title: Expression of the Isochrysis C18-delta9 polyunsaturated fatty acid specific elongase component alters Arabidopsis glycerolipid profiles.
abstract: 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 alpha-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 omega6 Delta8 desaturase and omega3 Delta8 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.
authors.affiliation: School of Biological Sciences, University of Bristol, Bristol BS8 1UG, United Kingdom. t.c.m.fraser@bristol.ac.uk
authors.forename: Thomas Colin Michael
authors.initials: TC
authors.lastname: Fraser
authors.forename: Baoxiu
authors.initials: B
authors.lastname: Qi
authors.forename: Salah
authors.initials: S
authors.lastname: Elhussein
authors.forename: Sunantha
authors.initials: S
authors.lastname: Chatrattanakunchai
authors.forename: Allan Keith
authors.initials: AK
authors.lastname: Stobart
authors.forename: Colin Michael
authors.initials: CM
authors.lastname: Lazarus
mesh_terms: D000123:Acetyltransferases / Q000235:genetics* / Q000378:metabolism; D020418:Algal Proteins / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D056890:Eukaryota / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*; D044943:Fatty Acid Desaturases / Q000378:metabolism; D000081031:Fatty Acid Elongases; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis* / Q000737:chemistry; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006017:Glycolipids / Q000096:biosynthesis* / Q000737:chemistry; D019787:Linoleic Acid / Q000096:biosynthesis / Q000737:chemistry; D008563:Membrane Lipids / Q000502:physiology; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism; D030821:Plants, Genetically Modified; D012639:Seeds / Q000737:chemistry / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017962:alpha-Linolenic Acid / Q000096:biosynthesis / Q000737:chemistry
chemical_list: D020418:Algal Proteins; D018076:DNA, Complementary; D005231:Fatty Acids, Unsaturated; D006017:Glycolipids; D008563:Membrane Lipids; D017962:alpha-Linolenic Acid; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases