| Title: | Rapid modification of the insect elicitor N-linolenoyl-glutamate via a lipoxygenase-mediated mechanism on Nicotiana attenuata leaves |
| Author(s): | VanDoorn A; Kallenbach M; Borquez AA; Baldwin IT; Bonaventure G; |
| Address: | "Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knoll Strasse 8, D-07745 Jena, Germany" |
| ISSN/ISBN: | 1471-2229 (Electronic) 1471-2229 (Linking) |
| Abstract: | "BACKGROUND: Some plants distinguish mechanical wounding from herbivore attack by recognizing specific constituents of larval oral secretions (OS) which are introduced into plant wounds during feeding. Fatty acid-amino acid conjugates (FACs) are major constituents of Manduca sexta OS and strong elicitors of herbivore-induced defense responses in Nicotiana attenuata plants. RESULTS: The metabolism of one of the major FACs in M. sexta OS, N-linolenoyl-glutamic acid (18:3-Glu), was analyzed on N. attenuata wounded leaf surfaces. Between 50 to 70% of the 18:3-Glu in the OS or of synthetic 18:3-Glu were metabolized within 30 seconds of application to leaf wounds. This heat-labile process did not result in free alpha-linolenic acid (18:3) and glutamate but in the biogenesis of metabolites both more and less polar than 18:3-Glu. Identification of the major modified forms of this FAC showed that they corresponded to 13-hydroxy-18:3-Glu, 13-hydroperoxy-18:3-Glu and 13-oxo-13:2-Glu. The formation of these metabolites occurred on the wounded leaf surface and it was dependent on lipoxygenase (LOX) activity; plants silenced in the expression of NaLOX2 and NaLOX3 genes showed more than 50% reduced rates of 18:3-Glu conversion and accumulated smaller amounts of the oxygenated derivatives compared to wild-type plants. Similar to 18:3-Glu, 13-oxo-13:2-Glu activated the enhanced accumulation of jasmonic acid (JA) in N. attenuata leaves whereas 13-hydroxy-18:3-Glu did not. Moreover, compared to 18:3-Glu elicitation, 13-oxo-13:2-Glu induced the differential emission of two monoterpene volatiles (beta-pinene and an unidentified monoterpene) in irlox2 plants. CONCLUSIONS: The metabolism of one of the major elicitors of herbivore-specific responses in N. attenuata plants, 18:3-Glu, results in the formation of oxidized forms of this FAC by a LOX-dependent mechanism. One of these derivatives, 13-oxo-13:2-Glu, is an active elicitor of JA biosynthesis and differential monoterpene emission" |
| Keywords: | Animals Cyclopentanes/metabolism Glutamine/*analogs & derivatives/metabolism Linolenic Acids/*metabolism Lipoxygenase/genetics/*metabolism Manduca/*physiology Monoterpenes/analysis Oxylipins/metabolism Plant Leaves/chemistry/*enzymology Tobacco/*enzymolog; |
| Notes: | "MedlineVanDoorn, Arjen Kallenbach, Mario Borquez, Alejandro A Baldwin, Ian T Bonaventure, Gustavo eng Research Support, Non-U.S. Gov't England 2010/08/11 BMC Plant Biol. 2010 Aug 9; 10:164. doi: 10.1186/1471-2229-10-164" |
