ALL PLANTS HAVE EXPERIENCED POLYPLOIDY, IN WHICH THE PLANT'S GENOME, INCLUDING ALL OF ITS GENES, ARE DOUBLED. WHILE THESE PLANTS THEN REDUCE THEIR NUMBER OF GENES TO PRE-POLYPLOIDY LEVELS OVER TIME, MANY PLANTS, INCLUDING MANY CROP SPECIES, ARE STILL CONSIDERED TO HAVE PARTIALLY DUPLICATED GENOMES TODAY. OUR KNOWLEDGE OF HOW THESE DUPLICATED GENES ARE INTEGRATED INTO PLANT DEVELOPMENT IS SPARSE. GRASSY TILLERS1 (GT1) AND SIX-ROWED SPIKE1 (VRS1) ARE TWO GENES THAT HAVE RESULTED FROM ONE OF THESE ANCIENT DUPLICATIONS. THEY HAVE BEEN STUDIED IN MAIZE AND BARLEY, RESPECTIVELY, AND HAVE BEEN SHOWN TO REPRESS GROWTH OF AXILLARY BRANCHES AND FLOWER STRUCTURES IN DIFFERENT WAYS IN THESE TWO PLANTS; MUTATIONS IN THESE GENES HAVE LED TO INCREASED YIELD. THESE TWO GENES, DESPITE HAVING KNOWN ROLES IN DEVELOPMENT, HAVE NOT BEEN PREVIOUSLY STUDIED IN THE SAME PLANT. TO UNDERSTAND HOW THESE GENES WORK TOGETHER IN PLANT DEVELOPMENT, HOW THEY REGULATE OTHER GENES, AND HOW THEY HAVE EVOLVED NEW FUNCTIONS AFTER DUPLICATION, WE MUST STUDY THESE GENES IN THE SAME PLANT SPECIES. HERE, I USE MAIZE AND BRACHYPODIUM DISTACHYON, A MODEL GRASS CLOSELY RELATED TO BARLEY AND WHEAT, TO STUDY GT1 AND VRS1.I WILL DETERMINE THE ROLES OF GT1 AND VRS1 BY GENERATING MUTANTS WITH BROKEN COPIES OF THESE GENES USING CRISPR/CAS9 GENOME EDITING, A CUTTING-EDGE TECHNOLOGY THAT CAN CREATE SMALL MISTAKES IN THE TARGETED GENES. I WILL PROFILE HOW THESE MUTANTS VARY FROM THE NORMAL PLANTS TO DETERMINE HOW THESE GENES ARE AFFECTING PLANT DEVELOPMENT. BASED ON PREVIOUS REPORTS, I EXPECT TO SEE DIFFERENCES IN THE FLORAL STRUCTURES AND BRANCHING PATTERNS. I WILL ALSO LOOK AT THE LOCALIZED EXPRESSION OF THESE GENES AND THEIR PROTEINS. ONCE I HAVE ESTABLISHED WHERE THE GENES ACT WITHIN THE PLANTS, I WILL PERFORM RNA-SEQ ON THESE PLANT TISSUES OF THE MUTANTS AND THE NORMAL PLANTS. THIS TECHNIQUE MEASURES THE EXPRESSION OF ALL THE GENES IN THE GENOME AT THE SAME TIME, WHICH WILL ALLOW ME TO DETERMINE WHICH GENESARE CHANGING IN EXPRESSION DUE TO THE BROKEN GENE COPIES. COMPARING THESE SETS OF GENES WILL HELP US TO DETERMINE WHY THESE GENES ARE SHOWING DIFFERENT DEVELOPMENTAL PATTERNS AND WILL TELL US HOW SIMILAR THESE PATTERNS ARE BETWEEN DIFFERENT SPECIES. I WILL NEXT TEST HOW GT1 AND VRS1 THEMSELVES ARE REGULATED. AGAIN USING CRISPR/CAS9 GENOME EDITING TECHNOLOGY, I WILL REMOVE SECTIONS OF THE REGION UPSTREAM OF THESE GENES THAT CONTAIN LIKELY REGULATORY REGIONS. CHANGES IN THE DEVELOPMENTAL PATTERNS OF THESE REGULATORY MUTANTS WILL REVEAL WHICH OF THESE REGIONS ARE CONTRIBUTING TO THE MAGNITUDE OR LOCALIZATION OF EXPRESSION FOR GT1 AND VRS1. FINALLY, I WILL TEST THE APPLICABILITY OF THESE GENES AND THE DEVELOPMENTAL MODULE THEY CONTROL TO CAUSE GROWTH REPRESSION IN NEW CONTEXTS BY EXPRESSING THEM UNDER NEW PROMOTER ELEMENTS IN TRANSGENIC PLANTS. THIS WILL SHOW HOW WELL THESE GENES COULD BE USED TO MODIFY AND CONTROL PLANT DEVELOPMENT FOR INCREASED YIELD. THUS, THE ULTIMATE GOAL I HOPE TO ACHIEVE THROUGH THIS RESEARCH IS A THOROUGH UNDERSTANDING OF GT1 AND VRS1 AS A MODEL FOR HOW ANCIENT DUPLICATES CAN DIVERGE TO REGULATE PLANT DEVELOPMENT THROUGH CONTROL OF DEVELOPMENTAL MODULES.