Omics Insights into Isoflavonoid Biosynthesis in Soybean: Functional Specificity of Gene Family Members

Soybean (Glycine max [L.] Merr) is one of the largest crops grown in Canada, yielding approximately 5.5 million acres, and producing $2.4 billion in profit per year. However, there is a significantly large yield loss due to root and stem rot disease caused by Phytophthora sojae. Many strategies have been implemented throughout the years to combat the pathogen such as the use of pesticides and certain agricultural practises. An alternative approach to this problem is to select a trait naturally found in soybean, such as glyceollin, an isoflavonoid coumpound, production, that can increase innate resistance. Glyceollins act as antimicrobial agents that are synthesized from the isoflavonoid branch of general phenylpropanoid pathway. Isoflavonoids are actors in symbiosis with nitrogen-fixing bacteria, and are also noted for their human health benefits. By transcriptomic analysis, we identified CHS7 and CHS8 as genes that are critical for isoflavonoid synthesis in soybean seeds. Further, specific members within the pathway gene families demonstrated tissue- and stress-specific responses suggesting that only selected members of a gene family function during pathogen infection. Additionally, proteomic study identified key players in the isoflavonoid metabolon, the long-postulated model of a subcellular isoflavonoid enzyme complex forming at the surface of the endoplasmic reticulum.