Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Life Sciences

First Committee Member

Jeffery Shen

Second Committee Member

Andrew Andres

Third Committee Member

Elizabeth Stacy

Fourth Committee Member

Mira Han

Fifth Committee Member

Christine Bergman

Number of Pages



Close to 40% of the world area — home to nearly 3/4 of the total population and source of more than half of global food production — suffers from drought. Increased severity can result in as much as $10.4 billion worth of losses annually. With the threats of aberrant weather changes and extant climate change, more frequent environmental stresses are likely to arise worldwide. One of the best tools that will lower the population's vulnerability to the impacts of abiotic stress is genetic engineering of plants for drought tolerance. Our work focused on the WRKY superfamily of transcription factors that are key regulators of many biotic and abiotic stress responses. In this study, we first used a comparative evolutionary biology approach to study how a prominent class of plant regulators have evolved across domesticated and wild rice species found in a wide range of geographical locations with highly varied phenotypes. Through this, we were able to select one highly conserved WRKY member in the rice genus (OsWRKY24) that has been previously linked to abiotic tolerance. OsWRKY24 has high homology to two other genes, OsWRKY53 and OsWRKY70, in the economically valued Asian cultivated rice (Oryza sativa). Using the CRISPR/Cas9-mediated genome editing system, coupled with synthetic genes with tandemly arrayed tRNA–gRNA architecture, we successfully produced single, double, and triple knockout mutants for these three genes in rice with high editing efficiency. Through functional studies we demonstrated that OsWRKY24 and OsWRKY53 function individually and in coordination during the response of rice plants to drought stress. In addition, these genes play key roles in other agronomically important traits such as seed dormancy, senescence, plant status, and grain morphology. Our study further elucidated the mechanisms by which plants respond to drought stress and provided additional toolkits for creating elite food crops able to combat debilitating environmental conditions. The end goal of this project is to contribute to the global efforts of finding solutions to food insecurity.


CRISPR/Cas9; drought stress; Oryza genomes; rice; WRKY genes


Bioinformatics | Molecular Biology | Plant Sciences

File Format


File Size

25000 KB

Degree Grantor

University of Nevada, Las Vegas




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Available for download on Wednesday, August 15, 2029