Dissertation Defence: Kynurenine Metabolism in Hypericum perforatum L. and Smoke Derived Karrikins in a Post-Fire Landscape
November 19 at 9:30 am - 1:30 pm
Daniel Andre Gaudet, supervised by Dr. Susan Murch and Dr. Lauren Erland, will defend their dissertation titled “Kynurenine Metabolism in Hypericum perforatum L. and Smoke Derived Karrikins in a Post-Fire Landscape” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biochemistry and Molecular Biology.
An abstract for Daniel Andre Gaudet’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Registration is not required for in-person exams.
Abstract
Plants coordinate growth, development and environmental responses through chemically diverse signals, including endogenous metabolites and external compounds. This thesis examined two underexplored classes of chemical signalling across biological scales: smoke derived karrikins in a post-fire landscape and kynurenine metabolism in St. John’s wort
(Hypericum perforatum L.).
Karrikins in Wildfire Impacted Ecosystems: I investigated post-fire plant community patterns and soil karrikin occurrence in the Skaha landscape five years after the 2020 Christie Mountain Fire. Plant community composition differed with fire severity, landcover, and their interaction. Four focal species were evaluated: the native bluebunch wheatgrass and pinegrass, and the invasive cheatgrass and sulphur cinquefoil. Bluebunch wheatgrass cover was highest at control sites, whereas pinegrass cover varied among fire severity x landcover combinations. Bluebunch wheatgrass and cheatgrass also showed positive co-occurrence. Karrikins were detected at 19 of 35 soil sites sampled in 2025, with KAR1 the most frequently detected compound. Among the 31 sites sampled in both years, karrikin detection decreased from 29 sites in 2023 to 12 sites in 2025. These findings show that post-fire vegetation patterns reflected disturbance and habitat context, while soil karrikin occurrence persisted but declined over time.
The Kynurenine Pathway in Plant Growth and Development: I developed and validated derivatized and underivatized UHPLC-Orbitrap mass spectrometry methods for kynurenine (KYN), kynurenic acid (KYNA), 3-hydroxykynurenine (3-HK), and 3-hydroxyanthranilic acid (3-HAA). KYN, KYNA, and 3-HAA were detected and quantified in tissue-cultured and greenhouse-
grown H. perforatum and in commercial products. I applied these methods in tissue culture bioassays to investigate associations between KYN metabolism and plant growth. Exogenous KYN increased root number and internodal length. Exogenous indole-3-acetic acid (IAA) reduced rooting and increased KYN and 3-HAA in shoots. Kynurenine pathway inhibitors were taken up by plant tissues and altered KYN metabolism. In a second bioassay, thidiazuron (TDZ) induced de novo shoot organogenesis, confirmed histologically by shoot meristem and vascular development without evidence of somatic embryogenesis. TDZ also reduced KYN concentrations, indicating an association between TDZ-induced organogenesis and kynurenine metabolism. Together, these studies establish analytical and experimental foundations for
investigating non-classical chemical regulation in plants.
