Expression of the Isochrysis $\text{C}18-\Delta ^{9}$ Polyunsaturated Fatty Acid Specific Elongase Component Alters Arabidopsis Glycerolipid Profiles

• Published in: Plant physiology (Bethesda) Vol. 135; no. 2; pp. 859 - 866
• Main Authors: Thomas Colin Michael Fraser, Baoxiu Qi, Salah Elhussein, Sunantha Chatrattanakunchai, Allan Keith Stobart, Colin Michael Lazarus
• Format: Journal Article
• Language: English
• Published: American Society of Plant Biologists 01.06.2004
• Subjects: Biochemical Processes and Macromolecular Structures; Biosynthesis; Chloroplasts; Fatty acids; Lipid metabolism; Lipids; Plant morphology; Plants; Seeds; Transgenic plants; Unsaturated fatty acids
• ISSN: 0032-0889; 1532-2548

A cDNA isolated from the prymnesiophyte micro-alga Isochrysis galbana, designated IgASE1, encodes a fatty acid elongating component that is specific for linoleic acid (C18:2n-6) and α-linolenic acid (C18:3n-3). Constitutive expression of IgASE1 in Arabidopsis resulted in the accumulation of eicosadienoic acid (EDA; C20:2n-6) and eicosatrienoic acid (ETrA; C20:3n-3) in all tissues examined, with no visible effects on plant morphology. Positional analysis of the various lipid classes indicated that these novel fatty acids were largely excluded from the sn-2 position of chloroplast galactolipids and seed triacylglycerol, whereas they were enriched in the same position in phosphatidylcholine. EDA and ETrA are precursors of arachidonic acid (C20:4n-6), eicosapentaenoic acid (C20:5n-3), and docosahexaenoic acid (C22:6n-3) synthesized via the so-called ω6 Δ8 desaturase and ω3 Δ8 desaturase biosynthetic pathways, respectively. The synthesis of significant quantities of EDA and ETrA in a higher plant is therefore a key step in the production of very long chain polyunsaturated fatty acid in oil-seed species. The results are further discussed in terms of prokaryotic and eukaryotic pathways of lipid synthesis in plants.