title: Heterologous expression of a fatty acid hydroxylase gene in developing seeds of Arabidopsis thaliana.
abstract: Expression of a cDNA encoding the castor bean ( Ricinus communis L.) oleate Delta12-hydroxylase in the developing seeds of Arabidopsis thaliana (L.) Heynh. results in the synthesis of four novel hydroxy fatty acids. These have been previously identified as ricinoleic acid (12-hydroxy-octadec- cis-9-enoic acid: 18:1-OH), densipolic acid (12-hydroxy-octadec- cis-9,15-enoic acid: 18:2-OH), lesquerolic acid (14-hydroxy-eicos- cis-11-enoic acid: 20:1-OH) and auricolic acid (14-hydroxy-eicos- cis-11,17-enoic acid: 20:2-OH). Using mutant lines of Arabidopsis that lack the activity of the FAE1 condensing enzyme or FAD3 ER Delta-15-desaturase, we have shown that these enzymes are required for the synthesis of C20 hydroxy fatty acids and polyunsaturated hydroxy fatty acids, respectively. Analysis of the seed fatty acid composition of transformed plants demonstrated a dramatic increase in oleic acid (18:1) levels and a decrease in linoleic acid (18:2) content correlating to the levels of hydroxy fatty acid present in the seed. Plants in which FAD2 (ER Delta12-desaturase) activity was absent showed a decrease in 18:1 content and a slight increase in 18:2 levels corresponding to hydroxy fatty acid content. Expression of the castor hydroxylase protein in yeast indicates that this enzyme has a low level of fatty acid Delta12-desaturase activity. Lipase catalysed 1,3-specific lipolysis of triacylglycerol from transformed plants demonstrated that ricinoleic acid is not excluded from the sn-2 position of triacylglycerol, but is the only hydroxy fatty acid present at this position.
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, Canada. msmith@mail.botany.ubc.ca
authors.forename: Mark A
authors.initials: MA
authors.lastname: Smith
authors.forename: Hangsik
authors.initials: H
authors.lastname: Moon
authors.forename: Gangamma
authors.initials: G
authors.lastname: Chowrira
authors.forename: Ljerka
authors.initials: L
authors.lastname: Kunst
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism; D000081031:Fatty Acid Elongases; D005227:Fatty Acids / Q000096:biosynthesis*; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D019787:Linoleic Acid / Q000096:biosynthesis; D009154:Mutation; D019301:Oleic Acid / Q000096:biosynthesis; D012277:Ricinoleic Acids / Q000378:metabolism; D012639:Seeds / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D014280:Triglycerides / Q000096:biosynthesis
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D012277:Ricinoleic Acids; D014280:Triglycerides; D019301:Oleic Acid; C105775:lesquerolic acid; C105774:densipolic acid; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases; C030521:ricinoleic acid