** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** OVER 72% OF FLOWERING PLANT SPECIES ARE CAPABLE OF MUTUALISTIC SYMBIOSES WITH ARBUSCULAR MYCORRHIZAL (AM) FUNGI. IN THIS NUTRITIONALLY-BASED MUTUALISM, THE FUNGI LIVE WITHIN AND AROUND THE ROOT AND TRANSFER PHOSPHATE AND NITROGEN FROM THE SOIL TO THE ROOT. IN RETURN, THE PLANT CELL PROVIDES THE FUNGI WITH CARBON, IN THE FORM OF LIPID AND SUGARS. THE SYMBIOSIS HAS A HUGE IMPACT ON PLANT MINERAL NUTRITION AND ON THE LEVEL OF CARBON DIRECTED UNDERGROUND, BOTH OF WHICH INFLUENCE MANY ASPECTS OF ECOSYSTEM FUNCTIONING. PHOSPHATE TRANSPORT PROTEINS MOVE PHOSPHATE ACROSS THE FUNGAL AND PLANT MEMBRANES. PREVIOUS WORK HAS IDENTIFIED PHOSPHATE TRANSPORT PROTEINS ACTIVE DURING SYMBIOSIS AND HAS REVEALED THAT PHOSPHATE TRANSPORT IS A KEY REGULATOR OF THE ASSOCIATION. THIS PROJECT SEEKS A MECHANISTIC UNDERSTANDING OF THE REGULATORY PROCESS AND AIMS TO IDENTIFY HOW THE PLANT ROOT CELLS SENSE PHOSPHATE AND REGULATE THEIR CELL BIOLOGY TO MAINTAIN THE SYMBIOSIS. THE FUNCTION OF A FUNGAL PHOSPHATE TRANSPORTER WILL ALSO BE ASSESSED. A MECHANISTIC UNDERSTANDING OF PI TRANSPORT AND ITS ROLE IN REGULATING THE SYMBIOSIS COULD PROVIDE KEY TARGETS FOR BREEDING CROPS THAT ARE OPTIMIZED FOR PI ACQUISITION THROUGH AM SYMBIOSIS. THIS COULDIMPROVE PHOSPHATE CAPTURE BY CROPS AND ULTIMATELY REDUCE HIGH FERTILIZER INPUTS IN AGRICULTURE AND ASSOCIATED ENVIRONMENTAL DAMAGE ARISING FROM EXCESS FERTILIZER RUN-OFF. THE PROJECT WILL PROVIDE TRAINING OPPORTUNITIES FOR SCIENTISTS AT ALL LEVELS OF THEIR CAREERS, FROM HIGH SCHOOL STUDENTS TO POSTDOCS. LECTURES ANDENGAGEMENT ACTIVITIES WITH THE PUBLIC WILL INCREASE AWARENESS OF AM SYMBIOSIS.