This project deals with the elucidation of the biological role of natural products in plant-bacteria interactions. Plant-associated bacteria synthesize a vast number of biologically active natural products that modulate the physiology and functioning of their host plants. For example, plant pathogens often cause devastating crop losses by secreting low molecular weightphytotoxins, while some symbiotic bacteria biosynthesize plant-protecting compounds that assist in lowering biotic and abiotic plant stresses. It is therefore surprising that although natural products seem to play key roles in the complex interaction network between bacteria and plants, most of their biological functions and molecular targets are still unknown.To date, almost all studies on plant-bacteria interactions have been performed with biological approaches. Here, we propose to investigate the biological role of plant-associated natural products with the aid of a chemistry-driven approach, relying on the power of chemical synthesis to i) generate these natural products and/or suitable natural product derivatives, ii) to elucidate their targets in plants, and iii) to apply them in plant-bacteria studies. Although natural products have long been in the focus of chemical research, such a systematic chemistry-driven approach has, to our knowledge, never been performed before in plant-bacteria interactions. Our project will therefore not only serve to i) decipher basic research questions and ii) identify potential lead structures for agricultural and medicinal applications, but will also contribute to iii) the refinement of chemical syntheses strategies, iv) the advancement of target finding approaches and v) the establishment of chemical biology approaches in plant biology.