High-affinity transporter for external inorganic phosphate. Acts as a H(+):phosphate symporter in both low- and high-Pi conditions. Confers sensitivity to arsenate. Inhibited by protonophores (e.g. 2,4-dinitrophenol and carbonylcyanide m-chlorophenylhydrazone), the plasma membrane H(+)-ATPase inhibitor diethylstilbestorol, and the phosphate analog arsenate. Mostly expressed in roots, especially in trichoblasts and in emerging secondary roots and root hairs, but not in root tips. Also present in hydathodes, axillary buds and peripheral endosperm of germinating seeds. In roots by phosphate starvation. Repressed by auxin, cytokinins, and 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.