Nitric oxide mediates isoflavone accumulation and the antioxidant system enhancement in soybean sprouts.

In this study, we investigated the relationships between endogenous NO signal transduction pathways, the antioxidant system and isoflavone accumulation induced by UV-B radiation in soybean sprouts. Results showed that UV-B-triggered NO generation induced isoflavone accumulation by up-regulating the activity and gene expression of key enzymes (phenylalanine ammonia lyase, PAL; chalcone isomerase, CHI; chalcone synthase, CHS; isoflavone synthase, IFS) that participate in isoflavone biosynthesis and enhanced the antioxidant system by regulating levels of antioxidants (glutathione reductase, GR; glutathione S-transferase, GST; ascorbate peroxidase, APX; glutathione GSH; ascorbic acid, ASC), antioxidant enzyme activities (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT) and their gene expression. These effects were inhibited by the addition of a specific NO-scavenger, carboxy-PTIO (cPTIO). The inhibition was reversed through application of the exogenous NO donor, SNP. Overall, NO is an essential signaling molecule, mediating UV-B-induced isoflavone accumulation and the antioxidant system enhancement in soybean sprouts.