Publication Type: Journal Article
Source: Plant Biotechnology Journal, Volume doi: 10.1111/pbi.12772, p.doi: 10.1111/pbi.12772 (2017)
Nannochloropsis oceanica is an oleaginous microalga rich in omega3long-chain polyunsaturated fatty acids (LC-PUFAs) content, in the form of eicosapentaenoic acid (EPA). We identified the enzymes involved in LC-PUFA biosynthesis in N. oceanica CCMP1779 and generated multigene expression vectors aiming at increasing LC-PUFA content in vivo. We isolated the cDNAs encoding four fatty acid desaturases (FAD) and determined their function by heterologous expression in S. cerevisiae. To increase the expression of multiple fatty acid desaturases in N. oceanica CCMP1779 we developed a genetic engineering toolkit that includes an endogenous bidirectional promoter and optimized peptide bond skipping 2A peptides. The toolkit also includes multiple epitopes for tagged fusion protein production and two antibiotic resistance genes. We applied this toolkit, towards building a gene stacking system for N. oceanica that consists of two vector series, pNOC-OX and pNOC-stacked. These tools for genetic engineering were employed to test the effects of the overproduction of one, two or three desaturase encoding cDNAs in N. oceanica CCMP1779 and prove the feasibility of gene stacking in this genetically tractable oleaginous microalga. All FAD overexpressing lines had considerable increases in the proportion of LC-PUFAs, with the overexpression of Delta12 and Delta5 FAD encoding sequences leading to an increase in the final omega3 product, EPA. This article is protected by copyright. All rights reserved.