Transgenic production of omega-3 very long chain polyunsaturated fatty acids in plants: Accomplishment and challenge

Omega-3 very long chain polyunsaturated fatty acids (VLC-PUFAs or VLCPUFAs) such as eicosapentaenoic acid (EPA, 22:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) have important roles in human health. The current source of these fatty acids is oil from marine fish and oleaginous microorganisms. However, sustainability of this source is questionable due to the declining fish population in ocean as well as the high cost associated with the microbial culturing and oil extraction. Transgenic plants producing a high level of VLCPUFAs have been proposed to be a potential alternative source for these fatty acids. Detections of EPA and DHA in transgenic plants expressing heterologous desaturases and elongases as well as a PUFA synthase from VLCPUFA-producing microorganisms have indeed optimistically proven the concept. However, the yield of VLCPUFAs in transgenics is still low and the desirable composition of these fatty acids is not achieved. This mini-review discusses what has been done on the reconstitution of VLCPUFA-biosynthetic pathways in transgenics and what kind of challenges and possible solutions could be in producing VLCPUFAs in plants.