Cell type-Specific Disease Resistance Against Vascular Xanthomonas Plant Pathogens

Plants restrict entry of pathogens through physical barriers, and via Plants restrict the entry of pathogens through physical barriers and an innate immune system that recognizes pathogenic activity and initiates immune responses to halt the infection. As pathogens employ distinct infection strategies to invade plant tissues, immune responses are not uniform but rather specific for different cell and tissue types. This highlights the need to challenge the current concept of plant immunity and expand it towards a tissue-specific perspective. Vascular pathogens belonging to the bacterial genera Xanthomonas and Clavibacter exploit hydathodes –small multicellular organs at the leaf margin, which extrude xylem sap and are directly connected to the vasculature– as entry point into the plant. Currently, we have little understanding of the immune mechanisms in hydathodes. To address this knowledge gap and overcome technical challenges of studying molecular processes in localized and low abundant hydathode tissue, I propose an ambitious and timely project using state-of-the-art approaches: 1) My goal is to identify elicitors, which are perceived by receptors in hydathodes, triggering immunity by using activity-guided screening of pathogen extracts and mass spectrometry. 2) I aim to isolate and characterise hydathode-inhabiting commensal microbes that play a role in plant protection by, amongst others, laser-microdissection of hydathode tissue and (spatial) microbiota profiling. 3) To dissect cell-specific responses towards pathogens and commensals and to identify hydathode-specific immune pathways, recently available single nucleus RNA sequencing combined with live-cell imaging of fluorescent reporters will be applied. Overall, hydathodes are a unique system to study both tissue-specificity of plant immunity and microbiota-mediated protection. Hence, this project will contribute to a comprehensive view of plant immunity and opens a path to novel plant protection strategies.