Plant-specific microtubule-associated protein (MAP) that regulates the orientation of cortical microtubules and the direction of organ growth (PubMed:18577573). Determines microtubule organization by modulating microtubule severing (PubMed:24055158). Interacts with WAV3. Bound to microtubules. Expressed in roots, hypocotyls, stems, flowers, siliques, inflorescences, petioles, cotyledons, and leaves. Particularly present in root tips and shoot meristems. Right-handed twisting of petioles. Enhanced twisting when associated with SP2L disruption.