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.
Highlights
Polyunsaturated 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
C18:4 content increased as the temperature decreased, indicating that a reduction in temperature promotes the expression of Δ6 desaturase, which converts α-Linolenic acid (ALA) to stearidonic acid (SDA). These results suggest that production of PUFAs is greater in transgenic Synechocystis organisms cultivated at 20°C than in those cultivated at higher temperatures
These results expand the current understanding of the role of FA desaturases and the molecular mechanisms that underlie PUFA accumulation at different temperatures in Synechocystis
Summary
Polyunsaturated 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. Because SDA is readily converted into EPA and DHA upon consumption, it may potentially be used to increase blood levels of ω-3 PUFAs [10,11]. Ancestral dietary fat compositions exhibited a ω-6 to ω-3 ratio of 2:1 to 4:1, but this ratio can be as high as 10:1 in modern diets [16]. These imbalances can increase the risk of hypertension [17], cardiovascular disease [18], rheumatoid arthritis [19,20,21], and inflammatory and autoimmune disease [22,23]
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