Endomicrobiome of in vitro and natural plants deciphering the endophytes-associated secondary metabolite biosynthesis in Picrorhiza kurrooa, a Himalayan medicinal herb.

IMPORTANCE: Picrorhiza kurrooa is a major source of picrosides, potent hepatoprotective molecules. Due to the ever-increasing demands, overexploitation has caused an extensive decline in its population in the wild and placed it in the endangered plants' category. At present plant in-vitro systems are widely used for the sustainable generation of P. kurrooa plants, and also for the conservation of other commercially important, rare, endangered, and threatened plant species. Furthermore, the in-vitro-generated plants had reduced content of therapeutic secondary metabolites compared to their wild counterparts, and the reason behind, not well-explored. Here, we revealed the loss of plant-associated endophytic communities during in-vitro propagation of P. kurrooa plants which also correlated to in-planta secondary metabolite biosynthesis. Therefore, this study emphasized to consider the essential role of plant-associated endophytic communities in in-vitro practices which may be the possible reason for reduced secondary metabolites in in-vitro plants.

Picroside III, an Active Ingredient of Picrorhiza scrophulariiflora, Ameliorates Experimental Colitis by Protecting Intestinal Barrier Integrity.

This study aims to explore the protective effects of Picroside III, an active ingredient of Picrorhiza scrophulariiflora, on the intestinal epithelial barrier in tumor necrosis factor-α (TNF-α) induced Caco-2 cells and dextran sulfate sodium (DSS) induced colitis in mice. Results show that Picroside III significantly alleviated clinical signs of colitis including body weight loss, disease activity index increase, colon shortening, and colon tissue damage. It also increased claudin-3, ZO-1 and occludin expressions and decreased claudin-2 expression in the colon tissues of mice with colitis. In vitro, Picroside III also significantly promoted wound healing, decreased the permeability of cell monolayer, upregulated the expressions of claudin-3, ZO-1 and occludin and downregulated the expression of claudin-2 in TNF-α treated Caco-2 cells. Mechanism studies show that Picroside III significantly promoted AMP-activated protein kinase (AMPK) phosphorylation in vitro and in vivo, and blockade with AMPK could significantly attenuate the upregulation of Picroside III in ZO-1 and occludin expressions and the downregulation of claudin-2 expression in TNF-α treated Caco-2 cells. In conclusion, this study demonstrates that Picroside III attenuated DSS-induced colitis by promoting colonic mucosal wound healing and epithelial barrier function recovery via the activation of AMPK.

ABC transporters mined through comparative transcriptomics associate with organ-specific accumulation of picrosides in a medicinal herb, Picrorhiza kurroa.

Picrorhiza kurroa Royle ex Benth is a valuable medicinal herb of North-Western Himalayas due to presence of two major bioactive compounds, picroside-I and picroside-II used in the preparation of several hepatoprotective herbal drugs. These compounds accumulate in stolons/rhizomes; however, biosynthesized in different organs, viz., picroside-I in shoots and picroside-II in roots. As of today, no information exists on what transporters are transporting these metabolites from shoots and roots to the final storage organ, stolon, which ultimately transforms into rhizome. The ATP-binding cassette (ABC) transporters are reported to transport majority of secondary metabolites, including terpenoids in plants, therefore, we mined P. kurroa transcriptomes to identify and shortlist potential candidates. A total of 99 ABC transporter-encoding transcripts were identified in 3 differential transcriptomes, PKSS (shoots), PKSTS (stolons), and PKSR (roots) of P. kurroa, based on in silico comparative analysis and transcript abundance. 15 of these transcripts were further validated for their association using qRT-PCR in shoots, roots and stolon tissues in P. kurroa accessions varying for picroside-I and picroside-II contents. Organ-specific expression analysis revealed that PkABCA1, PkABCG1, and PkABCB5 had comparatively elevated expression in shoots; PkABCB2 and PkABCC2 in roots; PkABCB3 and PkABCC1 in stolon tissues of P. kurroa. Co-expression network analysis using ABC genes as hubs further unravelled important interactions with additional components of biosynthetic machinery. Our study has provided leads, first to our knowledge as of today, on putative ABC transporters possibly involved in long distance and local transport of picrosides in P. kurroa organs, thus opening avenues for designing a suitable genetic intervention strategy.

