n-linolenoyl-l-glutamine and jasmonic-acid

The recognition of insect and pathogen attack requires the plant's ability to perceive chemical cues generated by the attacker. In contrast to the recognition of microbe-associated molecular patterns and effectors, little is known about the molecular recognition of herbivore-associated elicitors (HAEs) and the signaling mechanisms operating in plants after their perception. HAE perception depends strongly on the natural history of both plants and insects and it is therefore expected that many of the responses induced by different HAEs are specific to the species involved in the interaction. The interaction between Nicotiana attenuata and the specialist lepidopteran Manduca sexta presents a relevant biological system to understand HAE perception and signal transduction systems in plants.

Topics: alpha-Linolenic Acid; Animals; Cyclopentanes; Feeding Behavior; Gene Expression Regulation, Plant; Genes, Plant; Glutamine; Host-Parasite Interactions; Linolenic Acids; Manduca; Nicotiana; Oxylipins; Plant Leaves; Signal Transduction

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.. 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.. 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.

Topics: Animals; Cyclopentanes; Glutamine; Linolenic Acids; Lipoxygenase; Manduca; Monoterpenes; Nicotiana; Oxylipins; Plant Leaves