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Access Type

Open Access Thesis

Embargo Period


Degree Program

Molecular & Cellular Biology

Degree Type

Master of Science (M.S.)

Year Degree Awarded


Month Degree Awarded



Medicago truncatula is a model legume plant that is used extensively in research to study nitrogen fixation in plants. Among the techniques used to study this interaction, CRISPR-Cas9 mutagenesis is a recent advancement that has allowed researchers to experiment with the genome more easily and efficiently. Even with this new technology, issues still arise where the designed gRNAs often seem to suffer from low mutagenesis rate. In this study, I aim to uncover whether chromatin accessibility plays a role in gRNA cleavage success. To this end, I tested this hypothesis on a novel gene, Mt-Bell4, which is an evolutionarily conserved transcription factor proposed to function during nodulation across many species. The findings in this study showed that there appears a higher likelihood of successful large genomic deletions if regions of open chromatin are utilized as gRNA sites. Additionally, I showed that the Mt-Bell4 gene is highly expressed in nodule tissue, with its function possibly linked to many other transcription factors. The findings of this study highlight a new metric to consider when choosing gRNA sites, which can be generally applicable to engineering genomes whose chromatin accessibility is known. Additionally, understanding the function of Mt-Bell4 can show a new potential target to understand legume nitrogen fixation.

Available for download on Thursday, August 01, 2024