Biological Activity of Picrorhiza kurroa: A Source of Potential Antimicrobial Compounds against Yersinia enterocolitica.

Yersiniosis, caused by Yersinia enterocolitica, is the third most rampant zoonotic disease in Europe; the pathogen shows high antibiotic resistance. Herbs have multiple anti-microbial components that reduce microorganism resistance. Therefore, an extract of Picrorhiza kurroa (P. kurroa) was evaluated for potential antimicrobial activity. We report that the ethanolic extract of P. kurroa showed effective antimicrobial activity (zone of inhibition: 29.8 mm, Minimum inhibitory concentration (MIC): 2.45 mg/mL, minimum bactericidal concentration (MBC): 2.4 mg/mL) against Yersinia enterocolitica. Potential bioactive compounds from P. kurroa were identified using LC-MS, namely, cerberidol, annonidine A, benzyl formate, picroside-1, and furcatoside A. P. kurroa showed effective antimicrobial potential in skim milk at different pH, acidity, and water activity levels. P. kurroa affected the physiology of Yersinia enterocolitica and reduced the number of live cells. Yersinia enterocolitica, when incubated with P. kurroa extract, showed lower toxin production. Picroside-1 was isolated and showed higher antimicrobial potential in comparison to the standard antibiotic. Picroside-1 lysed the Yersinia enterocolitica cells, as observed under scanning electron microscopy. Docking revealed that picroside-1 (ligand) showed both hydrophilic and hydrophobic interactions with the dihydrofolate reductase (DHFR) protein of Yersinia enterocolitica and that DHFR is a possible drug target. The high activity and natural origin of Picroside-1 justify its potential as a possible drug candidate for Yersinia enterocolitica.

Capturing acyltransferase(s) transforming final step in the biosynthesis of a major Iridoid Glycoside, (Picroside-II) in a Himalayan Medicinal Herb, Picrorhiza kurroa.

BACKGROUND: Picrorhiza kurroa has been reported as an age-old ayurvedic hepato-protection to treat hepatic disorders due to the presence of iridoids such as picroside-II (P-II), picroside-I, and kutkoside. The acylation of catalpol and vanilloyl coenzyme A by acyltransferases (ATs) is critical step in P-II biosynthesis. Since accumulation of P-II occurs only in roots, rhizomes and stolons in comparison to leaves uprooting of this critically endangered herb has been the only source of this compound. Recently, we reported that P-II acylation likely happen in roots, while stolons serve as the vital P-II storage compartment. Therefore, developing an alternate engineered platform for P-II biosynthesis require identification of P-II specific AT/s. METHODS AND RESULTS: In that direction, egg-NOG function annotated 815 ATs from de novo RNA sequencing of tissue culture based 'shoots-only' system and nursery grown shoots, roots, and stolons varying in P-II content, were cross-compared in silico to arrive at ATs sequences unique and/or common to stolons and roots. Verification for organ and accession-wise upregulation in gene expression of these ATs by qRT-PCR has shortlisted six putative 'P-II-forming' ATs. Further, six-frame translation, ab initio protein structure modelling and protein-ligand molecular docking of these ATs signified one MBOAT domain containing AT with preferential binding to the vanillic acid CoA thiol ester as well as with P-II, implying that this could be potential AT decorating final structure of P-II. CONCLUSIONS: Organ-wise comparative transcriptome mining coupled with reverse transcription real time qRT-PCR and protein-ligand docking led to the identification of an acyltransferases, contributing to the final structure of P-II.

