Open AccessMolecular elucidation of a new allelic variation at the Sg-5 gene associated with the absence of group A saponins in wild soybean
Author(s) -
Jagadeesh Sundaramoorthy,
Gyu Tae Park,
Kyosuke Mukaiyama,
Chigen Tsukamoto,
Jeong Ho Chang,
JeongDong Lee,
Jeong Hoe Kim,
Hak Soo Seo,
Jong Tae Song
Publication year - 2018
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0192150
Subject(s) - mutant , genetics , gene , biology , locus (genetics) , missense mutation , allele , cytochrome p450 , single nucleotide polymorphism , saponin , glycine soja , coding region , biochemistry , amino acid , phenotype , glycine , enzyme , genotype , medicine , alternative medicine , pathology
In soybean, triterpenoid saponin is one of the major secondary metabolites and is further classified into group A and DDMP saponins. Although they have known health benefits for humans and animals, acetylation of group A saponins causes bitterness and gives an astringent taste to soy products. Therefore, several studies are being conducted to eliminate acetylated group A saponins. Previous studies have isolated and characterized the Sg-5 ( Glyma . 15g243300 ) gene, which encodes the cytochrome P450 72A69 enzyme and is responsible for soyasapogenol A biosynthesis. In this study, we elucidated the molecular identity of a novel mutant of Glycine soja , ′CWS5095′. Phenotypic analysis using TLC and LC-PDA/MS/MS showed that the mutant ′CWS5095′ did not produce any group A saponins. Segregation analysis showed that the absence of group A saponins is controlled by a single recessive allele. The locus was mapped on chromosome 15 (4.3 Mb) between Affx-89193969 and Affx-89134397 where the previously identified Glyma . 15g243300 gene is positioned. Sequence analysis of the coding region for the Glyma . 15g243300 gene revealed the presence of four SNPs in ′CWS5095′ compared to the control lines. One of these four SNPs (G1127A) leads to the amino acid change Arg376Lys in the EXXR motif, which is invariably conserved among the CYP450 superfamily proteins. Co-segregation analysis showed that the missense mutation (Arg376Lys) was tightly linked with the absence of group A saponins in ′CWS5095′. Even though Arg and Lys have similar chemical features, the 3D modelled protein structure indicates that the replacement of Arg with Lys may cause a loss-of-function of the Sg-5 protein by inhibiting the stable binding of a heme cofactor to the CYP72A69 apoenzyme.