EDGE-CAM · Edge-based mechanisms coordinating cell wall assembly during plant morphogenesis

A fundamental question in biology is how multicellular organisms robustly produce organ shapes. The underlying process of morphogenesis involves the integration of biochemical, genetic, and mechanical factors across multiple spatio-temporal scales. In plants, morphogenesis is dominated by the rigid cell wall, which fixes cells in their position. Adjacent cells must therefore coordinate their growth patterns, which are in turn controlled by the mechanical properties of the cell wall. Cell walls are assembled by a complex intracellular trafficking machinery that delivers cell wall components and their associated biosynthetic machinery to different subcellular regions. Based on our recent discovery that a trafficking route directed to cell edges is essential for cell wall assembly and directional growth at the cell and organ scale, we propose that morphogenesis is controlled by a signalling module at cell edges which integrates feedback from the cell wall. This hypothesis provides a mechanistic explanation for the integration of cell and tissue-level mechanical factors into coordinated cell wall assembly. We propose that a receptor-like protein recently identified as the first known cargo of edge-directed trafficking acts as a core component of a cell wall signalling pathway at edges. This proposal aims to test our hypothesis through a combination of experimental and computational methods: (1) at the molecular level, we will identify further components of the signalling module through ligand screening, comparative proteomics, and forward genetics; (2) at the cellular level, we will functionally characterise trafficking pathways and their regulation by edge signalling through quantitative imaging, glycomics, and computational mechanics; and (3) at the organ level, we will dissect how robust growth emerges from edge-based feedback on these trafficking pathways. Collectively, these results will provide a multi-scale mechanistic model of morphogenesis in plants.