Metabolic Profiling of a Fast Neutron Soybean Mutant Reveals an Increased Abundance of Isoflavones

A total of 718 metabolites were identified in leaves and seeds of the soybean (Glycine max (L.) Merr., Fabaceae) fast neutron (FN) mutant 2012CM7F040p05ar154bMN15, which was previously shown to have 21 genes deleted and higher protein content in seeds as compared to wild-type. Among the identified metabolites, 164 were found only in seeds, 89 only in leaves, and 465 in both leaves and seeds. Metabolites that exhibited higher abundance in the mutant leaf than in the wild type include the flavonoids afromosin, biochanin A, dihydrodaidzein, and apigenin. Mutant leaves also exhibited a higher accumulation of glycitein-glucoside, dihydrokaempferol, and pipecolate. The seed-only metabolites that were found in higher abundance in the mutant compared to the wild type included 3-hydroxybenzoate, 3-aminoisobutyrate, coenzyme A, N-acetyl-β-alanine, and 1-methylhistidine. Among several amino acids, the cysteine content increased in the mutant leaf and seed when compared to the wild type. We anticipate that the deletion of acetyl-CoA synthase created a negative feedback effect on carbon dynamics, resulting in increased amounts of cysteine and isoflavone-associated metabolites. Metabolic profiling provided new insight into the cascading effect of gene deletions that helps breeders to produce value-added nutritional seed traits.