**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** GIBBERELLIN A (GA) IS AN IMPORTANT PHYTOHORMONE, REGULATION OF WHICH HAS BEEN CRITICAL IN AGRICULTURE. FOR EXAMPLE, THE SEMI-DWARF VARIETIES OF WHEAT AND RICE THAT CAN CARRY MORE GRAIN UPON FERTILIZATION AND HENCE ENABLED THE GREEN REVOLUTION AROSE FROM DEFECTS IN GA BIOSYNTHESIS OR SIGNALING, RESPECTIVELY, ALTHOUGH THESE MUTATIONS ALSO REDUCE THE EFFICIENCY OF NITROGEN UPTAKE. NOTABLY, MANY AGRONOMICALLY RELEVANT PLANT GROWTH INHIBITORS BLOCK GA BIOSYNTHESIS. THESE OFFER THE BENEFIT OF POST-PLANTING CONTROL OF VEGETATIVE GROWTH, ENABLING OPTIMIZATION IN RESPONSE TO ENVIRONMENTAL CONDITIONS, WHICH IS PARTICULARLY IMPORTANT WITH THE ON-GOING CLIMATE CHANGE. HOWEVER, THE VAST MAJORITY INHIBIT BROAD CLASSES OF ENZYMES AND, THUS, BLOCK OTHER METABOLIC PROCESSES INVOLVED IN RESPONSES TO BIOTIC AND/OR ABIOTIC STRESSES. WE HAVE RECENTLY DISCOVERED THAT THE ENVIRONMENTALLY-FRIENDLY MEPIQUAT CHLORIDE (1,1-DIMETHYL-PIPERIDINIUM CHLORIDE, DPC) IS A SPECIES SPECIFIC INHIBITOR OF THE INITIATING CYCLASE, ENT-COPALYL DIPHOSPHATE SYNTHASE (CPS), FROM GA BIOSYNTHESIS. ALTHOUGH THIS OFFERS A TRANSGENIC APPROACH TO INTRODUCING SUCH SELECTIVE AGROCHEMICAL MANIPULATION OF GA METABOLISM, THAT BYPASSES THE EVOLVED TRANSCRIPTIONAL REGULATION OF THE NATIVE CPS GENE. STRIKINGLY, WE HAVE FURTHER DISCOVERED A SINGLE RESIDUE SWITCH THAT CAN ENGINEER SUSCEPTIBILITY INTO THE OTHERWISE INSENSITIVE CPS FOUND IN CEREAL CROP PLANTS SUCH AS RICE. ACCORDINGLY, WE PROPOSE HERE TO USE CRISPR/CAS9 TO KNOCK-IN THIS POINT MUTATION INTO THEENDOGENOUS OSCPS1 REQUIRED FOR RICE GA BIOSYNTHESIS TO SERVE AS PROOF-OF-CONCEPT FOR SUCH ENGINEERING OF SELECTIVE AGROCHEMICAL MANIPULATION OF GA, INCLUDING RETENTION OF CLOSELY RELATED MORE-SPECIALIZED METABOLISM THAT PLAYS IMPORTANT ROLES IN RESISTANCE TO BIOTIC AND ABIOTIC STRESSES.