Tissue-specific interactions between Xanthomonas campestris pv. campestris and its host plant

The work in this thesis focused on the interaction between the bacterial plant pathogen Xanthomonas campestris pv. campestris (Xcc) and the host plant Arabidopsis thaliana. As this pathogen displays an intricate infection process with multiple distinct phases, efforts were made to identify plant resistance mechanisms in the early phase of infection when the bacteria enter the plant hydathodes, which are organs involved in water homeostasis that are located at the leaf margins. An intracellular immune receptor was identified that confers resistance against Xcc early in hydathodes, but not in later stages of infection. To track progression of the bacteria through the plant, bioluminescence was applied to genetically modify the bacteria to emit light. Next, a high-throughput imaging method was developed to follow infection events Arabidopsis rosettes non-invasively over time. This method yielded insights in the infection process and allowed for phenotypic screening of large plant populations. Finally, a bacterial virulence factor was identified that contributed to the vascular phase of the bacteria, when they colonize the plant xylem vessels and spread systemically through the plant. Taken together, the findings in this thesis yielded insights on the tissue-specific interactions between Xcc and its host plant.