Functional Study On The Desaturases Involved In The Synthesis Of Polyunsaturated Fatty Acids In Phaeodactylum Tricornutum

Phaeodactylum tricornutum,as a typical algal species of unicellular diatom,has been sequenced and has become a model for further research.It can accumulate ?-3 long chain polyunsaturated fatty acid(e.g.EPA),which can be used as the source of EPA production.EPA and the other ?-3 long chain polyunsaturated fatty acids(PUFA)are important components of human nutrition,have a wide range of applications in medicine,health care,cosmetics and other aspects.In this study,we studied the biosynthetic pathway of polyunsaturated fatty acids of P.tricornutum.By means of molecular biology and genetic engineering,the ?9 desaturase genes SAD,PtD9,?12 desaturase gene PtD12,and short chain dehydrogenase SDR,were cloned,and the expression vectors were constructed,to study the effects of these genes on the synthetic pathway of polyunsaturated fatty acids.In addition,the co-expression of PtD9 and PtD12 in P.tricornutum was carried out to study the effect of co-expression of PtD9 and PtD12 on the synthesis of PUFA.The PHYsiological and biochemical indexes of the transformed algal strains with single gene and double gene overexpression were determined.It was found that there was no significant difference in growth cycle and photosynthesis efficiency between the transformed algal strains and wild type.But the content of the neutral lipid increased significantly in the transformed strains.And the content of the PUFAs,especially the content of EPA,increased significantly in the transformed strains of SDR and SAD.The contents of saturated fatty acids and monounsaturated fatty acids in PtD9 transformed algae and double gene transformed algae PtD9-D12 were significantly increased.In summary,the effects of ?9 desaturase gene SAD,PtD9,?12 desaturase gene PtD12 and short chain dehydrogenase gene SDR on fatty acid synthetic pathway were studied;at the same time,some PUFA-rich engineered algal strains were obtained,which provided a theoretical basis for further elucidating the synthetic pathway of PUFA of microalgae,and also provided a new idea for the high value utilization of microalgae resources.