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

Characterization of a new sg-5 variant with reduced biosynthesis of group A saponins in soybean (Glycine max (L.) Merr.)

Triterpenoid saponins are major secondary metabolites in soybean; they are classified into group A and DDMP saponins. Group A saponins cause bitterness and an astringent aftertaste, whereas DDMP saponins are less bitter and more beneficial to human health. Therefore, a need exists for genetic improvement to develop bitter-free soybeans without losing other beneficial saponins. In this study, an ethyl methanesulfonate (EMS)-induced mutant, PE1327, was isolated and characterized as having a reduced level of group A saponins by chromatography. The PE1327 phenotype, which exhibits no accumulation of group A saponins, resembles that of a previously reported sg-5 wild soybean mutant whose biosynthesis is controlled by the Sg-5 (Glyma.15G243300) gene. The Sg-5 gene sequence in PE1327 revealed a single-nucleotide polymorphism (G1036A) that causes an amino acid change from Glu(346) to Lys(346) in the sg-5 protein. Multiple alignment analysis of cytochrome P450 enzymes from numerous organisms revealed that Glu(346) is highly conserved in eukaryotes, including plants and animals, but not in prokaryotes. The predicted 3D model of the Sg-5 protein showed that the Glu(346) residue is located in the J helix and is likely involved in the linkage between the J and K helices and the stabilization of the J-K loop, suggesting that the amino acid substitution from Glu(346) to Lys(346) in the PE1327 mutant results in hypofunction of Sg-5. Co-segregation analysis revealed that the Sg-5 locus is tightly linked to reduced group A saponin biosynthesis in PE1327 and that the novel sg-5 variant is recessive to Sg-5.N

Comparison of saponin composition and content in wild soybean (<i>Glycine soja</i> Sieb. and Zucc.) before and after germination

<div><p>Eight wild soybean accessions with different saponin phenotypes were used to examine saponin composition and relative saponin quantity in various tissues of mature seeds and two-week-old seedlings by LC–PDA/MS/MS. Saponin composition and content were varied according to tissues and accessions. The average total saponin concentration in 1 g mature dry seeds of wild soybean was 16.08 ± 3.13 μmol. In two-week-old seedlings, produced from 1 g mature seeds, it was 27.94 ± 6.52 μmol. Group A saponins were highly concentrated in seed hypocotyl (4.04 ± 0.71 μmol). High concentration of DDMP saponins (7.37 ± 5.22 μmol) and Sg-6 saponins (2.19 ± 0.59 μmol) was found in cotyledonary leaf. In seedlings, the amounts of group A and Sg-6 saponins reduced 2.3- and 1.3-folds, respectively, while DDMP + B + E saponins increased 2.5-fold than those of mature seeds. Our findings show that the group A and Sg-6 saponins in mature seeds were degraded and/or translocated by germination whereas DDMP saponins were newly synthesized.</p></div