Metabolic engineering to enhance the accumulation of bioactive flavonoids licochalcone A and echinatin in Glycyrrhiza inflata (Licorice) hairy roots

Abstract

Echinatin and licochalcone A (LCA) are valuable chalcones preferentially accumulated in roots and rhizomes of licorice (Glycyrrhiza inflata). The licorice chalcones (licochalcones) are valued for their anti-inflammatory, antimicrobial, and antioxidant properties and have been widely used in cosmetic, pharmaceutical, and food industries. However, echinatin and LCA are accumulated in low quantities, and the biosynthesis and regulation of licochalcones have not been fully elucidated. In this study, we explored the potential of a R2R3-MYB transcription factor (TF) AtMYB12, a known regulator of flavonoid biosynthesis in Arabidopsis, for metabolic engineering of the bioactive flavonoids in G. inflata hairy roots. Overexpression of AtMYB12 in the hairy roots greatly enhanced the production of total flavonoids (threefold), echinatin (twofold), and LCA (fivefold). RNA-seq analysis of AtMYB12-overexpressing hairy roots revealed that expression of phenylpropanoid/flavonoid pathway genes, such as phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), and flavanone 3’-hydroxylase (F3’H), is significantly induced compared to the control. Transient promoter activity assay indicated that AtMYB12 activates the GiCHS1 promoter in plant cells, and mutation to the MYB-binding motif in the GiCHS1 promoter abolished activation. In addition, transcriptomic analysis revealed that AtMYB12 overexpression reprograms carbohydrate metabolism likely to increase carbon flux into flavonoid biosynthesis. Further, AtMYB12 activated the biotic defense pathways possibly by activating the salicylic acid and jasmonic acid signaling, as well as by upregulating WRKY TFs. The transcriptome of AtMYB12-overexpressing hairy roots serves as a valuable source in the identification of potential candidate genes involved in LCA biosynthesis. Taken together, our findings suggest that AtMYB12 is an effective gene for metabolic engineering of valuable bioactive flavonoids in plants.

Investigation of the effects of quercetin and xenograft on the healing of bone defects: An experimental study

“… 9 Some studies have shown their role in the prevention and treatment of cardiovascular diseases, osteoporosis, diabetes, obesity and menopausal symptoms. 10 , 11 Chemically speaking, osteogenic effects occur through interaction with ERa and ERb, both subtypes of estrogen receptors (ERs) located on the surface of osteoblast cells. They show structural similarity with 17-β-estradiol (E2), which enables them to modulate the mechanism.…”

“…While there are many studies in the literature on the anti-inflammatory, antioxidant and anticarcinogenic effects of quercetin, few studies have investigated its effects on the bone. 7 , 9 , 10 , 11 Pang et al aimed to study the effect of quercetin on the differentiation and proliferation of bone marrow mesenchymal stem cells in mice. The results showed that quercetin significantly increased bone marrow mesenchymal stem cell proliferation, alkaline phosphatase activity, extracellular matrix production and mineralization.…”

“…In addition, they found that quercetin increased the osteogenic differentiation of mesenchymal stem cells. 7 , 9 , 10 , 11 …”

Engineering the plant metabolic system by exploiting metabolic regulation

“…The versatility of A. rhizogenes strains to infect a range of different plant species is outstanding and can be used both on model and non‐model organisms. For example, overexpression of AtMYB12 , which encodes a master transcriptional regulator of flavonoid biosynthesis in Arabidopsis, in licorice ( Glycyrrhiza inflata ) hairy roots leads to a 2‐ to 5‐fold accumulation of the bioactive flavonoids licochalcone A and echinatin, which have anti‐inflammatory, antimicrobial, and antioxidant properties (Wu et al, 2022). Similarly, overexpression of the leaf color (LC) TF that regulates anthocyanin production in maize and of AtPAP1, a member of the MYB TF family in Arabidopsis, in hairy roots of the Asian medicinal plant Scutellaria baicalensis results in an enhanced total flavone content, especially of baicalin, baicalein, and wogonin, which all have health‐promoting traits (Park et al, 2021).…”

A Cotyledon-based Virus-Induced Gene Silencing (Cotyledon-VIGS) approach to study specialized metabolism in medicinal plants

“…Because the complex, dimerized TIAs are synthesized in C. roseus leaves, transformation of hairy roots, although useful in genetic characterization, does not allow the investigation of TIA pathway genes that are predominantly expressed in the leaves. Like C. roseus , the generation of stable transgenic plants are difficult and time consuming for many other medicinal plants, such as Glycyrrhiza inflata [ 46 ] which produce the bioactive agent licochalcones. An efficient VIGS technique certainly benefits the studies of the biosynthesis and regulation of the specialized metabolites in these plants.…”