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Abstract
SOYBEAN IS ONE OF THE WORLDS MOST IMPORTANT FOOD CROPS. TO ENSURE CONTINUED CROP SUCCESS AND REALIZE IMPROVED YIELDS, IT IS IMPORTANT TO UNDERSTAND THE FUNCTION OF THE SOYBEAN GENES AND HOW THEY INTERACT WITH THE ENVIRONMENT AND EACH OTHER. THE GENERATION AND IMPLEMENTATION OF MOLECULAR TOOLS IS USEFUL FOR UNDERSTANDING GENE ACTION IN SOYBEAN, AND ULTIMATELY THE IMPROVEMENT OF SOYBEAN AS A CROP.FUNCTIONAL-GENOMIC STUDIES RELY ON THE MANIPULATION OF GENES BY EITHER CONTROLLING THEIR EXPRESSION, OR IDENTIFYING NULL MUTANTS. RNA INTERFERENCE IS FREQUENTLY USED TO SILENCE THE EXPRESSION OF GENES. THERE ARE SEVERAL METHODS TO SILENCE GENES IN PLANTS, BUT THE TRANS-ACTING SMALL-INTERFERING RNA (TA-SIRNA) PATHWAY IS A PARTICULARLY SIMPLE SYSTEM. CHAPTER TWO DETAILS THE DESIGN AND IMPLEMENTATION OF TA-SIRNA VECTORS TO PRODUCE SIRNAS AND INDUCE GENE SILENCING IN SOYBEAN.IN ADDITION TO RNAI, THE ABILITY TO CREATE TARGETED DNA MODIFICATIONS IS POWERFUL GENOMICS TOOL. THE CRISPR/CAS SYSTEM HAS RECENTLY BEEN USED TO CREATE KNOCK-OUT MUTATIONS IN A WIDE RANGE OF ORGANISMS. CHAPTER THREE DESCRIBES THE DEVELOPMENT OF A CRISPR/CAS SYSTEM TO EFFICIENTLY MODIFY SPECIFIC DNA SEQUENCES IN SOYBEAN. TARGETED DNA MODIFICATIONS WERE OBTAINED IN NEARLY 95% OF THE EVENTS EVALUATED. A HIGH-THROUGHPUT SEQUENCING METHOD WAS USEFUL FOR IDENTIFYING AND QUANTIFYING MODIFICATIONS MADE AT TARGET AND NON-TARGET LOCI.IN CHAPTER FOUR, THE SAME SEQUENCING APPROACH WAS MODIFIED TO IDENTIFY TRANSGENE INSERTION SITES IN NINE SOYBEAN EVENTS AND TRANSPOSITION SITES OF MPING IN SOYBEAN. SEGREGATION OF THE INSERTIONS WAS EVALUATED IN FIVE TRANSGENIC LINES. THE METHODOLOGY IS SIMPLE, STRAIGHTFORWARD AND HUNDREDS OF LIBRARIES CAN BE GENERATED WITHIN A WEEK.AS A FUNCTIONAL TEST OF RNAI IN SOYBEAN, CHAPTER FIVE DESCRIBES TRANSGENIC EVENTS MADE WITH THE GOAL OF CREATING NEMATODE-RESISTANT SOYBEAN PLANTS BY ENGINEERING THEM WITH THE ABILITY TO SILENCE GENES IN THE NEMATODE NECESSARY FOR PARASITISM. THE WORK FOCUSSES ON THE CHARACTERIZATION AND SELECTION OF TRANSGENIC PLANTS TO IDENTIFY THOSE VECTORS AND EVENTS ABLE TO PRODUCE SMALL RNAS. IT IS CLEAR THAT SMALL RNA PRODUCTION IS NECESSARY BUT NOT SUFFICIENT, TO OBTAIN CONSISTENT NEMATODE RESISTANCE. HOWEVER, THIS WORK PROVIDES A FOUNDATION FROM WHICH ADDITIONAL ATTEMPTS CAN BE MADE.