POTASSIUM (K) IS AN ESSENTIAL MACRONUTRIENT FOR PLANTS. SINCE ONLY A SMALL FRACTION OF THE SOIL K CONTENT IS PLANT AVAILABLE, PLANTS MUST DEVELOP EFFICIENT STRATEGIES FOR ITS UPTAKE FROM THE SOIL. THE MOST IMPORTANT STRATEGY USED BY PLANTS TO ACQUIRE NUTRIENTS IS THE ARBUSCULAR MYCORRHIZAL (AM) SYMBIOSIS, A MUTUALISTIC ASSOCIATION BETWEEN THE MAJORITY OF LAND PLANTS AND UBIQUITOUS SOIL FUNGI. WE HAVE RECENTLY DEMONSTRATED THAT AM FUNGI CAN ALSO HAVE A POSITIVE IMPACT ON LEGUME K NUTRITION, BUT THE PHYSIOLOGICAL AND MOLECULAR MECHANISMS UNDERPINNING THIS SYMBIOTIC EXCHANGE ARE ONLY POORLY UNDERSTOOD.THE OVERALL OF THIS PROJECT IS TO (1) DEMONSTRATE THE FACTORS THAT AFFECT K TRANSLOCATION THROUGH AM FUNGAL HYPHAE, (2) CHARACTERIZE THE SIGNIFICANCE OF FUNGAL K TRANSPORT FOR THE RESOURCE EXCHANGE PROCESSES BETWEEN PLANTS AND AM FUNGI IN LABORATORY AND FIELD EXPERIMENTS, (3) IDENTIFY PLANT GENES THAT ARE DIRECTLY INVOLVED IN MYCORRHIZAL-DEPENDENT K NUTRITION, AND (4) FUNCTIONALLY CHARACTERIZE KEY CANDIDATE GENES THAT CONTROL K FLUX FROM THE SOIL TO LEGUME ROOTS THROUGH THE AM SYMBIOSIS.AS LAND GRANT UNIVERSITIES, NORTH CAROLINA STATE UNIVERSITY AND SOUTH DAKOTA STATE UNIVERSITY APPLY THEIR RESEARCH TO BENEFIT THE ECONOMIC, INTELLECTUAL, AND SOCIAL ENDEAVORS OF CITIZENS. OUR PROJECT WILL PROVIDE FUNDAMENTAL INSIGHTS INTO THE MOLECULAR MECHANISMS GOVERNING THE SYMBIOTIC ACQUISITION OF K, AND THIS IS CRITICAL TO DEVELOPING NEW STRATEGIES TO REDUCE THE DEPENDENCE ON ENERGY-INTENSIVE CHEMICAL FERTILIZERS. OUR PROJECT ADDRESSES THE "AGRICULTURAL MICROBIOMES" AREA PRIORITY BY INVESTIGATING HOW THE MICROBIO-COMPONENTS OF AGRICULTURAL SYSTEMS CAN BE MANAGED TO IMPROVE CROP PRODUCTIVITY AND RESILIENCE TO LOW NUTRIENT AVAILABILITY.