Precursors and elicitor induced enhancement of cell biomass and phenolic compounds in cell suspensions of Indian basil-Ocimum basilicum (CIM-Saumya).

CIM-Saumya is an improved, methyl chavicol rich variety of Ocimum basilicum (Family-Lamiaceae), developed by Council of Scientific and Industrial Research-Central Institute of Medicinal and Aromatic Plants. This plant possesses analgesic, anti-ulcerogenic, anti-inflammatory, anti-oxidant, cardiac stimulant, Central Nervous System depressant, hepatoprotective and immunomodulator activities due to the presence of various phytoconstituents. Among them rosmarinic acid, caffeic acid and ferulic acid are the three major phenolic compounds responsible for its therapeutic utility. These compounds are produced in very low amounts in the in vivo plants. Therefore, the present study has been conducted for establishment of cell suspensions, optimization of inoculums size, growth kinetics and screening of elicitor and precursors for the accumulation of cell biomass and the production of the three important phenolic compounds in cell suspension of O. basilicum (CIM-Saumya). Leaf derived friable callus was used for establishing the cell suspension in liquid Murashige and Skoog's medium fortified with 1 g/L casein hydrolysate + 2.26 µM 2,4-dichlorophenoxyacetic acid + 0.465 µM kinetin + 2.68 µM naphthalene acetic acid. The growth kinetic analysis pattern of cell suspension revealed the maximum biomass increments (% BI = 486.7) and production of RA 8.086 mg/g dry weight was found in 30th day harvested cells. Whereas, the other two phenolic compounds i.e. ferulic acid (0.0125 mg/g dry weight) and caffeic acid (0.38 mg/g dry weight) was recorded highest on 25th day of growth cycle. In the present study, one biotic elicitor i.e. yeast extract and three precursors [peptone, tryptone and lactalbumin hydrolysate] were tested, among them, lactalbumin hydrolysate (100 mg/L; added at 16th day) treated cells recorded highest estimated phenolic compounds yield (251.5 mg/L; 6.81 fold compared to the control) and biomass increments i.e. % BI = 1207 with 1.85 fold compared to the control. The highest rosmarinic acid content i.e. 25.47 mg/g DW (4.4 fold compared to the control) and 24.42 mg/g dry weight (4.1 folds compared to the control) was noticed in 30th day harvested cells treated with yeast extract (1 g/L on 0 day) and lactalbumin hydrolysate (100 mg/L added on 16th day), respectively. While caffeic acid content (0.91 mg/g dry weight) showed 2.9 folds higher compared to the control in cells treated with peptone 200 mg/L added on 16th day of culture cycle. All the treated cells showed enhanced phenylalanine ammonia-lyase enzyme activity with highest specific activity in lactalbumin hydrolysate followed by tryptone, peptone, and yeast extract. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01316-6.

De Novo Shoot Bud Induction from the Catharanthus roseus Leaf Explants and Agrobacterium tumefaciens-Mediated Technique to Raise Transgenic Plants.

The regeneration of a whole plant from a single cell or organ explant was a valuable task for plant biotechnology. However, important medicinal plants such as Catharanthus roseus have shown recalcitrance to regeneration protocols, thus limiting investigations on MIA metabolism and metabolic engineering in this plant system. In this chapter, successful regeneration protocols were detailed for Catharanthus roseus, either by direct shoot bud induction from leaf explants and Agrobacterium-mediated genetic transformation.

ZCTs knockdown using antisense LNA GapmeR in specialized photomixotrophic cell suspensions of Catharanthus roseus: Rerouting the flux towards mono and dimeric indole alkaloids.

