IMK2-IMK3 module monitors biogenesis of nascent cell walls in land plants

Cell walls in land plants originate during cytokinesis from a membrane compartment called the cell plate. Arising as the trans-Golgi compartment, each cell plate acquires a unique molecular identity of lipids and proteins, associates with microtubules, and accumulates oligosaccharides in its lumen. Oligosaccharide deposition triggers microtubule depolymerisation and initiates a transition toward the molecular identity of the plasma membrane. How cells monitor cell plate biogenesis and coordinate it with microtubule behavior remains unknown. Here, we identify a novel signalling mod-ule composed of the receptor-like kinases IMK2 and IMK3, which integrates TRAPPII- and exocyst-dependent vesicle trafficking, the anti-parallel architecture and stabilization of microtubules, and the synthesis of oligosaccharide callose. Our findings reveal a mechanism for monitoring biogenesis of nascent cell walls.