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Selective sequestration and metabolism of plant derived pyrrolizidine alkaloids by chrysomelid leaf beetles
Auteur(s)
Hartmann, Thomas
Witte, Ludger
Ehmke, Adelheid
Theuring, Claudine
Pasteels, Jacques M.
Date de parution
1997
In
Phytochemistry, Elsevier, 1997/45/3/489-497
Mots-clés
Résumé
Pyrrolizidine alkaloids (PAs) are assumed to function as plant defence compounds against herbivory. A number of adapted insects are known to sequester plant derived PAs for their own benefit. Here we summarize the chemical interactions between leaf beetles of the genus <i>Oreina</i> (Coleoptera, Chrysomelidae) and their host plants <i>Adenostyles</i> spp., <i>Senecio nemorensis</i>, and <i>S. fuchsii</i> (Asteraceae, tribe Senecioneae). Seneciphylline <i>N</i>-oxide and senecionine <i>N</i>-oxide, the main PAs of <i>Adenostyles</i>, are sequestered in the bodies and exocrine defensive glands of the leaf beetles. The comparison with the PA patterns of the <i>Senecio</i> host plant indicates a selective PA uptake. The uptake into the body (hemolymph) is less specific, whereas the translocation into the defensive glands is highly specific. Only the <i>N</i>-oxides of macrocyclic retronecine esters of the senecionine type are found in significant amounts in the defensive secretions. Many other PAs such as monoesters and open-chain diesters as well as PAs of other structural types (e.g. monocrotaline <i>N</i>-oxide and senkirkine) are not transferred into the defensive glands. Leaf beetles sequester PAs exclusively as <i>N</i>-oxides. A novel PA not found in the food plants was detected in the defensive secretions of Oreina elongata; it was identified as 13,19-expoxisenecionine <i>N</i>-oxide (oreine), the epoxidation product of seneciphylline <i>N</i>-oxide. Besides this transformation, leaf beetles are able to catalyse further transformations such as the O-dealkylation of heliotrine <i>N</i>-oxide to rinderine <i>N</i>-oxide and the O-deacetylation of acetylseneciphylline <i>N</i>-oxide to seneciphylline <i>N</i>-oxide. The plant-beetle interactions are discussed in the functional context of PAs as powerful plant defensive chemicals.
Identifiants
Type de publication
journal article
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