Identification of Genes Responsible for the Synthesis of Glycitein Isoflavones in Soybean Seeds

• Published in: Plants (Basel) 2024-01, Vol.13 (2), p.156
• Main Authors: Horitani, Masaki, Yamada, Risa, Taroura, Kanami, Maeda, Akari, Anai, Toyoaki, Watanabe, Satoshi
• Format: Article
• Language: English
• Subjects: 6-hydroxydaidzein; Amino acids; Bioaccumulation; Biosynthesis; Cytochrome; Daidzein; Endoplasmic reticulum; Enzymes; Experiments; Flavonoid 6-hydroxylase; Gene polymorphism; Genes; Genetic aspects; Genetic diversity; Genistein; Genomes; Genotype & phenotype; Glycine max; glycitein; Hairy root; Identification and classification; isoflavone; Isoflavones; Liquid chromatography; Metabolites; Methyltransferase; Mutants; Mutation; Nonsense mutation; Nucleotides; Nutritional aspects; Phenotypes; Physiological aspects; Polymorphism; QTL; Retention time; Secondary metabolites; Seeds; Single-nucleotide polymorphism; Soybean; Soybeans; Stop codon; Structural analysis
• ISSN: 2223-7747; 2223-7747
• DOI: 10.3390/plants13020156

Soybean ( (L.) Merrill) isoflavones are among the most important secondary metabolites, with functional benefits for human health. Soybeans accumulate three aglycone forms of isoflavones: genistein, daidzein, and glycitein. Soybean landrace Kumachi-1 does not accumulate malonylglycitin at all. Gene structure analysis indicated that ( ) of Kumachi-1 has a 3.8-kbp insertion, resulting in a truncated flavonoid 6-hydroxylase ( ) sequence compared to the wild-type sequence in Fukuyutaka. Mapping experiments using a mutant line (MUT1246) with a phenotype similar to that of Kumachi-1, with a single-nucleotide polymorphism (SNP) in , revealed co-segregation of this mutation and the absence of glycitein isoflavones. We also identified a mutant line (K01) that exhibited a change in the HPLC retention time of glycitein isoflavones, accumulating glycoside and malonylglycoside forms of 6-hydroxydaidzein. K01 contains an SNP that produces a premature stop codon in ( ), a novel soybean isoflavone O-methyltransferase ( ) gene. We further analyzed transgenic hairy roots of soybeans expressing ( ) and ( ). Those overexpressing accumulated malonylglycoside forms of 6-hydroxydaidzein (M_6HD), and co-expression of and increased the level of malonylglycitin but not of M_6HD. These results indicate that and are responsible for glycitein biosynthesis in soybean seed hypocotyl.