Biosynthesis of very long chain polyunsaturated fatty acids in the leafy vegetable chicory

Abstract

The synthesis of very long chain polyunsaturated fatty acids (VLCPUFAs) was investigated in five cultivars of chicory. Genes for enzymes of the ù3/6 Ä8-desaturation biosynthetic pathways for the formation of C20 VLCPUFAs were inserted into chicory by Agrobacterium-mediated transformation of leaf explants. Plants were transformed by genes encoding Ä9-specific elongating activity from Isochrysis galbana, Ä8-desaturase from Euglena gracilis and Ä5-desaturase from Mortierella alpina, either separately or in combination; transgenic plants were selected on culture medium containing glufosinate ammonium for those transformed with the Ä9-elongase gene alone or in combination with the Ä8-desaturase gene, or kanamycin for plants transformed with the Ä5-desaturase gene. PCR showed the presence of the transgenes within the genome of selected plants, with RT-PCR confirming gene expression. Gas Chromatography of fatty acid methyl esters extracted from freeze-dried leaves of transgenic plants quantified the synthesis of omega-6 arachidonic acid and its precursors eicosadienoic and dihomo-ã-linolenic acids, and omega-3 eicosapentaenoic acid together with its precursors eicosatrienoic and eicosatetraenoic acids. This is the first report of the production of VLCPUFAs in a leafy vegetable. Since VLCPUFAs are the precursors of prostaglandins, the formation of prostaglandins was also investigated in chicory following a second transformation event using the PGHS-1 gene from Mus musculus.