Santiago Bataller, Ph.D. Candidate

Department of Life Sciences

WRKYng Hard: The Role of a WRKY Transcription Factor in Rice Seed Germination

Committee Members:

• Dr. Jeffery Shen, Advisory Committee Chair
• Dr. Mira Han, Advisory Committee Member
• Dr. Paul Schulte, Advisory Committee Member
• Dr. Elizabeth Stacy, Advisory Committee Member
• Dr. Hui Zhang, Graduate College Representative

Abstract

Rice is the primary staple food for half the world’s population. Climate change challenges and food insecurity supports the need for rice with agronomically advantageous traits. Seed germination is a crucial process in a plant’s life cycle and an essential trait for the agriculture and brewing industry. There have been many reports on the mechanisms of seed germination; however, how seed germination speed is controlled remains unclear. My research has focused on OsWRKY71, a transcription factor expressed abundantly in rice seed tissues. Transposon insertional rice OsWRKY71 mutants display an early seed germination phenotype due to their hyposensitivity to abscisic acid (ABA), a hormone promoting seed dormancy and hence inhibiting seed germination. Comprehensive RNA-seq studies revealed the transcriptomic changes in the wildtype and mutant embryos at the key phases of seed germination. Our data clearly demonstrate that OsWRKY71 negatively regulates seed germination by positively controlling the abundance of a critical ABA signaling node (VP1, SDR4, DOG1Ls) and negatively regulating seed storage mobilization in the embryo. Association studies revealed an OsWRKY71-containing quantitative trait locus (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 OsWRKY71 is the primary gene of qLTG-2. Hence, the WRKY-dependent regulation of ABA signaling during rice germination could be used to drive the breeding of crops with improved seed germination and dormancy traits. Before positioning these mutants for human consumption, risk assessments for genetically modified crops were performed by evaluating vital nutritional components, proximate composition analysis, and comparative metabolomics on threshed grain samples. Physical traits and compositional parameters analyzed were mostly similar and within the range or very close to being considered safe for consumption by the International Life Sciences Institute Crop Composition Database. Our study provides a deeper understanding of the molecular mechanisms of rice seed germination which is crucial to improving rice crops' yield and resilience.