Tung Tree DGAT1 and DGAT2 Have Nonredundant Functions in Triacylglycerol Biosynthesis and Are Localized to Different Subdomains of the Endoplasmic Reticulum

Shockey, Jay; Gidda, Satinder K.; Chapital, Dorselyn C.; Kuan, Jui-Chang W.; Dhanoa, Preetinder K.; Bland, John M.; Rothstein, Steven J.; Mullen, Robert T.; Dyer, John M.

doi:10.1105/tpc.106.043695

Cited by 493 publications

(629 citation statements)

References 80 publications

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“…Many studies have shown that Arabidopsis DGAT1 is important for TAG biosynthesis, whereas DGAT2 is not a major determining factor (Shockey et al, 2006). In addition, although PDAT1 and DGAT1 have overlapping functions for TAG synthesis in Arabidopsis , the transcription profile of PDAT1 changed less than that of DGAT1 when N concentration was reduced.…”

Section: Abi4 Is Essential For the Activation Of Dgat1 Expression Inmentioning

confidence: 99%

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

et al. 2011

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Triacylglycerol (TAG) is the major seed storage lipid and is important for biofuel and other renewable chemical uses. Acylcoenzyme A:diacylglycerol acyltransferase1 (DGAT1) is the rate-limiting enzyme in the TAG biosynthesis pathway, but the mechanism of its regulation is unknown. Here, we show that TAG accumulation in Arabidopsis (Arabidopsis thaliana) seedlings increased significantly during nitrogen deprivation (0.1 mM nitrogen) with concomitant induction of genes involved in TAG biosynthesis and accumulation, such as DGAT1 and OLEOSIN1. Nitrogen-deficient seedlings were used to determine the key factors contributing to ectopic TAG accumulation in vegetative tissues. Under low-nitrogen conditions, the phytohormone abscisic acid plays a crucial role in promoting TAG accumulation in Arabidopsis seedlings. Yeast one-hybrid and electrophoretic mobility shift assays demonstrated that ABSCISIC ACID INSENSITIVE4 (ABI4), an important transcriptional factor in the abscisic acid signaling pathway, bound directly to the CE1-like elements (CACCG) present in DGAT1 promoters. Genetic studies also revealed that TAG accumulation and DGAT1 expression were reduced in the abi4 mutant. Taken together, our results indicate that abscisic acid signaling is part of the regulatory machinery governing TAG ectopic accumulation and that ABI4 is essential for the activation of DGAT1 in Arabidopsis seedlings during nitrogen deficiency.

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Section: Abi4 Is Essential For the Activation Of Dgat1 Expression Inmentioning

confidence: 99%

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

et al. 2011

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“…This greater desaturation occurring on PC is likely an important reason for the increased 18:3n-3 content, suggesting that the enzymes taking over the TAG production from DGAT1 are allowed to access acyl groups at a later stage of desaturation, due to a relatively higher activity of FAD2/FAD3 or localization to different subdomains within the ER. A previous study has shown that DGAT1 and DGAT2 of tung tree localizes to different subdomains of the ER (Shockey et al, 2006), whereas it is currently not known if this is true also for PDAT. Our microsomal data, however, suggest that there is more to it than increased desaturation in the DGAT1-silencing lines.…”

Section: Dgat1 Down-regulationmentioning

confidence: 99%

“…DGAT1 is localized in the endoplasmic reticulum (ER), and the enzyme contributes significantly to oil accumulation in Arabidopsis seeds (Zhang et al, 2009). DGAT2 has been shown to be important in plants accumulating unusual fatty acids in their seeds, such as castor bean (Ricinus communis; Kroon et al, 2006) and tung tree (Vernicia fordii; Shockey et al, 2006). However, when DGAT2 is knocked out in Arabidopsis, neither the oil content nor the fatty acid profile is affected, and they show no difference compared with the mutant of DGAT1 when both genes are knocked out (Zhang et al, 2009).…”

Section: Dgat1 Down-regulationmentioning

confidence: 99%

Two Acyltransferases Contribute Differently to Linolenic Acid Levels in Seed Oil

et al. 2017

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ORCID IDs: 0000-0001-6929-7859 (S.M.); 0000-0003-3152-0394 (D.S.); 0000-0001-8255-3255 (C.H.); 0000-0003-0489-3072 (K.C.); 0000-0002-9888-7003 (I.F.).Acyltransferases are key contributors to triacylglycerol (TAG) synthesis and, thus, are of great importance for seed oil quality. The effects of increased or decreased expression of ACYL-COENZYME A:DIACYLGLYCEROL ACYLTRANSFERASE1 (DGAT1) or PHOSPHOLIPID:DIACYLGLYCEROL ACYLTRANSFERASE (PDAT) on seed lipid composition were assessed in several Camelina sativa lines. Furthermore, in vitro assays of acyltransferases in microsomal fractions prepared from developing seeds of some of these lines were performed. Decreased expression of DGAT1 led to an increased percentage of 18:3n-3 without any change in total lipid content of the seed. The tri-18:3 TAG increase occurred predominantly in the cotyledon, as determined with matrix-assisted laser desorption/ionization-mass spectrometry, whereas species with two 18:3n-3 acyl groups were elevated in both cotyledon and embryonal axis. PDAT overexpression led to a relative increase of 18:2n-6 at the expense of 18:3n-3, also without affecting the total lipid content. Differential distributions of TAG species also were observed in different parts of the seed. The microsomal assays revealed that C. sativa seeds have very high activity of diacylglycerol-phosphatidylcholine interconversion. The combination of analytical and biochemical data suggests that the higher 18:2n-6 content in the seed oil of the PDAT overexpressors is due to the channeling of fatty acids from phosphatidylcholine into TAG before being desaturated to 18:3n-3, caused by the high activity of PDAT in general and by PDAT specificity for 18:2n-6. The higher levels of 18:3n-3 in DGAT1-silencing lines are likely due to the compensatory activity of a TAG-synthesizing enzyme with specificity for this acyl group and more desaturation of acyl groups occurring on phosphatidylcholine.

