Genetic analysis of variations in the sugar chain composition at the C-3 position of soybean seed saponins

Takada, Yoshitake; Tayama, Ippei; Sayama, Takashi; Sasama, Hiroko; Saruta, Masayasu; Kikuchi, Akio; Ishimoto, Masao; Tsukamoto, Chigen

doi:10.1270/jsbbs.61.639

Cited by 33 publications

(13 citation statements)

References 32 publications

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“…The diversity of sugar moieties in soybean saponins is influenced by seven alleles at three different loci: Sg-1, Sg-3, and Sg-4 (Shiraiwa et al, 1990;Tsukamoto et al, 1993;Kikuchi et al, 1999;Takada et al, 2010Takada et al, , 2012. Sg-1 (Gly-ma07g38460) was recently cloned and encodes a uridine diphosphate (UDP)-sugar-dependent glycosyltransferase .…”

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confidence: 99%

Metabolic switching of astringent and beneficial triterpenoid saponins in soybean is achieved by a loss‐of‐function mutation in cytochrome P450 72A69

et al. 2017

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Triterpenoid saponins are major components of secondary metabolites in soybean seeds and are divided into two groups: group A saponins, and 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP) saponins. The aglycone moiety of group A saponins consists of soyasapogenol A (SA), which is an oxidized β-amyrin product, and the aglycone moiety of the DDMP saponins consists of soyasapogenol B (SB). Group A saponins produce a bitter and astringent aftertaste in soy products, whereas DDMP saponins have known health benefits for humans. We completed map-based cloning and characterization of the gene Sg-5, which is responsible for SA biosynthesis. The naturally occurring sg-5 mutant lacks group A saponins and has a loss-of-function mutation (L164*) in Glyma15g39090, which encodes the cytochrome P450 enzyme, CYP72A69. An enzyme assay indicated the hydroxylase activity of recombinant CYP72A69 against SB, which also suggested the production of SA. Additionally, induced Glyma15g39090 mutants (R44* or S348P) lacked group A saponins similar to the sg-5 mutant, indicating that Glyma15g39090 corresponds to Sg-5. Endogenous levels of DDMP saponins were higher in the sg-5 mutant than in the wild-type lines due to the loss of the enzyme activity that converts SB to SA. Interestingly, the genomes of palaeopolyploid soybean and the closely related common bean carry multiple Sg-5 paralogs in a genomic region syntenic to the soybean Sg-5 region. However, SA did not accumulate in common bean samples, suggesting that Sg-5 activity evolved after gene duplication event(s). Our results demonstrate that metabolic switching of undesirable saponins with beneficial saponins can be achieved in soybean by disabling Sg-5.

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Section: Introductionmentioning

confidence: 99%

Metabolic switching of astringent and beneficial triterpenoid saponins in soybean is achieved by a loss‐of‐function mutation in cytochrome P450 72A69

et al. 2017

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“…Degradation of DDMP saponins during processing for food use generates group B and E saponins (Kudou et al, , 1993(Kudou et al, , 1994. DDMP and group B saponins seem to be ubiquitously distributed with some variation in sugar chain structure at the C-3 position Takada et al, 2012), suggesting that DDMP and group B saponins might have a primary biological function in soybean. In general, saponins are considered to contribute to defense responses in plants because of their antimicrobial, antivirus, and anti-insect activities, although direct evidence in support of this notion is limited (Osbourn, 1996;Papadopoulou et al, 1999;Kuzina et al, 2009).…”

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confidence: 99%

The Sg-1 Glycosyltransferase Locus Regulates Structural Diversity of Triterpenoid Saponins of Soybean

et al. 2012

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Triterpene saponins are a diverse group of biologically functional products in plants. Saponins usually are glycosylated, which gives rise to a wide diversity of structures and functions. In the group A saponins of soybean (Glycine max), differences in the terminal sugar species located on the C-22 sugar chain of an aglycone core, soyasapogenol A, were observed to be under genetic control. Further genetic analyses and mapping revealed that the structural diversity of glycosylation was determined by multiple alleles of a single locus, Sg-1, and led to identification of a UDP-sugar-dependent glycosyltransferase gene (Glyma07g38460). Although their sequences are highly similar and both glycosylate the nonacetylated saponin A0-ag, the Sg-1 a allele encodes the xylosyltransferase UGT73F4, whereas Sg-1 b encodes the glucosyltransferase UGT73F2. Homology models and site-directed mutagenesis analyses showed that Ser-138 in Sg-1 a and Gly-138 in Sg-1 b proteins are crucial residues for their respective sugar donor specificities. Transgenic complementation tests followed by recombinant enzyme assays in vitro demonstrated that sg-1 0 is a loss-of-function allele of Sg-1. Considering that the terminal sugar species in the group A saponins are responsible for the strong bitterness and astringent aftertastes of soybean seeds, our findings herein provide useful tools to improve commercial properties of soybean products.

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“…Several structurally diverse groups of soyasaponins have been identified from the seeds of the subgenus Soja which includes the cultivated and wild soybean. [3][4][5][6][7][8][9][10][11][12] Based on the aglycone structure, soyasaponins have been classified into group A, DDMP (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one), group H, group I, and group J saponins (Fig. 1).…”

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

Krishnamurthy

Tsukamoto

Takahashi

et al. 2014

Bioscience, Biotechnology, and Biochemistry

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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.

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Genetic analysis of variations in the sugar chain composition at the C-3 position of soybean seed saponins

Cited by 33 publications

References 32 publications

Metabolic switching of astringent and beneficial triterpenoid saponins in soybean is achieved by a loss‐of‐function mutation in cytochrome P450 72A69

Metabolic switching of astringent and beneficial triterpenoid saponins in soybean is achieved by a loss‐of‐function mutation in cytochrome P450 72A69

The Sg-1 Glycosyltransferase Locus Regulates Structural Diversity of Triterpenoid Saponins of Soybean

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

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