Metabolic engineering of Phaeodactylum tricornutum for the enhanced accumulation of omega-3 long chain polyunsaturated fatty acids

Abstract

We have engineered the diatom Phaeodactylum tricornutum to accumulate the high value omega-3 long chain polyunsaturated fatty acid docosahexaenoic acid (DHA). This was achieved by the generation of transgenic strains in which the Δ5-elongase from the picoalga Ostreococcus tauri was expressed to augment the endogenous fatty acid biosynthetic pathway. Expression of the heterologous elongase resulted in an eight-fold increase in docosahexaenoic acid content, representing a marked and valuable change in the fatty acid profile of this microalga. Importantly, DHA was shown to accumulate in triacylglycerols, with several novel triacylglycerol species being detected in the transgenic strains. In a second iteration, co-expression of an acyl-CoA-dependent Δ6-desaturase with the Δ5-elongase further increased DHA levels. Together, this demonstrates for the first time the potential of using iterative metabolic engineering to optimise omega-3 content in algae.

Enhancing LC-PUFA production in Thalassiosira pseudonana by overexpressing the endogenous fatty acid elongase genes

“…6), which would be when carbon flux into FA storage forms would be minimal compared with stationary phase or Si starvation. Previous work in P. tricornutum, in which a heterologous delta 5 elongase from Ostreococcus tauri was overexpressed, indicated 2-fold less EPA during exponential growth and 2.1-fold less in stationary phase (Hamilton et al 2014). DHA increased 3.7-fold in exponential phase and 8-fold in stationary phase.…”

Metabolic engineering toward enhanced LC-PUFA biosynthesis in Nannochloropsis oceanica : Overexpression of endogenous Δ12 desaturase driven by stress-inducible promoter leads to enhanced deposition of polyunsaturated fatty acids in TAG

“…Here we present the first approach for metabolic engineering of the PUFA biosynthesis pathway in N. oceanica by stable integration and stress-induced expression of an endogenous Δ12-desaturase, leading to enhanced production of n − 6 PUFA, LA and AA, under nitrogen starvation and their incorporation into the algal TAG fraction. A recent successful approach for LC-PUFA metabolic engineering in microalgae, using heterologous microalgal elongase and desaturase, was demonstrated in Phaeodactylum tricornutum, whereby the co-expression of an acylCoA-dependent Δ6-desaturase with the Δ5-elongase from the picoalga Ostreococcus tauri led to significant DHA production at the expense of EPA [70].…”

Exploring Valuable Lipids in Diatoms

“…However, certain positive mutants have lower expression of phospholipids and some mutants accumulated long FIGURE 2 | A scheme of long chain fatty acid biosynthesis pathway in the model species P. tricornutum and compartmentation of biosynthesis processes in plastid (left) and endoplasmic reticulum (right). Major biosynthetic routes for EPA and DHA biosynthesis are illustrated as examples, and for other routes one can refer to the previous studies (Arao and Yamada, 1994;Hamilton et al, 2014). Abbreviations: ACCase, acetyl-CoA Carboxylase; MAT, malonyl-CoA acyl carrier protein transacylase; KAS I, II, and III, isoform I, II, and III of ketoacyl-acyl carrier protein synthase; FAD, fatty acid desaturase; TE, thioesterase; FAE, fatty acid elongase.…”