title: Two Defensive Lines in Juvenile Leaf Beetles; Esters of 3-nitropropionic Acid in the Hemolymph and Aposematic Warning.
abstract: Juveniles of the leaf beetles in subtribe Chrysomelina have efficient defense strategies against predators. When disturbed, they transiently expose volatile deterrents in large droplets from nine pairs of defensive glands on their back. Here, we report on an additional line of defense consisting of the non-volatile isoxazolin-5-one glucoside and its 3-nitropropanoyl ester in the larval hemolymph. Because isoxazolin-5-one derivatives were not detectable in related leaf beetle taxa, they serve as a diagnostic marker for the Chrysomelina subtribe. Conjugation of isotopically labelled 3-nitropropionic acid to isoxazolin-5-one glucoside in vivo demonstrates its function as a carrier for the 3-nitropropanoyl esters. The previous identification of characteristic glucosides as precursors of the volatile deterrents underlines the general importance of glucosides for sequestration from food plants, and the subsequent transport in the hemolymph to the defense system. The combination of repellent volatiles with non-volatile toxic compounds in the hemolymph has the potential to create synergistic effects since the odorant stimulus may help predators learn to avoid some foods. The combination of the two defense lines has the advantage, that the hemolymph toxins provide reliable and durable protection, while the repellents may vary after a host plant change.
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Pauls
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Becker
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Rahfeld
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Rene R
authors.initials: RR
authors.lastname: Gretscher
authors.affiliation: Biosynthesis and Nuclear Magnetic Resonance Group, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Paetz
authors.affiliation: Department of Biology, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Jacques
authors.initials: J
authors.lastname: Pasteels
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Stephan H
authors.initials: SH
authors.lastname: von Reuss
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Burse
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany. boland@ice.mpg.de.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Boland
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000378:metabolism / Q000502:physiology*; D004952:Esters; D006458:Hemolymph / Q000378:metabolism*; D009574:Nitro Compounds / Q000378:metabolism*; D010802:Phylogeny; D011235:Predatory Behavior; D011422:Propionates / Q000378:metabolism*
chemical_list: D004952:Esters; D009574:Nitro Compounds; D011422:Propionates; C015392:3-nitropropionic acid
keywords: 3-nitropropionate esters; Aposematic warning; Chemical defense; Chrysomelidae; Isoxazolin-5-one glucoside