High-affinity transporter for external inorganic phosphate. Acts as a H(+):phosphate symporter in both low- and high-Pi conditions. Confers sensitivity to arsenate. Mostly expressed in roots, in tissues connecting the lateral roots to the primary root. Also present in flowers, in senescing anther filaments and in the abscission zone at the base of siliques. Expressed in hydathodes and axillary buds, and in some senescing leaves. After Pi starvation, localized in all cells of undifferentiated root segments, including root tips and root hairs, and in the epidermis, cortex and stellar regions of mature root segments. In roots by phosphate starvation. Repressed by the Pi analog phosphite (Phi). Although related to the sugar transporter family, it does not transport sugars. Belongs to the major facilitator superfamily. phosphate:H(+) symporter (TC 2.A.1.9) family.