volicitin and indole

The indole-3-glycerol phosphate lyase Igl is the structural gene of volatile indole biosynthesis in the tritrophic interaction in maize. The gene is activated on transcriptional level with the same kinetics and to the same level by the fatty acid-amino acid conjugates (FAC's) volicitin (17S)-(N-(17-hydroxylinolenoyl)-L-glutamine) and N-linolenoyl-L-glutamine. Both conjugates are present in the regurgitates of herbivorous caterpillars. Modifications of the fatty acid moiety of the FACs greatly reduces the elicitation of Igl and only the L-stereo-isomer of the FACs shows biological activity in the system. Volicitin treatment leads to a fast increase of AOS and AOC transcription levels and methyl jasmonate application induces Igl transcription. Hence, the induction of jasmonate biosynthesis appears to be an integral part of the elicitor mediated increase of Igl gene transcription.

Topics: Acetates; alpha-Linolenic Acid; Amino Acids, Cyclic; Animals; Aristolochic Acids; Aspirin; Cyclooxygenase Inhibitors; Cyclopentanes; Genes, Plant; Glutamine; Indole-3-Glycerol-Phosphate Synthase; Indoles; Intramolecular Oxidoreductases; Lepidoptera; Linolenic Acids; Oxylipins; Pyrazoles; Stereoisomerism; Structure-Activity Relationship; Transcriptional Activation; Zea mays

Maize and a variety of other plant species release volatile compounds in response to herbivore attack that serve as chemical cues to signal natural enemies of the feeding herbivore. N-(17-hydroxylinolenoyl)-l-glutamine is an elicitor component that has been isolated and chemically characterized from the regurgitant of the herbivore-pest beet armyworm. This fatty acid derivative, referred to as volicitin, triggers the synthesis and release of volatile components, including terpenoids and indole in maize. Here we report on a previously unidentified enzyme, indole-3-glycerol phosphate lyase (IGL), that catalyzes the formation of free indole and is selectively activated by volicitin. IGL's enzymatic properties are similar to BX1, a maize enzyme that serves as the entry point to the secondary defense metabolites DIBOA and DIMBOA. Gene-sequence analysis indicates that Igl and Bx1 are evolutionarily related to the tryptophan synthase alpha subunit.

Topics: alpha-Linolenic Acid; Animals; Base Sequence; DNA, Plant; Fatty Acids; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant; Glutamine; Glycerophosphates; Indole-3-Glycerol-Phosphate Synthase; Indoles; Molecular Sequence Data; Recombinant Fusion Proteins; RNA, Messenger; Spodoptera; Transcriptional Activation; Zea mays