Transgenic expression of delta-6 and delta-15 fatty acid desaturases enhances omega-3 polyunsaturated fatty acid accumulation in Synechocystis sp. PCC6803

Abstract

BackgroundPolyunsaturated fatty acids (PUFAs), which contain two or more double bonds in their backbone, are the focus of intensive global research, because of their nutritional value, medicinal applications, and potential use as biofuel. However, the ability to produce these economically important compounds is limited, because it is both expensive and technically challenging to separate omega-3 polyunsaturated fatty acids (ω-3 PUFAs) from natural oils. Although the biosynthetic pathways of some plant and microalgal ω-3 PUFAs have been deciphered, current understanding of the correlation between fatty acid desaturase content and fatty acid synthesis in Synechocystis sp. PCC6803 is incomplete.ResultsWe constructed a series of homologous vectors for the endogenous and exogenous expression of Δ6 and Δ15 fatty acid desaturases under the control of the photosynthesis psbA2 promoter in transgenic Synechocystis sp. PCC6803. We generated six homologous recombinants, harboring various fatty acid desaturase genes from Synechocystis sp. PCC6803, Gibberella fujikuroi and Mortierella alpina. These lines produced up to 8.9 mg/l of α-linolenic acid (ALA) and 4.1 mg/l of stearidonic acid (SDA), which are more than six times the corresponding wild-type levels, at 20°C and 30°C. Thus, transgenic expression of Δ6 and Δ15 fatty acid desaturases enhances the accumulation of specific ω-3 PUFAs in Synechocystis sp. PCC6803.ConclusionsIn the blue-green alga Synechocystis sp. PCC6803, overexpression of endogenous and exogenous genes encoding PUFA desaturases markedly increased accumulation of ALA and SDA and decreased accumulation of linoleic acid and γ-linolenic acid. This study lays the foundation for increasing the fatty acid content of cyanobacteria and, ultimately, for producing nutritional and medicinal products with high levels of essential ω-3 PUFAs.

Acyl-lipid desaturases and Vipp1 cooperate in cyanobacteria to produce novel omega-3 PUFA-containing glycolipids

“…2 health-promoting EPA in humans, fish and livestock, a great deal of effort has gone into finding natural systems and designing new engineered pathways that produce high quantities of SDA and high ratios of n-3 to n-6 PUFAs (55). SDA is seldom naturally found in cyanobacteria (56) unless at least one acyl-lipid desaturase is provided on a multicopy vector (47), and even then, the maximal content of 26.6% SDA reached in the current study is as we have noted at least twofold higher than previous engineered strains (Table 3) (46,47). SDA-producing transgenic soybean oil contains 20-26% of the total fatty acids as SDA with n-3 to n-6 PUFA ratios of ~ 1 or lower (19,21,55,57), and seed oil from Echium plantagineum naturally contains ~13% of the total fatty acids as SDA (15,58,59).…”

Biocatalytic Oxidation Reactions: A Chemist's Perspective

“…Therefore,i nvitro applications of FADs do not appear practical nowadays.A few reports deal with the in vivo overexpression of some desaturases in whole cells,g enerating af ew mg L À1 of,f or example, a-linoleic acid. [68] Overall, oxidative desaturation is an interesting but not yet very far developed reaction.…”

Metabolic engineering of microorganisms to produce omega-3 very long-chain polyunsaturated fatty acids

“…EPA at 56.6% of total fatty acids and accumulated lipids at up to 627 30% of dry cell weight after 6 days in high-glucose medium [89]. 628 Genetic analysis revealed that in addition to the PEX10 gene, three 629 other ORFs were also disrupted by integration events: LIP1 encod- 30°C, 5-fold higher than the wild-type strain [91]. In addition 662 to increased yields of these x3-C 18 -PUFAs, improvement of 663 x3-VLCPUFA production levels has also been achieved in some Acyl-exchange can also be reduced in part by heterologous expres-967 sion of a D9-elongase pathway (Fig.…”

“…EPA can be converted to 86 eicosanoids, a group of biologically active chemicals including pros- 87 taglandin, thromboxane and leucotriene, which play crucial roles in 88 regulation of blood pressure and blood coagulation and participate in 89 many important physiological processes such as inflammatory and 90 immunological reactions [15]. For humans, the most common die- 91 tary intake of essential PUFAs is linoleic acid (LA, 18:2D ) and a-linolenic acid (ALA, 18:3D 9,12,15 ), the precursor 96 of x3-VLCPUFAs, to EPA and DHA. The conversion of ALA to 97 x3-VLCPUFAs in humans is based on the positive link between 98 increased intakes of dietary ALA and enhancement of EPA and DHA 99 in plasma and cell lipids [17,18] as well as the results of stable-iso- 100 tope-tracer studies [19].…”