Effects of arachidonic acid on the growth, total lipids content and related gene expression in Phaeodactylum tricornutum

To improve the ability of Phaeotactylum tricornutum to produce biodiesel, The effect of arachidonic acid (AA) on the cell growth, lipid and fatty acid content in algae Phaeodactylum tricornutum were studied in this paper. And using quantitative PCR, variant expressions of genes, which were related to the pathway of biosynthesis of lipid were detected. Results showed that low concentration (0.1-62.5 mg · L^-1) of AA promoted the cell growth of the Phaeodactylum tricornutum while high concentration of AA (312.5 mg · L^-1) restrained the cell growth. At 12.5 mg · L^-1 AA, the free fatty acid content reached its maximum and was four times higher than control group. The total lipid content reached the maximum at AA concentration of 62.5 mg · L^-1, which was increased by 54% than the control group. The quantitive PCR results showed that when the concentration of AA reached at 312.5 mg · L^-1, the reletive genes, include LPAAT, GPAT, KAS II, ACCase involved in the pathway of biosynthesis of lipid, were significant higher than the control (P < 0.01). These findings indicate that AA may stimulate the accumulation of lipid in Phaeodactylum tricornutum by increase-regulating the expressing of related genes. The results of this study provide a theoretical basis for using genetic engineering to achieve the purpose of energy enrichment of microalgae oil. (authors)