The present study was carried out to silence the transcription factor genes ZCT1, ZCT2 and ZCT3 via lipofectamine based antisense LNA GapmeRs transfection into the protoplasts of established photomixotrophic cell suspensions. The photomixotrophic cell suspensions with a threshold of 0.5% sucrose were raised and established using two-tiered CO2 providing flasks kept under high light intensity. The photomixotrophic cell suspensions showed morphologically different thick-walled cells under scanning electron microscopic analysis in comparison to the simple thin-walled parenchymatous control cell suspensions. The LC-MS analysis registered the vindoline production (0.0004 ± 0.0001 mg/g dry wt.) in photomixotrophic cell suspensions which was found to be absent in control cell suspensions. The protoplasts were isolated from the photomixotrophic cell suspensions and subjected to antisense LNA GapmeRs silencing. Three lines, viz. Z1A, Z2C and Z3G were obtained where complete silencing of ZCT1, ZCT2 and ZCT3 genes, respectively, was observed. The Z3G line was found to show maximum production of vindoline (0.038 ± 0.001 mg/g dry wt.), catharanthine (0.165 ± 0.008 mg/g dry wt.) and vinblastine (0.0036 ± 0.0003 mg/g dry wt.). This was supported by the multifold increment in the gene expression of TDC, SLS, STR, SGD, d4h, dat, CrT16H and Crprx. The present work indicates the master regulation of ZCT3 knockdown among all three ZCTs transcription factors in C. roseus to enhance the terpenoid indole alkaloids production. The successful silencing of transcription repressor genes has been achieved in C. roseus plant system by using photomixotrophic cell cultures through GapmeR based silencing. The present study is a step towards metabolic engineering of the TIAs pathway using protoplast transformation in C. roseus. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01017-y.

Confirmation of "pre-plasmolysis mediated ex-osmosis hypothesis" to obtain shoot bud morphogenesis in Catharanthus roseus.

The antineoplastic herb, Catharanthus roseus is a classified high-value low-volume medicinal herb which is in global attention of scientific research for modulation of its monoterpenoid indole alkaloids (MIA) pathway through genetic engineering. These secondary metabolites are generally stored in specific types of structures/compartments due to their cytotoxic nature and designated roles in plant defense response. However, their presence can hinder the genetic engineering process used to develop transgenic plants through de novo morphogenesis and regeneration of plants from cultured cells/tissues and hence, it always remained a critical impediment in transgenic research in C. roseus. The pre-plasmolysis treatment of leaf explants can help to tackle the recalcitrant nature of leaf explant and can support the direct regeneration response by ex-osmosis that minimizes the concentration of alkaloids. Therefore, this study was performed to chase the effect of osmotic conditions on recalcitrant leaves of C. roseus engaged in vitro plant regeneration and hypothesis of alkaloids ex-osmosis is confirmed by HPLC analysis.

TIAs pathway genes and associated miRNA identification in Vinca minor: supporting aspidosperma and eburnamine alkaloids linkage via transcriptomic analysis.

V. minor contains monomeric eburnamine-type of indole alkaloids having utilization as a neuro-medicinal plant. The biosynthetic pathway studies using miRNAs has been the focal point for plant genomic research in recent years and this technique is utilized to get an insight into a possible pathway level study in V. minor as understanding of genes in this prized medicinal plant is meagrely understood. The de novo transcriptomic analysis using Illumina Next gen sequencing has been performed in glasshouse shifted plant and transformed roots to elucidate the possible non confirmed steps of terpenoid indole alkaloids (TIAs) pathway in V. minor. A putative TIA pathway is elucidated in the study including twelve possible TIAs biosynthetic genes. The specific miRNA associated with TIAs pathway were identified and their roles were discussed for the first time in V. minor. The comparative analysis of transcriptomic data of glasshouse shifted plant and transformed roots showed that the raw reads of transformed roots were higher (83,740,316) compared to glasshouse shifted plant (67,733,538). The EST-SSR prediction showed the maximum common repeats among glasshouse shifted plant and transformed roots, although small variation was found in trinucleotide repeats restricted to glasshouse shifted plant. The study reveals overall 37 miRNAs which were observed to be true and can have a role in pathway as they can regulate the growth and alkaloid production. The identification of putative pathway genes plays an important role in establishing linkage between Aspidosperma and Eburnamine alkaloids.

Present status of Catharanthus roseus monoterpenoid indole alkaloids engineering in homo- and hetero-logous systems.

