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Master of Science




Dhaubhadel, Sangeeta


Agriculture and Agri-Food Canada

2nd Supervisor

Hill, Kathleen



Soybean (Glycine max L. Merr.) is leguminous crop widely consumed for its health benefits. Isoflavonoids are stress-induced compounds found in plants with various roles in defense mechanisms. Isoflavonoids are phytoalexins, which are small molecules that combat microbial infection. Two transcription factors, GmMYB176 and GmbZIP5, regulate the biosynthesis of multiple isoflavonoids in soybean hairy roots. When overexpressing GmMYB176 and GmbZIP5 in soybean hairy roots, an unidentifiable O-methylhydroxy isoflavone is upregulated significantly compared to control roots. This isoflavone has an O-methyl group at a unique position compared to other known isoflavones. The aim of this project was to identify and functionally characterize the isoflavone O-methyltransferase (GmIOMT) that synthesizes the novel O-methylhydroxy isoflavone from one of five known soybean isoflavone aglycones. This research revealed that soybean has 20 putative GmIOMTs and provided valuable insight into their expression. More research is required to understand the biosynthesis of isoflavonoids to improve plant stress responses.

Summary for Lay Audience

Soybean is an oilseed crop that contributes substantially to Canada’s agriculture industry. Isoflavonoids are compounds produced in legumes that not only provide health benefits when consumed, but that also play various roles in the stress response pathways of plants. An unknown isoflavonoid, an isoflavone with an O-methylhydroxy functional group, was detected in soybean hairy roots overexpressing two proteins, GmMYB176 and GmbZIP5. These two proteins are known to regulate the production of isoflavonoids in soybean, including the unknown O-methylhydroxy isoflavone.

The goal of this research project was to identify the unknown isoflavone. This was attempted by implementing two research objectives. The first objective was to identify the enzyme, an isoflavone O-methyltransferase, that catalyzes the production of the unknown isoflavone in soybean. The second objective was to determine if GmMYB176 and GmbZIP5 regulate the expression of the isoflavone O-methyltransferase. I identified 20 putative soybean isoflavone O-methyltransferase sequences, where six were induced in response to microbial infection. However, I was unable to successfully identify the one that produces the unknown isoflavone. Nonetheless, this research provided valuable information on the identification and expression of putative isoflavone O-methyltransferases in soybean.

Understanding how isoflavonoids are produced is increasingly important. Uncovering how isoflavonoids mediate stress responses in plants can allow for the development of crops resistant to various stressors, such as drought or disease, that are expected to worsen with climate change.

Available for download on Wednesday, January 01, 2025

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