the desired gene of interest so as to redesign the plant oil metabolism for greater yields (3).TAG is usually synthesized by the sequential incorporation of acyl groups to glycerol 3-phosphate by substrate-specific acyltransferases to give lysophosphatidic acid and phosphatidic acid, respectively (4, 5). The synthesized phosphatidic acid is dephosphorylated to diacylglycerol (DAG). The last step in this pathway is catalyzed by acyl-CoA:DAG acyltransferase (DGAT; EC 2.3.1.20) that transfers an acyl group to DAG to form the TAG. DAG lies at the branch point between phospholipid and storage lipid biosynthesis. Therefore, much research has been focused on the acyl-CoA-dependent reaction catalyzed by the DAG acyltransferase, which is an integral endoplasmic reticulum protein (6) and has also been shown to be present in the oil bodies (7) and plastids (8). Several lines of evidence suggest that the TAG biosynthesis and DGAT activity are ...

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Triacylglycerol synthesis and metabolism in germinating soybean cotyledons

Cited by 23 publications

References 24 publications

Arabidopsis Mutants Deficient in Diacylglycerol Acyltransferase Display Increased Sensitivity to Abscisic Acid, Sugars, and Osmotic Stress during Germination and Seedling Development

Arabidopsis Mutants Deficient in Diacylglycerol Acyltransferase Display Increased Sensitivity to Abscisic Acid, Sugars, and Osmotic Stress during Germination and Seedling Development

Developmental Profile of Diacylglycerol Acyltransferase in Maturing Seeds of Oilseed Rape and Safflower and Microspore-Derived Cultures of Oilseed Rape

Defective in Cuticular Ridges (DCR) of Arabidopsis thaliana, a Gene Associated with Surface Cutin Formation, Encodes a Soluble Diacylglycerol Acyltransferase

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