Evaluating Peptides of Picrorhiza kurroa and Their Inhibitory Potential against ACE, DPP-IV, and Oxidative Stress.

Picrorhiza kurroa Royle ex Benth. is a high-altitude plant having great medicinal value. However, its medicinal value at the peptide level is still unknown, which limits its utility in the development of peptide-based therapeutics. Here, we identify 65 peptides fromP. kurroa hydrolysate. Sequence analysis suggests that one novel bioactive peptide, ASGLCPEEAVPRR (BP1), has antioxidant potential and shows angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibitory activities. The molecular docking study showed that BP1 has a lower binding energy and strong affinity toward active pockets of ACE and DPP-IV, which explains its higher ACE [IC50 = 59.90 ± 9.52 µg/mL (43.40 µM)] and DPP-IV [IC50 = 3.04 ± 0.26 µg/mL (2.2 µM)] inhibitory activities. BP1 protects HEK293 cells from H2O2-induced oxidative damage by inhibiting intracellular reactive oxygen species (ROS) and malondialdehyde accumulation and activating the intrinsic antioxidant defense system. Additionally, phase-contrast microscopy studies revealed that pre-treatment of BP1 to HEK293 cells before exposure to H2O2 retains the normal morphology and blocks apoptosis. Furthermore, it also suppresses ROS-induced mitochondrial apoptosis via restoring the mitochondrial membrane potential (ΔΨm) and inhibiting caspase 3/7 activity. Therefore, BP1 has antioxidant potential and ACE and DPP-IV inhibitory activities that could be used for peptide-based formulation(s) in pharmaceuticals to treat diabetes, cardiovascular diseases, and other diseases associated with ROS.

Transcriptome profiling reveal key hub genes in co-expression networks involved in Iridoid glycosides biosynthetic machinery in Picrorhiza kurroa.

Picrorhiza kurroa is a medicinal herb rich in hepatoprotective iridoid glycosides, picroside-I (P-I) and picroside-II (P-II). The biosynthetic machinery of picrosides is poorly understood, therefore, 'no-direction' gene co-expression networks were used to extract linked/closed and separated interactions in terpenoid glycosides-specific sub-networks. Transcriptomes generated from different organs, varying for P-I and P-II contents such as shoots grown at 15 and 25 °C and nursery-grown shoots, stolons, and roots resulted in 47,726, 44,958, 40,117, 66,979, and 55,578 annotated transcripts, respectively. Occurrence of 2810 ± 136 nodes and 15,626 ± 696 edges in these networks indicated intense, co-expressed, closed loop interactions. Either deregulation/inhibition of abscisic acid (ABA) biosynthesis/signaling or constitutive degradation of ABA resulted in organ-specific accumulation of P-I and P-II. Biosynthesis, condensation and glucosylation of isoprene units may occur in shoots, roots or stolons; but addition of phenylpropanoid moiety and further modification/s of the iridoid backbone occurs mainly inside vacuoles in roots.

Advances in Ethnobotany, Synthetic Phytochemistry and Pharmacology of Endangered Herb Picrorhiza kurroa (Kutki): A Comprehensive Review (2010-2020).

Picrorhiza kurroa Royle ex Benth. (Family: Plantaginaceae) is a well-recognized Ayurvedic herb. It is commonly called "Kutki" or "Kurro" and 'Indian gentian'. Iridoid glycosides are the plant's bioactive constituents accountable for the bitter taste and medicinal properties of the plant. The iridoid glycosides such as picrosides and other active metabolites of the plant exhibit many pharmacological activities like hepatoprotective, antioxidant, anti-inflammatory, anticancer, immunomodulator, anti-ulcerative colitis, antimicrobial, etc. This review aims to provide updated information on the ethnobotany, synthetic phytochemistry, pharmacological potential, safety and toxicology of P. kurroa and its active metabolites. Indiscriminate exploitation, ecological destruction of natural habitats, slower plant growth and unawareness regarding cultivation and uprooting of plants have brought kutki an endangered status. Therefore, various techniques used for the conservation and production of bioactive metabolites from P. kurroa have also been reported. Information on the plant has been collected from Science Direct, Google Scholar, PubMed, Scopus using 'Picrorhiza kurroa', 'Picroside-', 'Picroside-II', 'Picroliv', 'Immunomodulator' keywords. All studies on ethnobotany, phytochemistry and pharmacology of plant from 2010- 2020 were comprised in this review article. The possible directions for future research have also been outlined briefly in this review article.

