Browsing by Subject "Brassicaceae"

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    ItemOpen Access
    A Hyb-Seq phylogeny of Boechera and related genera using a combination of Angiosperms353 and Brassicaceae-specific bait sets.
    (American journal of botany, 2023-10) Hay, Nikolai M; Windham, Michael D; Mandáková, Terezie; Lysak, Martin A; Hendriks, Kasper P; Mummenhoff, Klaus; Lens, Frederic; Pryer, Kathleen M; Bailey, C Donovan

    Premise

    Although Boechera (Boechereae, Brassicaceae) has become a plant model system for both ecological genomics and evolutionary biology, all previous phylogenetic studies have had limited success in resolving species relationships within the genus. The recent effective application of sequence data from target enrichment approaches to resolve the evolutionary relationships of several other challenging plant groups prompted us to investigate their usefulness in Boechera and Boechereae.

    Methods

    To resolve the phylogeny of Boechera and closely related genera, we utilized the Hybpiper pipeline to analyze two combined bait sets: Angiosperms353, with broad applicability across flowering plants; and a Brassicaceae-specific bait set designed for use in the mustard family. Relationships for 101 samples representing 81 currently recognized species were inferred from a total of 1114 low-copy nuclear genes using both supermatrix and species coalescence methods.

    Results

    Our analyses resulted in a well-resolved and highly supported phylogeny of the tribe Boechereae. Boechereae is divided into two major clades, one comprising all western North American species of Boechera, the other encompassing the eight other genera of the tribe. Our understanding of relationships within Boechera is enhanced by the recognition of three core clades that are further subdivided into robust regional species complexes.

    Conclusions

    This study presents the first broadly sampled, well-resolved phylogeny for most known sexual diploid Boechera. This effort provides the foundation for a new phylogenetically informed taxonomy of Boechera that is crucial for its continued use as a model system.
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    ItemOpen Access
    The Evolution of the Glucosinolate Pathway in the Brassicaceae
    (2013) OlsonManning, Carrie Frances

    Understanding the mechanisms that underlie the formation of, and innovation in biochemical pathways is an important goal in evolutionary biology. The following work addresses the problem of biochemical pathway evolution in two ways. In the first chapter, I combine genetic manipulations and population genetic analyses to investigate the whether flux control in the aliphatic glucosinolate pathway of Arabidopsis thaliana drives evolutionary rate heterogeneity. My results indicate that the first enzyme in the pathway, CYP79F1, has majority flux control and is the only one to show convincing evidence for positive selection. The second chapter builds on the first by asking whether flux control is stable under a variety of environmental conditions. I find that flux control remains with CYP79F1, in all my environmental treatments. In the final chapter, I address the evolution of one enzyme in this pathway from Boechera stricta that is responsible for a gain-in-function polymorphism that results in increased fitness in nature. With molecular phylogenetic analysis, site-directed mutagenesis, structural biology and enzymatic assays, I determine what residues are under selection and test their functional effects. I find that just two mutations in this enzyme are responsible for the change in function, and discuss their position within the enzyme. Strikingly, the enzyme with majority flux control in A. thaliana is homologous to the enzyme responsible for the novel function in Boechera. Together these results suggest that selection may predictably exploit the same small subset of genes to optimize biochemical pathway output and for evolutionary innovation.