Yeast extract elicitation increases vinblastine and vincristine yield in protoplast derived tissues and plantlets in Catharanthus roseus

Unleashing plant synthetic capacity: navigating regulatory mechanisms for enhanced bioproduction and secondary metabolite discovery

Plant natural products (PNPs) hold significant pharmaceutical importance. The sessile nature of plants has led to the evolution of chemical defense mechanisms over millions of years to combat environmental challenges, making it a crucial and essential defense weapon. Despite their importance, the abundance of these bioactive molecules in plants is typically low, and conventional methods are time-consuming for enhancing production. Moreover, there is a pressing need for novel drug leads, exemplified by the shortage of antibiotics and anticancer drugs. Understanding how plants respond to stress and regulate metabolism to produce these molecules presents an opportunity to explore new avenues for discovering compounds that are typically under the detection limit or not naturally produced. Additionally, this knowledge can contribute to the advancement of plant engineering, enabling the development of new chassis for the biomanufacturing of these valuable molecules. In this perspective, we explore the intricate regulation of PNP biosynthesis in plants, and discuss the biotechnology strategies that have been and can be utilized for the discovery and production enhancement of PNPs in plants.

An update on biotechnological intervention mediated by plant tissue culture to boost secondary metabolite production in medicinal and aromatic plants

Since prehistoric times, medicinal and aromatic plants (MAPs) have been employed for various therapeutic purposes due to their varied array of pharmaceutically relevant bioactive compounds, i.e. secondary metabolites. However, when secondary metabolites are isolated directly from MAPs, there is occasionally very poor yield and limited synthesis of secondary metabolites from particular tissues and certain developmental stages. Moreover, many MAPs species are in danger of extinction, especially those used in pharmaceuticals, as their natural populations are under pressure from overharvesting due to the excess demand for plant-based herbal remedies. The extensive use of these metabolites in a number of industrial and pharmaceutical industries has prompted a call for more research into increasing the output via optimization of large-scale production using plant tissue culture techniques. The potential of plant cells as sources of secondary metabolites can be exploited through a combination of product recovery technology research, targeted metabolite production, and in vitro culture establishment. The plant tissue culture approach provides low-cost, sustainable, continuous, and viable secondary metabolite production that is not affected by geographic or climatic factors. This study covers recent advancements in the induction of medicinally relevant metabolites, as well as the conservation and propagation of plants by advanced tissue culture technologies.

Enhancement of Plumbagin Production through Elicitation in In Vitro-Regenerated Shoots of Plumbago indica L

Plumbago indica L. contains a valuable bioactive compound called plumbagin. Elicited regenerated shoots grown in vitro could be another source of high-yielding plumbagin. The purpose of this investigation was to examine the effects of elicitor type and concentration, as well as elicitation period, on plumbagin content in in vitro-regenerated shoots of P. indica. Nodal explants were cultured on Murashige and Skoog (MS) medium containing 1 mg/L benzyladenine (BA) in combination with 0-150 mg/L yeast extract or 50-150 µM salicylic acid for four weeks. Plumbagin levels of 3.88 ± 0.38% and 3.81 ± 0.37% w/w g dry extract were achieved from the 50 and 100 mg/L yeast extract-elicited shoots, which were higher than the value obtained for the control. However, the addition of salicylic acid did not increase the plumbagin content. In the elicitation period experiment, nodal explants were cultured on MS medium supplemented with 1 mg/L BA and 50 mg/L yeast extract for durations of three, four and five weeks. The 4-week yeast extract-elicited shoot had a maximum plumbagin content of 3.22 ± 0.12% w/w g dry extract, greater than that of the control. In summary, the plumbagin content of the in vitro P. indica shoots was enhanced by 4-week elicitation using 50 mg/L yeast extract.

Gibberellic acid 3 enhanced the anticancer activity of Abeliophyllum distichum adventitious roots by activating the diterpenoid biosynthesis pathway

The industrial value of various plants has been improved through the of plant cell culture systems with elicitation. In this study, the adventitious root of Abeliophyllum distichum (AdAR) was treated with gibberellic acid 3 (GA3) to improve its anticancer property. The hexane fraction of the GA3-treated A. distichum adventitious root exhibited a stronger cytotoxic activity against A549 cells than the hexane fraction of AdAR. Through GC/MS and principal component analysis, we identified ferruginol and sugiol as anticancer compounds, which were induced by GA3 treatment in AdAR. Gene expression analysis combined with functional characterisation suggests that the GA3 treatment increased the transcription of geranylgeranyl pyrophosphate synthases and copalyl diphosphate synthase, which led to the accumulation of diterpenoids, including ferruginol and sugiol. Overall, these findings can contribute to the advancement of metabolic engineering for enhancing the biosynthesis of active diterpenoids, and facilitate the large-scale production of bioactive compounds sourced from A. distichum.

