Planta

, Volume 217, Issue 3, pp 507–516 | Cite as

Heterologous expression of a fatty acid hydroxylase gene in developing seeds of Arabidopsis thaliana

  • Mark A. Smith
  • Hangsik Moon
  • Gangamma Chowrira
  • Ljerka Kunst
Original Article

Abstract

Expression of a cDNA encoding the castor bean (Ricinus communis L.) oleate Δ12-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 Δ-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 Δ12-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 Δ12-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.

Keywords

Arabidopsis Fatty acid hydroxylase Ricinoleic acid Seed oil 

Abbreviations

DAG

diacylglycerol

ER

endoplasmic reticulum

FAE1

Fatty Acid Elongation 1

FAMES

fatty acid methyl esters

MAG

monoacylglycerol

ODP

Oleate Derivative Proportion

PC

phosphatidylcholine

TAG

triacylglycerol

VLCFA

very long chain fatty acid (C20 and longer)

X:Y

a fatty acid containing X carbons with Y double bonds

Notes

Acknowledgements

The authors acknowledge the financial support of Linnaeus Plant Sciences Inc. and The Science Council of British Columbia.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Mark A. Smith
    • 1
  • Hangsik Moon
    • 2
  • Gangamma Chowrira
    • 1
  • Ljerka Kunst
    • 1
  1. 1.Department of BotanyUniversity of British ColumbiaVancouverCanada
  2. 2.Department of BotanyIowa State UniversityAmesUSA

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