** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** BIOTECHNOLOGY FOR CROP GENETIC IMPROVEMENT BECOMES INCREASINGLY IMPORTANT FOR ENHANCING AGRICULTURAL PRODUCTION. HOWEVER, WHEN INTRODUCING FOREIGN GENES INTO TARGET CROPS USING TRANSGENIC APPROACH, OR MANIPULATING ENDOGENOUS GENE EXPRESSION IN TARGET CROPS USING GENOME EDITING FOR TRAIT MODIFICATION, THE PRESENCE OF UNDESIRABLE DNAS PERMANENTLY RESIDING IN THE HOST GENOMES OF THE FINAL TRANSGENIC PRODUCTS RAISES QUESTIONS OF POTENTIAL HAZARDS OR ADVERSE EFFECTS OF THESE COMPONENTS TO THE HOST, ENVIRONMENT AND HUMAN HEALTH. IT IS THEREFORE CRITICAL TO REMOVE THESE UNDESIRABLE DNAS IN THE FINAL PRODUCTS. SITE-SPECIFIC DNA RECOMBINASES CATALYZE RECIPROCAL DNA EXCHANGE BETWEEN SPECIFIC DNA TARGET SITES AND THEREFORE CAN ALTER GENOMIC DNA SEQUENCES IN SPECIFIC WAYS PROVIDING POWERFUL TOOLS IN PLANT BIOTECHNOLOGY AND BIOSAFETY, FOR EXAMPLE THEIR USE FOR DNA EXCISION IN REMOVING UNDESIRABLE DNA TO PRODUCE CLEAN AND ENVIRONMENTALLY FRIENDLY TRANSGENICS, AND THEIR USE IN DEVELOPING GENE CONTAINMENT STRATEGIES. HOWEVER, THE OBSERVATIONS OF RECOMBINASES-MEDIATED UNEXPECTED PHENOTYPIC IMPACT ON MODEL AND CROP PLANTS RAISE VALID CONCERNS ABOUT THE POTENTIALLY UNINTENDED AND OFF-TARGET HOST PHENOTYPIC, GENOME AND EPIGENOME MODIFICATIONS BY RECOMBINASES. THE MAJOR OBJECTIVE OF THIS PROJECT IS TO INVESTIGATE HOW THE COMMONLY USED SITE-SPECIFIC RECOMBINASE GENES, CRE, FLP AND PHIC31, WHEN CONSTITUTIVELY EXPRESSED OR INDUCED IN CREEPING BENTGRASS - AN ECONOMICALLY AND ENVIRONMENTALLY IMPORTANT MONOCOT PERENNIAL GRASS SPECIES, AND IN ARABIDOPSIS - A DICOT MODEL PLANT, WOULD HAVE UNINTENDED OFF-TARGET EFFECTS TO HOST GENOMES, EPIGENOMES AND PHENOTYPES, AND THUS NEGATIVELY OR POSITIVELY AFFECT PLANT TRAITS INCLUDING DEVELOPMENT, GROWTH, AND STRESS RESPONSES AND PRESENT HAZARDS TO ENVIRONMENT. WE WILL EXAMINE WHETHER AND HOW THE RECOMBINASES-MEDIATED PHENOTYPIC CHANGES ARE ASSOCIATED WITH UNINTENDED AND OFF-TARGET MODIFICATIONS IN HOST GENE EXPRESSION AND EPIGENETIC MODIFICATIONS AT GLOBAL SCALE. DATA OBTAINED WILL ALLOW FEASIBILITY EVALUATION OF SITE-SPECIFIC RECOMBINATION SYSTEM AS A VIABLE PLATFORM FOR GENE EXCISION TO FACILITATE PLANT TRANSFORMATION AND ENABLE EXPANDED APPLICATION OF GENOME EDITING AND OTHER BIOTECHNOLOGY STRATEGIES FOR CROP PERFORMANCE AND BIOSAFETY ENHANCEMENT. THE RESEARCH WILL PROVIDE INFORMATION FOR REGULATORY AGENCIES TO ASSESS SITE-SPECIFIC RECOMBINATION SYSTEM-RELATED BIOTECHNOLOGY STRATEGIES DEVELOPED FOR TRANSGENE EXCISION AND CONTAINMENT. THE PROJECT SPECIFICALLY ADDRESSES PROGRAM AREA 5A: RESEARCH ADDRESSING PHENOTYPIC EFFECTS ASSOCIATED WITH UNINTENDED AND OFF-TARGET MODIFICATIONS IN GE ORGANISMS DEVELOPED USING GENOME EDITING TECHNOLOGY OR OTHER GENETIC ENGINEERING TECHNIQUES AND POTENTIAL HAZARDS OR ADVERSE EFFECTS (E.G., RESISTANCE) ASSOCIATED WITH THESE PHENOTYPIC EFFECTS TO THE ENVIRONMENT. THE PROJECT ALSO INDIRECTLY ADDRESSES PROGRAM AREA 1D, DEVELOPMENT OR EVALUATION OF EFFECTIVE STRATEGIES, INCLUDING MOLECULAR AND/OR GENETIC,,TO LIMIT GENE TRANSFER (GENE FLOW) OR OUTCROSSING TO SEXUALLY COMPATIBLE ORGANISMS OR TRANSFER OF GENETIC MATERIAL BETWEEN VIRUSES, INSECTS, OR MICROORGANISMS.