Mechanical forces in extendable tissue matrix orient cell divisions via microtubule stabilization in Arabidopsis

Plant morphogenesis relies exclusively on oriented cell expansion and division. Nonetheless, the mechanism(s) determining division plane orientation remain elusive. Here we studied tissue healing after laser-assisted wounding in roots and uncovered how mechanical forces of cell expansion stabilize and reorient microtubule cytoskeleton for orientation of cell division. We revealed that root tissue functions as interconnected cell matrix with a radial gradient of tissue extendibility causing a predictable tissue deformation after wounding. This causes instant redirection of expansion in the surrounding cells and reorientation of microtubule arrays ultimately predicting cell division orientation. Microtubules are destabilized under low tension, whereas stretching of cells, either through wounding or external aspiration immediately induce their polymerisation. The higher microtubule abundance in the stretched cell parts leads to reorientation microtubule arrays and ultimately cell division planes. This provides a long-sought mechanism for flexible re-arrangement of cell divisions by mechanical forces for tissue reconstruction and plant architecture.