Biosynthesis of a Novel O-methylhydroxy Isoflavone in Soybean: Expression Analysis and Identification of Isoflavone O-methyltransferases
Abstract
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.