Metabolic Effects of Elicitors on the Biosynthesis of Tropane Alkaloids in Medicinal Plants

Tropane alkaloids (TAs) are large secondary metabolite alkaloids that find extensive applications in the synthesis of antidotes, anesthetics, antiemetics, motion sickness drugs, and antispasmodics. The current production method primarily depends on extraction from medicinal plants of the Solanaceae family. Elicitation, as a highly effective biotechnological approach, offers significant advantages in augmenting the synthesis of secondary metabolites. The advantages include its simplicity of operation, low cost, and reduced risk of contamination. This review focuses on the impact of elicitation on the biosynthesis of TAs from three aspects: single-elicitor treatment, multiple-elicitor treatment, and the combination of elicitation strategy with other strategies. Some potential reasons are also proposed. Plant hormones and growth regulators, such as jasmonic acid (JA), salicylic acid (SA), and their derivatives, have been extensively employed in the separate elicitation processes. In recent years, novel elicitors represented by magnetic nanoparticles have emerged as significant factors in the investigation of yield enhancement in TAs. This approach shows promising potential for further development. The current utilization of multi-elicitor treatment is constrained, primarily relying on the combination of only two elicitors for induction. Some of these combinations have been found to exhibit synergistic amplification effects. However, the underlying molecular mechanism responsible for this phenomenon remains largely unknown. The literature concerning the integration of elicitation strategy with other strategies is limited, and several research gaps require further investigation. In conclusion, the impact of various elicitors on the accumulation of TAs is well-documented. However, further research is necessary to effectively implement elicitation strategies in commercial production. This includes the development of stable bioreactors, the elucidation of regulatory mechanisms, and the identification of more potent elicitors.

Vinca alkaloids as a potential cancer therapeutics: recent update and future challenges

Vinca alkaloids including vincristine, vinblastine, vindesine, and vinflunine are chemotherapeutic compounds commonly used to treat various cancers. Vinca alkaloids are one of the first microtubule-targeting agents to be produced and certified for the treatment of hematological and lymphatic neoplasms. Microtubule targeting agents like vincristine and vinblastine work by disrupting microtubule dynamics, causing mitotic arrest and cell death. The key issues facing vinca alkaloids applications include establishing an environment-friendly production technique based on microorganisms, as well as increasing bioavailability without causing harm to patient's health. The low yield of these vinca alkaloids from the plant and the difficulty of meeting their huge colossal demand around the globe prompted researchers to create a variety of approaches. Endophytes could thus be selected to produce beneficial secondary metabolites required for the biosynthesis of vinca alkaloids. This review covers the significant aspects of these vital drugs, from their discovery to the present day, in a concise manner. In addition, we emphasize the major hurdles that must be overcome in the coming years to improve vinca alkaloid's effectiveness.

Improving Flavonoid Accumulation of Bioreactor-Cultured Adventitious Roots in Oplopanax elatus Using Yeast Extract

Oplopanax elatus is an endangered medicinal plant, and adventitious root (AR) culture is an effective way to obtain its raw materials. Yeast extract (YE) is a lower-price elicitor and can efficiently promote metabolite synthesis. In this study, the bioreactor-cultured O. elatus ARs were treated with YE in a suspension culture system to investigate the elicitation effect of YE on flavonoid accumulation, serving for further industrial production. Among YE concentrations (25-250 mg/L), 100 mg/L YE was the most suitable for increasing the flavonoid accumulation. The ARs with various ages (35-, 40-, and 45-day-old) responded differently to YE stimulation, where the highest flavonoid accumulation was found when 35-day-old ARs were treated with 100 mg/L YE. After YE treatment, the flavonoid content increased, peaked at 4 days, and then decreased. By comparison, the flavonoid content and antioxidant activities in the YE group were obviously higher than those in the control. Subsequently, the flavonoids of ARs were extracted by flash extraction, where the optimized extraction process was: 63% ethanol, 69 s of extraction time, and a 57 mL/g liquid-material ratio. The findings provide a reference for the further industrial production of flavonoid-enriched O. elatus ARs, and the cultured ARs have potential application for the future production of products.

