Low-affinity transporter for external inorganic phosphate (Pi) probably involved in the acquisition of phosphate released by arbuscular mycorrhizal (AM) fungi (e.g. Rhizophagus irregularis and Glomus intraradices) during AM symbiosis (Probable). Acts as a Pi-sensing machinery at the root tip level, independently of AM fungi, involved in the regulation of early root branching and lateral roots formation (By similarity). NH4(+)(in) = NH4(+)(out) Present on the periarbuscular membrane in cells containing arbuscules during arbuscular mycorrhizal (AM) symbiosis with AM fungi. Regulated positively by RAM1 during arbuscular mycorrhiza (AM) formation after inoculation with AM fungi (e.g. Rhizophagus irregularis and Glomus intraradices). 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.