Main content area

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

Spychalla, J.P., Kinney, A.J., Browse, J.
Proceedings of the National Academy of Sciences of the United States of America 1997 v.94 no.4 pp. 1142-1147
Arabidopsis thaliana, transgenic plants, gene expression, stearoyl-CoA desaturase, complementary DNA, Caenorhabditis elegans, nucleotide sequences, amino acid sequences, linolenic acid, fatty acids, lipids, cell membranes, roots, polyunsaturated fatty acids, chemical constituents of plants
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.