As a contribution to the changing legislation and evolving societal attitudes concerning environmental issues, this project aims to enhance and manipulate the plants’ own natural defense mechanisms... Show moreAs a contribution to the changing legislation and evolving societal attitudes concerning environmental issues, this project aims to enhance and manipulate the plants’ own natural defense mechanisms against western flower thrips (WFT). Accordingly, an approach based on treatments of seeds (Solanum lycopersicum) and cuttings (Chrysanthemum morifolium) was undertaken to protect plants from their early critical young stage onwards. Known putative defense secondary metabolites were exogenously applied whereas, external application of plant hormones was explored as a means to trigger innate defense responses. Natural Deep Eutectic Solvents (NADES), as environmentally benign solvents, significantly improved the solubilizing properties of poorly-soluble insecticidal metabolites but did not enhance resistance against WFT. On the contrary, seed treatments with the ubiquitous plant hormone jasmonic acid (JA) appeared to induce cultivar dependent defenses as it only reduced silver damage in tomato cultivar Carousel. Sulfuric acid scarification, prior to JA seed incubation, significantly augmented the embryonic receptivity of a non-responsive cultivar thus, highlighting the importance of seed coat permeability. Moreover, we demonstrate that water dipping of indole-3-butyric acid (IBA)-coated chrysanthemum cuttings repeatedly reduced herbivory, both by thrips as well as by leaf miner. Show less
Plants produce an astonishing variety of secondary metabolites (SMs) which are thought to play vital roles in the fitness of plants through ecological interactions. The most characteristic features... Show morePlants produce an astonishing variety of secondary metabolites (SMs) which are thought to play vital roles in the fitness of plants through ecological interactions. The most characteristic features of SMs are their striking chemical diversity and inter- or intraspecific variation. Due to the large number, high structural diversity and multifunctionality of SMs, it is still an ongoing challenge to understand how this SM diversity comes about, and why such a large diversity is maintained in nature. In this thesis this question was studied using the pyrrolizidine alkaloids (PAs) of Jacobaea species as the study system from an evolutionary and biosynthetic perspective. PA variations were studied among and within Jacobaea species, and species-specific PA profiles were observed. In order to understand how PA diversity is related to species phylogeny, the evolutionary histories and phylogenetic signals of individual PAs were investigated under the phylogenetic context of Jacobaea species and no strong phylogenetic signals were found. To shed light on the mechanisms underlying PA diversity, a gene-to-metabolite approach targeting cytochrome P450 monooxygenases which play an important role in the evolution of chemical diversity was applied to study their involvement in PA biosynthesis and PA diversity. Show less
Cheng, D.; Mulder, P.P.J.; Meijden, E. van der; Klinkhamer, P.G.L.; Vrieling, K. 2017
