'Filling the gaps' in the Schengen pathway for plant root Casparian strip integrity

ended

Plants have developed sophisticated barriers in various tissues and organs to safeguard integrity. To monitor barrier integrity, plants appear to have evolved similar systems that share signalling modules. The receptor/ligand signalling pathway initiated by SGN3/CIFs establishes the integrity of the Casparian strip (CS), a root diffusion barrier that is essential for controlling nutrient and water homeostasis. The CS starts off as aligned microdomains that eventually fuse to forge a continuous barrier. The SGN pathway is crucial to “find and seal gaps” between the microdomains. However, the mechanism that ensures perfect domain fusion is not well understood. Here, I aim to uncover missing mechanistic details and characterise central unknown elements in a proposed, branched SGN pathway. I intend to identify potential SGN3 co-receptors and additional membrane transducers, and to investigate the elusive role of MAPKs during CS formation. The findings will be crucial to resolve pathway features that the current linear model cannot explain. First, identifying co-receptors is necessary to understand how SGN3 is activated. SGN3 also appears to be involved in embryonic cuticle and pollen coat formation. Therefore, co-receptor identification would clarify whether SGN3 perceives the same or different ligand to govern distinct barrier formation processes. Secondly, identifying additional transducers will provide a molecular basis for understanding two potentially distinct lignification processes regulated by SGN3. This will provide broad insights into how receptors regulate specific sub-functions. Thirdly, MAPK cascades are activated downstream of many receptor/ligand pathways. Elucidating their function in the SGN pathway will give insights into diverse biological processes. Overall, this project will provide a key model to study specificity and localisation of signalling modules, leading towards tissue-specific and inducible barrier engineering in plants.