Internal and External Regulatory Elements Controlling Somatic Embryogenesis in Catharanthus: A Model Medicinal Plant

Somatic or in vitro embryogenesis is a unique embryo producing process from vegetative cells observed in plants since 1958. Even over 60 years of research, the transition of somatic cells into embryonic fate is still not elucidated fully. Various networks and signaling elements have been noted to play important role in this "vegetative to reproductive" transition process. The networks include genotypes, explant types, the sugar/carbohydrate sources, cultural/environmental conditions like light quality and intensity, dissolved oxygen (DO) level, cell density, plant growth regulator (PGR) (auxin and cytokinin) signaling, PGR-gene interplay, stresses are important and cause new cellular reprogramming during embryonic acquisition. A wide array of genes, specific to zygotic embryogenesis, also express during somatic embryogenesis. A few embryogenesis-specific genes such as SOMATIC EMBRYOGENESIS LIKE RECEPTOR KINASE, LEAFY COTYLEDON, AGAMOUS-LIKE 15, and BABY BOOM are crucial and have been discussed. The chapter focuses the importance of these gene products, e.g., proteins, enzymes, and transcription factors in regulating embryogenesis. Many of these encoded proteins act as potential somatic embryogenesis markers. Besides, important elements such as genotype, herbaceous/woody plants' response in culture in inducing embryos have been discussed. All these elements are connected and form network in complex fashion thus difficult to unfold fully; some of the current progress and developments have been presented in this chapter.

Terpenoid indole alkaloid biosynthesis in Catharanthus roseus: effects and prospects of environmental factors in metabolic engineering

Plants synthesize a vast array of specialized metabolites that primarily contribute to their defense and survival under adverse conditions. Many of the specialized metabolites have therapeutic values as drugs. Biosynthesis of specialized metabolites is affected by environmental factors including light, temperature, drought, salinity, and nutrients, as well as pathogens and insects. These environmental factors trigger a myriad of changes in gene expression at the transcriptional and posttranscriptional levels. The dynamic changes in gene expression are mediated by several regulatory proteins that perceive and transduce the signals, leading to up- or down-regulation of the metabolic pathways. Exploring the environmental effects and related signal cascades is a strategy in metabolic engineering to produce valuable specialized metabolites. However, mechanistic studies on environmental factors affecting specialized metabolism are limited. The medicinal plant Catharanthus roseus (Madagascar periwinkle) is an important source of bioactive terpenoid indole alkaloids (TIAs), including the anticancer therapeutics vinblastine and vincristine. The emerging picture shows that various environmental factors significantly alter TIA accumulation by affecting the expression of regulatory and enzyme-encoding genes in the pathway. Compared to our understanding of the TIA pathway in response to the phytohormone jasmonate, the impacts of environmental factors on TIA biosynthesis are insufficiently studied and discussed. This review thus focuses on these aspects and discusses possible strategies for metabolic engineering of TIA biosynthesis. PURPOSE OF WORK: Catharanthus roseus is a rich source of bioactive terpenoid indole alkaloids (TIAs). The objective of this work is to present a comprehensive account of the influence of various biotic and abiotic factors on TIA biosynthesis and to discuss possible strategies to enhance TIA production through metabolic engineering.

Cadmium chloride (CdCl2) elicitation improves reserpine and ajmalicine yield in Rauvolfia serpentina as revealed by high-performance thin-layer chromatography (HPTLC)

In vitro cultures play a promising role for production of pharmaceutically important plant secondary metabolites and the use of elicitation can mitigate the low productivity of active compounds. In the present study, the influence of cadmium chloride (CdCl₂) elicitation on alkaloid yield was investigated in Rauvolfia serpentina. This heavy metal was employed to enhance the yield of reserpine and ajmalicine in leaf derived callus, leaves, stems and roots of in vitro grown cultures. Different concentrations [0.05 mM (C1), 0.10 mM (C2), 0.15 mM (C3) and 0.20 mM (C4)] of CdCl₂ were added to the MS medium. The elicitor's influence on callus biomass, biochemical attributes and the yield of alkaloids was monitored at regular intervals. The amendment of CdCl₂ improved growth and maximum callus biomass (1.29 g fresh weight and 0.16 g dry weight) was noted at 0.15 mM (C3) after 6 days of elicitation. The addition of elicitor in medium caused cellular stress and to analyse the role of CdCl₂ in plant defence responses various antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities were measured in treated and non-treated cultures. The antioxidant enzyme activity increased linearly with elevated levels of CdCl₂ in medium; highest APX (0.88 EU min^-1 mg^-1protein), SOD (5.40 EU min^-1 mg^-1protein) and CAT (4.21 EU min^-1 mg^-1protein) activity were observed in leaves of in vitro regenerated plants at C4. The quantitative analyses of reserpine and ajmalicine were conducted in different elicitated tissues using high-performance thin-layer chromatography (HPTLC) method. The study reveals enriched level of reserpine and ajmalicine in cultivated tissues and the enhancement was noted up to C3 (0.15 mM) elicitor level. Reserpine yield was maximum (0.191 mg g^-1 DW) in roots of in vitro regenerated plants. The accumulation of ajmalicine was, however, better in leaf derived callus at C3 (0.131 mg g^-1 DW). Higher elicitor dose (0.20 mM) inhibited callus biomass growth and subsequent alkaloid accumulation. The present study indicates the use of CdCl₂ as a propitious method in enhancing reserpine and ajmalicine yield in R. serpentina.