Complexity of gene paralogues resolved in biosynthetic pathway of hepatoprotective iridoid glycosides in a medicinal herb, Picrorhiza kurroa through differential NGS transcriptomes.

Picrorhiza kurroa is a medicinal herb with diverse pharmacological applications due to the presence of iridoid glycosides, picroside-I (P-I), and picroside-II (P-II), among others. Any genetic improvement in this medicinal herb can only be undertaken if the biosynthetic pathway genes are correctly identified. Our previous studies have deciphered biosynthetic pathways for P-I and P-II, however, the occurrence of multiple copies of genes has been a stumbling block in their usage. Therefore, a methodological strategy was designed to identify and prioritize paralogues of pathway genes associated with contents of P-I and P-II. We used differential transcriptomes varying for P-I and P-II contents in different tissues of P. kurroa. All transcripts for a particular pathway gene were identified, clustered based on multiple sequence alignment to notify as a representative of the same gene (≥ 99% sequence identity) or a paralogue of the same gene. Further, individual paralogues were tested for their expression level via qRT-PCR in tissue-specific manner. In total 44 paralogues in 14 key genes have been identified out of which 19 gene paralogues showed the highest expression pattern via qRT-PCR. Overall analysis shortlisted 6 gene paralogues, PKHMGR3, PKPAL2, PKDXPS1, PK4CL2, PKG10H2 and PKIS2 that might be playing role in the biosynthesis of P-I and P-II, however, their functional analysis need to be further validated either through gene silencing or over-expression. The usefulness of this approach can be expanded to other non-model plant species for which transcriptome resources have been generated.

Physiological and genomic evidence supports the role of Serratia quinivorans PKL:12 as a biopriming agent for the biohardening of micropropagated Picrorhiza kurroa plantlets in cold regions.

The medicinal herb, Picrorhiza kurroa Royle ex Benth has become endangered because of indiscriminate over-harvesting. Although micropropagation has been attempted for mass propagation of the plant, survival of in vitro plantlets under green house/open field poses a major challenge. Biopriming of micropropagated plantlets with plant growth-promoting rhizobacteria (PGPR) are among the successful methods to combat this problem. Serratia quinivorans PKL:12 was the best-characterized PGPR from rhizospheric soil of P. kurroa as it increased the vegetative growth and survival of the micropropagated plantlets most effectively. Complete genome (5.29 Mb) predicted genes encoding proteins for cold adaptation and plant growth-promoting traits in PKL:12. Antibiotic and biosynthetic gene cluster prediction supported PKL:12 as a potential biocontrol agent. Comparative genomics revealed 226 unique genes with few genes associated with plant growth-promoting potential. Physiological and genomic evidence supports S. quinivorans PKL:12 as a potential agent for bio-hardening of micropropagated P. kurroa plantlets in cold regions.

Hepatoprotective activity assessment of amino acids derivatives of picroside I and II.

