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First published online July 14, 2006; 10.1104/pp.106.082115 Plant Physiology 142:28-39 (2006) © 2006 American Society of Plant Biologists Wounding Stimulates the Accumulation of Glycerolipids Containing Oxophytodienoic Acid and Dinor-Oxophytodienoic Acid in Arabidopsis Leaves1,[W]Division of Biology (C.M.B., P.T., A.A.S., E.J.B., S.M., M.R.R., S.W.E., J.S., R.W.) and Department of Biochemistry (J.Z.), Kansas State University, Manhattan, Kansas 66506; and University of Kansas Mass Spectrometry Laboratory, University of Kansas, Lawrence, Kansas 66045 (S.W.E., T.D.W.)
Although oxylipins can be synthesized from free fatty acids, recent evidence suggests that oxylipins are components of plastid-localized polar complex lipids in Arabidopsis (Arabidopsis thaliana). Using a combination of electrospray ionization (ESI) collisionally induced dissociation time-of-flight mass spectrometry (MS) to identify acyl chains, ESI triple-quadrupole (Q) MS in the precursor mode to identify the nominal masses of complex polar lipids containing each acyl chain, and ESI Q-time-of-flight MS to confirm the identifications of the complex polar lipid species, 17 species of oxylipin-containing phosphatidylglycerols, monogalactosyldiacylglycerols (MGDG), and digalactosyldiacylglycerols (DGDG) were identified. The oxylipins of these polar complex lipid species include oxophytodienoic acid (OPDA), dinor-OPDA (dnOPDA), 18-carbon ketol acids, and 16-carbon ketol acids. Using ESI triple-Q MS in the precursor mode, the accumulation of five OPDA- and/or dnOPDA-containing MGDG and two OPDA-containing DGDG species were monitored as a function of time in mechanically wounded leaves. In unwounded leaves, the levels of these oxylipin-containing complex lipid species were low, between 0.001 and 0.023 nmol/mg dry weight. However, within the first 15 min after wounding, the levels of OPDA-dnOPDA MGDG, OPDA-OPDA MGDG, and OPDA-OPDA DGDG, each containing two oxylipin chains, increased 200- to 1,000-fold. In contrast, levels of OPDA-hexadecatrienoic acid MGDG, linolenic acid (18:3)-dnOPDA MGDG, OPDA-18:3 MGDG, and OPDA-18:3 DGDG, each containing a single oxylipin chain, rose 2- to 9-fold. The rapid accumulation of high levels of galactolipid species containing OPDA-OPDA and OPDA-dnOPDA in wounded leaves is consistent with these lipids being the primary products of plastidic oxylipin biosynthesis.
1 This work was supported by grants from the National Science Foundation (grant nos. MCB 0455318 and DBI 0520140). Support of the Kansas Lipidomics Research Center was from the National Science Foundation's EPSCoR program (grant no. EPS–0236913) with matching support from the State of Kansas through Kansas Technology Enterprise Corporation and Kansas State University, as well as from Core Facility Support from the National Institutes of Health (grant no. P20 RR016475) from the INBRE program of the National Center for Research Resources. Accurate mass analysis was performed at the University of Kansas Mass Spectrometry Laboratory, using a Micromass Q-TOF2, which was purchased with funds from the University of Kansas, the University of Kansas Mass Spectrometry Laboratory, and Kansas National Science Foundation EPSCoR. This is contribution 06–180–J from the Kansas Agricultural Experiment Station. 2 Present address: The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390. 3 Present address: Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Ruth Welti (welti@ksu.edu). [W] The online version of this article contains Web-only data. www.plantphysiol.org/cgi/doi/10.1104/pp.106.082115 * Corresponding author; e-mail welti{at}ksu.edu; fax 785–532–6653. Received April 13, 2006; accepted June 30, 2006. This article has been cited by other articles:
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