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. 1997 Feb 18;94(4):1142-7.
doi: 10.1073/pnas.94.4.1142.

Identification of an animal omega-3 fatty acid desaturase by heterologous expression in Arabidopsis

J P Spychalla  1 , A J Kinney, J Browse
Affiliations

Identification of an animal omega-3 fatty acid desaturase by heterologous expression in Arabidopsis

J P Spychalla et al. Proc Natl Acad Sci U S A. .

Abstract

In animals, fatty acid desaturases catalyze key reactions in the synthesis of arachidonic acid and other polyunsaturated fatty acids. A search of the Caenorhabditis elegans DNA databases, using the sequences of Arabidopsis genes, identified several putative desaturases. Here we describe the characterization of the first of these genes, fat-1. The predicted protein encoded by a fat-1 cDNA showed 32-35% identity with both FAD2 and FAD3 of Arabidopsis. When expressed in transgenic plants, fat-1 resulted in a 90% increase in the proportion of alpha-linolenic acid in root lipids. Wild-type Arabidopsis incorporated omega-6 fatty acids (delta8,11,14-20:3 and delta5,8,11,14-20:4) into membrane lipids but did not desaturate them. By contrast, fat-1 transgenic plants efficiently desaturated both of these fatty acids to the corresponding omega-3 products. These findings indicate that the C. elegans fat-1 gene encodes the first animal representative of a class of glycerolipid desaturases that have previously been characterized in plants and cyanobacteria. The FAT-1 protein is an omega-3 fatty acyl desaturase that recognizes a range of 18- and 20-carbon omega-6 substrates.

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Figures

Figure 1
Figure 1
Deduced amino acid sequences and shared identities of the fat-1 gene of C. elegans (fat-1) and the FAD2 and FAD3 genes of A. thaliana (fad2 and fad3).
Figure 2
Figure 2
Gel blot analysis of fat-1 transcript levels in wild-type and transgenic Arabidopsis. Total RNA (25 μg) isolated from leaves was separated by electrophoresis on a 1.2% agarose–formaldehyde gel, transferred to a nylon membrane, and probed with a HindIII/SacI DNA fragment of pCE8.
Figure 3
Figure 3
Partial gas chromatograph traces of the component fatty acids of phosphatidylcholine extracted from leaves of (A) wild-type Arabidopsis, (B) wild-type Arabidopsis sprayed with the sodium soap of arachidonic acid (Δ5,8,11,14–20:4; AA), (C) wild-type Arabidopsis sprayed with the sodium soap of homogamma-linolenic acid (Δ8,11,14–20:3; HGL), (D) transgenic Arabidopsis line 9.7 expressing a fat-1 cDNA, (E) transgenic Arabidopsis line 9.7 sprayed with the sodium soap arachidonic acid, and (F) transgenic Arabidopsis line 9.7 sprayed with the sodium soap of homogamma-linolenic acid.
See this image and copyright information in PMC

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