Picrorhiza kurroa has a long medicinal history as a traditional medicinal plant in China and India that is widely used in clinical treatments. It is a common treatment for liver diseases, fever, diarrhoea, indigestion, and some other diseases. Modern pharmacological studies proved that P. kurroa rhizomes have high levels of picroside I and II, which were identified as main constituents with anti-inflammatory and hepatoprotective activities. In our study, we used picroside I and II as the lead compounds to generate derivatives by reactions with Boc-valine or Boc-proline, which underwent dehydration and condensation with the hydroxyl groups in the lead compounds in the presence of coupling reagent N,N'-dicyclohexylcarbodiimide. We synthesized 11 derivatives and examined their hepatoprotective effects in vitro by assessing the proliferation rates of H2 O2 -exposed HepG2 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. We found that some derivatives promoted higher proliferation rates in HepG2 cells than the natural compounds before derivatization, suggesting that those derivatives possessed an improved hepatoprotective capacity. The novel derivatization strategy for picrosides had the additional benefit that the esterification of their hydroxyl groups created derivatives not only with increased stability but also with improved pharmacokinetic properties and potentially prolonged half-life.

Growth Kinetics, Metabolites Production and Expression Profiling of Picrosides Biosynthetic Pathway Genes in Friable Callus Culture of Picrorhiza kurroa Royle ex Benth.

The rising demand for picrosides commercially and over-exploitation of Picrorhiza kurroa from natural habitat has to initiate alternative strategies for sustainable production of metabolites. In the present research, wild leaf explant of P. kurroa was used to produce friable callus under different culture condition, i.e., dark and light with two temperature variants (15 °C and 25 °C). Afterward, callus cell lines were screened based on growth biomass and metabolites content accumulation. The results revealed, maximum callus growth index along with antioxidant potential (IC50-40.88 µg/mL) and total phenol content (41.35 µg/mg) were observed under dark 25 °C. However, under light 15 °C, highest accumulation of picroside II (0.58 µg/mg), cinnamic acid (0.15 µg/mg), p-hydroxy acetophenone (0.30 µg/mg), total flavonoids (77.30 µg/mg), nitrogen (7.06%), carbohydrates (18.03%), and protein (44.12%) were detected. Major reported metabolite in callus was picroside I (1.63 µg/mg) under dark 15 °C. For the first time, picroside III content (range 0.15-0.56 µg/mg) was also detected and quantified in leaf-derived calli. Expression profiling of picroside biosynthetic pathway genes showed a positive correlation with the observed metabolites. Furthermore, an optimized protocol of metabolites enriched callus biomass could be used as potential strategy for sustainable production of picrosides at commercial scale.

Metabolic signatures provide novel insights to Picrorhiza kurroa adaptation along the altitude in Himalayan region.

INTRODUCTION: Along the altitude, environmental conditions vary significantly that might influence plant performance and distribution. Adaptation to these changing conditions is a complex biological process that involves reprogramming of genes, proteins and metabolites. The metabolic response of medicinal plants along the altitude has been less explored yet. OBJECTIVES: In the present study, we investigated the adaptation strategies of Picrorhiza kurroa Royle ex Benth. along the altitude in organ specific manner using metabolomic approach. METHODS: Picrorhiza kurroa plants at flowering stage were randomly sampled from three altitudes viz. 3400, 3800 and 4100 masl in the Himalayan region. Leaf, root and rhizome were used for LC-MS based non-targeted metabolite profiling and targeted analysis of sugars, amino acids, picrosides and their corresponding phenolic acids. RESULTS: A total of 220, primary and secondary metabolites (SMs) were identified (p < 0.05) representing an extensive inventory of metabolites and their spatial distribution in P. kurroa. Differential accumulation of metabolites suggests source-sink carbon partitioning, occurrence of partial TCA cycle, ascorbate metabolism, purine catabolism and salvage route, pyrimidine synthesis, lipid alteration besides gibberellins and cytokinin inhibition might be an adaptive strategy to alpine environmental stress along the altitude. Further, marked differences of organ and altitude specific SMs reflect alteration in secondary metabolic pathways. Significant accumulation of picrosides suggests their probable role in P. kurroa adaptation. CONCLUSION: This study provides a platform that would be useful in deciphering the role of metabolites considered to be involved in plant adaptation.

