Identification of a putative seipin ortholog involved in lipid accumulation in marine microalga Phaeodactylum tricornutum

There is a huge interest in exploiting microalgae as an alternative bioenergy resource. Genetic improvement of microalgal strains with significant commercial potential is urgently demanded. Seipin has been shown to be associated with adipocyte differentiation and lipid droplet (LD) formation in mammals. However, very little is known about seipin in microalgae. Here, we identified a putative seipin in the oleaginous marine diatom Phaeodactylum tricornutum and developed a transgenic strain with overexpressed seipin. The transgenic strain possessed higher neutral lipid content and larger LDs than the wild type, and neutral lipid content was increased by 57%. Moreover, in this transgenic strain, the relative content of saturated fatty acids in total fatty acids was increased significantly, which improved lipid quality for the oil refinery. Our findings elucidated the significant potential role of seipin in regulating lipid accumulation and LD formation in microalgae for the first time.