This item is under embargo and not available online per the author's request. For access information, please visit http://libanswers.wustl.edu/faq/5640.

ORCID

http://orcid.org/0000-0001-6231-1435

Date of Award

Summer 8-15-2021

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Evolution, Ecology & Population Biology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

The mustard family, Brassicaceae, is a large and economically important group of plants comprising ~350 genera and ~4060 species. Within the family, one genus, Camelina, has been neglected and nearly forgotten until recent decades. This genus comprises between 7 – 9 species, and includes Camelina sativa, an ancient oilseed crop cultivated for thousands of years in Europe. An allohexaploid, C. sativa contains high levels of omega-3 fatty acids and a seed oil composition amenable for production of aviation jet fuel. With a short generation time and ability to be cultivated on marginal soils with few inputs, C. sativa is set up well to take center stage as a next-generation biofuel crop. However, information has been lacking on how the allohexaploid genome of C. sativa formed or its relationship to wild relatives. Recent setbacks in agricultural field trials and low genetic diversity in breeding stock necessitates further research on the diversity, evolutionary history, and seed oil properties of C. sativa and its related species. My PhD research suggests that wild diversity in the genus harbors a wealth of genetic variation that may be valuable for introduction to the genetically depauperate C. sativa. Further, I characterize the phylogenetic relationships among wild Camelina species, and detail the history of hybridization and polyploidization resulting in four polyploid lineages of distinct origin. Genetic and archaeological analyses reveal a history of domestication in C. sativa that runs contrary to a previously hypothesized European domestication origin. Finally, I detail aspects of subgenome expression-level dominance in C. sativa and investigate the relative role of each subgenome in shaping the oil composition of this emerging aviation biofuel. Combining phylogenetic, population genetic, chemical, taxonomic, and archaeological data, I paint a new picture in the fascinating story of this long-neglected genus. In Chapter 1, I provide the first genetic evidence to demonstrate that wild C. microcarpa was domesticated to produce the oilseed crop C. sativa. In chapter 2, I use chemical analytics and describe the role of environment and genetics in shaping seed fatty acid variation across geographical and temperature gradients. I conduct whole chloroplast genome sequencing in Chapter 3 and reveal the direction of hybridization between wild Camelina species that produced polyploid genomes, and I provide estimates of the relative timing of these events. Chapter 4 represents a comprehensive genetic and archaeological analysis of C. sativa and its wild congener, C. microcarpa, supporting a Caucasus origin of domestication. In Chapter 5, I undertake a targeted transcriptome analysis of the lipid biosynthesis pathway in C. sativa and its wild relatives and show the relative contribution of previously characterized genes in the accumulation of seed oils. Overall, the work encapsulated in this thesis provides a holistic view of the evolutionary history of this emerging biofuel crop and delivers new evidence for its very recent hybrid origin. Finally, my insights indicate that resynthesis of Camelina polyploids is likely possible, and this work sets the foundation for the development of Camelina as a model system for addressing fundamental questions in the field of polyploidy research.

Language

English (en)

Chair and Committee

Kenneth Olsen

Committee Members

Elizabeth Kellogg, Toni Kutchan, David Queller, Allan Larson,

Available for download on Thursday, August 17, 2023

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