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Functional characterization of the β-amyrin synthase gene involved in platycoside biosynthesis in Platycodon grandiflorum

Abstract

Platycodon grandiflorum A. DC. contains a variety of triterpene saponins induced from the base structure of oleanane-type in roots. The β-amyrin synthase (bAS) plays an important role in controlling the biosynthesis of triterpene saponins and we obtained the full-length cDNA of the gene, which is named PlgOSC1 in P. grandiflorum. To identify the PlgOSC1 products, we expressed it in heterologous yeast cells. Results of GC-MS analysis showed a unique peak that was consistent with that of the authentic β-amyrin standard with exactly the same retention time. Furthermore, the pattern of MS fragments of the peak was also exactly the same as that of the β-amyrin. In qRT-PCR analysis of four organs of P. grandiflorum, no difference in PlgOSC1 expression level was observed; therefore, platycosides derived from β-amyrin might be present in all P. grandiflorum tissues. In conclusion, PlgOSC1 encodes a bAS enzyme that catalyzes the first committed step of platycosides biosynthesis in P. grandiflorum.

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Correspondence to Ok Tae Kim.

Electronic supplementary material

Supplementary Table 1.

Accession data for the OSCs used in the phylogenetic analyses.

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Um, Y., Jin, M.L., Lee, D.Y. et al. Functional characterization of the β-amyrin synthase gene involved in platycoside biosynthesis in Platycodon grandiflorum. Hortic. Environ. Biotechnol. 58, 613–619 (2017). https://doi.org/10.1007/s13580-017-0054-z

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Additional key words

  • beta-amyrin synthase
  • oxidosqualene cyclase
  • platycosides
  • triterpenoids