Application of Hairy Root Culture for Bioactive Compounds Production in Medicinal Plants

Variability in growth and biosynthetic activity of Calendula officinalis hairy roots

Calendula officinalis is a widespread medicinal plant with a sufficiently well-studied chemical composition. Secondary metabolites synthesized by C.officinalis plants have pharmacological value for treating numerous diseases, and various types of aseptic in vitro cultures can be used as a source of these compounds. From this perspective, hairy roots attract considerable attention for the production of bioactive chemicals, including flavonoids with antioxidant activity. This paper shows the possibility of C.officinalis hairy roots obtaining with 100% frequency by Agrobacterium rhizogenes genetic transformation. Hairy root lines differed in growth rate and flavonoid content. In particular, flavonoids were accumulated in the amount of up to 6.68 ± 0.28 mg/g of wet weight. Methyl jasmonate in the concentration of 10 µM inhibited root growth to a small extent but stimulated the synthesis of flavonoids. The antioxidant activity and the reducing power increased in the roots grown in the medium with methyl jasmonate. The strong correlation of antioxidant activity and reducing power with flavonoid content was detected. The influence of extraction conditions on the content of flavonoids in the extracts and their bioactivity was determined. The potent reducing activity of extracts from hairy roots allowed the production of silver nanoparticles, which was confirmed by transmission electron microscopy.

Enhancing Withanolide Production in the Withania Species: Advances in In Vitro Culture and Synthetic Biology Approaches

Withanolides are naturally occurring steroidal lactones found in certain species of the Withania genus, especially Withania somnifera (commonly known as Ashwagandha). These compounds have gained considerable attention due to their wide range of therapeutic properties and potential applications in modern medicine. To meet the rapidly growing demand for withanolides, innovative approaches such as in vitro culture techniques and synthetic biology offer promising solutions. In recent years, synthetic biology has enabled the production of engineered withanolides using heterologous systems, such as yeast and bacteria. Additionally, in vitro methods like cell suspension culture and hairy root culture have been employed to enhance withanolide production. Nevertheless, one of the primary obstacles to increasing the production of withanolides using these techniques has been the intricacy of the biosynthetic pathways for withanolides. The present article examines new developments in withanolide production through in vitro culture. A comprehensive summary of viable traditional methods for producing withanolide is also provided. The development of withanolide production in heterologous systems is examined and emphasized. The use of machine learning as a potent tool to model and improve the bioprocesses involved in the generation of withanolide is then discussed. In addition, the control and modification of the withanolide biosynthesis pathway by metabolic engineering mediated by CRISPR are discussed.

Induction and metabolomic analysis of hairy roots of Atractylodes lancea

Atractylodes lancea is an important source of traditional Chinese medicines. Sesquiterpenoids are the key active compounds in A. lancea, and their presence determines the quality of the material. Hairy hoot (HR) culture is a potential method to produce medicinally active compounds industrially; however, the induction and metabolic profiling of A. lancea HR have not been reported. We found that optimal induction of A. lancea HR was achieved by Agrobacterium rhizogenes strain C58C1 using the young leaves of tissue culture seedlings in the rooting stage as explants. Ultra-performance liquid chromatography-tandem mass spectrometric analyses of the chemical compositions of HR and normal root (NR) led to the annotation of 1046 metabolites. Over 200 differentially accumulated metabolites were identified, with 41 found to be up-regulated in HR relative to NR and 179 down-regulated in HR. Specifically, atractylodin levels were higher in HR, while the levels of β-eudesmol and hinesol were higher in NR. Metabolic pathway analyses showed a significant difference in metabolites of the shikimate acid pathway between HR and NR. Five A. lancea compounds are potential biomarkers for evaluation of HR and NR quality. This study provides an important reference for the application of HR for the production of medicinally active compounds. KEY POINTS: • We established an efficient protocol for the induction of HR in A. lancea • HR was found to have a significantly higher amount of atractylodin than did NRs • Metabolic pathway analyses showed a significant difference in metabolites of the shikimate acid pathway between HR and NR.

Production of Two Isomers of Sphaeralcic Acid in Hairy Roots from Sphaeralcea angustifolia

The Sphaeralcea angustifolia plant is used as an anti-inflammatory and gastrointestinal protector in Mexican traditional medicine. The immunomodulatory and anti-inflammatory effects have been attributed to scopoletin (1), tomentin (2), and sphaeralcic acid (3) isolated from cells in suspension cultures and identified in the aerial tissues of the wild plant. The hairy roots from S. angustifolia established by infecting internodes with Agrobacterium rhizogenes were explored to produce active compounds based on biosynthetic stability and their capacity to produce new compounds. Chemical analysis was resumed after 3 years in these transformed roots, SaTRN12.2 (line 1) produced scopoletin (0.0022 mg g^-1) and sphaeralcic acid (0.22 mg g^-1); instead, the SaTRN7.1 (line 2) only produced sphaeralcic acid (3.07 mg g^-1). The sphaeralcic acid content was 85-fold higher than that reported for the cells in the suspension cultivated into flakes, and it was similar when the cells in suspension were cultivated in a stirring tank under nitrate restriction. Moreover, both hairy root lines produced stigmasterol (4) and β-sitosterol (5), as well as two new naphthoic derivates: iso-sphaeralcic acid (6) and 8-methyl-iso-sphaeralcic acid (7), which turned out to be isomers of sphaeralcic acid (3) and have not been reported. The dichloromethane-methanol extract from SaTRN7.1 hairy root line had a gastroprotective effect on an ulcer model in mice induced with ethanol.

