Unexpected Connections: Salicinoid Biosynthesis in Poplar

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dc.contributor.authorGordon, Harley Oliver William
dc.contributor.supervisorConstabel, Carsten Peter
dc.date.accessioned2022-12-22T19:48:43Z
dc.date.copyright2022en_US
dc.date.issued2022-12-22
dc.degree.departmentDepartment of Biology
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractPopulus is a genus distributed across the northern hemisphere. Poplars (Salicaceae) are subject to stresses in their environment such as herbivory, drought, and fire. These perennial hardwoods produce abundant phenylpropanoid derived anti-herbivory molecules called salicinoids. Understanding salicinoid function and biosynthesis is crucial for understanding the chemical ecology, carbon balance, and adaptability of poplars to changing ecosystems. The full biosynthetic pathway of salicinoids is unknown; however, recent progress has identified a biosynthetic gene for salicinoids. The gene is a UDP-dependent glycosyl transferase called UGT71L1. Using CRISPR/Cas9 genome editing, UGT71L1 was disrupted in the hybrid poplar Populus tremula x Populus alba. Through metabolomic, transcriptomic, and biochemical techniques the co-dependent nature of growth, defence and salicinoid biosynthesis in poplars was explored. Following the elimination of UGT71L1, the exogenous application of deuterated benzenoids and mass spectroscopic analysis was used to examine biochemical connections across metabolic pathways. A carbon limited growth experiment was used to assess the capacity for glucosylated salicinoids to contribute to carbon reserves in resprouting trees. In addition, a second glycosyltransferase gene, UGT78M1, was disrupted in genome-edited poplars. Interruption of UGT71L1 disrupted salicinoid biosynthesis. UGT71L1 knockout plants had small crinkled leaves, reduced growth, and were preferred by insect herbivores. Growth impacts were caused by the abundance of salicylic acid, which increased in concentration following salicinoid biosynthesis interruption. Furthermore, we determined that benzyl benzoate is a precursor to salicortin biosynthesis. Salicinoids are also an inaccessible carbon sink in poplar that cannot be remobilized during carbon starvation. The hypothesized salicinoid biosynthetic gene UGT78M1 does not contribute to salicinoid biosynthesis; however, UGT78M1 is crucial for salicyl benzoate glucoside homeostasis. This dissertation highlights the small molecule trichotomy of plant biochemistry and identifies connections between specialized metabolites, phytohormones, and primary metabolites.en_US
dc.description.scholarlevelGraduateen_US
dc.identifier.urihttp://hdl.handle.net/1828/14585
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectPoplaren_US
dc.subjectsalicinoiden_US
dc.subjectmetabolomicsen_US
dc.subjectstable isotopeen_US
dc.subjectchemical ecologyen_US
dc.subjectphenolic glycosideen_US
dc.titleUnexpected Connections: Salicinoid Biosynthesis in Poplaren_US
dc.typeThesisen_US

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