Comparative transcriptome analysis in different tissues of a medicinal herb, Picrorhiza kurroa pinpoints transcription factors regulating picrosides biosynthesis.

Transcriptional regulation of picrosides biosynthesis, the iridoid glycosides of an endangered medicinal herb, Picrorhiza kurroa, is completely unknown. P. kurroa plants obtained from natural habitat accumulate higher picrosides than in-vitro cultured plants, which necessitates identification of transcription factors (TFs) regulating their differential biosynthesis. The current study investigates complete spectrum of different TF classes in P. kurroa transcriptomes and discerns their association with picrosides biosynthesis. Transcriptomes of differential picroside-I content shoots and picroside-II content roots were mined for seven classes of TFs implicated in secondary metabolism regulation in plants. Key TFs were identified through in silico transcript abundance and qPCR analysis was performed to confirm transcript levels of TFs under study in differential content tissues and genotypes. Promoter regions of key picrosides biosynthetic pathway genes were explored to hypothesize which TFs can possibly regulate target genes. A total of 131, 137, 107, 82 and 101 transcripts encoding different TFs families were identified in PKS-25, PKS-15, PKSS, PKR-25 and PKSR transcriptomes, respectively. ERF-18, bHLH-104, NAC-25, 32, 94 and SUF-4 showed elevated expression in roots (up to 37 folds) and shoots (up to 195 folds) of plants obtained from natural habitat, indicating their role as activators of picrosides biosynthesis whereas, elevated expression of WRKY-17, 40, 71 and MYB-4 in low picrosides content conditions suggested their down-regulatory role. In silico analysis of key picrosides biosynthetic pathway gene promoter regions revealed binding domains for ERF-18, NAC-25, WRKY-40 and MYB-4. Identification of candidate TFs contributing towards picrosides biosynthesis is a pre-requisite for designing appropriate metabolic engineering strategies aimed at enhancing picrosides content in vitro and in vivo.

Exogenous feeding of immediate precursors reveals synergistic effect on picroside-I biosynthesis in shoot cultures of Picrorhiza kurroa Royle ex Benth.

In the current study, we asked how the supply of immediate biosynthetic precursors i.e. cinnamic acid (CA) and catalpol (CAT) influences the synthesis of picroside-I (P-I) in shoot cultures of P. kurroa. Our results revealed that only CA and CA+CAT stimulated P-I production with 1.6-fold and 4.2-fold, respectively at 2.5 mg/100 mL concentration treatment. Interestingly, feeding CA+CAT not only directed flux towards p-Coumaric acid (p-CA) production but also appeared to trigger the metabolic flux through both shikimate/phenylpropanoid and iridoid pathways by utilizing more of CA and CAT for P-I biosynthesis. However, a deficiency in the supply of either the iridoid or the phenylpropanoid precursor limits flux through the respective pathways as reflected by feedback inhibition effect on PAL and decreased transcripts expressions of rate limiting enzymes (DAHPS, CM, PAL, GS and G10H). It also appears that addition of CA alone directed flux towards both p-CA and P-I production. Based on precursor feeding and metabolic fluxes, a current hypothesis is that precursors from both the iridoid and shikimate/phenylpropanoid pathways are a flux limitation for P-I production in shoot cultures of P. kurroa plants. This work thus sets a stage for future endeavour to elevate production of P-I in cultured plant cells.

In vitro - In vivo metabolism and pharmacokinetics of picroside I and II using LC-ESI-MS method.

