Award Date

May 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Life Sciences

First Committee Member

Jeffery Shen

Second Committee Member

Mira Han

Third Committee Member

Paul Schulte

Fourth Committee Member

Elizabeth Stacy

Fifth Committee Member

Hui Zhang

Number of Pages

323

Abstract

This dissertation provides genetic evidence that addresses the biological function of OsWRKY71, a transcription factor expressed abundantly in rice seed tissues. This work is significant as it is the first report on oswrky71 mutants, which display an early seed germination phenotype hyposensitive to ABA. This dissertation first focused on providing the most thorough-to-date RNA-seq time course analysis of rice embryos during germination. Since embryo and aleurone layers communication during germination is a crucial process, we then studied the aleurone transcriptomics, which provided further insight into the regulatory mechanisms involved in the germination of oswrky71 seeds. By profiling the transcriptomes, we identified key genes regulated by OsWRKY71 in both embryos and aleurone cells that are involved in the control of the germination process. We provide a working model where OsWRKY71 negatively regulates seed germination by positively regulating the abundance of a critical ABA signaling node and negatively regulating seed storage mobilization, cell wall loosening, water transport, and epiblast tissue weakening. Association studies revealed an OsWRKY71-containing QTL, qLTG-2, which is known to be associated with seed germination speed at low temperatures. Indeed, oswrky71 mutants germinate early at low temperatures, suggesting that WRKY71 is the primary gene of qLTG-2. As such, this dissertation provides new knowledge on the WRKY-dependent regulation of ABA signaling during rice germination. This information is valuable in developing strategies to improve seed germination rates and ensure optimal crop yields to alleviate food insecurity. Rice germinating faster is needed in water-limited growing regions and will allow the production of pregerminated rice for food processing applications to be created using less energy. Lastly, we performed a comprehensive and high-throughput characterization of the metabolomes of wild type and oswrky71 threshed grains in conjunction with standard analytical methods for grain nutrient contents. This work allowed us to identify differential metabolites between the wild type and oswrky71 mutant for risk assessment if we position this mutant for human consumption. Overall, our study provides a deeper understanding of the molecular mechanisms of rice seed germination that is crucial to improving rice crops' yield and resilience.

Keywords

hormone signaling; metabolomics; OsWRKY71; rice germination; transcriptomics

Disciplines

Bioinformatics | Molecular Biology | Plant Sciences

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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