Research Results
Metabolic engineering of seeds can achieve levels of omega-7 fatty acids comparable to the highest level PDF Print E-mail
Written by nguyen   
Tuesday, 19 October 2010 16:04

Published on Plant Physiology Journal, October 13, 2010

Authors: Huu Tam Nguyen, Girish Mishra, Edward Whittle, Scott A. Bevan, Ann Owens Merlo, Terence A. Walsh and John Shanklin

Financial Source: This work was supported by the Office of Basic Energy Sciences of the US Department of Energy, and The Dow Chemical Company and Dow AgroSciences.


Abstract :

Plant oils containing omega-7 fatty acids (FA) (palmitoleic 16:1 delta9 and cis-vaccenic 18:1delta11) have potential as sustainable feedstocks for producing industrially important octene via metathesis chemistry. Engineering plants to produce seeds that accumulate high levels of any unusual FA has been an elusive goal. We have achieved high levels of omega-7 FA accumulation by systematic metabolic engineering of Arabidopsis thaliana. A plastidial 16:0-ACP desaturase has been engineered to convert 16:0 to 16:1?9 with specificity >100-fold that that of naturally-occurring paralogs such as that from Doxantha unguis-cati L. Expressing this engineered enzyme (Com25) in seeds increased omega-7 FA accumulation from <2% to 14%. Reducing competition for 16:0-ACP by downregulating the KASII 16:0 elongase further increased accumulation of omega-7 FA to 56%. The level of 16:0 exiting the plastid without desaturation also increased to 21%. Coexpression of a pair of fungal 16:0 desaturases in the cytosol reduced the 16:0 level to 11% and increased omega-7 FA to as much as 71%, equivalent to levels found in Doxantha seeds.

 

Introduction

There is increasing interest in the use of plant oils as renewable sources of industrial chemical feedstocks (Dyer et al., 2008; Carlsson, 2009). Recent developments in olefin metathesis have demonstrated that long chain monoene FA from vegetable oils can be efficiently split into the corresponding short chain alpha olefin and ?-alkenoic acids (Rybak et al., 2008; Meier, 2009). Thus ethenolytic metathesis of ?-7 FA such as palmitoleic or cis-vaccenic acids yields 1-octene and 9-decenoate. 1-Octene is a high-demand feedstock with a global consumption of over half a million tonnes per year that is primarily used as a comonomer in the expanding production of linear low density polyethylene. It is mainly synthesized from petroleum-derived ethylene via oligomerization to yield a complex mixture of alpha olefins, or from coal-derived syngas (Systems, 2007).

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Last Updated on Thursday, 09 December 2010 17:38
 
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