Cryo-EM structure and dynamic basis of phosphate uptake by PHT1 in rice

Phosphorus is an essential macronutrient for plants, primarily absorbed from the soil as inorganic phosphate (Pi) through root-located Pi transporters. Despite decades of research into these transporters as targets for developing Pi-efficient crops, their mechanisms for Pi import remain poorly understood. Here, we present the cryo-electron microscopy (cryo-EM) structures of the rice Pi importer OsPHT1;11 in both Pi-bound and unbound forms, characterize its conformational dynamics, and demonstrate how these dynamics contribute to its transport function. Pi is recognized through conserved residues found in plants, with its translocation facilitated by a typical alternating-access mechanism. Single-molecule fluorescence resonance energy transfer (smFRET) analyses show that this transporter undergoes dynamic conformational fluctuations, which are differentially linked to its Pi transport capability, with a predominance of extracellular open conformations favoring Pi transport, while more populated intracellular open conformations hinder it. These findings highlight key conformational determinants of transport activity and provide mechanistic insights into Pi uptake in plants.