HMG-CoA reductase from Camphor Tulsi (Ocimum kilimandscharicum) regulated MVA dependent biosynthesis of diverse terpenoids in homologous and heterologous plant systems

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.

Plant terpenoid biosynthetic network and its multiple layers of regulation

Terpenoids constitute one of the largest and most chemically diverse classes of primary and secondary metabolites in nature with an exceptional breadth of functional roles in plants. Biosynthesis of all terpenoids begins with the universal five‑carbon building blocks, isopentenyl diphosphate (IPP) and its allylic isomer dimethylallyl diphosphate (DMAPP), which in plants are derived from two compartmentally separated but metabolically crosstalking routes, the mevalonic acid (MVA) and methylerythritol phosphate (MEP) pathways. Here, we review the current knowledge on the terpenoid precursor pathways and highlight the critical hidden constraints as well as multiple regulatory mechanisms that coordinate and homeostatically govern carbon flux through the terpenoid biosynthetic network in plants.

3-Hydroxy-3-methylglutaryl coenzyme A reductase genes from Glycine max regulate plant growth and isoprenoid biosynthesis

Isoprenoids, a large kind of plant natural products, are synthesized by the mevalonate (MVA) pathway in the cytoplasm and the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway in plastids. As one of the rate-limiting enzymes in the MVA pathway of soybean (Glycine max), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is encoded by eight isogenes (GmHMGR1-GmHMGR8). To begin, we used lovastatin (LOV), a specific inhibitor of GmHMGR, to investigate their role in soybean development. To further investigate, we overexpressed the GmHMGR4 and GmHMGR6 genes in Arabidopsis thaliana. The growth of soybean seedlings, especially the development of lateral roots, was inhibited after LOV treatment, accompanied by a decrease in sterols content and GmHMGR gene expression. After the overexpression of GmHMGR4 and GmHMGR6 in A. thaliana, the primary root length was higher than the wild type, and total sterol and squalene contents were significantly increased. In addition, we detected a significant increase in the product tocopherol from the MEP pathway. These results further support the fact that GmHMGR1-GmHMGR8 play a key role in soybean development and isoprenoid biosynthesis.

Overexpression of LT, an Oncoprotein Derived from the Polyomavirus SV40, Promotes Somatic Embryogenesis in Cotton

Although genetic transformation has opened up a new era for cotton molecular breeding, it still suffers from the limitation problem of long transformation periods, which slows down the generation of new cotton germplasms. In this study, LT gene (SV40 large T antigen), which promotes the transformation efficiency of animal cells, was codon-optimized. Its overexpression vector was transformed into cotton. It was observed that EC (embryogenic callus) formation period was 33% shorter and transformation efficiency was slightly higher in the LT T0 generation than that of control. RNA-seq data of NEC (non-embryonic callus) and EC from LT and control revealed that more DEGs (differential expression genes) in NEC were identified than that of EC, indicating LT mainly functioned in NEC. Further KEGG, GO, and transcription factor analyses showed that DEGs were significantly enriched in brassinosteroid biosynthesis pathways and that bHLH, MYB, and AP2/ERF were the top three gene families, which are involved in EC formation. In addition, the key genes related to the auxin pathway were differentially expressed only in LT overexpression NEC, which caused early response, biosynthesis, and transportation of the hormone, resulting in EC earlier formation. In summary, the results demonstrated that LT can promote somatic embryogenesis in cotton, which provides a new strategy for improving cotton transformation and shortening EC formation time.

Metabolome and transcriptome analyses identify the plant immunity systems that facilitate sesquiterpene and lignan biosynthesis in Syringa pinnatifolia Hemsl

BACKGROUND

Syringa pinnatifolia Hemsl. is a shrub belonging to the Oleaceae family. The peeled woody stems and roots of S. pinnatifolia are used in Chinese traditional medicine. This plant has been used for centuries, and modern pharmacological research has revealed its medicinal value. However, the wild populations of S. pinnatifolia have been decreasing, and it has been listed as an endangered plant in China. To elucidate the molecular mechanism leading to the synthesis of the major components of S. pinnatifolia for its further development and sustainable use, this study compared peeled stems and twigs at the metabolic and molecular levels.

