Modulates the action of auxin, and may function as plant growth regulator that alters phytohormone responses. Expressed during rhizobium-induced nodule formation. In 4-day old nodules it is found in all the cells of the center of the nodule primordium and also occurs in the region of the root pericycle facing the nodule primordium. At day 5, expression is seen in the complete central tissue. At day 20 expressed in the complete prefixation zone II, and in the proximal part of this zone it is found only in the infected cells but not in the uninfected cells. At the transition of prefixation zone II into interzone II-III expression decreases in the infected cells. In the fixation zone III, expression is induced in the uninfected cells and in the proximal part of this zone it is undetectable. Present at high levels in the pericycle of the nodule vascular bundle.