Catharanthus roseus synthesizes one of the most structurally, chemically and biologically active phytomolecules monoterpenoids indole alkaloids (MIAs) with having a wide range of pharmaceutical activities. Being the sole source of antineoplastic MIAs vinblastine and vincristine C. roseus has become one of the most valued plant. The low in planta availability of these MIAs and unavailability of alternative chemical synthesis system has enhanced their demand and equally let to the exorbitant market cost. To bridge this gap alternative production systems have been investigated using MIAs metabolic engineering (ME) in the homologous and heterologous systems. The availability of improved recombinant technologies along with genomics and metabolomics tools has opened the door of tremendous new potentials of ME. To encash these potentials of ME for MIAs pathway, efforts were made by expressing constitutive structure biosynthesis enzymes, transporters, and transcription factors of C. roseus MIAs biosynthesis in both homologous and heterologous systems. Here we review the knowledge of C. roseus MIAs pathway metabolic engineering in homologous and heterologous systems, gained in the past 35 years of C. roseus research.

Overexpression of tryptophan decarboxylase and strictosidine synthase enhanced terpenoid indole alkaloid pathway activity and antineoplastic vinblastine biosynthesis in Catharanthus roseus.

Terpenoid indole alkaloid (TIA) biosynthetic pathway of Catharanthus roseus possesses the major attention in current metabolic engineering efforts being the sole source of highly expensive antineoplastic molecules vinblastine and vincristine. The entire TIA pathway is fairly known at biochemical and genetic levels except the pathway steps leading to biosynthesis of catharanthine and tabersonine. To increase the in-planta yield of these antineoplastic metabolites for the pharmaceutical and drug industry, extensive plant tissue culture-based studies were performed to provide alternative production systems. However, the strict spatiotemporal developmental regulation of TIA biosynthesis has restricted the utility of these cultures for large-scale production. Therefore, the present study was performed to enhance the metabolic flux of TIA pathway towards the biosynthesis of vinblastine by overexpressing two upstream TIA pathway genes, tryptophan decarboxylase (CrTDC) and strictosidine synthase (CrSTR), at whole plant levels in C. roseus. Whole plant transgenic of C. roseus was developed using Agrobacterium tumefaciens LBA1119 strain having CrTDC and CrSTR gene cassette. Developed transgenic lines demonstrated up to twofold enhanced total alkaloid production with maximum ninefold increase in vindoline and catharanthine, and fivefold increased vinblastine production. These lines recorded a maximum of 38-fold and 65-fold enhanced transcript levels of CrTDC and CrSTR genes, respectively.

Genetic engineering approach using early Vinca alkaloid biosynthesis genes led to increased tryptamine and terpenoid indole alkaloids biosynthesis in differentiating cultures of Catharanthus roseus.

Catharanthus roseus today occupies the central position in ongoing metabolic engineering efforts in medicinal plants. The entire multi-step biogenetic pathway of its very expensive anticancerous alkaloids vinblastine and vincristine is fairly very well dissected at biochemical and gene levels except the pathway steps leading to biosynthesis of monomeric alkaloid catharanthine and tabersonine. In order to enhance the plant-based productivity of these pharma molecules for the drug industry, cell and tissue cultures of C. roseus are being increasingly tested to provide their alternate production platforms. However, a rigid developmental regulation and involvement of different cell, tissues, and organelles in the synthesis of these alkaloids have restricted the utility of these cultures. Therefore, the present study was carried out with pushing the terpenoid indole alkaloid pathway metabolic flux towards dimeric alkaloids vinblastine and vincristine production by over-expressing the two upstream pathway genes tryptophan decarboxylase and strictosidine synthase at two different levels of cellular organization viz. callus and leaf tissues. The transformation experiments were carried out using Agrobacterium tumefaciens LBA1119 strain having tryptophan decarboxylase and strictosidine synthase gene cassette. The callus transformation reported a maximum of 0.027% dry wt vindoline and 0.053% dry wt catharanthine production, whereas, the transiently transformed leaves reported a maximum of 0.30% dry wt vindoline, 0.10% catharanthine, and 0.0027% dry wt vinblastine content.

Artificial neural network-based model for the prediction of optimal growth and culture conditions for maximum biomass accumulation in multiple shoot cultures of Centella asiatica.

