Analysis of the Fatty Acid Desaturase Gene Family and Construction and Screening of High-EPA Transgenic Strains in Phaeodactylum tricornutum

Fatty acid desaturase (FAD) is a key enzyme that catalyzes the biosynthesis of polyunsaturated fatty acids (PUFAs) and is widely present in animals, plants and microorganisms. In this study, Phaeodactylum tricornutum was used as the material. Bioinformatics methods were employed to identify the FAD gene family within the entire genome of P. tricornutum. The genomic distribution, gene structure, conserved domains, phylogenetic relationships, and physicochemical properties of proteins were systematically analyzed. The results showed that a total of 15 FAD genes were identified in the genome of P. tricornutum, which could be classified into 4 subfamilies. These genes are unevenly distributed on the 11 chromosomes. Motif analysis predicted that motif1 and motif2 are not only highly conserved but also play a key role in the synthesis of unsaturated fatty acids. To verify the gene function, we transferred the exogenous Ptd5α gene into P. tricornutum. Through screening and verification, we successfully obtained three transgenic algal strains (5D1, 5D2, 5D3). Compared with the wild algal strain (WT), overexpression of the Ptd5α gene did not have a significant impact on the growth and development of P. tricornutum. Moreover, the total fatty acid content of the transgenic algal strain was significantly increased, and the proportion of EPA in the total fatty acids could be raised to over 30%. The results of this study lay an important foundation for in-depth analysis of the biological functions of the FAD gene family in P. tricornutum, and also provide experimental and theoretical basis for the large-scale industrial production of EPA using model microalgae.