A Novel Class of Oxylipins,sn1-O-(12-Oxophytodienoyl)-sn2-O-(hexadecatrienoyl)-monogalactosyl Diglyceride, from Arabidopsis thaliana

• Published in: The Journal of biological chemistry 2001-04, Vol.276 (16), p.12832-12838
• Main Authors: Stelmach, Boguslawa A., Müller, Axel, Hennig, Peter, Gebhardt, Steffen, Schubert-Zsilavecz, Manfred, Weiler, Elmar W.
• Format: Article
• Language: English
• Subjects: Arabidopsis - chemistry; Arabidopsis - physiology; Diglycerides - chemistry; Diglycerides - isolation & purification; Diglycerides - metabolism; Galactolipids; Gas Chromatography-Mass Spectrometry; Glycolipids - chemistry; Glycolipids - isolation & purification; Glycolipids - metabolism; Intramolecular Oxidoreductases - metabolism; Kinetics; Lipase - metabolism; Lipoxygenase - metabolism; Magnetic Resonance Spectroscopy; Molecular Conformation; Molecular Structure; Plant Leaves - metabolism; Plastids - chemistry; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M010743200

The cyclic derivative of 13( S )-hydroperoxolinolenic acid, 12-oxophytodienoic acid, serves as a signal transducer in higher plants, mediating mechanotransductory processes and plant defenses against a variety of pathogens, and also serves as a precursor for the biosynthesis of jasmonic acid, a mediator of plant herbivore defense. Biosynthesis of 12-oxophytodienoic acid from α-linolenic acid occurs in plastids, mainly in chloroplasts, and is thought to start with free linolenic acid liberated from membrane lipids by lipase action. In Arabidopsis thaliana , the glycerolipid fraction contains esterified 12-oxophytodienoic acid, which can be released enzymatically by sn 1-specific, but not by sn 2-specific, lipases. The 12-oxophytodienoyl glycerolipid fraction was isolated, purified, and characterized. Enzymatic, mass spectrometric, and NMR spectroscopic data allowed us to establish the structure of the novel oxylipin as sn 1- O -(12-oxophytodienoyl)- sn 2- O -(hexadecatrienoyl)-monogalactosyl diglyceride. The novel class of lipids is localized in plastids. Purified monogalactosyl diglyceride was not converted to the sn 1-(12-oxophytodienoyl) derivative by the combined action of (soybean) lipoxygenase and ( A. thaliana ) allene oxide synthase, an enzyme ensemble that converts free α-linolenic acid to free 12-oxophytodienoic acid. When leaves were wounded, a significant and transient increase in the level of (12-oxophytodienoyl)-monogalactosyl diglyceride was observed. In A. thaliana , the major fraction of 12-oxophytodienoic acid occurs esterified at the sn1 position of the plastid-specific glycerolipid, monogalactosyl diglyceride.