Transcription factor involved in phosphate starvation signaling (PubMed:18263782, 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 PHR2 and PHR3 in regulating Pi starvation response and Pi homeostasis (PubMed:26082401). Expressed in roots, stems, leaves and fruits (PubMed:18263782). Expressed in the root cap and the root vascular tissues, in the stele of lateral roots, in the mestome sheath cells and the phloem 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 in node I (PubMed:26082401). Expressed throughout all stages of plant growth. Not regulated by Pi starvation.