Graduation Term

2020

Degree Name

Master of Science (MS)

Department

School of Biological Sciences

Committee Chair

John Sedbrook

Abstract

Pennycress (Thlaspi arvense L.) is a Brassica species being developed into an oilseed-producing winter cash cover crop. Similar to its relatives, rapeseed (Brassica napus L.) and camelina (Camelina sativa L.), pennycress seeds produce high levels of oil and protein (~34% oil and ~19% protein dry weight). For pennycress to be economically viable and environmentally sustainable as a crop, both the oil and seed meal must be utilized. Pennycress like other Brassicaceae, produces high levels of glucosinolates in the seed coat. Glucosinolates taste bitter and can be metabolized by the enzyme, myrosinase, into toxic isothiocyanates, nitriles, and epithionitriles. Seed meal containing high levels of glucosinolates has been shown to cause decreased feeding and increased instance of goiter in pigs. Glucosinolate biosynthetic pathways are comprised of three major steps: elongation, core assembly, and chain modification. In rapeseed and Arabidopsis thaliana (Arabidopsis), the HAG1 (HIGH ALIPHATIC GLUCOSINOLATE1), HAG2, and HAG3 genes were found to be transcription factors that initiate these biosynthetic pathways. Through CRISPR genome editing and selective breeding we have targeted, in different combinations, the three putative HAG transcription factors in pennycress and identified a range of glucosinolate reductions, from wild-type levels, to nearly a 90% reduction in glucosinolates stored in seeds. We determined that HAG1 and HAG3 function redundantly in controlling glucosinolate production and that, while some mutant allele combinations likely cause delays in seed germination and plant growth, other allele combinations have only minor impacts on plant growth and development while reducing seed glucosinolate content to agronomically-relevant levels.

Access Type

Thesis-Open Access

DOI

https://doi.org/10.30707/ETD2020.1606247535.297019ab

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