Identification of a novel UDP-glycosyltransferase gene from Rhodiola rosea and its expression during biotransformation of upstream precursors in callus culture.

Roseroot (Rhodiola rosea L.) is a medicinal plant with adaptogenic properties and several pharmaceutically important metabolites. In this study, a full length cDNA encoding a UDPG gene of roseroot was identified, cloned and characterized. Its ORF (1425 bp) was transferred into E. coli, where the expression of the recombinant enzyme was confirmed. To monitor the enzyme activity, 3 precursors (tyramine, 4-hydroxyphenylpyruvate & tyrosol) of salidroside biosynthesis pathway were added to roseroot callus cultures and samples were harvested after 1, 6, 12, 24, 48 & 96 h. Along with the controls (without precursor feeding), each sample was subjected to HPLC and qRT-PCR for phytochemical and relative UDP-glycosyltransferase gene expression analysis, respectively. The HPLC analysis showed that the salidroside content significantly increased; reaching 0.5% of the callus dry weight (26-fold higher than the control) after 96 h when 2 mM tyrosol was given to the media. The expression of the UDP-glycosyltransferase increased significantly being the highest at 12 h after the feeding. The effect of tyramine and 4-hydroxyphenylpyruvate was not as pronounced as of tyrosol. Here, we introduce a R. rosea specific UDPG gene and its expression pattern after biotransformation of intermediate precursors in in vitro roseroot callus cultures.