Engineering Salidroside Biosynthetic Pathway in Hairy Root Cultures of Rhodiola crenulata Based on Metabolic Characterization of Tyrosine Decarboxylase

Abstract

Tyrosine decarboxylase initializes salidroside biosynthesis. Metabolic characterization of tyrosine decarboxylase gene from Rhodiola crenulata (RcTYDC) revealed that it played an important role in salidroside biosynthesis. Recombinant 53 kDa RcTYDC converted tyrosine into tyramine. RcTYDC gene expression was induced coordinately with the expression of RcUDPGT (the last gene involved in salidroside biosynthesis) in SA/MeJA treatment; the expression of RcTYDC and RcUDPGT was dramatically upregulated by SA, respectively 49 folds and 36 folds compared with control. MeJA also significantly increased the expression of RcTYDC and RcUDPGT in hairy root cultures. The tissue profile of RcTYDC and RcUDPGT was highly similar: highest expression levels found in stems, higher expression levels in leaves than in flowers and roots. The gene expressing levels were consistent with the salidroside accumulation levels. This strongly suggested that RcTYDC played an important role in salidroside biosynthesis in R. crenulata. Finally, RcTYDC was used to engineering salidroside biosynthetic pathway in R. crenulata hairy roots via metabolic engineering strategy of overexpression. All the transgenic lines showed much higher expression levels of RcTYDC than non-transgenic one. The transgenic lines produced tyramine, tyrosol and salidroside at higher levels, which were respectively 3.21–6.84, 1.50–2.19 and 1.27–3.47 folds compared with the corresponding compound in non-transgenic lines. In conclusion, RcTYDC overexpression promoted tyramine biosynthesis that facilitated more metabolic flux flowing toward the downstream pathway and as a result, the intermediate tyrosol was accumulated more that led to the increased production of the end-product salidroside.

Rhodiola rosea L.: from golden root to green cell factories

“…TyrDC has a genotype and tissue dependent expression. Its expression is significantly higher in the roots than in leaves, stems or flowers in R. rosea and R. crenulata, which is in accordance with the high salidroside content it the roots Lan et al 2013). The salidroside content is significantly higher in transgenic hairy roots of the same species (Lan et al 2013), as well as in R.…”

“…These challenges could be overcome by developing biotechnological methods to improve the production of R. rosea secondary metabolites through in vitro culture systems (Lan et al 2013;Mirmazloum et al 2014). However, the in vitro produced metabolites are in lower engineering is possible but dependent on the discovery of the genes expressing the relevant enzymes (Lan et al 2013).…”

“…However, the in vitro produced metabolites are in lower engineering is possible but dependent on the discovery of the genes expressing the relevant enzymes (Lan et al 2013). …”

“…The second view for tyrosol biosynthesis is that it derives from Tyr (figure 2, B and E type arrows) (Ma et al 2008;Zhang et al 2011;Lan et al 2013). Tyr is converted to tyramine by tyrosine decarboxylase (TyrDC; EC: 4.1.1.25) (figure 2, B type arrows).…”

“…Tyr is converted to tyramine by tyrosine decarboxylase (TyrDC; EC: 4.1.1.25) (figure 2, B type arrows). TyrDC has a decisive role and crucial function not only in the initial conversion of tyrosol, but also a key regulatory function in the salidroside biosynthesis pathway as a whole (Ma et al 2008;Zhang et al 2011;Lan et al 2013). TyrDC has a genotype and tissue dependent expression.…”