Journal article
Fatty acid synthesis is inhibited by inefficient utilization of unusual fatty acids for glycerolipid assembly
Proceedings of the National Academy of Sciences - PNAS, Vol.111(3), pp.1204-1209
01/21/2014
Handle:
https://hdl.handle.net/2376/105832
PMCID: PMC3903203
PMID: 24398521
Abstract
Many plants produce valuable fatty acids in seed oils that provide renewable alternatives to petrochemicals for production of lubricants, coatings, or polymers. However, most plants producing these unusual fatty acids are unsuitable as crops. Metabolic engineering of oilseed crops, or model species, to produce the high-value unusual fatty acids has produced only low yields of the desired products, and previous research has indicated fatty acid degradation as a potential major factor hindering oilseed engineering. By contrast, we here present evidence that inefficient utilization of unusual fatty acids within the endoplasmic reticulum can induce posttranslational inhibition of acetyl–CoA carboxylase activity in the plastid, thus inhibiting fatty acid synthesis and total oil accumulation.
Degradation of unusual fatty acids through β-oxidation within transgenic plants has long been hypothesized as a major factor limiting the production of industrially useful unusual fatty acids in seed oils.
Arabidopsis
seeds expressing the castor fatty acid hydroxylase accumulate hydroxylated fatty acids up to 17% of total fatty acids in seed triacylglycerols; however, total seed oil is also reduced up to 50%. Investigations into the cause of the reduced oil phenotype through in vivo [
14
C]acetate and [
3
H]
2
O metabolic labeling of developing seeds surprisingly revealed that the rate of de novo fatty acid synthesis within the transgenic seeds was approximately half that of control seeds. RNAseq analysis indicated no changes in expression of fatty acid synthesis genes in hydroxylase-expressing plants. However, differential [
14
C]acetate and [
14
C]malonate metabolic labeling of hydroxylase-expressing seeds indicated the in vivo acetyl–CoA carboxylase activity was reduced to approximately half that of control seeds. Therefore, the reduction of oil content in the transgenic seeds is consistent with reduced de novo fatty acid synthesis in the plastid rather than fatty acid degradation. Intriguingly, the coexpression of triacylglycerol synthesis isozymes from castor along with the fatty acid hydroxylase alleviated the reduced acetyl–CoA carboxylase activity, restored the rate of fatty acid synthesis, and the accumulation of seed oil was substantially recovered. Together these results suggest a previously unidentified mechanism that detects inefficient utilization of unusual fatty acids within the endoplasmic reticulum and activates an endogenous pathway for posttranslational reduction of fatty acid synthesis within the plastid.
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Details
- Title
- Fatty acid synthesis is inhibited by inefficient utilization of unusual fatty acids for glycerolipid assembly
- Creators
- Philip D Bates - Department of Chemistry and BiochemistrySean R Johnson - Institute of Biological ChemistryXia Cao - Department of Plant BiologyJia Li - , St. LouisJeong-Won Nam - , St. LouisJan G Jaworski - , St. LouisJohn B Ohlrogge - Department of Plant BiologyJohn Browse - Institute of Biological Chemistry
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.111(3), pp.1204-1209
- Academic Unit
- Biological Chemistry, Institute of
- Publisher
- National Academy of Sciences
- Identifiers
- 99900546876401842
- Language
- English
- Resource Type
- Journal article