An artificial neural network (ANN)-based modelling approach is used to determine the synergistic effect of five major components of growth medium (Mg, Cu, Zn, nitrate and sucrose) on improved in vitro biomass yield in multiple shoot cultures of Centella asiatica. The back propagation neural network (BPNN) was employed to predict optimal biomass accumulation in terms of growth index over a defined culture duration of 35 days. The four variable concentrations of five media components, i.e. MgSO4 (0, 0.75, 1.5, 3.0 mM), ZnSO4 (0, 15, 30, 60 µM), CuSO4 (0, 0.05, 0.1, 0.2 µM), NO3 (20, 30, 40, 60 mM) and sucrose (1, 3, 5, 7 %, w/v) were taken as inputs for the ANN model. The designed model was evaluated by performing three different sets of validation experiments that indicated a greater similarity between the target and predicted dataset. The results of the modelling experiment suggested that 1.5 mM Mg, 30 µM Zn, 0.1 µM Cu, 40 mM NO3 and 6 % (w/v) sucrose were the respective optimal concentrations of the tested medium components for achieving maximum growth index of 1654.46 with high centelloside yield (62.37 mg DW/culture) in the cultured multiple shoots. This study can facilitate the generation of higher biomass of uniform, clean, good quality C. asiatica herb that can efficiently be utilized by pharmaceutical industries.

Envisaging the Regulation of Alkaloid Biosynthesis and Associated Growth Kinetics in Hairy Roots of Vinca minor Through the Function of Artificial Neural Network.

Artificial neural network based modeling is a generic approach to understand and correlate different complex parameters of biological systems for improving the desired output. In addition, some new inferences can also be predicted in a shorter time with less cost and labor. As terpenoid indole alkaloid pathway in Vinca minor is very less investigated or elucidated, a strategy of elicitation with hydroxylase and acetyltransferase along with incorporation of various precursors from primary shikimate and secoiridoid pools via simultaneous employment of cyclooxygenase inhibitor was performed in the hairy roots of V. minor. This led to the increment in biomass accumulation, total alkaloid concentration, and vincamine production in selected treatments. The resultant experimental values were correlated with algorithm approaches of artificial neural network that assisted in finding the yield of vincamine, alkaloids, and growth kinetics using number of elicits. The inputs were the hydroxylase/acetyltransferase elicitors and cyclooxygenase inhibitor along with various precursors from shikimate and secoiridoid pools and the outputs were growth index (GI), alkaloids, and vincamine. The approach incorporates two MATLAB codes; GRNN and FFBPNN. Growth kinetic studies revealed that shikimate and tryptophan supplementation triggers biomass accumulation (GI = 440.2 to 540.5); while maximum alkaloid (3.7 % dry wt.) and vincamine production (0.017 ± 0.001 % dry wt.) was obtained on supplementation of secologanin along with tryptophan, naproxen, hydrogen peroxide, and acetic anhydride. The study shows that experimental and predicted values strongly correlate each other. The correlation coefficient for growth index (GI), alkaloids, and vincamine was found to be 0.9997, 0.9980, 0.9511 in GRNN and 0.9725, 0.9444, 0.9422 in FFBPNN, respectively. GRNN provided greater similarity between the target and predicted dataset in comparison to FFBPNN. The findings can provide future insights to calculate growth index, alkaloids, and vincamine in combination to different elicits.

Solvent-based extraction optimisation for efficient ultrasonication-assisted ginsenoside recovery from Panax quinquefolius and P. sikkimensis cell suspension lines.

The present study aims at developing an extraction protocol for efficient ginsenoside recovery from cell suspensions of Panax quinquefolius and P. sikkimensis. Methanol (100%, 70% and 30%), water (40°C, 90°C), water-saturated butanol and butanol-saturated water were compared for their ultrasonication-assisted ginsenoside retrieval efficacy. HPLC and HP-TLC analysis revealed 100% methanol as the best solvent for maximum retrieval of Rb (diol) and Rg (triol) ginsenosides (P. quinquefolius: Rb: 0.189, Rg: 3.163 mg/g DW; P. sikkimensis: Rb: 0.245, Rg: 4.073 mg/g DW), followed by water (90°C). Methanolic solutions, especially 70%, proved to be significant retrievers of Rg1 (1.812 and 1.327 mg/g DW in P. quinquefolius and P. sikkimensis), with poor Re recovery (0.328 and 0.342 mg/g DW). Water-saturated butanol also led to significant ginsenoside extraction (72.4% of content extracted by methanol), selectively in P. quinquefolius, with a less than 50% of total content extracted by methanol, in P. sikkimensis.

