Characterization of 3-ketoacyl-coA synthase in a nervonic acid producing oleaginous microalgae Mychonastes afer

Nervonic acid (C24:1, Δ15), a monounsaturated long chain fatty acid, is a major component of mammalian neural tissue. Lack of nervonic acid in human usually leads to neurological disorder. Recently, production of nervonic acid from plant for pharmaceutical, nutraceutical, and functional food received increasing attention. We have previously isolated a microalgal strain Mychonastes afer HSO-3-1, which can accumulate approximately 6% of nervonic acid and <0.5% of erucic acid in triacylglycerol. In this study, the full length of 3-ketoacyl-coA synthase gene MaKCS, encoding the first component of fatty acid elongation complex, was cloned and expressed in Saccharomyces cerevisiae BY4741 under the control of GAL1 promoter. S. cerevisiae harboring pYC230-Gal-MaKCS resulted in the production of 1.5% nervonic acid in total lipid. The expression of KCS gene in M. afer was found to be induced under stress conditions such as nitrogen deficiency and high light, which was revealed by real-time PCR analysis. MaKCS was demonstrated to be able to extend very long chain monounsaturated fatty acids including nervonic acid, which provides insights into how nervonic acid is synthesized in microalgae.