Transcription factor involved in phosphate starvation signaling (PubMed:26082401). Binds to P1BS, an imperfect palindromic sequence 5'-GNATATNC-3', to promote the expression of inorganic phosphate (Pi) starvation-responsive genes (PubMed:26082401). Functionally redundant with PHR1 and PHR2 in regulating Pi starvation response and Pi homeostasis (PubMed:26082401). Expressed in the root cap and in the exodermis of the root, in the root tip of lateral roots, in the mesophyll cells of the leaf, in pollen, vascular cylinder of the anther and the veins of the lemma, palea and pistils, and in the xylem and phloem regions of large vascular bundles, small vascular bundles and diffuse vascular bundles in node I (PubMed:26082401). Expressed throughout all stages of plant growth. Increased expression in leaves before the booting stage. Up-regulated under Pi starvation conditions.