SOSEKI proteins (SOK1-5) locally interpret global polarity cues and can influence cell division orientation to coordinate cell polarization relative to body axes, probably by guiding ANGUSTIFOLIA (AN) polarized localization (PubMed:30737509). Positive regulator of auxin (indole-3-acetic acid, IAA) biosynthesis and signaling pathway leading to the modulation of seedling growth, plant and inflorescence development (PubMed:31207460). Negative regulator of stress responses (e.g. salinity and osmotic stress) (PubMed:31207460). Homodimer (By similarity). Forms long polymer filaments with other SOKs proteins polymers (e.g. SOK1, SOK2, SOK3 and SOK4) crucial for polar localization and biological activity (PubMed:32004461). Binds to ANGUSTIFOLIA (AN) (PubMed:32004461). SOSEKI proteins integrate apical-basal and radial organismal axes to localize to polar cell edges. Expressed during embryogenesis and in roots. During embryogenesis, first observed at the globular stage and accumulates in cells next to the suspensor, including lens-shaped cells (PubMed:30737509). Observed at low levels in few vascular cells of the primary root (PubMed:30737509). Also expressed in lateral root (PubMed:30737509). The DIX-like oligomerization domain is required for polymerization, edge localization and biological activity. 'Soseki' means cornerstone in Japanese. Belongs to the SOSEKI family.