SUFFICIENT PHOSPHATE SUPPLY IS CRUCIAL FOR CROP PRODUCTION, BUT EXTENSIVE USE OF PHOSPHATE FERTILIZERS HAS LED TO A DEPLETION OF THIS NON-RENEWABLE RESOURCE AND CONSIDERABLE ENVIRONMENTAL DEGRADATION. ONE OF THE STRATEGIES FOR SUSTAINABLE CROP PRODUCTION IS TO UTILIZE ARBUSCULAR MYCORRHIZAL (AM) SYMBIOSIS IN AGRICULTURE, AN ANCIENT ASSOCIATION THAT OCCURS TO ~72% OF THE FLOWERING PLANTS. ROOTS OF THE PLANT HOST OFTEN TAKE UP SUBSTANTIAL PHOSPHATE FROM THE AM FUNGAL SYMBIONT THROUGH AM-SPECIFIC H+/PHOSPHATE TRANSPORTERS. ALTHOUGH THE MECHANISM OF THE MYCORRHIZAL PHOSPHATE ACQUISITION HAS BEEN INVESTIGATED, PROFILING OF THE INTRACELLULAR PHOSPHATE LEVELS DURING DIFFERENT AM SYMBIOSES HAS NOT BEEN DONE. USING A PLANT-SPECIFIC, GENETICALLY ENCODED PHOSPHATE BIOSENSOR AND A HIGHLY EFFECTIVE EXPERIMENTAL SYSTEM TO TRACE PHOSPHATE TRANSLOCATION FROM THE FUNGI TO THE ROOTS, I WILL VISUALIZE THE INTRACELLULAR PHOSPHATE PROFILES DURING DIFFERENT AM SYMBIOSES SPATIALLY AND TEMPORALLY AND CHARACTERIZE THE ROLES OF THE AM SYMBIOSIS-INDUCED PHOSPHATE TRANSPORTERS DURING THE SYMBIOTIC PHOSPHATE UPTAKE. THE OUTCOME OF THIS RESEARCH WILL PROVIDE NOVEL AND FUNDAMENTAL KNOWLEDGE OF PHOSPHATE DYNAMICS DURING DIFFERENT AM SYMBIOSES.