title: Transgenic expression of delta-6 and delta-15 fatty acid desaturases enhances omega-3 polyunsaturated fatty acid accumulation in Synechocystis sp. PCC6803.
abstract: BACKGROUND
  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 Synechocystis sp. PCC6803 is incomplete.
  
  
  RESULTS
  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 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.
  
  
  CONCLUSIONS
  In 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.
authors.forename: Gao
authors.initials: G
authors.lastname: Chen
authors.forename: Shujie
authors.initials: S
authors.lastname: Qu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Bian
authors.forename: Zhenying
authors.initials: Z
authors.lastname: Peng
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Haitao
authors.initials: H
authors.lastname: Ge
authors.forename: Jinhui
authors.initials: J
authors.lastname: Yu
authors.forename: Ning
authors.initials: N
authors.lastname: Xuan
authors.affiliation: Biotechnology Research Center, Shandong Academy of Agricultural Sciences, Jinan 250100, P, R, China. yuping_bi@hotmail.com.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Bi
authors.forename: Qingfang
authors.initials: Q
authors.lastname: He