Efficient production and capture of 8-prenylnaringenin and leachianone G-biosynthetic intermediates of sophoraflavanone G--by the addition of cork tissue to cell suspension cultures of Sophora flavescens

Estrogenic Prenylated Flavonoids in Sophora flavescens

Sophora flavescens is a medicinal herb distributed widely in Japan and it has been used to treat various diseases and symptoms. To explore its pharmacological use, we examined the estrogenic activity of four prenylated flavonoids, namely kurarinone, kushenols A and I, and sophoraflavanone G, which are characterized by the lavandulyl group at position 8 of ring A, but have variations in the hydroxyl group at positions 3 (ring C), 5 (ring A) and 4' (ring B). These prenylated flavonoids were examined via cell proliferation assays using sulforhodamine B, Western blotting, and RT-PCR, corresponding to cell, protein, and transcription assays, respectively, based on estrogen action mechanisms. All the assays employed here found weak but clear estrogenic activities for the prenylated flavonoids examined. Furthermore, the activities were inhibited by an estrogen receptor antagonist, suggesting that the activities were likely being mediated by the estrogen receptors. However, there were differences in the activity, attributable to the hydroxyl group at position 4', which is absent in kushenol A. While the estrogenic activity of kurarinone and sophoraflavanone G has been reported before, to the best of our knowledge, there are no such reports on kushenols A and I. Therefore, this study represents the first report of their estrogenic activity.

A grobacterium-mediated genetic transformation and cloning of candidate reference genes in suspension cells of Artemisia pallens Wall. ex DC

A reliable and stable Agrobacterium-mediated genetic transformation system for Artemisia pallens has been developed using cell suspension cultures derived from cotyledon explants. Cotyledon, attached cotyledon, and compound leaves were found to be suitable for the induction of callus among five different types of explants tested. The yellow friable callus derived from attached cotyledon was used to initiate suspension cultures in Suspension Culture Medium (SCM) which was supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) at 2.0 mg L-1 and in combination with different concentrations of Zeatin (ZEA) at 0.25 mg L-1. Two different shock treatments, cold shock (at 4 ℃) for 20 min and heat shock (at 45 ℃) treatment for 5 min, heat shock treatment increased the transformation efficiency. The supplementation of Pluronic F-68 (0.05%) significantly enhanced the transformation efficiency of suspension cultures, whereas Silwet L-77 (0.05%) leads to more browning of the cells and reduced the transformation efficiency. The maximum GUS intensity was recorded with an optimal intensity of blue spots in the transformed cells. The highest GUS fluorometric activity measured was 879.4 ± 113.7 nmol 4MU/mg/min in transformed cell suspension cultures. The hygromycin-resistant calli showed intense blue color in GUS histochemical assay. The transgene integration into the plant genome was confirmed by polymerase chain reaction (PCR) using uidA specific primers in six hygromycin-resistant cell lines. The partial coding sequence of three candidate reference genes, i.e., ADP-ribosylation factor (Arf), β-actin (Act), and ubiquitin (Ubi), and carotenoid biosynthesis pathway gene, i.e., Phytoene desaturase (Pds) were cloned, sequenced, and submitted to NCBI for the first time. The quantitative mRNA expression of the transgene (uidA) and internal ApPds gene were evaluated in transgenic callus lines. The present Agrobacterium-mediated genetic transformation protocol could help in better understanding of the metabolic pathways of this medicinally important plant and its genetic improvement.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03251-x.

Toward Developing a Yeast Cell Factory for the Production of Prenylated Flavonoids

Prenylated flavonoids possess a wide variety of biological activities, including estrogenic, antioxidant, antimicrobial, and anticancer activities. Hence, they have potential applications in food products, medicines, or supplements with health-promoting activities. However, the low abundance of prenylated flavonoids in nature is limiting their exploitation. Therefore, we investigated the prospect of producing prenylated flavonoids in the yeast Saccharomyces cerevisiae. As a proof of concept, we focused on the production of the potent phytoestrogen 8-prenylnaringenin. Introduction of the flavonoid prenyltransferase SfFPT from Sophora flavescens in naringenin-producing yeast strains resulted in de novo production of 8-prenylnaringenin. We generated several strains with increased production of the intermediate precursor naringenin, which finally resulted in a production of 0.12 mg L^-1 (0.35 μM) 8-prenylnaringenin under shake flask conditions. A number of bottlenecks in prenylated flavonoid production were identified and are discussed.

Medicinal plant cell suspension cultures: pharmaceutical applications and high-yielding strategies for the desired secondary metabolites

The development of plant tissue (including organ and cell) cultures for the production of secondary metabolites has been underway for more than three decades. Plant cell cultures with the production of high-value secondary metabolites are promising potential alternative sources for the production of pharmaceutical agents of industrial importance. Medicinal plant cell suspension cultures (MPCSC), which are characterized with the feature of fermentation with plant cell totipotency, could be a promising alternative "chemical factory". However, low productivity becomes an inevitable obstacle limiting further commercialization of MPCSC and the application to large-scale production is still limited to a few processes. This review generalizes and analyzes the recent progress of this bioproduction platform for the provision of medicinal chemicals and outlines a range of trials taken or underway to increase product yields from MPCSC. The scale-up of MPCSC, which could lead to an unlimited supply of pharmaceuticals, including strategies to overcome and solution of the associated challenges, is discussed.

