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Background: The dried roots and rhizomes of medicinal licorices are widely used worldwide as a traditional medicinal herb, which are mainly attributed to a variety of bioactive compounds that can be extracted from licorice root. Endophytes and plants form a symbiotic relationship, which is an important source of host secondary metabolites., Results: In this study, we used high-throughput sequencing technology and high-performance liquid chromatography to explore the composition and structure of the endophytic bacterial community and the content of bioactive compounds (glycyrrhizic acid, liquiritin and total flavonoids) in different species of medicinal licorices (Glycyrrhiza uralensis, Glycyrrhiza glabra, and Glycyrrhiza inflata) and in different planting years (1-3 years). Our results showed that the contents of the bioactive compounds in the roots of medicinal licorices were not affected by the species, but were significantly affected by the main effect growing year (1-3) (P < 0.05), and with a trend of stable increase in the contents observed with each growing year. In 27 samples, a total of 1,979,531 effective sequences were obtained after quality control, and 2432 effective operational taxonomic units (OTUs) were obtained at 97% identity. The phylum Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes, and the genera unified-Rhizobiaceae, Pseudomonas, Novosphingobium, and Pantoea were significantly dominant in the 27 samples. Distance-based redundancy analysis (db-RDA) showed that the content of total flavonoids explained the differences in composition and distribution of endophytic bacterial communities in roots of cultivated medicinal liquorices to the greatest extent. Total soil salt was the most important factor that significantly affected the endophytic bacterial community in soil factors, followed by ammonium nitrogen and nitrate nitrogen. Among the leaf nutrition factors, leaf water content had the most significant effect on the endophytic bacterial community, followed by total phosphorus and total potassium., Conclusions: This study not only provides information on the composition and distribution of endophytic bacteria in the roots of medicinal licorices, but also reveals the influence of abiotic factors on the community of endophytic bacteria and bioactive compounds, which provides a reference for improving the quality of licorice.

Flavonoids are key components of licorice plant that directly affect its medicinal quality. Importantly, the MYB family of transcription factors serves to regulate the synthesis of flavonoids in plants. The MYB transcription factors represent one of the largest families of transcription factors in plants and play important roles in the process of plant growth and development. MYB gene expression is induced by a number of plant hormones, including the lipid-based hormone jasmonate (JA). Methyl jasmonate (MeJA) is an endogenous plant growth regulator that can induce the JA signaling pathway, which functions to regulate the synthesis of secondary metabolites, including flavonoids. In this study, MeJA was added to licorice cell suspensions, and RNA-seq analysis was performed to identify the differentially expressed genes. As a result, the MYB transcription factors GlMYB4 and GlMYB88 were demonstrated to respond significantly to MeJA induction. Subsequently, the GlMYB4 and GlMYB88 protein were shown to localize to the cell nucleus, and it was verified that GlMYB4 and GlMYB88 could positively regulate the synthesis of flavonoids in licorice cells. Overall, this research helps illustrate the molecular regulation of licorice flavonoid biosynthesis induced by MeJA., Competing Interests: The authors have declared that no competing interests exist.

Licorice ( Glycyrrhiza uralensis ) is a popular medicinal plant containing more than 70 flavonoid and triterpenoid glycosides. Thus far, only a few reports are available on the glycosylation enzymes involved in their biosynthesis. In this work, we mined the transcriptome data of G. uralensis and discovered 43 candidate genes for O -glycosyltransferase ( O -GT). Among them, 17 genes could be expressed in E. coli , and functions of the enzymes were analyzed by catalyzing eight native substrates. As a result, we characterized 11 O -GTs, including isoflavone 7- O -GTs, flavonol 3- O -GTs, and promiscuous O -GTs catalyzing flavones, chalcones, and triterpenoids. They could efficiently synthesize key licorice compounds such as liquiritin, isoliquiritin, ononin, and 3- O -β-d-glucuronosyl glycyrrhetinic acid. The diversity of O -GTs contributes to the biosynthesis of various glycosides in licorice. These enzymes could also be used as biocatalytic tools to synthesize other bioactive O -glycosides.