Picroside I and II, iridoid glycosides, are the major active markers of roots and rhizomes of Picrorhiza kurroa (family: Scrophulariaceae). The rhizomes of P. kurroa have been traditionally used to treat worms, constipation, low fever, scorpion sting, asthma and ailments affecting the liver. Various Ayurvedic and herbal preparations are available in the market which contains P. kurroa e.g. Arogyavadhini vati, Tiktadi kwath, Picrolax capsules and suspension. These preparations are used without any significant pharmacokinetics data. Previously, we have reported that oral bioavailability of picroside I and II is low. Most of the iridoid glycosides are primarily metabolized by intestinal microbial flora. So, it is necessary to determine the metabolic profile of picroside I and II and check the correlation with lower bioavailability. Therefore, this study was designed to check metabolic (in vitro and in vivo) profile along with pharmacokinetic profile of picroside I and II. For this, a sensitive and selective LC-ESI-MS method was developed and validated for simultaneous determination of picroside I and II in rat plasma. Chromatographic separations were performed on C18 column. The mobile phase consisted of acetonitrile: 10 mM ammonium acetate buffer [90:10 v/v], pH 3.5. In-vitro Metabolic study was performed on rat liver microsomes and primary hepatocytes. In-vivo pharmacokinetic and metabolic profile of picroside I and II was generated after oral administration of Kutkin (mixture of picroside I and II) to Sprague-Dawley rats. Various pharmacokinetic parameters viz. Cmax, Tmax, AUC(0-t) were determined. In metabolic study, eight metabolites of picroside I and six metabolites of picroside II were identified in vitro, out of which four metabolites for each picroside I and picroside II were identified in vivo.

Discerning picroside-I biosynthesis via molecular dissection of in vitro shoot regeneration in Picrorhiza kurroa.

KEY MESSAGE: Expression analysis of primary and secondary metabolic pathways genes vis-à-vis shoot regeneration revealed developmental regulation of picroside-I biosynthesis in Picrorhiza kurroa. Picroside-I (P-I) is an important iridoid glycoside used in several herbal formulations for treatment of various disorders. P-I is synthesized in shoots of Picrorhiza kurroa and Picrorhiza scrophulariiflora. Current study reports on understanding P-I biosynthesis in different morphogenetic stages, viz. plant segment (PS), callus initiation (CI), callus mass (CM), shoot primordia (SP), multiple shoots (MS) and fully developed (FD) stages of P. kurroa. Expression analysis of genes involved in primary and secondary metabolism revealed that genes encoding HMGR, PMK, DXPS, ISPE, GS, G10H, DAHPS and PAL enzymes of MVA, MEP, iridoid and shikimate/phenylpropanoid pathways showed significant modulation of expression in SP, MS and FD stages in congruence with P-I content compared to CM stage. While HK, PK, ICDH, MDH and G6PDH showed high expression in MS and FD stages of P. kurroa, RBA, HisK and CytO showed high expression with progress in regeneration of shoots. Quantitative expression analysis of secondary metabolism genes at two temperatures revealed that 7 genes HMGR, PMK, DXPS, GS, G10H, DAHPS and PAL showed high transcript abundance (32-87-folds) in FD stage derived from leaf and root segments at 15 °C compared to 25 °C in P. kurroa. Further screening of these genes at species level showed high expression pattern in P. kurroa (6-19-folds) vis-à-vis P. scrophulariiflora that was in corroboration with P-I content. Therefore, current study revealed developmental regulation of P-I biosynthesis in P. kurroa which would be useful in designing a suitable genetic intervention study by targeting these genes for enhancing P-I production.

Yield enhancement strategies for the production of picroliv from hairy root culture of Picrorhiza kurroa Royle ex Benth.

