Required for the coordination of cell differentiation and cell elongation in the root tip (PubMed:23498857). Required for the coordination of cell processes necessary for correct root growth in response to phosphate starvation, through the modulation of the auxin transporter protein PIN7 (PubMed:23498857). Expressed in the root tip of primary and lateral roots, specifically in the meristematic region, including the quiescent center and lateral root cap cells. Down-regulated by phosphate deficiency. Defects in primary root elongation and enhanced root hair elongation.