Genetic and Molecular Characterization of a New EMS-Induced Mutant without the Third Glucose Moiety at the C-3 Sugar Chain of Saponin in Glycine max (L.) Merr.

Saponin, a secondary metabolite, is produced by various plant species, including soybean (Glycine max (L.) Merr.). Soybeans synthesize triterpenoid saponins, which are classified by their aglycone structure and sugar chain composition. Here, we characterized an ethyl methanesulfonate-induced mutant, PE1539, without saponin and with a glucose moiety at the third position of the C-3 sugar chain. The saponin phenotype of PE1539 is described by the accumulation of Ab-gamma g saponin and deficiency of Ab-alpha g saponin and DDMP-alpha g saponin, similar to a previously reported sg-3 mutant in soybean. Genetic analysis showed that the saponin phenotype of PE1539 is controlled by a recessive mutation. We mapped the gene responsible for the phenotype of PE1539 and the mapped region included Sg-3 (Glyma.10G104700). Further analysis of Sg-3 in PE1539 using DNA sequencing revealed a single-nucleotide substitution in the exon (G804A), resulting in a premature stop codon; thus, PE1539 produced a PSPG box-truncated protein. Saponin phenotype analysis of the F-2 population-from a cross between wild-type Uram and PE1539-showed that the phenotype of saponin was cosegregated with the genotype of Sg 3. Quantitative real-time PCR showed reduced expression of Sg-3 in PE1539 cells. Together, our data indicate that the saponin phenotype of PE1539 results from a mutation in Sg-3

Antioxidative Capacity of Soyfoods and Soy Active Compounds

Soyfood isoflavones and soyasaponins are the effective compounds relating to their health-promoting properties. Their chemical structure plays an important role in their antioxidative activity. Thus, six isoflavones and four soyasaponins that are targeted in soyfood were evaluated for their peroxyl radical scavenging capacities by the hydrophilic-oxygen radical absorbance capacity (H-ORAC) method. The antioxidant capacity of non-fermented and fermented soyfoods was also determined by the same method. The results revealed that isoflavones showed higher peroxyl radical scavenging capacities than soyasaponin, with their activities found to depend on their chemical structure. The aglycone isoflavones promoted higher H-ORAC values than glycoside and malonyl glycoside isoflavones, respectively. On the other hand, DDMP saponin promoted a higher H-ORAC value than its derived compound, group B saponin, and the aglycone soyasaponin. In the case of soyfoods, fermented soyfoods had higher antioxidative capacity that the non-fermented ones, especially the long-term fermented products. Soybean-koji miso presented the highest H-ORAC value, followed by natto, soy sauce, and tempeh. Moreover, lightness (L*) of miso and soy sauce showed a negative correlation with H-ORAC value probably due to browning substances which might derive from the amino-carbonyl reaction. Considering the high antioxidant capacity of fermented soyfoods, it might relate to aglycone isoflavones which promote strong radical scavenging capacity. Thus, fermented soyfoods, especially miso and natto, could be considered as health-promoting foods

Determination of saponin contents in raw soybean and fermented soybean foods of India

533-538Saponin composition and contents in seeds of raw dry soybean and fermented soybean foods of India (kinema, bekang and tungrymbai) were investigated by liquid chromatography-tandem mass spectrometry analysis. Saponin contents were found as follows: raw soybeans, 401.8±46.8 - 686.9±33.9; seed hypocotyls, 2118.5±160.7 - 9049.3±788.6; seed cotyledon, 226.5±5.0 - 508.3±19.2; and fermented soybean foods, 243.4±25.8 - 590.3±29.0 mg/100g.Due to large amount of Group B saponin in ethnic fermented soybeans of India, it is presumed that soybean foods have health promoting benefits

Weeding volatiles reduce leaf and seed damage to field-grown soybeans and increase seed isoflavones

