초록
<P><B>Background</B></P><P>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. 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 <I>Synechocystis</I> sp. PCC6803 is incomplete.</P><P><B>Results</B></P><P>We 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 <I>psbA2</I> promoter in transgenic <I>Synechocystis</I> sp. PCC6803. We generated six homologous recombinants, harboring various fatty acid desaturase genes from <I>Synechocystis</I> sp. PCC6803, <I>Gibberella fujikuroi</I> and <I>Mortierella alpina.</I> 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 <I>Synechocystis</I> sp. PCC6803.</P><P><B>Conclusions</B></P><P>In the blue-green alga <I>Synechocystis</I> 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.</P>