James Petrie, Thomas Vanhercke, Allan Green and Surinder Singh
CSIRO Food, Nutrition and Bioproducts Flagship, ACT, Australia
Supply of vegetable oils as a major commodity faces continuous pressure. Global demand is expected to double in the next two decades due to increasing world population and rising petroleum prices. Increasing limitations on arable land and agricultural inputs mean it will be difficult to meet this additional demand with current oilseed-based production systems. The concept of producing oil in the leaves and stems of high biomass species has attracted attention as a way to intensify oil production. The engineering of such a new oil production platform would not only yield greater amount of oil for a given land area but also provide a way to more easily segregate bioeconomy traits such as unusual fatty acids away from food production. We previously reported the accumulation of up to 17% triacylglycerol (TAG, dry weight) in leaf tissue of Nicotiana species. This was achieved by combinatorial metabolic engineering in which we increased fatty acid biosynthesis (‘Push’) by limited overexpression of the WRI1 transcription factor, increased TAG assembly (‘Pull’) by expressing DGAT1, and encouraged oil body formation (‘Packaging’) by expressing oleosin in plant leaves1,2.
In this presentation, we will describe some of our second generation construct designs which have more than doubled the previously reported TAG content. Oil content in leaves now matches elite oilseed crop seed levels of +40%. We will describe the implications that this technology has for global plant oil production from a yield and intensification perspective, as well as the challenges that remain for integration into the existing industry. We will also present data demonstrating that the newly produced fatty acids can be modified for industrial or nutritional applications as well as preliminary data of a transcriptome comparison between wild type and high oil leaf tissue, harvested at different stages during plant development.
REFERENCES
[1] Vanhercke et al., 2012. Synergistic effect of WRI1 and DGAT1 coexpression on triacylglycerol biosynthesis in plants. FEBS
Letters 587(4):364-9.
[2] Vanhercke et al., 2014. Metabolic engineering of biomass for high energy density: oilseed-like triacylglycerol yields from
plant leaves. Plant Biotechnology Journal 12(2):231-9.