Enhanced flavonoid production in hairy root cultures of Glycyrrhiza uralensis Fisch by combining the over-expression of chalcone isomerase gene with the elicitation treatment.

Economically important compounds, such as licorice flavonoids, are present in insufficient amounts in the hairy roots. To overcome this problem, we took the transgenic approach combined with the elicitation technique to increase the flavonoid production. The Glycyrrhiza uralensis Fisch cDNA encoding chalcone isomerase gene (chi) was over-expressed in hairy roots of G. uralensis Fisch mediated by the disarmed Agrobacterium rhizogenes A4. Stable genetic transformation was confirmed by Southern blot analysis. The transgenic and wild cultures were subsequently elicited with PEG8000 (2%) alone, yeast extract (YE) (0.1%) alone, or both of them, and then the total flavonoids were extracted and measured. The results showed that over a culture period of 3 weeks, the wild-type hairy roots, the untreated transgenic hairy roots, and the double-treated transgenic hairy roots accumulated 0.842, 1.394, and 2.838 (g/100 g DW) of total flavonoids, respectively. Moreover, the enhanced accumulation of flavonoids were correlated with the elevated level of chi transcripts and CHI activity, confirming the key role of chi in the flavonoids synthesis. This research demonstrated that the combination of the metabolic engineering and PEG8000-YE elicitation treatment was an effective strategy to increase the flavonoids production in hairy roots of G. uralensis Fisch.