Genomics and Associated Biotechnology of Accumulating Oil in Seeds and Leaves

Engineering leaves to produce 'fresh' oil may help reduce the global dependence on ‘fossil’ oils. “Transient’ leaf based assays in Nicotiana benthamiana are a useful transgene expression platform where complicated lipid-related transgenic pathways can be rapidly assembled and interchanged (Wood et al Plant Biotech Journal 2009). To help understand the underlying biology of these remarkable leaf assays we have recently published a draft genome resource of N. benthamiana (Naim et al., PLOS ONE 2012, www.benthgenome.com), spanning over 75% of the 3.1 Gb haploid genome. This resource has revealed a wealth of lipid synthesis and lipid handling genes, some of which we have silenced to shunt endogenous lipid metabolism into new engineered industrial oils. Such ‘transient’ leaf assays were also the platform to increase leaf oils (Vanhercke et al., FEBS Letter 2013). Metabolic engineering approaches to increase plant oil levels can generally be divided into categories which increase fatty acid biosynthesis (WRINKLED), are involved in TAG assembly (DGAT) or increase TAG storage/decrease breakdown (Oleosins). Co-expression of ‘push’ and ‘pull’ genes in the ‘transient’ leaf expression system resulted in TAG levels exceeding those expected from an additive effect and biochemical tracer studies confirmed increased flux of carbon through fatty acid and TAG synthesis pathways. Leaf fatty acid profile also synergistically shifts from polyunsaturated to monounsaturated fatty acids. Overall, I will outline how the genomics of ‘transient’ leaf assays has underpinned the engineering of new fatty acids at high concentrations, potentially leading the way for a reduced dependence on ‘fossil’ oils.