Metabolic engineering of medium-chain fatty acid biosynthesis in Nicotiana benthamiana plant leaf lipids.

Kyle B Reynolds,Craig C Wood,Thomas Vanhercke,Christopher L Blanchard,James R Petrie,Surinder P Singh,Xue-Rong Zhou,Matthew C Taylor

doi:10.3389/fpls.2015.00164

Kyle B Reynolds, Craig C Wood + Show 6 more

Open Access

https://doi.org/10.3389/fpls.2015.00164

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Abstract

Various research groups are investigating the production of oil in non-seed biomass such as leaves. Recently, high levels of oil accumulation have been achieved in plant biomass using a combination of biotechnological approaches which also resulted in significant changes to the fatty acid composition of the leaf oil. In this study, we were interested to determine whether medium-chain fatty acids (MCFA) could be accumulated in leaf oil. MCFA are an ideal feedstock for biodiesel and a range of oleochemical products including lubricants, coatings, and detergents. In this study, we explore the synthesis, accumulation, and glycerolipid head-group distribution of MCFA in leaves of Nicotiana benthamiana after transient transgenic expression of C12:0-, C14:0-, and C16:0-ACP thioesterase genes. We demonstrate that the production of these MCFA in leaf is increased by the co-expression of the WRINKLED1 (WRI1) transcription factor, with the lysophosphatidic acid acyltransferase (LPAAT) from Cocos nucifera being required for the assembly of tri-MCFA TAG species. We also demonstrate that the newly-produced MCFA are incorporated into the triacylglycerol of leaves in which WRI1 + diacylglycerol acyltransferase1 (DGAT1) genes are co-expressed for increased oil accumulation.

Highlights

Vegetable oils, in the form of triacylglycerol (TAG), are an important global commodity with over 150 million tonnes being produced every year (FAO, 2003), which has remained relatively constant over recent years
A variety of metabolic engineering approaches have resulted in increased biomass oil (Vanhercke et al, 2014b; Wood, 2014) including reducing TAG and fatty acid turnover (Slocombe et al, 2009), ectopic expression of transcription factors that regulate processes of seed development and maturation (Santos Mendoza et al, 2005), down-regulation of metabolic pathways that compete for available carbon (Sanjaya et al, 2011), and the over-expression of acetyl-CoA carboxyalse (ACCase) (Klaus et al, 2004)
This accumulation to 15% TAG in Nicotiana tabacum leaves was achieved by the coordinated transgenic expression of the WRINKLED1 transcription factor (WRI1), diacylglycerol acyltransferase (DGAT1) and oleosin genes

Summary

Introduction

In the form of triacylglycerol (TAG), are an important global commodity with over 150 million tonnes being produced every year (FAO, 2003), which has remained relatively constant over recent years. Much higher levels of oil accumulation in plant biomass was achieved using a combination of biotechnological approaches (Vanhercke et al, 2014a) This accumulation to 15% TAG in Nicotiana tabacum leaves was achieved by the coordinated transgenic expression of the WRINKLED1 transcription factor (WRI1), diacylglycerol acyltransferase (DGAT1) and oleosin genes. This breakthrough in leaf oil accumulation was ascribed to the synergistic increase in both fatty acid synthesis and oil synthesis (via WRI1 and DGAT1, respectively) (Vanhercke et al, 2013) and the formation of stabilized oil bodies (via oleosin). Was oil accumulated in leaves, the composition of the leaf oil was dramatically altered, including a reduction in α-linolenic acid in favor of oleic acid

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