The pathway of triacylglycerol synthesis through phosphatidylcholine in Arabidopsis produces a bottleneck for the accumulation of unusual fatty acids in transgenic seeds
Article first published online: 4 AUG 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 68, Issue 3, pages 387–399, November 2011
How to Cite
Bates, P. D. and Browse, J. (2011), The pathway of triacylglycerol synthesis through phosphatidylcholine in Arabidopsis produces a bottleneck for the accumulation of unusual fatty acids in transgenic seeds. The Plant Journal, 68: 387–399. doi: 10.1111/j.1365-313X.2011.04693.x
- Issue published online: 25 OCT 2011
- Article first published online: 4 AUG 2011
- Accepted manuscript online: 28 JUN 2011 11:45AM EST
- Received 19 May 2011; revised 23 June 2011; accepted 24 June 2011.
- ricinoleic acid;
- metabolic engineering
Engineering of oilseed plants to accumulate unusual fatty acids (FAs) in seed triacylglycerol (TAG) requires not only the biosynthetic enzymes for unusual FAs but also efficient utilization of the unusual FAs by the host-plant TAG biosynthetic pathways. Competing pathways of diacylglycerol (DAG) and subsequent TAG synthesis ultimately affect TAG FA composition. The membrane lipid phosphatidylcholine (PC) is the substrate for many FA-modifying enzymes (desaturases, hydroxylases, etc.) and DAG can be derived from PC for TAG synthesis. The relative proportion of PC-derived DAG versus de novo synthesized DAG utilized for TAG synthesis, and the ability of each pathway to utilize unusual FA substrates, are unknown for most oilseed plants, including Arabidopsis thaliana. Through metabolic labeling experiments we demonstrate that the relative flux of de novo DAG into the PC-derived DAG pathway versus direct conversion to TAG is ∼14/1 in wild-type Arabidopsis. Expression of the Ricinus communis FA hydroxylase reduced the flux of de novo DAG into PC by ∼70%. Synthesis of TAG directly from de novo DAG did not increase, resulting in lower total synthesis of labeled lipids. Hydroxy-FA containing de novo DAG was rapidly synthesized, but it was not efficiently accumulated or converted to PC and TAG, and appeared to be in a futile cycle of synthesis and degradation. However, FA hydroxylation on PC and conversion to DAG allowed some hydroxy-FA to accumulate in sn-2 TAG. Therefore, the flux of DAG through PC represents a major bottleneck for the accumulation of unusual FAs in TAG of transgenic Arabidopsis seeds.