Sequestration of plant derived metabolites by leaf beetle larvae: phylogeny and mechanism of glucoside carrier
ANTJE BURSE
Abt. Bioorganische Chemie
Max-Planck-Institut für Chemische Ökologie
Hans-Knoell-Str.8
07745 Jena
aburse@ice.mpg.de
http://www.ice.mpg.de
Larvae of leaf beetles use an extensive variety of toxic compounds to repulse predators. The compounds can be synthesized either by the larvae autogenously or they can come from precursors which are sequestered from the host plant. Larvae of the subtribe Chrysomelina sequester only glucosidic bound plant secondary metabolites. These compounds are transferred from the gut lumen into dorsal defensive glands where they are converted into the active substances. Our recent experiments provided strong evidence that transport proteins mediate the uptake of these polar compounds into the larvae. The objective of the present project is to investigate which influence the transport proteins have on the evolution of the diversity of defensive compounds found within the larvae of the subtribe Chrysomelina. The transport systems are adapted to the secondary metabolites of the host plant and following enzymatic reactions in the defensive glands have to be optimized for the incorporated compounds. Host plant changes in the course of Chrysomelina evolution resulted in the uptake of different metabolites and thus, in changes in the defensive compound pattern because of a changed substrate specificity of the enzymes. In the course of the DFG project we plan the isolation and characterization of transport systems which mediate the uptake of plant derived glucosides from the gut lumen into the defensive glands. Phylogenetic analyses of transporter sequences obtained from Chrysomelina species can give information about the co-evolution of leaf beetles and host plants and thus, the evolution of the metabolic diversity of the defensive compounds.
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