As calcium signal sensors, calcium-dependent protein kinases (CPKs) play vital roles in stimulating the production of secondary metabolites to participate in plant development and response to environmental stress. However, investigations of the Glycyrrhiza uralensis CPK family genes and their multiple functions are rarely reported. In this study, a total of 23 GuCPK genes in G. uralensis were identified, and their phylogenetic relationships, evolutionary characteristics, gene structure, motif distribution, and promoter cis -acting elements were analyzed. Ten GuCPKs showed root-specific preferential expressions, and GuCPKs indicated different expression patterns under treatments of CaCl 2 and NaCl. In addition, under 2.5 mM of CaCl 2 and significant accumulations of glycyrrhizic acid and flavonoids suggested the possible important function of GuCPKs in regulating the production of glycyrrhizic acid and flavonoids. Our results provide a genome-wide characterization of GuCPKs in regulating the production of glycyrrhizic acid and flavonoids. Our results provide a genome-wide characterization of CPK family genes in G. uralensis in promoting the biosynthesis of glycyrrhizic acid and flavonoids under salt stress.GuCPKs in promoting the biosynthesis of glycyrrhizic acid and flavonoids under salt stress.

Glycyrrhiza uralensis has acquired significant importance due to its medicinal properties and health function. In this study, the quality of G. uralensis adventitious roots was evaluated in terms of genetic stability, active compounds, and anti-inflammatory activity. Monomorphic banding pattern obtained from the mother plant and tissue cultures of G. uralensis with randomly amplified polymorphic DNA markers confirmed the genetic stability of adventitious roots. Neoliquiritin (neoisoliquiritin), ononin, liquiritin, and glycyrrhizic acid were identified from G. uralensis adventitious roots on the basis of high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry analysis. This study also revealed that adventitious roots possessed a better anti-inflammatory effect than native roots. To increase the contents of G. uralensis active components, elicitors were used in the adventitious roots culture. The combination of methyl jasmonate and phenylalanine synergistically stimulated the accumulation of glycyrrhetinic acid (0.22 mg/g) and total flavonoid (5.43 mg/g) compared with single treatment. In conclusion, G. uralensis adventitious roots can be an exploitable system for the production of licorice., (© 2016 International Union of Biochemistry and Molecular Biology, Inc.)

Objective: To study the effects of carbon source and nitrogen source on callus growth, and flavonoid content in Glycyrrhiza uralensis., Method: Induction and culture of callus were conducted in the media of different concentrations of sucrose, and fructose and ratio of NH4+/NO3- ,and flavonoid content was measured by HPLC., Result: The results showed that fructose was superior to sucrose for callus growth and flavonoid formation, and the optimum concentration was 2%. The flavonoids content was 2 times higher than that of sucrose as carbon sources. In the range of 2% -6% of fructose concentration, the flavonoid content was decreased along with the concentration of fructose, but the licochalcone was increased 5-fold. The highest flavonoid content of 151.47 microg x g(-1) was obtained when the ratio of NH4+/NO3- in the medium was 1/2. NH; inhibited the callus growth and flavonoid formation of G. uralensis., Conclusion: Fructose as carbon source was superior to sucrose for callus growth and flavonoid formation, and NO3- was favorable to the callus growth and flavonoids accumulation.

The effect of rare-earth element Eu3+ on callus growth and its flavonoids content in Glycyrrhiza uralensis was studied. The results showed that lower concentration of rare-earth element Eu3+ could promote the callus growth and flavonoids productions. 0.1 mg/l Eu3+ was the most suitable for the biomass accumulation of the callus and flavonoids biosynthesis. In that concentration flavonoids content was 2.7 times and liquiritigenin was 4 times as that of the control.