title: Metabolic switching of astringent and beneficial triterpenoid saponins in soybean is achieved by a loss-of-function mutation in cytochrome P450 72A69.
abstract: 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.
authors: National Institute of Agrobiological Sciences (NIAS), 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.|Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8572, Japan.
authors: Ryoichi
authors: R
authors: Yano
authors: National Institute of Agrobiological Sciences (NIAS), 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors: Kyoko
authors: K
authors: Takagi
authors: Western Region Agricultural Research Center, NARO, 1-3-1 Senyu, Zentsuji, Kagawa, 765-8508, Japan.
authors: Yoshitake
authors: Y
authors: Takada
authors: Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan.
authors: Kyosuke
authors: K
authors: Mukaiyama
authors: Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan.
authors: Chigen
authors: C
authors: Tsukamoto
authors: National Institute of Agrobiological Sciences (NIAS), 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.|Institute of Crop Science, NARO, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8518, Japan.
authors: Takashi
authors: T
authors: Sayama
authors: National Institute of Agrobiological Sciences (NIAS), 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.|Genetic Resources Center, NARO, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors: Akito
authors: A
authors: Kaga
authors: Laboratory of Plant Genetics and Breeding, Faculty of Agriculture, Saga University, Honjyo-machi 1, Saga, 840-8502, Japan.
authors: Toyoaki
authors: T
authors: Anai
authors: RIKEN Center for Sustainable Resource Science (CSRS), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan.
authors: Satoru
authors: S
authors: Sawai
authors: RIKEN Center for Sustainable Resource Science (CSRS), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan.|Department of Chemistry and Materials Science, Tokyo Institute of Technology, Oh-okayama 2-12-1, Meguro-ku, Tokyo, 152-8551, Japan.
authors: Kiyoshi
authors: K
authors: Ohyama
authors: RIKEN Center for Sustainable Resource Science (CSRS), 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan.|Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8675, Japan.
authors: Kazuki
authors: K
authors: Saito
authors: National Institute of Agrobiological Sciences (NIAS), 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.|Institute of Crop Science, NARO, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8518, Japan.
authors: Masao
authors: M
authors: Ishimoto
mesh_terms: D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D014644:Genetic Variation; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D009154:Mutation; D009828:Oleanolic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012503:Saponins / Q000737:chemistry / Q000378:metabolism*; D013025:Glycine max / Q000235:genetics / Q000378:metabolism*; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D012503:Saponins; D014315:Triterpenes; C116604:soyasapogenol A; D009828:Oleanolic Acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C036380:beta-amyrin
keywords: cytochrome P450; functionalization; gene evolution; secondary metabolism; soybean; triterpenoid saponins