草刈りの匂いで作物の防衛力を強化 --草刈り時の匂いを受容した大豆株では葉と豆の被害が減少し、豆中のイソフラボン量が増加する--. 京都大学プレスリリース. 2017-02-01.Field experiments were conducted over 3 years (2012, 2013, and 2015), in which half of the young stage soybean plants were exposed to volatiles from cut goldenrods three times over 2–3 weeks, while the other half remained unexposed. There was a significant reduction in the level of the total leaf damage on exposed soybean plants compared with unexposed ones. In 2015, the proportion of damage to plants by Spodoptera litura larvae, a dominant herbivore, was significantly less in the exposed field plots than in the unexposed plots. Under laboratory conditions, cut goldenrod volatiles induced the direct defenses of soybean plants against S. litura larvae and at least three major compounds, α-pinene, β-myrcene, and limonene, of cut goldenrod volatiles were involved in the induction. The number of undamaged seeds from the exposed plants was significantly higher than that from unexposed ones. Concentrations of isoflavones in the seeds were significantly higher in seeds from the exposed plants than in those from the unexposed plants. Future research evaluating the utility of weeding volatiles, as a form of plant–plant communications, in pest management programs is necessary

Molecular analysis of two novel missense mutations in the sg-1 gene associated with group a saponin biosynthesis in soybean

Soybean [Glycine max (L.) Merr.] accumulates several different types of saponins, including the Aa and Ab series of saponins, which contribute to the bitter and astringent aftertaste in soy food products. Modification of the soybean genome is being applied to develop bitter-free soybean cultivars. In this study, two new ethyl-methanesulfonate (EMS)-induced mutants, PE937 and PE1015, were characterized for their ability to accumulate the bitter-free A0-alpha g saponin and low level of the bitter Ab-series saponins compared with the wild cultivar. These phenotypes resemble that of previously reported sg-1 degrees mutants that accumulate A0-alpha g and no Ab-series saponins, which are controlled by the Sg-1(b) (Glyma.07G254600) gene. Sequence analysis of Sg-1(b) in PE937 and PE1015 revealed that each mutant has a single-nucleotide polymorphism that causes an amino acid change from Gly(349) to Asp 349 and from Gly(241) to Asp(241) in the Sg-1(b) proteins. We therefore designated these mutations as alleles sg-1(b1) and sg-1(b2), respectively. Multiple alignment analysis showed that the Gly(349) and Gly(241) are highly conserved among the UDP-dependent glycosyltransferase (UGT) proteins. In light of the above results, the fact that there are low levels of Ab-series saponins in both of the mutants indicates that these mutations may reduce the UGT activity of Sg-1(b) proteins in the biosynthesis of Ab-series saponins. Cosegregation analysis revealed that the novel sg-1(b1) and sg-1(b2) variants are recessive to Sg-1(b) and are tightly linked to A0-alpha g saponin accumulation.N

Biosynthesis of DDMP saponins in soybean is regulated by a distinct UDP-glycosyltransferase

2,3-Dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP) saponins are one of the major saponin groups that are widely distributed in legumes such as pea, barrel medic, chickpea, and soybean. The steps involved in DDMP saponin biosynthesis remain uncharacterized at the molecular level. We isolated two recessive mutants that lack DDMP saponins from an ethyl methanesulfonate-induced mutant population of soybean cultivar Pungsannamul. Segregation analysis showed that the production of DDMP saponins is controlled by a single locus, named Sg-9. The locus was physically mapped to a 130-kb region on chromosome 16. Nucleotide sequence analysis of candidate genes in the region revealed that each mutant has a single-nucleotide polymorphism in the Glyma.16G033700 encoding a UDP-glycosyltransferase UGT73B4. Enzyme assays and mass spectrum-coupled chromatographic analysis reveal that the Sg-9 protein has glycosyltransferase activity, converting sapogenins and group B saponins to glycosylated products, and that mutant proteins had only partial activities. The tissue-specific expression profile of Sg-9 matches the accumulation pattern of DDMP saponins. This is the first report on a new gene and its function in the biosynthesis of DDMP saponins. Our findings indicate that Sg-9 encodes a putative DDMP transferase that plays a critical role in the biosynthesis of DDMP saponins.N