Mechanics and growth coordination define SOSEKI-based polarity fields

The formation of organs requires the coordinated growth of cells and tissues relative to the main body axes. Plant growth is typically anisotropic and mechanically coupled through contiguous cell walls, yet how these physical patterns link to cell and tissue polarity remains unclear. Here, we use SOSEKI (SOK) proteins—previously thought to report global polarity fields—as markers to dissect how polarity arises during lateral root (LR) organogenesis. Live imaging revealed that SOK polarisation does not follow a uniform global field but instead responds to local differences in growth and mechanical state between neighbouring tissues. SOKs accumulate at interfaces separating domains of distinct growth behaviour and dissipate under compressive stress. After perturbing tissue interfaces or the mechanical continuity of the tissue, the coherence of the polarity was disrupted, indicating that stable axis establishment requires mechanical coupling across the cell wall network. Our results suggest that SOK polarisation is mechanoresponsive, linking tissue mechanics to polarity and axis establishment.