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“…Castor bean DGAT2 prefers ricinoleoyl-DAG acceptors (46), and its coexpression with the castor bean hydroxylase increases ricinoleic accumulation in Arabidopsis seeds (47). DGAT2 also has been studied in the Tung tree (which accumulates conjugated FAs in TAG), and it is localized to a subdomain of the ER that is different from that of DGAT1, suggesting that these two proteins may cooperate to synthesize TAG in Tung seeds but in spatially distinct subcellular locations (48). Although DGAT2 has been examined mostly in plant species with unusual FAs (47-50), it likely contributes to TAG accumulation in plants that do not accumulate unusual FAs based on expression levels in palm, olive, and other plants, even though its relative contribution may vary between species.…”

Section: Conventional Kennedy Pathwaymentioning

confidence: 99%

Compartmentation of Triacylglycerol Accumulation in Plants

Chapman

Ohlrogge

2012

Journal of Biological Chemistry

393

352

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Triacylglycerols from plants, familiar to most people as vegetable oils, supply 25% of dietary calories to the developed world and are increasingly a source for renewable biomaterials and fuels. Demand for vegetable oils will double by 2030, which can be met only by increased oil production. Triacylglycerol synthesis is accomplished through the coordinate action of multiple pathways in multiple subcellular compartments. Recent information has revealed an underappreciated complexity in pathways for synthesis and accumulation of this important energyrich class of molecules. Regulation of Fatty Acid Supply by PlastidsPlant fatty acid (FA) 2 synthesis differs from almost all other eukaryotes in two fundamental features. First, unlike the cytosolic location in other kingdoms, FAs for triacylglycerol (TAG) and membrane synthesis are produced in the plastid compartment of plant cells: chloroplasts in green tissues and proplastids (or leucoplasts) in non-green tissues. Second, the plant FA synthase (FAS) is a dissociable complex with separate proteins for the acyl carrier protein (ACP) and each enzyme (1). After assembly of C 16 and C 18 acyl chains by FAS and desaturation of C 18:0 to C 18:1 , FAs destined for TAG assembly are released from ACP in the plastid stroma by chain-terminating acyl-ACP thioesterases. Two classes of thioesterases designated FATA and FATB are responsible for hydrolysis of unsaturated and saturated acyl-ACPs, respectively, and thus determine in large part the chain length and saturated FA content of plant oils (2). The FA products of FATA and FATB are activated to CoA before export to the endoplasmic reticulum (ER). The subsequent reactions of TAG synthesis belong to the so-called "eukaryotic" pathway of glycerolipid synthesis, which occurs outside the plastid (3, 4). An overview of the compartmentalization of FA supply for TAG is shown in Fig. 1. FA production by plastids can limit TAG accumulation in seeds (5, 6), so increasing flux through FA biosynthesis may perhaps have the single greatest influence on the amount of TAG produced in plant tissues. As in bacteria, fungi, and animals, both in vitro and in vivo evidence indicates that acetylCoA carboxylase (ACCase) is a key rate-determining step that controls FA biosynthesis. ACCase activity is under complex regulation by light, phosphorylation, thioredoxin, PII protein, and product feedback control (7,8). Of course, the flux of carbon to FA synthesis can have multiple regulatory steps, which may explain why efforts to increase seed oil by up-regulating ACCase were only modestly successful (9).Transcriptional regulation of the production of FA for TAG biosynthesis is most directly controlled by the WRINKLED1 transcription factor (7, 10, 11). Arabidopsis wri1 mutants are reduced by 80% in seed oil, and overexpression of WRI1 can increase oil content in seeds of several plants. Targets of WRI1 include ACCase, many enzymes of FAS, and key enzymes and transporters that provide pyruvate and acetyl-CoA in the plastid. Thus, WRI1 can be considered as ...

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Tung Tree DGAT1 and DGAT2 Have Nonredundant Functions in Triacylglycerol Biosynthesis and Are Localized to Different Subdomains of the Endoplasmic Reticulum

Cited by 493 publications

References 80 publications

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

Two Acyltransferases Contribute Differently to Linolenic Acid Levels in Seed Oil

Compartmentation of Triacylglycerol Accumulation in Plants

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