Pyrrolizidine alkaloid variation in Jacobaea plants : from plant organ to cell level

Abstract

The aim of this thesis is to understand the diversity of pyrrolizidine alkaloids (PAs) in Jacobaea plants with respect to their spatial distribution and its consequences for generalist insects. Chapter 2 reports on the role of endophytes in the production of PAs in Jacobaea. Plants were treated with different systemic fungicides to eliminate endophytic fungi and the effect on PA concentration and composition was determined. Chapter 3, 4 and 5 deal with the variation of PA distribution at organ, tissue and cell levels. Chapter 3 describes the capacity of different plant organs to produce PAs, using different types of in-vitro organ cultures including roots, shoots and complete plants. Chapter 4 reports on the metabolomics of different leaf tissues, focusing on differences of PA distribution between epidermis and mesophyll. Chapter 5 deals with a metabolomic study on the different cell types of Jacobaea leaves resi stant to thrips. Laser micro dissection coupled with NMR was used in this study. Chapter 6 describes structure activity relationships for the effect of different PAs on S. exigua larvae and cell cultures. The results on the variation of PA distribution in Jacobaea plants and their consequence to generalist insects are summarised and discussed in Chapter 7