Current status and future prospects in cannabinoid production through in vitro culture and synthetic biology

For centuries, cannabis has been a rich source of fibrous, pharmaceutical, and recreational ingredients. Phytocannabinoids are the most important and well-known class of cannabis-derived secondary metabolites and display a broad range of health-promoting and psychoactive effects. The unique characteristics of phytocannabinoids (e.g., metabolite likeness, multi-target spectrum, and safety profile) have resulted in the development and approval of several cannabis-derived drugs. While most work has focused on the two main cannabinoids produced in the plant, over 150 unique cannabinoids have been identified. To meet the rapidly growing phytocannabinoid demand, particularly many of the minor cannabinoids found in low amounts in planta, biotechnology offers promising alternatives for biosynthesis through in vitro culture and heterologous systems. In recent years, the engineered production of phytocannabinoids has been obtained through synthetic biology both in vitro (cell suspension culture and hairy root culture) and heterologous systems. However, there are still several bottlenecks (e.g., the complexity of the cannabinoid biosynthetic pathway and optimizing the bioprocess), hampering biosynthesis and scaling up the biotechnological process. The current study reviews recent advances related to in vitro culture-mediated cannabinoid production. Additionally, an integrated overview of promising conventional approaches to cannabinoid production is presented. Progress toward cannabinoid production in heterologous systems and possible avenues for avoiding autotoxicity are also reviewed and highlighted. Machine learning is then introduced as a powerful tool to model, and optimize bioprocesses related to cannabinoid production. Finally, regulation and manipulation of the cannabinoid biosynthetic pathway using CRISPR- mediated metabolic engineering is discussed.

Overexpression of TwSQS, TwSE, and TwOSC Regulates Celastrol Accumulation in Cambial Meristematic Cells and Dedifferentiated Cells

Squalene synthase (SQS), squalene epoxidase (SE), and oxidosqualene cyclase (OSC) are encoding enzymes in downstream biosynthetic pathway of triterpenoid in plants, but the relationship between three genes and celastrol accumulation in Tripterygium wilfordii still remains unknown. Gene transformation system in plant can be used for studying gene function rapidly. However, there is no report on the application of cambial meristematic cells (CMCs) and dedifferentiated cells (DDCs) in genetic transformation systems. Our aim was to study the effects of individual overexpression of TwSQS, TwSE, and TwOSC on terpenoid accumulation and biosynthetic pathway related gene expression through CMCs and DDCs systems. Overexpression vectors of TwSQS, TwSE, and TwOSC were constructed by Gateway technology and transferred into CMCs and DDCs by gene gun. After overexpression, the content of celastrol was significantly increased in CMCs compared with the control group. However, there was no significant increment of celastrol in DDCs. Meanwhile, the relative expression levels of TwSQS, TwSE, TwOSC, and terpenoid biosynthetic pathway related genes were detected. The relative expression levels of TwSQS, TwSE, and TwOSC were increased compared with the control group in both CMCs and DDCs, while the pathway-related genes displayed different expression trends. Therefore, it was verified in T. wilfordii CMCs that overexpression of TwSQS, TwSE, and TwOSC increased celastrol accumulation and had different effects on the expression of related genes in terpenoid biosynthetic pathway, laying a foundation for further elucidating the downstream biosynthetic pathway of celastrol through T. wilfordii CMCs system.

Spontaneous Regeneration of Plantlets Derived from Hairy Root Cultures of Lopezia racemosa and the Cytotoxic Activity of Their Organic Extracts

A histological analysis was performed with the aim of elucidating the spontaneous regeneration process of the hairy root lines LRT 2.3 and LRT 6.4, derived from Lopezia racemosa leaf explants and genetically transformed with the Agrobacterium rhizogenes strain ATCC15834/pTDT. The analysis showed both lines regenerate via indirect somatic embryogenesis; LRT 6.4 also regenerated by direct organogenesis. The morphogenic characteristics of the regenerated plantlets from both lines showed the typical characteristics, described previously, including a higher number of axillary shoot formation, short internodes, and plagiotropic roots compared with wild-type seedlings. The regeneration process occurred without the addition of plant growth regulators and was linked to the sucrose concentration in the culture medium. Reducing the sucrose concentration from 3% to 2%, 1%, and 0.5% increased the regeneration rate in LRT 6.4; the effect was less pronounced in LRT 2.3. The cytotoxic activity of different organic extracts obtained from roots and shoots were evaluated in the cancer cell lines HeLa (cervical carcinoma), HCT-15 (colon adenocarcinoma), and OVCAR (ovary carcinoma). The hexane and dichloromethane extracts from roots of both lines showed cytotoxic activity against the HeLa cell line. Only the dichloromethane extract from the roots of PLRT 2.3 showed cytotoxic activity against the OVCAR cell line. None of the methanol extracts showed cytotoxic activity, nor the shoot extracts from any solvent.

An Efficient Method for the Genetic Transformation of Acmella oleracea L. (Spilanthes acmella Linn.) with Agrobacterium tumefaciens

Acmella oleracea L. is an important medicinal plant, commonly known as the toothache plant. It is a rich source of secondary metabolites used for the treatment of different human disorders. The demand for Acmella oleracea L. has increased due to its putative health benefits (in terms of both biomass quantity and bioactive compound purification). In vitro plant cultures have allowed the rapid increase of raw material availability through the use of suitable regeneration and multiplication systems. On the other hand, there is a general lack of methods for Acmella genetic transformation as a promising new technological approach for the improvement of secondary metabolites. In this work, an efficient transformation protocol has been established using the Agrobacterium tumefaciens LBA4404 strain bearing the binary vector pBI121 containing the NPTII gene for the resistance to kanamycin. Plant genetic transformation has been verified by direct polymerase chain reaction and GUS assay on regenerants. Transformation efficiency has been affected by the high level of the selection agent kanamycin. To our knowledge, this is the first report on the genetic transformation of A. oleracea, paving the way to further studies to improve in vitro plant growth and secondary metabolite production.