Morphogenetic and chemical stability of long-term maintained Agrobacterium-mediated transgenic Catharanthus roseus plants.

Transgenic Catharanthus roseus plants (transgenic Dhawal [DT] and transgenic Nirmal [NT]) obtained from the Agrobacterium tumefaciens and Agrobacterium rhizognenes-mediated transformations, respectively, have been maintained in vitro for 5 years. Plants were studied at regular intervals for various parameters such as plant height, leaf size, multiplication rate, alkaloid profile and presence of marker genes. DT plant gradually lost the GUS gene expression and it was not detected in the fifth year while NT plant demonstrated the presence of genes rolA, rolB and rolC even in the fifth year, indicating the more stable nature of Ri transgene. Vindoline content in the DT was two times more than in non-transformed control plants. Alkaloid and tryptophan profiles were almost constant during the 5 years. The cluster analysis revealed that the DT plant is more close to the control Nirmal plant followed by NT plant.

A dual purpose cell line of an Indian congener of ginseng--Panax sikkimensis with distinct ginsenoside and anthocyanin production profiles.

The age-dependent production kinetics of ginsenosides and an anthocyanin pigment in a cell suspension line of Panax sikkimensis was followed in vitro. Highest total saponin content [7.37 mg/g dry weight (DW)] and biomass accumulation (% biomass increase = 209.67) in this line occurred after 3 and 5 weeks of culture, respectively. Accumulation of individual protopanaxatriol (Re, Rg1, and Rg2) and protopanaxadiol (Rb1, Rb2, and Rc) ginsenosides showed a variable pattern of accumulation independent of cell biomass buildup during the 7-week culture cycle. However, total content of triol ginsenosides was always significantly more than the diol group of ginsenosides, being 183.2-, 63.5-, and 72.1-folds at third, fourth, and fifth week stage of cell growth. Interestingly, in addition to these ginsenosides, the cell line also co-accumulated an anthocyanin pigment in vitro. The pigment content increased gradually from 8.66 to 14.29 mg/g DW after first to fifth week followed by a marginal fall to 12.79 and 10.95 mg/g DW during next 2 weeks. Therefore, in terms of total recovery of saponins (77.4 mg/l) and anthocyanin (199.16 mg/l), harvesting of cells after 3 and 5 weeks of growth was most profitable, respectively. The possible utility of this dual purpose cell line in nutraceutical industry is discussed.

Regulation of vincamine biosynthesis and associated growth promoting effects through abiotic elicitation, cyclooxygenase inhibition, and precursor feeding of bioreactor grown Vinca minor hairy roots.

Hydroxylase/acetyltransferase elicitors and cyclooxygenase inhibitor along with various precursors from primary shikimate and secoiridoid pools have been fortified to vincamine less hairy root clone of Vinca minor to determine the regulatory factors associated with vincamine biosynthesis. Growth kinetic studies revealed that acetyltransferase elicitor acetic anhydride and terpenoid precursor loganin significantly reduce the growth either supplemented alone or in combination (GI = 140.6 ± 18.5 to 246.7 ± 24.3), while shikimate and tryptophan trigger biomass accumulation (GI = 440.2 ± 31.5 to 540.5 ± 40.3). Loganin also downregulates total alkaloid biosynthesis. Maximum flux towards vincamine production (0.017 ± 0.001 % dry wt.) was obtained when 20-day-old hairy roots were fortified with secologanin (10 mg/l) along with tryptophan (100 mg/l), naproxen (8.4 mg/l), hydrogen peroxide (20 µg/l), and acetic anhydride (32.4 mg/l). This was supported by RT PCR (qPCR) analysis where 2- and 3-fold increase in tryptophan decarboxylase (TDC; RQ = 2.0 ± 0.09) and strictosidine synthase (STR; RQ = 3.3 ± 0.36) activity, respectively, was recorded. The analysis of variance (ANOVA) for growth kinetics, total alkaloid content, and gene expression studies favored highly significant data (P < 0.05-0.01). Above treated hairy roots were also up-scaled in a 5-l stirred-tank bioreactor where a 40-day cycle yielded 8-fold increase in fresh root mass.

In vitro conservation of twenty-three overexploited medicinal plants belonging to the Indian sub continent.

