JXB Advance Access originally published online on March 6, 2008
Journal of Experimental Botany 2008 59(4):907-915; doi:10.1093/jxb/ern010
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© 2008 The Author(s).
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RESEARCH PAPER |
Divinyl ether synthesis in garlic bulbs*

Georg-August-University Göttingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, D-37077 Göttingen, Germany
To whom correspondence should be addressed. E-mail: ifeussn{at}uni-goettingen.de
Formation of 13-lipoxygenase-derived divinyl ethers has been described in garlic bulbs. Here, the identification of a cDNA from garlic is described, which encodes for an enzyme that corresponds to divinyl ether synthases (DES). The recombinant protein was expressed in Escherichia coli and shown to metabolize 13-hydroperoxy as well as 9-hydroperoxy linole(n)ic acid to etherole(n)ic and colnele(n)ic acid, respectively. This biochemical feature classifies it as a member of the CYP74C subfamily of cytochrome P-450 enzymes. Product analysis after incubation of purified recombinant enzyme and fatty acid hydroperoxides revealed the formation of a mixture of different cis/trans isomers with one isomer often dominant. RNA blot analyses showed a constitutive expression of DES transcripts predominant in below-ground organs of garlic. By exogenous application of salicylic acid and sorbitol, but not by methyljasmonate, the transcript was also induced in leaves. Whereas the prominent divinyl ether in garlic was the 13-lipoxygenase-derived etheroleic acid, analysis of transgenic Arabidopsis expressing garlic DES showed that 9-lipoxygenase-derived colnelenic acid dominated 24 h after wounding. These data indicate that the product pattern of this DES from garlic depends on the substrate availability and that the enzyme is the first member in the group of 9/13-DES.
Key words: Allium sativum, cytochrome P-450, oxylipin metabolism, product specificity, substrate specificity
* The nucleotide sequence reported in this paper has been submitted to the GenBank/EMBL data bank with accession number AJ867809.
Received 30 November 2007; Revised 4 January 2008 Accepted 7 January 2008