Carbohydrate polymers exhibit great potential as effective elicitors in organic agriculture: A review

Some carbohydrate polymers, usually oligosaccharides or polysaccharides, have great potential as an elicitor of plant defense. However, due to the complexity and diversity of poly- and oligosaccharide structure, the molecular mechanisms and structure-activity relationships of carbohydrate elicitors are still not well understood, which hinders the application of carbohydrate elicitors in agriculture. This review introduces the mechanisms of carbohydrate elicitor perception and signaling in plants. The structure and activity relationships of main poly- and oligosaccharides studied for the control of plant diseases are discussed and summarized. Additionally, the effects of carbohydrate elicitors on the secondary metabolite production are also summarized.

Essential oil yield estimation by Gas chromatography-mass spectrometry (GC-MS) after Methyl jasmonate (MeJA) elicitation in in vitro cultivated tissues of Coriandrum sativum L

Coriandrum sativum is an important spice plant known for its unique fragrance. Coriander oil is also one of the major essential oils in world global market. The oil yield varies with different coriander varieties; and the content and quality of oil is governed by several factors. In recent times, a variety of technologies have been exploited to improve phyto-compounds including essential oils. In this present study, Methyl jasmonate (MeJA) was amended in medium and the yield of essential oil was measured and compared in different cultivating tissues. The cultured tissues were nonembryogenic callus and embryogenic tissues (induction, proliferation and maturation stages of embryos). MeJA acts as a signaling molecule in accumulating secondary metabolites. Four different MeJA treatments i.e. T1 = 50, T2 = 100, T3 = 150 and T4 = 200 μM, along with a control (T0) were used and the yield of coriander essential oil was estimated in different in vitro cultivating tissues by using Gas chromatography-mass spectrometry (GC-MS). The addition of MEJA enriched essential oil yield, maximum oil being in maturation stage of embryos at T3 (150 μM). Other added treatments also had varied stimulatory role. The addition of MeJA induced stress as the stress marker enzymes like superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) content were high compared to non treated tissue (T0). In T4, the CAT activity was maximum i.e. 5.83 and 6.28 mg-1 protein min-1 in Co-1 and RS respectively in matured somatic embryos. The SOD activity was also high at maturation stage of embryos at T4 (5.3 mg-1 protein min-1 in RS). The APX activity on the other, was high (3.32 mg-1 protein min-1) in induction stage of embryogenesis at T3. The comparative biochemical (sugar, protein and proline) analyses of tissues were performed and presented that had high and low essential oil. MeJA induced stress may help in accumulating essential oils in C. sativum.

Antioxidative and Potentially Anti-inflammatory Activity of Phenolics from Lovage Leaves Levisticum officinale Koch Elicited with Jasmonic Acid and Yeast Extract

The effect of elicitation with jasmonic acids (JA) and yeast extract (YE) on the production of phenolic compounds as well as the antioxidant and anti-inflammatory properties of phenolic extracts of lovage was evaluated. The analysis of phenolic compounds carried out with the UPLC-MS technique indicated that rutin was the dominant flavonoid, while 5-caffeoylquinic acid was the main component in the phenolic acid fraction in the lovage leaves. The application of 10 µM JA increased the content of most of the identified phenolic compounds. The highest antioxidant activities estimated as free radical scavenging activity against ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and reducing power were determined for the sample elicited with 10 µM JA, while this value determined as iron chelating ability was the highest for the 0.1% YE-elicited lovage. The 0.1% and 1% YE elicitation also caused significant elevation of the lipoxygenase (LOX) inhibition ability, while all the concentrations of the tested elicitors significantly improved the ability to inhibit cyclooxygenase 2 (COX2) (best results were detected for the 10 µM JA and 0.1% YE2 sample). Thus, 0.1% yeast extract and 10 µM jasmonic acid proved to be most effective in elevation of the biological activity of lovage.