Fast-growing hairy root cultures of Picrorhiza kurroa induced by Agrobacterium rhizogenes offers a potential production system for iridoid glycosides. In present study we have investigated the effects of various nutrient medium formulations viz B5, MS, WP and NN, and sucrose concentrations (1-8%) on the biomass and glycoside production of selected clone (14-P) of P. kurroa hairy root. Full strength B5 medium was found to be most suitable for maximum biomass yield on the 40th day of culture (GI = 32.72 ± 0.44) followed by the NN medium of the same strength (GI = 22.9 ± 0.43). Secondary metabolite production was 1.1 and 1.3 times higher in half strength B5 medium respectively in comparison to MS medium. Maximum biomass accumulation along with the maximum picroliv content was achieved with 4% sucrose concentration in basal medium. RT vitamin and Thiamine-HCl effected the growth and secondary metabolite production of hairy roots growing on MS medium but did not show any effect on other media. The pH of the medium played significant role in growth and secondary metabolite production and was found to be highest at pH 6.0 while lowest at pH 3.0 and pH 8.0. To enhance the production of biomass and Picroliv 5 liter working capacity bioreactor was used, 27-fold (324 g FW) higher growth was observed in bioreactor than shake flask and secondary metabolite production was similarly enhanced.

Mining NGS transcriptomes for miRNAs and dissecting their role in regulating growth, development, and secondary metabolites production in different organs of a medicinal herb, Picrorhiza kurroa.

MAIN CONCLUSION: This study is the first endeavor on mining of miRNAs and analyzing their involvement in development and secondary metabolism of an endangered medicinal herb Picrorhiza kurroa (P. kurroa ). miRNAs are ubiquitous non-coding RNA species that target complementary sequences of mRNA and result in either translational repression or target degradation in eukaryotes. The role of miRNAs has not been investigated in P. kurroa which is a medicinal herb of industrial value due to the presence of secondary metabolites, picroside-I and picroside-II. Computational identification of miRNAs was done in 6 transcriptomes of P. kurroa generated from root, shoot, and stolon organs varying for growth, development, and culture conditions. All available plant miRNA entries were retrieved from miRBase and used as backend datasets to computationally identify conserved miRNAs in transcriptome data sets. Total 18 conserved miRNAs were detected in P. kurroa followed by target prediction and functional annotation which suggested their possible role in controlling various biological processes. Validation of miRNA and expression analysis by qRT-PCR and 5' RACE revealed that miRNA-4995 has a regulatory role in terpenoid biosynthesis ultimately affecting the production of picroside-I. miR-5532 and miR-5368 had negligible expression in field-grown samples as compared to in vitro-cultured samples suggesting their role in regulating P. kurroa growth in culture conditions. The study has thus identified novel functions for existing miRNAs which can be further validated for their potential regulatory role.

Differential proteomics of Picrorhiza kurrooa Royle ex Benth. in response to dark stress.

Picrorhiza (Picrorhiza kurrooa Royle ex Benth.) an important medicinal herb of western Himalayan region has been used to treat various diseases and disorders. Over-harvesting and lack of cultivation has led to its entry in Red Data Book as an endangered species. Further, its very restrictive habitat and lesser biomass production are major limitations for bringing it under commercial cultivation. All these issues necessitate deeper insights into mechanisms governing its growth and interaction with the environmental cues. Light may be one of the important factors to be studied for its role in regulating growth and adaptation of Picrorhiza as in natural habitat it prefers shady niches. Keeping this in view, proteome of Picrorhiza kept under light vis-à-vis under dark was analysed and compared. Leaf as well as root proteome of Picrorhiza was studied. Denaturing two dimensional gel electrophoresis and mass spectrometry techniques were used to detect and identify differentially expressed proteins, respectively. Twenty two proteins from leaf and 25 proteins from root showed differential expression levels under dark and light conditions. Among the differentially expressed proteins, majority were those involved in metabolism, protein synthesis, and stress and defense response. Other differentially expressed proteins were those involved in photosynthetic process, photorespiration and few proteins were with unknown function indicating that many different processes work together to establish a new cellular homeostasis in response to dark and light conditions. Proteins found to be differentially expressed under light vis-à-vis dark conditions suggested a range of biochemical pathways and processes being associated with response of plant to dark conditions. The identified proteins may be utilized for developing strategies for improving the biomass production/performance of Picrorhiza under varied light/dark habitats.