Differential Expression of Key Isoflavone Synthesis Genes in Soybean Sprouts under Two LED Treatments

Soybean seeds and sprouts contain isoflavones, including aglycones, glucosides, and malonylated glucosides, and their contents vary across soybean varieties. During germination and photomorphogenesis, blue light-emitting diode (LED) irradiation suppressed hypocotyl growth and enhanced the expression levels of chalcone synthase 7, isoflavone synthase (IFS), and isoflavone reductase (IFR). Conversely, red LED irradiation enhanced hypocotyl growth and decreased the expression levels of IFS and IFR. The contents of some glycosides or malonylated glycosides in sprouts and young green soybeans were significantly higher under blue LED irradiation than under red LED irradiation. These results imply that blue light more effectively increased the concentrations of some isoflavones during early germination and/or hydroponics cultivation.