Twenty-three pharmaceutically important plants, namely, Elaeocarpus spharicus, Rheum emodi, Indigofera tinctoria, Picrorrhiza kurroa, Bergenia ciliata, Lavandula officinalis, Valeriana wallichii, Coleus forskohlii, Gentiana kurroo, Saussurea lappa, Stevia rebaudiana, Acorus calamus, Pyrethrum cinerariaefolium, Aloe vera, Bacopa monnieri, Salvia sclarea, Glycyrrhiza glabra, Swertia cordata, Psoralea corylifolia, Jurinea mollis, Ocimum sanctum, Paris polyphylla, and Papaver somniferum, which are at the verge of being endangered due to their overexploitation and collection from the wild, were successfully established in vitro. Collections were made from the different biodiversity zones of India including Western Himalaya, Northeast Himalaya, Gangetic plain, Western Ghats, Semiarid Zone, and Central Highlands. Aseptic cultures were raised at the morphogenic level of callus, suspension, axillary shoot, multiple shoot, and rooted plants. Synseeds were also produced from highly proliferating shoot cultures of Bacopa monnieri, Glycyrrhiza glabra, Stevia rebaudiana, Valeriana wallichii, Gentiana kurroo, Lavandula officinalis, and Papaver somniferum. In vitro flowering was observed in Papaver somniferum, Psoralea corylifolia, and Ocimum sanctum shoots cultures. Out of 23 plants, 18 plants were successfully hardened under glasshouse conditions.

Emerging trends in research on spatial and temporal organization of terpenoid indole alkaloid pathway in Catharanthus roseus: a literature update.

Catharanthus roseus (The Madagaskar Periwinkle) plant is commercially valued for harbouring more than 130 bioactive terpenoid indole alkaloids (TIAs). Amongst these, two of the leaf-derived bisindole alkaloids-vinblastine and vincristine-are widely used in several anticancer chemotherapies. The great pharmacological values, low in planta occurrence, unavailability of synthetic substitutes and exorbitant market cost of these alkaloids have prompted scientists to understand the basic architecture and regulation of biosynthesis of these TIAs in C. roseus plant and its cultured tissues. The knowledge gathered over a period of 30 years suggests that the TIA biosynthesis is highly regulated by developmental and environmental factors and operates through a complex multi-step enzymatic network. Extensive spatial and temporal cross talking also occurs at inter- and intracellular levels in different plant organs during TIA biogenesis. A close association of indole, methylerythritol phosphate and secoiridoid monoterpenoid pathways and involvement of at least four cell types (epidermis, internal phloem-associated parenchyma, laticifers and idioblasts) and five intracellular compartments (chloroplast, vacuole, nucleus, endoplasmic reticulum and cytosol) have been implicated with this biosynthetic mechanism. Accordingly, the research in this area is primarily advancing today to address and resolve six major issues namely: precise localization and expression of pathway enzymes using modern in situ RNA hybridization tools, mechanisms of intra- and intercellular trafficking of pathway intermediates, cloning and functional validation of genes coding for known or hitherto unknown pathway enzymes, mechanism of global regulation of the pathway by transcription factors, control of relative diversion of metabolite flux at crucial branch points and finally, strategising the metabolic engineering approaches to improve the productivity of the desired TIAs in plant or corresponding cultured tissues. The present literature update has been compiled to provide a brief overview of some of the emerging developments in our current understanding of TIA metabolism in C. roseus.

Agrobacterium tumefaciens-mediated transgenic plant production via direct shoot bud organogenesis from pre-plasmolyzed leaf explants of Catharanthus roseus.

Production of Agrobacterium tumefaciens-mediated transgenic plants, via direct shoot bud organogenesis from leaves of Catharanthus roseus, is reported. A. tumefaciens harbouring the plasmid pBI121 with GUS gene uidA and kanamycin resistance gene nptII was used. Highest transformation efficiency of 1.4 transgenic shoots/responded explant was obtained when pre-plasmolysed leaves, pre-incubated on shoot bud induction medium for 10 days, were subjected to sonication for 30 s prior to transformation. Using a selection medium containing 50 mg kanamycin l(-1), transformants grew into micro-shoots and formed roots on a hormone-free half strength MS medium. The transgenic nature of the regenerated plants was confirmed by PCR amplification of uidA gene and GUS histochemical assay.