THE FOCUS OF THE PROPOSED WORK IS TO UNDERSTAND THE ROLE OF THE PHYTOHORMONE CYTOKININ IN THE GROWTH AND DEVELOPMENT OF RICE ROOTS AND IN THE CHANGES INDUCED BY ALTERED NITROGEN AVAILABILITY. HOW PLANTS MODULATE THE FUNCTION OF ROOTS TO OPTIMIZE NUTRIENT UPTAKE IS A CRUCIAL ISSUE IN AGRICULTURE. PREVIOUS STUDIES HAVE DEMONSTRATED A MAJOR ROLE FOR CYTOKININ IN REGULATING ROOT GROWTH AND DEVELOPMENT, PRIMARILY IN THE MODEL DICOT ARABIDOPSIS. HERE WE PROPOSE TO EXTEND THESE STUDIES TO THE MONOCOT RICE BY EMPLOYING A COLLECTION OF CYTOKININ SIGNALING MUTANTS THAT WE HAVE GENERATED. WE WILL QUANTIFY VARIOUS ASPECTS OF ROOT GROWTH AND ARCHITECTURE AND IN THESE LINES WITH ALTERED CYTOKININ RESPONSIVENESS TO DETERMINE THE CONTRIBUTION OF EACH GENE FAMILY MEMBER TO VARIOUS ASPECTS OF ROOT GROWTH AND DEVELOPMENT. WE WILL THEN ASSESS HOW THE DISRUPTION OF CYTOKININ SIGNALING ALTERS THE RESPONSE OF ROOTS TO ALTERED NITROGEN AVAILABILITY, BOTH AT THE LEVEL OF ROOT ARCHITECTURE AND GENE EXPRESSION.THESE STUDIES SHOULD PROVIDE FOUNDATIONAL UNDERSTANDING OF THE ROLE OF CYTOKININ IN SHAPING ROOT DEVELOPMENT IN A MONOCOT IN BOTH NUTRIENT LIMITING AND REPLETE CONDITIONS, ULTIMATELY HELPING TO ENGINEER ROOT SYSTEM ARCHITECTURE TO OPTIMIZE NUTRIENT AND WATER ACQUISITION IN VARIOUS AGRICULTURAL SETTINGS.