The role of phosphatidylcholine in fatty acid exchange and desaturation in Brassica napus L. leaves

Williams, John P.; Imperial, Valerie; Khan, Mobashsher U.; Hodson, Joanna N.

doi:10.1042/bj3490127

Cited by 44 publications

(40 citation statements)

References 19 publications

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“…In light of the rather subtle alterations of FA composition in the lpcat1 lpcat2-2 mutant, the view of the Lands cycle as a major factor in modulating FA composition in PC needs to be revised. The significant alterations in the acyl-CoA pool in the mutant appear to suggest that LPCATs are a component of the Lands cycle that shield fluctuations of the acyl-CoA pool from imminently affecting de novo DAG synthesis via the Kennedy pathway (Williams et al, 2000). This is of great significance because cellular membranes as well as signaling molecules of glycerolipid origin, most of which use DAG as substrate, will not suffer from any sudden changes in the acyl-CoA pool and certain developmental stages or environmental conditions will inevitably instigate fluctuations in the FA composition of the acyl-CoA pool.…”

Section: Discussionmentioning

confidence: 99%

Metabolic Interactions between the Lands Cycle and the Kennedy Pathway of Glycerolipid Synthesis in Arabidopsis Developing Seeds

et al. 2012

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It has been widely accepted that the primary function of the Lands cycle is to provide a route for acyl remodeling to modify fatty acid (FA) composition of phospholipids derived from the Kennedy pathway. Lysophosphatidylcholine acyltransferase (LPCAT) is an evolutionarily conserved key enzyme in the Lands cycle. In this study, we provide direct evidence that the Arabidopsis thaliana LPCATs, LPCAT1 and LPCAT2, participate in the Lands cycle in developing seeds. In spite of a substantially reduced initial rate of nascent FA incorporation into phosphatidylcholine (PC), the PC level in the double mutant lpcat1 lpcat2-2 remained unchanged. LPCAT deficiency triggered a compensatory response of de novo PC synthesis and a concomitant acceleration of PC turnover that were attributable at least in part to PC deacylation. Acyl-CoA profile analysis revealed complicated metabolic alterations rather than merely reduced acyl group shuffling from PC in the mutant. Shifts in FA stereospecific distribution in triacylglycerol of the mutant seed suggested a preferential retention of saturated acyl chains at the stereospecific numbering (sn)-1 position from PC and likely a channeling of lysophosphatidic acid, derived from PC, into the Kennedy pathway. Our study thus illustrates an intricate relationship between the Lands cycle and the Kennedy pathway.

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Section: Discussionmentioning

confidence: 99%

Metabolic Interactions between the Lands Cycle and the Kennedy Pathway of Glycerolipid Synthesis in Arabidopsis Developing Seeds

et al. 2012

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“…The proposed candidates include PC (Tanaka et al, 1980), lysophosphatidylcholine (Mongrand et al, 2000;Jessen et al, 2015), or DAG (Williams et al, 2000). In addition, detailed characterization of the Arabidopsis trigalactosyldiacylglycerol (tgd) mutants and functional analyses of the respective TGD proteins implicate PA as the lipid transferred from the ER to chloroplasts for the synthesis of thylakoid glycolipids (Xu et al, 2005;Awai et al, 2006;Wang et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Arabidopsis TRIGALACTOSYLDIACYLGLYCEROL5 Interacts with TGD1, TGD2, and TGD4 to Facilitate Lipid Transfer from the Endoplasmic Reticulum to Plastids

et al. 2015

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The biogenesis of photosynthetic membranes in the plastids of higher plants requires an extensive supply of lipid precursors from the endoplasmic reticulum (ER). Four TRIGALACTOSYLDIACYLGLYCEROL (TGD) proteins (TGD1,2,3,4) have thus far been implicated in this lipid transfer process. While TGD1, TGD2, and TGD3 constitute an ATP binding cassette transporter complex residing in the plastid inner envelope, TGD4 is a transmembrane lipid transfer protein present in the outer envelope. These observations raise questions regarding how lipids transit across the aqueous intermembrane space. Here, we describe the isolation and characterization of a novel Arabidopsis thaliana gene, TGD5. Disruption of TGD5 results in similar phenotypic effects as previously described in tgd1,2,3,4 mutants, including deficiency of ER-derived thylakoid lipids, accumulation of oligogalactolipids, and triacylglycerol. Genetic analysis indicates that TGD4 is epistatic to TGD5 in ER-to-plastid lipid trafficking, whereas double mutants of a null tgd5 allele with tgd1-1 or tgd2-1 show a synergistic embryo-lethal phenotype. TGD5 encodes a small glycine-rich protein that is localized in the envelope membranes of chloroplasts. Coimmunoprecipitation assays show that TGD5 physically interacts with TGD1, TGD2, TGD3, and TGD4. Collectively, these results suggest that TGD5 facilitates lipid transfer from the outer to the inner plastid envelope by bridging TGD4 with the TGD1,2,3 transporter complex.

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“…Two distinct pathways lead to the prokaryotic and to the eukaryotic basic structures of 1,2-sn-diacylglycerol (DAG), and as a consequence, to the galactolipids directly produced from DAG owing to the MGDG synthase and DGDG synthase activities. The envelope membranes which surround plastids contain all the enzymatic activities responsible for the biosynthesis of prokaryotic DAG, whereas it is commonly assumed that the eukaryotic DAG available for plastid galactolipid biosynthesis originates from an extraplastidic pool, generated from phosphatidylcholine (PC) [8,9]. In this respect, the FA composition of DGDG produced after Pi deprivation was shown to be enriched in C 18 at the sn-2 position and C 16 at the sn-1 position of the glycerol backbone [10,11], a signature that suggests a synthesis from a DAG hypothetically originated from nonplastidial PC.…”

Section: Introductionmentioning

confidence: 99%

Transient increase of phosphatidylcholine in plant cells in response to phosphate deprivation

et al. 2003

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In plants, phosphate deprivation is normally known to decrease the phospholipid content consistent with a mobilization of the phosphate reserve, and conversely to increase nonphosphorous membrane lipids such as digalactosyldiacylglycerol. We report here that unexpectedly, at an early stage of phosphate starvation, phosphatidylcholine (PC) increases transiently. We also show that a signi¢cant pool of diacylglycerol (DAG) with the same fatty acid composition as that of PC is present and moreover increases in response to phosphate deprivation. The evolution of the molecular pro¢le of the newly synthesized galactolipids is compatible with a utilization of DAG accumulating from PC hydrolysis, achieved after selection of their acyl molecular species by the galactolipid synthesizing enzymes. ß

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The role of phosphatidylcholine in fatty acid exchange and desaturation in Brassica napus L. leaves

Cited by 44 publications

References 19 publications

Metabolic Interactions between the Lands Cycle and the Kennedy Pathway of Glycerolipid Synthesis in Arabidopsis Developing Seeds

Metabolic Interactions between the Lands Cycle and the Kennedy Pathway of Glycerolipid Synthesis in Arabidopsis Developing Seeds

Arabidopsis TRIGALACTOSYLDIACYLGLYCEROL5 Interacts with TGD1, TGD2, and TGD4 to Facilitate Lipid Transfer from the Endoplasmic Reticulum to Plastids

Transient increase of phosphatidylcholine in plant cells in response to phosphate deprivation

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