Dr. Roy Kirsch

   Department of Insect Symbiosis
   Molecular Biology of the Insect Digestive System
 Phone:+49 (0)3641 57 1562Max Planck Institute for Chemical Ecology
 Fax:+49 (0)3641 57 1202Hans-Knöll-Straße 8
  emailD-07745 Jena

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PhD Thesis

Identification and characterization of defense related enzymes in Chrysomelina larvae (Coleoptera:Chrysomelidae): contributions to understand the evolutionary and molecular dynamics of chemical defense in leaf beetles
Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät
First Supervisor: Prof. Dr. W. Boland
Co-Supervisor(s): Prof. Dr. G. Theißen (Institute of Genetics, FSU)
Retrieved from Thesis (hosted by dbt)

Leaf beetles of the subfamily Chrysomelinae defend themselves against predators by the use of glandular secretions. In the larval stages these are basically synthesized and stored in ectodermal glands. Although a variety of defensive compounds have been identified, little is known about the enzymes involved in their biosynthesis. This study focuses on the enzymatic equipment of defensive glands of larval Chrysomela lapponica. This species uses host plant derived and endogenous metabolites as precursors for secretion synthesis. As most defensive compounds are esters acyltransferases seem to be very interesting under different aspects. Biochemical characterization will gain insights in enzymatic mechanisms and reasons of its high substrate tolerance, causes the production of more than 60 different esters. As there are some other leaf beetles producing similar defensive compounds the question rises up whether they use a homologous enzyme. Phylogenetic studies with sequences of orthologous genes encoding for these enzymes isolated from different species shall prove already existing analyses. The elucidation of precursor activation by a glucose moiety gave us a clue of the protein family from which the acyltransferase was maybe recruited for their current function. In plants enzymes catalyzing acyltransfer of a glucose activated acid are known to belong to serine-carboxypeptidase like proteins (SCPL). By database search and alignment of SCPLs well conserved regions were determined. Adapted from this a fragment out of a glandular cDNA pool was amplified, which shows sequence similarity to SCPLs. Enzyme assasy of the secretion in combination with serine protease inhibitor also argues for this candidate. We try to isolate and sequence the proteins out of the secretion directly by SDS-GE. This will be a test whether the candidate gene product is present in the secretion.