Overexpressing GmCHI1A increases the isoflavone content of transgenic soybean (Glycine max (L.) Merr.) seeds

Isoflavones, which are secondary metabolites synthesised through the phenylpropanoid pathway, play important roles in many essential physiological processes of the soybean plant. Isoflavones are well-known for their antioxidant, antimicrobial, anti-inflammatory and anticancer activities; however, soybean plants contain very low amount of isoflavone. Therefore, increasing isoflavone content is one of major concerns in soybean research. An effective approach to enhance isoflavone content in soybean is by overexpression of the Glycine max chalcone isomerase 1A (GmCHI1A) gene. In this study, the GmCHI1A gene was transformed into soybean plants and the T2 generation was selected for high isoflavone content (daidzein, genistein) in transgenic soybean germs. GmCHI1A gene expression was enhanced in T1 transgenic lines, which led to an increase in recombinant CHI1A (rCHI1A) protein content. In soybean germs of the T2 transgenic lines, the content of daidzein and genistein increased from 166.46 to 187.23% and from 329.77 to 463.93%, respectively. Four T2 transgenic soybean lines (T2-1, T2-4, T2-21 and T2-24) with high daidzein and genistein content were selected for future progeny evaluation.