The effect of drought stress on the expression of key genes involved in the biosynthesis of triterpenoid saponins in liquorice ( Glycyrrhiza glabra )

Abstract

Glycyrrhiza glabra is an important medicinal plant throughout the world. Glycyrrhizin is a triterpenoid that is among the most important secondary metabolites produced by liquorice. Drought stress is proposed to enhance the levels of secondary metabolites. In this study, the effect of drought stress on the expression of important genes involved in the glycyrrhizin biosynthetic pathway was examined. Drought stress at the seedling stage was applied to 8-day-old plants using polyethylene glycol. Subsequently, the samples were collected 0, 4, 8 or 24 h post-treatment. At the adult plant stage, 10-month-old plants were subjected to drought stress by discontinuing irrigation. Subsequently, samples were collected at 2, 16 and 28 days after drought imposition (S(2d), S(16d) and S(28d), respectively). We performed semi-quantitative RT-PCR assays to evaluate the gene expression levels of sequalene synthase (SQS), β-amyrin synthase (bAS), lupeol synthase (LUS) and cycloartenol synthase (CAS) during stress. Finally, the glycyrrhizin content of stolons was determined via HPLC. The results revealed that due to osmotic stress, the gene expression levels of SQS and bAS were increased, whereas those of CAS were relatively unchanged at the seedling stage. At the adult plant stage, the expression levels of SQS and bAS were increased under drought stress conditions, whereas the gene expression level of CAS remained relatively constant. The glycyrrhizin content in stolons was increased only under severe drought stress conditions (S(28d)). Our results indicate that application of controlled drought stress up-regulates the expression of key genes involved in the biosynthesis of triterpenoid saponins and directly enhances the production of secondary metabolites, including glycyrrhizin, in liquorice plants.

Climatic Factors Shape the Spatial Distribution of Concentrations of Triterpenoids in Barks of White Birch (Betula Platyphylla Suk.) Trees in Northeast China

“…Our results indicate that most of the summer time locally during June and July may be proper to harvest triterpenoids in BTB due to significant increase of accumulation. The low relative humidity can cause a drought event which can promote the synthesis of triterpenoids [17,20]. Therefore, the negative relationship between relative humidity and betulin and lupeol concentrations (Figures 3b and 4b) may be shaped by the drought level.…”

Acclimation mechanisms elicited by sprayed abscisic acid, solar UV-B and water deficit in leaf tissues of field-grown grapevines

“…Values are means (n ¼ 5) and different letters indicate statistically significant differences between treatments at the P 0.05 level according to Fisher's LSD test. synthesis of membrane sterols that protect the cytosol (Douglas, 1985;Gil et al, 2012;Nasrollahi et al, 2014). Table 2 shows that linolenic acid in grapevine leaves was highest in eUV-B/eD/eABA combined treatment and lowest in þUV-B/þD/ eABA combined treatment.…”

Improving the Concentrations of the Active Components in the Herbal Tea Ingredient, Uraria crinita: The Effect of Post-harvest Oven-drying Processing

“…As a result, water depletion during the drying process will cause a series of dehydration-related physiological reactions that maintain the normal physiological function29303132, particularly the increase in the levels of some secondary metabolites that are involved in defense mechanisms33. The increase in the levels of betaine and free amino acids in plants as a result of drought stress can regulate the osmotic balance to maintain the ability to resist drought3031; the biosyntheses of betaine, flavonoids and triterpenoids improve the plants’ resistance to the increased oxidative stress caused by drought stress, thus protecting the plant cells and maintaining normal function293234. Salicylic acid can regulate the expression of anti-oxidase to improve the plants’ resistance by changing active oxygen metabolism and associated signal transduction pathways35.…”