Isolation and Characterization of the Soybean Sg-3 Gene that is Involved in Genetic Variation in Sugar Chain Composition at the C-3 Position in Soyasaponins

Ryoichi Yano, Kyoko Takagi, Saeko Tochigi, Yukiko Fujisawa, Yuhta Nomura, Hiroki Tsuchinaga, Yuya Takahashi, Yoshitake Takada, Akito Kaga, Toyoaki Anai, Chigen Tsukamoto, Hikaru Seki, Toshiya Muranaka, Masao Ishimoto

Research output: Contribution to journalArticlepeer-review

Abstract

Soyasaponins are specialized metabolites present in soybean seeds that affect the taste and quality of soy-based foods. The composition of the sugar chains attached to the aglycone moiety of soyasaponins is regulated by genetic loci such as sg-1, sg-3 and sg-4. Here, we report the cloning and characterization of the Sg-3 gene, which is responsible for conjugating the terminal (third) glucose (Glc) at the C-3 sugar chain of soyasaponins. The gene Glyma.10G104700 is disabled in the sg-3 cultivar, € Mikuriya-ao', due to the deletion of genomic DNA that results in the absence of a terminal Glc residue on the C-3 sugar chain. Sg-3 encodes a putative glycosyltransferase (UGT91H9), and its predicted protein sequence has a high homology with that of the product of GmSGT3 (Glyma.08G181000; UGT91H4), which conjugates rhamnose (Rha) to the third position of the C-3 sugar chain in vitro. A recombinant Glyma.10G104700 protein could utilize UDP-Glc as a substrate to conjugate the third Glc to the C-3 sugar chain, and introducing a functional Glyma.10G104700 transgene into the mutant complemented the sg-3 phenotype. Conversely, induction of a premature stop codon mutation in Glyma.10G104700 (W270∗) resulted in the sg-3 phenotype, suggesting that Glyma.10G104700 was Sg-3. The gmsgt3 (R339H) mutant failed to accumulate soyasaponins with the third Rha at the C-3 sugar chain, and the third Glc and Rha conjugations were both disabled in the sg-3 gmsgt3 double mutant. These results demonstrated that Sg-3 and GmSGT3 are non-redundantly involved in conjugation of the third Glc and Rha at the C-3 sugar chain of soyasaponins, respectively.

Original languageEnglish
Pages (from-to)792-805
Number of pages14
JournalPlant and Cell Physiology
Volume59
Issue number4
DOIs
Publication statusPublished - Apr 1 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Plant Science
  • Cell Biology

Fingerprint

Dive into the research topics of 'Isolation and Characterization of the Soybean Sg-3 Gene that is Involved in Genetic Variation in Sugar Chain Composition at the C-3 Position in Soyasaponins'. Together they form a unique fingerprint.

Cite this