**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE GOAL OF THIS PROPOSAL IS TO DETERMINE THE MOLECULAR PROGRAMS CONTROLLING THE INITIATION AND EARLY DEVELOPMENT OF LATERAL ROOTS AND NODULES IN THREE LEGUME SPECIES (MEDICAGO, SOYBEAN, AND COMMON BEAN). WE WILL STATE-OF-THE-ART TECHNOLOGY ON SELECTED PLANT CELLS TO PRECISELY CAPTURE THE ACTIVITY OF THE GENES OF THE MERISTEMATIC AND DIFFERENTIATED CELLS COMPOSING THE LATERAL ROOTS AND NODULES. WE WILL COMPARE THE SETS OF DIFFERENTIALLY EXPRESSED GENES BETWEEN CELLS AND ACROSS SPECIES TO IDENTIFY PATTERNS OF EVOLUTIONARY CONSERVATION AND DIVERGENCE. WE WILL VALIDATE THE ROLES OF DIFFERENTIALLY EXPRESSED TRANSCRIPTION FACTOR GENES BY EVALUATING LATERAL ORGAN INITIATION IN KNOCKDOWN, KNOCKOUT, AND OVEREXPRESSING MUTANTS. TOGETHER, WE EXPECT TO DETERMINE KEY REGULATORY GENES THAT DICTATE THE INITIATION AND DEVELOPMENT OF LATERAL ROOTS AND NODULES IN LEGUMES. THESE WILL BE IDEAL TARGETS FOR MANIPULATION BY BIOTECHNOLOGY OR BREEDING TO DEVELOP BETTER-ADAPTED AND MORE EFFICIENT ROOT SYSTEMS. ULTIMATELY, THIS NEW GENERATION OF CROPS WILL BE RESILIENT TO ADVERSE ENVIRONMENTAL CONDITIONS SUCH AS DROUGHT STRESS AND WILL PROMOTE SUSTAINABLE AGRICULTURAL PRACTICES THROUGH OPTIMIZED WATER AND NUTRIENT UPTAKES WITHOUT REDUCING CROP YIELDS.