Effects of disrupted omega-3 desaturase gene construct on fatty acid composition and expression of four fatty acid biosynthetic genes in transgenic Chlorella vulgaris

This study demonstrated the genetic modification of Chlorella vulgaris by introducing a copy of disrupted omega-3 desaturase (ω-3 FAD) gene into its genome to study the effect on fatty acid biosynthesis pathway. Results revealed that the expression of endogenous ω-3 FAD gene in transgenic lines (C28 and C30) was temporarily suppressed during the early stage of sub-culture and then reactivated subsequently after six months of alternate sub-culturing. Furthermore, the endogenous ω-3 FAD expression was found to be upregulated to > 3-fold without any notable changes in C18:3n3 composition when cultured under nitrate-deficient medium. Interestingly, a significant shift in fatty acid saturation profile towards the production of higher C16:0 was observed along with a reduction in C18:1 composition in transgenic lines. In addition, PCR walking experiment confirmed that the entire T-DNA region and vector backbone were co-transferred and randomly integrated into the host genome. These findings provide valuable insight in understanding the regulation of fatty acid biosynthesis pathway in C. vulgaris and could pave the way for further genetic improvement of the species for various downstream applications.