Dimorphecolic Acid Is Synthesized by the Coordinate Activities of Two Divergent Δ12-Oleic Acid Desaturases

Edgar B. Cahoon, Anthony J. Kinney

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Dimorphecolic acid (9-OH-18:2Δ10trans,12trans) is the major fatty acid of seeds of Dimorphotheca species. This fatty acid contains structural features that are not typically in plant fatty acids, including a C-9 hydroxyl group, Δ1012-conjugated double bonds, and trans-Δ12 unsaturation. Expressed sequence tag analysis was conducted to determine the biosynthetic origin of dimorphecolic acid. cDNAs for two divergent forms of Δ12-oleic acid desaturase, designated DsFAD2-1 and DsFAD2-2, were identified among expressed sequence tags generated from developing Dimorphotheca sinuata seeds. Expression of DsFAD2-1 in Saccharomyces cerevisiae and soybean somatic embryos resulted in the accumulation of the trans-Δ12 isomer of linoleic acid (18: 2Δ 9cis,12trans) rather than the more typical cis-Δ12 isomer. When co-expressed with DsFAD2-1 in soybean embryos or yeast, DsFAD2-2 converted 18:2Δ9cis,12trans into dimorphecolic acid. When DsFAD2-2 was expressed alone in soybean embryos or together with a typical cis-Δ12-oleic acid desaturase in yeast, trace amounts of the cis-Δ12 isomer of dimorphecolic acid (9-OH-18:2Δ 9cis,12cis) were formed from DsFAD2-2 activity with cis-Δ 12-linoleic acid. These results indicate that DsFAD2-2 catalyzes the conversion of the Δ9 double bond of linoleic acid into a C-9 hydroxyl group and Δ10trans double bond and displays a substrate preference for the trans-Δ12, rather than the cis-Δ12, isomer of linoleic acid. Overall these data are consistent with a biosynthetic pathway of dimorphecolic acid involving the concerted activities of DsFAD2-1 and DsFAD2-2. The evolution of two divergent Δ12-oleic acid desaturases for the biosynthesis of an unusual fatty acid is unprecedented in plants.

Original languageEnglish (US)
Pages (from-to)12495-12502
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number13
DOIs
StatePublished - Mar 26 2004

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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