Plant-specific microtubule-associated protein (MAP) that regulates the orientation of cortical microtubules and the direction of organ growth. Bound to microtubules. Expressed at low levels in roots, hypocotyls, stems, flowers, siliques, cotyledons, and leaves. Particularly present in hydathodes of cotyledons and root hairs. Right-handed twisting of petioles when associated with SPR2 disruption. Truncated N-terminus.