title: Biosynthesis of very-long-chain polyunsaturated fatty acids in transgenic oilseeds: constraints on their accumulation.
abstract: Omega6- and omega3-polyunsaturated C20 fatty acids represent important components of the human diet. A more regular consumption and an accordingly sustainable source of these compounds are highly desirable. In contrast with the very high levels to which industrial fatty acids have to be enriched in plant oils for competitive use as chemical feedstocks, much lower percentages of very-long-chain polyunsaturated fatty acids (VLCPUFA) in edible plant oils would satisfy nutritional requirements. Seed-specific expression in transgenic tobacco (Nicotiana tabacum) and linseed (Linum usitatissimum) of cDNAs encoding fatty acyl-desaturases and elongases, absent from all agronomically important plants, resulted in the very high accumulation of Delta6-desaturated C18 fatty acids and up to 5% of C20 polyunsaturated fatty acids, including arachidonic and eicosapentaenoic acid. Detailed lipid analyses of developing seeds from transgenic plants were interpretated as indicating that, after desaturation on phosphatidylcholine, Delta6-desaturated products are immediately channeled to the triacylglycerols and effectively bypass the acyl-CoA pool. Thus, the lack of available Delta6-desaturated acyl-CoA substrates in the acyl-CoA pool limits the synthesis of elongated C20 fatty acids and disrupts the alternating sequence of lipid-linked desaturations and acyl-CoA dependent elongations. As well as the successful production of VLCPUFA in transgenic oilseeds and the identification of constraints on their accumulation, our results indicate alternative strategies to circumvent this bottleneck.
authors.affiliation: Institut für Allgemeine Botanik, Universität Hamburg, 22609 Hamburg, Germany. abbadi@botanik.uni-hamburg.de <abbadi@botanik.uni-hamburg.de>
authors.forename: Amine
authors.initials: A
authors.lastname: Abbadi
authors.forename: Fréderic
authors.initials: F
authors.lastname: Domergue
authors.forename: Jörg
authors.initials: J
authors.lastname: Bauer
authors.forename: Johnathan A
authors.initials: JA
authors.lastname: Napier
authors.forename: Ruth
authors.initials: R
authors.lastname: Welti
authors.forename: Ulrich
authors.initials: U
authors.lastname: Zähringer
authors.forename: Petra
authors.initials: P
authors.lastname: Cirpus
authors.forename: Ernst
authors.initials: E
authors.lastname: Heinz
mesh_terms: D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism*; D014026:Nicotiana / Q000378:metabolism*
chemical_list: D005231:Fatty Acids, Unsaturated