Graduation Term

2023

Degree Name

Master of Science (MS)

Department

School of Biological Sciences

Committee Chair

John C. Sedbrook

Abstract

Drought damage to crops is a significant threat to food security and a growing problem due to climate change. Amongst all abiotic stresses, drought is the most impactful on soil biota and crop productivity. According to the National Integrated Drought Information System (NIDIS), in 2020, 40% of the United States was under drought, and it is predicted that this number will continue to rise in the forthcoming years due to global warming. Pennycress (Thlaspi arvense L.) is a member of the Brassicaceae family related to canola and Arabidopsis that is rapidly being developed as an oilseed-producing winter cash cover crop for the U.S. Midwest and other temperate growing regions. As part of our efforts in domesticating this new crop, we are focusing on furthering our understanding of how pennycress responds to drought and identifying genetic changes that can improve drought tolerance without negatively impacting plant growth and seed yields. The primary purpose of this work was to generate, characterize, and test genetic changes to pennycress that we hypothesized would result in increased drought tolerance without compromising plant fitness and seed yield. To study the possible roles of AUXIN RESPONSE FACTOR (ARF) genes in pennycress drought resilience, we used the CRISPR-Cas9 genome editing technique to generate knockout mutations in AUXIN RESPONSE FACTOR 10 (ARF10), AUXIN RESPONSE FACTOR 16 (ARF16), and AUXIN RESPONSE FACTOR 17 (ARF17). While ARF genes have been shown in other species to have functional specificity, they have also been found to have overlapping functions. Therefore, we also generated pennycress lines having double knockout mutations targeting combinations of ARF10, ARF16, and ARF17, as well as triple knockout. To assess phenotypes of these lines and possible underlying molecular mechanisms, we developed assays to test pennycress mutant seedlings and plants’ responses to drought, including water withholding and chemical treatments that mimic drought. Our preliminary analyses indicated that pennycress naturally has drought tolerance, which may overlap with its extreme cold tolerance. In addition, using CRISPR-Cas9 mutagenesis, we generated pennycress single, double, and triple mutants targeting ten other genes shown to negatively regulate drought responsiveness in other species. Preliminary phenotypic analyses of these mutant lines also support our hypotheses that pennycress may have relatively higher drought tolerance than its close relative, the model plant Arabidopsis thaliana, which may lead to new understandings of how economically relevant Brassicas and other plant species can be genetically improved to cope with drought stress.

Access Type

Thesis-Open Access

DOI

https://doi.org/10.30707/ETD2023.20240124055107475777.999995

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