Triacylglycerol biosynthesis (WP627)

Arabidopsis thaliana

Triacylglycerol (TAG) is the major lipid reserve in plants and animals. The assembly of TAG occurs in the endoplasmic reticulum (ER). Four consecutive reactions are catalyzed by ER membrane bound enzymes. The two intermediates, phosphatidate and 1,2-diacylglycerol, are also substrates for the synthesis of membrane lipids glycosylglycerides and phosphoglycerides. Thus, the last step in the pathway, catalyzed by diacylglycerol acyltransferase, is the only dedicated step in triacylglycerol synthesis. The traditional Kennedy pathway does not include the reaction (EC, phospholipid:diacylglycerol acyltransferase, PDAT) where phospholipid is utilized as the acyl donor in TAG formation. The role of the PDAT route in TAG biosynthesis was clearly shown in yeast[ Dahlqvist00 ]. PDAT activity in plants was demonstrated in a few oil seed plants including caster bean[ Dahlqvist00 ]. The caster bean seeds have a high content of ricinoleat in the seed oil. Ricinoleat and other unusual fatty acids are modified from acyl groups linked to phospholipids, and transferred to TAG afterwards. PDAT was proposed playing an important role in the last step. However, the contribution of PDAT to TAG biosynthesis in other plants is not clear. Overexpressing or knockout of the Arabidopsis PDAT had no effect on TAG biosynthesis[ Stahl04 , Mhaske05 ]. The constitution of different species of saturated and unsaturated fatty acids at the sn-1, sn-2, and sn-3 positions of the glycerol backbone varies among different plants, and is determined by substrate specificities of the three acyltransferases involved in this pathway. The composition of distinct fatty acids in TAG determines the quality and property of lipids of different plants, and also contributes to cold temperature sensitivity of different plants. The pathway and description were copied from Gramene and AraCyc:


Thomas Kelder , Pankaj Jaiswal , Daniela Digles , Egon Willighagen , Alex Pico , and Eric Weitz


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Arabidopsis thaliana



Pathway Ontology

triacylglycerol biosynthetic pathway


Label Type Compact URI Comment
sn-glyceryl-3-phosphate Metabolite kegg.compound:C00093
a fatty acyl CoA Metabolite chebi:37554
Coenzyme A Metabolite cas:85-61-0
L-Phosphatidic acid Metabolite kegg.compound:C00416
Coenzyme A Metabolite cas:85-61-0
a fatty acyl CoA Metabolite chebi:37554
Water Metabolite kegg.compound:C00001
Phosphate Metabolite cas:14265-44-2
a triacylglycerol Metabolite chebi:17855
a phosphatidylcholine Metabolite kegg.compound:C00157
a fatty acyl CoA Metabolite chebi:37554
Coenzyme A Metabolite cas:85-61-0
acyltransferase GeneProduct
glycerol-3-phosphate acyltransferase GeneProduct
1-acylglycerol-3-phosphate O-acyltransferase GeneProduct
LPP1 GeneProduct
LPP2 GeneProduct
PAP2 GeneProduct
LPP3 GeneProduct
PDAT GeneProduct
diacylglycerol acyltransferase GeneProduct
TAG1 GeneProduct


  1. The Arabidopsis thaliana TAG1 mutant has a mutation in a diacylglycerol acyltransferase gene. Zou J, Wei Y, Jako C, Kumar A, Selvaraj G, Taylor DC. Plant J. 1999 Sep;19(6):645–53. PubMed Europe PMC Scholia
  2. Phospholipid:diacylglycerol acyltransferase: an enzyme that catalyzes the acyl-CoA-independent formation of triacylglycerol in yeast and plants. Dahlqvist A, Stahl U, Lenman M, Banas A, Lee M, Sandager L, et al. Proc Natl Acad Sci U S A. 2000 Jun 6;97(12):6487–92. PubMed Europe PMC Scholia
  3. Cloning and functional characterization of a phospholipid:diacylglycerol acyltransferase from Arabidopsis. Ståhl U, Carlsson AS, Lenman M, Dahlqvist A, Huang B, Banas W, et al. Plant Physiol. 2004 Jul;135(3):1324–35. PubMed Europe PMC Scholia
  4. Isolation and characterization of an Arabidopsis thaliana knockout line for phospholipid: diacylglycerol transacylase gene (At5g13640). Mhaske V, Beldjilali K, Ohlrogge J, Pollard M. Plant Physiol Biochem. 2005 Apr;43(4):413–7. PubMed Europe PMC Scholia