Tissue culture and generation of autotetraploid plants of Sophora flavescens Aiton

BACKGROUND

Sophora flavescens Aiton is an important medicinal plant in China. Early in vitro researches of S. flavescens were focused on callus induction and cell suspension culture, only a few were concerned with in vitro multiplication.

OBJECTIVE

To establish and optimize the rapid propagation technology of S. flavescens and to generate and characterize polyploid plants of S. flavescens.

MATERIALS AND METHODS

The different concentrations of 6-benzylaminopurine (BAP), indole-3-acetic acid (IAA) and kinetin (KT) were used to establish and screen the optimal rapid propagation technology of S. flavescens by orthogonal test; 0.2% colchicine solution was used to induce polyploid plants and the induced buds were identified by root-tip chromosome determination and stomatal apparatus observation.

RESULTS

A large number of buds could be induced directly from epicotyl and hypocotyl explants on the Murashige and Skoog medium (MS; 1962) supplemented with 1.4-1.6 mg/l 6-benzylaminopurine (BAP) and 0.3 mg/l indole-3-acetic acid (IAA). More than 50 lines of autotetraploid plants were obtained. The chromosome number of the autotetraploid plantlet was 2n = 4× = 36. All tetraploid plants showed typical polyploid characteristics.

CONCLUSION

Obtained autotetraploid lines will be of important genetic and breeding value and can be used for further selection and plant breeding.

Regulation of isoflavone production in hydroponically grown Pueraria montana (kudzu) by cork pieces, XAD-4, and methyl jasmonate

A mini-hydroponic growing system was employed for seedlings of kudzu vine (Pueraria montana) and contents of isoflavones (daidzein, genistein, daidzin, genistin, and puerarin) from shoot and root parts of seedlings were analyzed quantitatively. In addition, exogenous cork pieces, polymeric adsorbent, XAD-4, and universal elicitor, methyl jasmonate (MeJA), were used to regulate the production of these isoflavones. It was shown that cork pieces up-regulate the production of daidzein and genistein up to seven- and eight-fold greater than the levels obtained for control roots. In contrast, levels of glucosyl conjugates, daidzin and genistin, decrease up to five- and eight-fold, respectively. Cork treatment also induces the excretion of the root isoflavone constituents into the growth medium. Minimal levels of isoflavones are absorbed by the cork pieces. XAD-4 stimulates the production of glucosyl conjugates, daidzin and genistin, in root parts about 1.5-fold greater than that obtained in control roots. These are the highest amounts of daidzin and genistin that are observed (5.101 and 6.759 mg g(-1) dry weight, respectively). In contrast to these two adsorbents, MeJA increases the accumulation of isoflavones in shoot rather than in root parts of seedlings, about three- to four-fold over control levels, with the exception of genistein. These studies reveal new observations on the regulation of isoflavone production in hydroponically grown Pueraria montana plants by two adsorbents (cork pieces and XAD-4) and MeJA elicitor.

Stimulating the production of homoisoflavonoids in cell suspension cultures of Caesalpinia pulcherrima using cork tissue

It has previously been demonstrated that cork tissue increases the efficiency of the production of lipophilic secondary metabolites in diverse plant cell suspension cultures. In the present study, three new homoisoflavonoids--named dihydrobonducellin, 2'-methoxydihydrobonducellin, and 2'-methoxybonducellin--and bonducellin and isobonducellin were isolated from Caesalpinia pulcherrima cultured cells coincubated with cork tissue. Cork tissue increased the production of 2'-methoxybonducellin by about 7-fold relative to control cells, and more than 80% of the product was recoverable from the cork tissue. When cork tissue and methyl jasmonate or yeast extract were added simultaneously to the medium, the amount of 2'-methoxybonducellin produced increased further. The production of the other four homoisoflavonoids was enhanced by variable amounts. Our results indicate that the addition of cork tissue would be an effective technique for investigating formation of secondary metabolites that usually accumulate only in trace amounts.

Characterization of leachianone G 2"-dimethylallyltransferase, a novel prenyl side-chain elongation enzyme for the formation of the lavandulyl group of sophoraflavanone G in Sophora flavescens Ait. cell suspension cultures

Leachianone G (LG) 2"-dimethylallyltransferase, a novel prenyl side-chain elongation enzyme, was identified in Sophora flavescens Ait. cultured cells. The enzyme transfers a dimethylallyl group to the 2" position of another dimethylallyl group attached at position 8 of LG to form sophoraflavanone G, a branched monoterpenoid-conjugated flavanone characteristic to this plant. This membrane-bound dimethylallyltransferase required Mg2+ (optimum concentration was 10 mm) for the reaction and had an optimum pH of 8.8. It utilized dimethylallyl diphosphate as the sole prenyl donor, and the 2'-hydroxy function in LG was indispensable to the activity. The apparent Km values for dimethylallyl diphosphate and LG were 59 and 2.3 microm, respectively. Subcellular localization of three enzymes that participated in the formation of the lavandulyl group was also investigated by sucrose density gradient centrifugation. Two prenyltransferases, naringenin 8-dimethylallyltransferase and LG 2"-dimethylallyltransferase, were localized in the plastids, whereas 8-dimethylallylnaringenin 2'-hydroxylase, which catalyzes the crucial step in the lavandulyl-group formation, was associated with the endoplasmic reticulum. These results suggest the close cooperation between the plastids and the endoplasmic reticulum in the formation of lavandulyl groups.