** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** HEAT INCREASINGLY THREATENS THE US AND WORLD WHEAT PRODUCTION AS CLIMATE CHANGE CONTINUES. IN THE GREAT PLAINS, HEAT IS ONE OF THE TWO TOP YIELD KILLERS, AND HEAT TOLERANT CULTIVARS ARE URGENTLY NEEDED. BREEDING HEAT TOLERANCE IN WHEAT, HOWEVER, IS HINDERED BY THE LACK OF GERMPLASM OF SATISFIED HEAT TOLERANCE AND THE COMPLICATED GENETIC MECHANISMS. OUR GOAL IS TO IMPROVE HEAT TOLERANCE OF WHEAT VIA PRECISION GENOME EDITING TECHNOLOGY.RUBISCO ACTIVASE (RCA) EMERGED RECENTLY AS A PROMISING TARGET FOR ENHANCING PLANT HEAT TOLERANCE AND PHOTOSYNTHESIS. SEVERAL CONSERVED AMINO ACID SUBSTATIONS IN WHEAT RCA2 PROTEIN SIGNIFICANTLY INCREASED TEMPERATURE OPTIMUM OF THE PROTEIN. IN THIS PROJECT, WE WILL DEVELOP NOVEL WHEAT GERMPLASM WITH ENHANCED PHOTOSYNTHETIC EFFICIENCY AND HEAT TOLERANCE BY PRECISE EDITING OF TARCA2 GENE AS PROOF OF CONCEPT WITH THREE SPECIFIC OBJECTIVES:1) CREATE NOVEL RCA2 VARIATIONS FOR ENHANCED THERMOSTABILITY.2) EVALUATE MUTATION EFFECT ON PHOTOSYNTHETIC EFFICIENCY AND HEAT TOLERANCE.3) DEVELOP BREEDING-READY GERMPLASM.THESE RESULTS ARE EXPECTED TO HAVE A POSITIVE IMPACT ON THE IMPROVEMENT OF WHEAT HEAT TOLERANCE.