Abstract
SummaryThe synthesis and accumulation of omega‐3 long‐chain polyunsaturated fatty acids in transgenic Camelina sativa is demonstrated using the so‐called alternative pathway. This aerobic pathway is found in a small number of taxonomically unrelated unicellular organisms and utilizes a C18 Δ9‐elongase to generate C20 PUFAs. Here, we evaluated four different combinations of seed‐specific transgene‐derived activities to systematically determine the potential of this pathway to direct the synthesis of eicosapentaenoic acid (EPA) in transgenic plants. The accumulation of EPA and the related omega‐3 LC‐PUFA eicosatetraenoic acid (ETA) was observed up to 26.4% of total seed fatty acids, of which ETA was 9.5%. Seed oils such as these not only represent an additional source of EPA, but also an entirely new source of the bona fide fish oil ETA. Detailed lipidomic analysis of the alternative pathway in Camelina revealed that the acyl‐substrate preferences of the different activities in the pathway can still generate a substrate‐dichotomy bottleneck, largely due to inefficient acyl‐exchange from phospholipids into the acyl‐CoA pool. However, significant levels of EPA and ETA were detected in the triacylglycerols of transgenic seeds, confirming the channelling of these fatty acids into this storage lipid.
Highlights
It is well accepted that omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs), especially eicosapentaenoic acid (EPA; 20:5D5,8,11,14,17) and docosahexaenoic acid (DHA; 22:6D4,7,10,13,16,19), are vital for human health and nutrition and play a crucial role in preventing cardiovascular diseases and associated precursor conditions such as metabolic syndrome and obesity (Swanson et al, 2012)
We investigated the effects of different combinations of genes and promoters on the accumulation of n-3 LC-PUFAs in Arabidopsis and C. sativa using the conventional D6-pathway (Ruiz-Lopez et al, 2009, 2013, 2014; Ruiz-Lopez et al, 2012; Sayanova et al, 2011a)
We included other additional genes encoding an omega-3 desaturase and a D12-desaturase, to optimize the production of EPA in seeds and to allow a direct comparison with analogous studies in Arabidopsis and C. sativa using the D6-pathway containing these additional activities (RuizLopez et al, 2013, 2014). These constructs were initially evaluated in Arabidopsis, and after transformation via floral dip, mature seeds from KanR-plants were analysed by GC–MS for total fatty acid composition
Summary
The synthesis and accumulation of omega-3 long-chain polyunsaturated fatty acids in transgenic Camelina sativa is demonstrated using the so-called alternative pathway. This aerobic pathway is found in a small number of taxonomically unrelated unicellular organisms and utilizes a C18 D9elongase to generate C20 PUFAs. Here, we evaluated four different combinations of seedspecific transgene-derived activities to systematically determine the potential of this pathway to direct the synthesis of eicosapentaenoic acid (EPA) in transgenic plants. The accumulation of EPA and the related omega-3 LC-PUFA eicosatetraenoic acid (ETA) was observed up to 26.4% of total seed fatty acids, of which ETA was 9.5%. Significant levels of EPA and ETA were detected in the triacylglycerols of transgenic seeds, confirming the channelling of these fatty acids into this storage lipid
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