Isolation of a novel C18-Δ9 polyunsaturated fatty acid specific elongase gene from DHA-producing Isochrysis galbana H29 and its use for the reconstitution of the alternative Δ8 pathway in Saccharomyces cerevisiae

Abstract

A novel gene (IgASE2) encoding a C18-Δ9 polyunsaturated fatty acids specific (C18-Δ9-PUFAs-specific) elongase was isolated and characterized from DHA-rich microalga, Isochrysis galbana H29. The IgASE2 gene was 1,653 bp in length, contained a 786 bp ORF encoding a protein of 261 amino acids that shared 87% identity with Δ9 elongase, IgASE1, and possessed a 44 bp 5'-untranslated region (5'-UTR) and a 823 bp 3'-untranslated region (3'-UTR). IgASE2, by its heterologous expression in Saccharomyces cerevisiae, elongated linoleic acid (LA, 18:2n-6) and α-linolenic (ALA, 18:3n-3) to eicosadienoic acid (EDA, 20:2n-6) and eicosatrienoic acid (ETrA, 20:3n-3), respectively. The conversions of LA to EDA and ALA to ETrA were 57.6 and 56.1%, respectively. Co-expression of this elongase with Δ8 desaturase required for the synthesis of C20-polyunsaturated fatty acids resulted in the accumulation of dihomo-γ-linolenic acid (20:3n-6) from LA and eicosatetraenoic acid (20:4n-6) from ALA. These results demonstrated that IgASE2 exhibited C18-Δ9-PUFAs-specific elongase activity and the alternative Δ8 pathway was reconstituted.

Microbial oils as food additives: recent approaches for improving microbial oil production and its polyunsaturated fatty acid content

“…from LA to C20:2v-6 then to C20:3v-6) and eicosatetraenoic acid (C20:4v-3) (i.e. from ALA to C20:3v-3 then to C20:4v-3) [79]. EPA synthesis was also achieved in S. cerevisiae heterologously expressing five desaturases and one elongase.…”

Enhancing LC-PUFA production in Thalassiosira pseudonana by overexpressing the endogenous fatty acid elongase genes

“…Organisms such as the microalgae Euglena gracilis or Isochrysis galbana contain genes that encode for delta 9-elongase and delta 8-desaturase and therefore use the alternative pathway in which elo9 elongates ALA to generate a C20:3 chain and then des8 adds the double bond to make C20:4 ( Fig. 1 and Li et al 2011;Qi et al 2002;Wallis and Browse 1999).…”

Identification of a Δ6 fatty acid elongase gene for arachidonic acid biosynthesis localized to the endoplasmic reticulum in the green microalga Myrmecia incisa Reisigl

“…Saccharomyces cerevisiae Hansen has been reported to contain all of the fatty acid elongation components and is a valuable system for the functional identification of elongase genes from various organisms (Toke and Martin, 1996;Beaudoin et al, 2000;Parker-Barnes et al, 2000;Trenkamp et al, 2004;Ponnusamy et al, 2008;Li et al, 2011;Tan et al, 2011). This study, therefore, focuses on the functional identification and subcellular localization of the cloned MiFAE gene from M. incisa by the heterologous expression of this gene in yeast.…”