Form under pressure: Mechanical and environmental control of cell wall assembly

CPSC seminar with Dr. Arun Sampathkumar

How a plant cell builds its wall determines its shape and the properties of the tissue it forms. Mechanical forces from turgor and growing neighbours order the microtubule cytoskeleton, which guides deposition of the stiff cellulose microfibrils that resist them. Using puzzle-shaped pavement cells, we find that assemblies at the plasma membrane–cell wall interface are required for this response, and I will show how this feedback scales to organ morphogenesis during flower development.

Cellulose, however, is a point of convergence for more than mechanics. Salt stress transiently dismantles the cortical microtubule array and the cellulose synthase complexes that track along it. We have identified two LEA_2-domain proteins that travel with the synthase complexes and bind microtubules, yet act differently from their CC1 and CC2 relatives: rather than rebuilding the array after stress, they are required for the microtubule reorientation that steers root growth away from salt. We are extending this towards understanding how temperature and nitrogen influences cellulose synthesis.

Our approach is multidisciplinary, spanning molecules to organs. The spatiotemporal regulation of cell wall synthesis and remodeling matters on two counts: form underpins cell and organ function, and understanding how walls are built will allow us to engineer both morphogenesis and biomass properties.