Uptake and metabolism of pyrrolizidine alkaloids in<Emphasis Type="Italic"> Longitarsus</Emphasis> flea beetles (Coleoptera: Chrysomelidae) adapted and non-adapted to alkaloid-containing host plants |
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Authors: | Email author" target="_blank">I?NarberhausEmail author C?Theuring T?Hartmann S?Dobler |
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Institution: | (1) Zoologisches Institut und Museum, Universität Hamburg, Martin-Luther-King Platz 3, 20146 Hamburg, Germany;(2) Institut für Pharmazeutische Biologie, Technische Universität Braunschweig, Mendelssohnstrasse 1, 38106 Braunschweig, Germany |
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Abstract: | Several Longitarsus flea beetle species sequester pyrrolizidine alkaloids acquired from their Asteraceae and Boraginaceae host plants. We carried out feeding and injection experiments using radioactively labeled pyrrolizidine alkaloids to investigate the physiological mechanisms of uptake, metabolism and storage of alkaloids in adult beetles. We examined six Longitarsus species belonging to different phylogenetic clades in a comparative approach. All species that accepted pyrrolizidine alkaloids in a preceding food choice study showed the ability both to store pyrrolizidine alkaloid N-oxides and to metabolize tertiary pyrrolizidine alkaloids into their N-oxides. Regardless of whether the beetles' natural host plants contain pyrrolizidine alkaloids or not, these species were found to possess an oxidizing enzyme. This oxygenase appears to be specific to pyrrolizidine alkaloids: 3H]Atropine and 14C]nicotine, two alkaloids not related to pyrrolizidine alkaloids, were neither stored nor N-oxidized by any of the tested species. One species, L. australis, that strictly avoids pyrrolizidine alkaloids behaviorally, exhibited a lack of adaptations to pyrrolizidine alkaloids on a physiological level as well. After injection of tertiary 14C]senecionine, beetles of this species neither N-oxidized nor stored the compounds, in contrast to L. jacobaeae, an adapted species that underwent the same treatment. L. jacobaeae demonstrated the same efficiency in N-oxidation and storage when fed or injected with tertiary 14C]senecionine.Communicated by G. Heldmaier |
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Keywords: | Chemical defense Chrysomelidae Longitarsus Pyrrolizidine alkaloids Sequestration |
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