Mechanisms of Feronia-dependent growth control

Plant growth is highly sensitive to environmental stresses, which threatens crop yield. To obtain basic understanding of plant growth, we aim to unravel plant specific mechanisms, controlling growth at cellular and subcellular scale. Plant cells are surrounded by a rigid extracellular matrix, which is called the cell wall. The sensing of the extracellular space provides a feedback on intracellular processes and is crucial for the coordination of cellular expansion. Despite its fundamental importance, very little is currently known about these integrative mechanisms in plants. The vacuole is the largest plant organelle and it increases its cellular occupancy during cellular expansion. This space filling function of the vacuole allows fast plant cell elongation with relatively little increase in the intracellular fluid (cytosol). We showed that interference with cell wall sensing impacts on intracellular expansion of the vacuole. Our work reveals that the extracellular cell wall binding proteins of the Leucine-Rich Repeat Extensin (LRX) family interact with the receptor like kinase Feronia (FER), which is crucial to repress vacuolar expansion. Here we investigate the mechanistic interaction of LRX and Feronia as well as its importance for integrating growth relevant processes. To approach how the external signals are translated into an internal growth controlling signal, we will initially investigate already known components of FER signalling and their potential impact on vacuolar expansion. Finally, we aim to characterise novel, putative interactors of FER, presumably linking FER signaling with intracellular growth process, such as the regulation of vacuolar size. Our work will provide fundamental insight into FER-dependent growth integration and may reveal mechanisms that will allow us to engineer plant growth responses in a tissue specific manner.

Plant growth is a complex process that involves the loosening of rigid cell walls and the expansion of vacuoles, large internal compartments that occupy most of a mature cell. This project, funded by the Austrian Science Fund (FWF), investigated how mechanical and chemical cues in the cell wall are perceived and relayed to control vacuole size and, consequently, cell expansion. Our research focused on the receptor-like kinase FERONIA and its partners, leucine-rich repeat extensins (LRXs), which together sense cell wall stiffness and influence both growth and immunity. Through our studies, we demonstrated that endocytic trafficking-the recycling of membrane from the cell surface to the vacuole-is essential for rapid vacuole enlargement. Blocking this membrane flow results in smaller vacuoles and slower growth, underscoring the critical role of endocytic trafficking in plant cell expansion. Additionally, we revealed that the chemistry of pectin, a component of the cell wall, determines how the peptide hormone RALF1 binds to the wall and triggers FERONIA-dependent growth inhibition. This finding highlights the intricate interplay between cell wall chemistry and signaling pathways that regulate plant growth. Together, these findings highlight that membrane recycling, wall chemistry, and protein turnover are tightly integrated processes that collectively control plant growth. Our research contributes to a deeper understanding of the molecular mechanisms underlying plant cell expansion and offers new avenues for manipulating plant growth and development.