The actin cytoskeleton is required to maintain plant cell division orientation against cellular geometry

In multicellular organisms, cell division shapes tissue architecture, cell identity, and function. In walled organisms like plants, division plane orientation irreversibly defines tissue topology and is tightly regulated. While divisions often follow the shortest path enclosing cell volume, certain cells deviate, dividing perpendicular to the growth axis. Tissue-scale mechanical stress has been proposed to guide such orientation, but how these cues are integrated remains unclear. Here, we reexamine the role of the actin cytoskeleton in orienting cell division in Arabidopsis root epidermis. Combining cell biology, genetics, pharmacological treatments, 3D segmentation, and modeling, we show that actin is a central molecular actor required to establish cell division orientation against the geometrical rules, highlighting its role in integrating spatial information.