RESULTS

Peeled stems with the purple substance visible (SSP) and peeled twigs without the purple substance (TSP) were compared at different levels. Microscopic observation showed resin-like fillers in SSP and wood fiber cell walls approximately 1.0 μm thicker than those in TSP (wood fiber cell thickness approximately 2.7 μm). In addition, 104 volatile organic compounds and 870 non-volatile metabolites were detected in the non-targeted and widely-targeted metabolome analyses, respectively. Among the 76 differentially accumulated metabolites (DAMs) detected, 62 were up-accumulated in SSP. Most of these DAMs were terpenes, of which 90% were identified as sesquiterpenes in the volatile organic compound analysis. In the analysis of the non-volatile metabolites, 21 differentially accumulated lignans were identified, of which 18, including five subtypes, were accumulated in SSP. RNA sequencing revealed 4,421 upregulated differentially expressed genes (DEGs) and 5,522 downregulated DEGs in SSP compared with TSP, as well as 33,452 genes that were not differentially expressed. Analysis of the DEGs suggested that sesquiterpenes and lignans were mostly biosynthesized via the mevalonate and phenylpropanoid pathways, respectively. Additionally, in SSP, the enriched Gene Ontology terms included response to biotic stimulus and defense response, while the enriched Kyoto Encyclopedia of Genes and Genomes pathways included plant-pathogen interaction and many other pathways related to plant immunity.

CONCLUSIONS

This study provides metabolome and transcriptome information for S. pinnatifolia, suggesting that biotic stimuli, including pathogens, are potential and valuable approaches to promoting the biosynthesis of the metabolites linked to the medicinal properties of this plant.

A glance at the chemodiversity of Ocimum species: Trends, implications, and strategies for the quality and yield improvement of essential oil

Ocimum species represent commercially important medicinal and aromatic plants. The essential oil biosynthesized by Ocimum species is enriched with specialized metabolites specifically, terpenoids and phenylpropanoids. Interestingly, various Ocimum species are known to exhibit diverse chemical profiles, and this chemical diversity has been at the center of many studies to identify commercially important chemotypes. Here, we present various chemotypes from the Ocimum species and emphasize trends, implications, and strategies for the quality and yield improvement of essential oil. Globally, many Ocimum species have been analyzed for their essential oil composition in over 50 countries. Asia represents the highest number of chemotypes, followed by Africa, South America, and Europe. Ocimum basilicum L. has been the most widespread and well-studied species, followed by O. gratissimum L., O. tenuiflorum L., O. canum Sims, O. americanum and O. kilimandscharicum Gürke. Moreover, various molecular reasons, benefits, adverse health effects and mechanisms behind this vast chemodiversity have been discussed. Different strategies of plant breeding, metabolic engineering, transgenic, and tissue-culture, along with anatomical modifications, are surveyed to enhance specific chemotypic profiles and essential oil yield in numerous Ocimum species. Consequently, chemical characterization of the essential oil obtained from Ocimum species has become indispensable for its proper utilization. The present chemodiversity knowledge from Ocimum species will help to exploit various applications in the industrial, agriculture, biopharmaceutical, and food sectors.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-021-09767-z.

Defining the role of a caffeic acid 3-O-methyltransferase from Azadirachta indica fruits in the biosynthesis of ferulic acid through heterologous over-expression in Ocimum species and Withania somnifera

The recombinant caffeic acid 3-O-methyltransferase gene has been cloned and characterized from Neem. The gene is involved in ferulic acid biosynthesis, a key intermediate component of lignin biosynthesis. Azadirachta indica (Neem) is a highly reputed traditional medicinal plant and is phytochemically well-known for its limonoids. Besides limonoids, phenolics are also distinctively present, which add more medicinal attributes to Neem. Caffeic acid is one of such phenolic compound and it can be converted enzymatically into another bioactive phytomolecule, ferulic acid. This conversion requires transfer of a methyl group from a donor to caffeic acid under the catalytic action of an appropriate methyltransferase. In this study, caffeic acid 3-O-methyltransferase gene from Neem (NCOMT) fruits has been isolated and heterologously expressed in E. coli. The recombinant NCOMT enzyme was purified, which exhibited efficient catalytic conversion of caffeic acid into ferulic acid, a highly potential pharmaceutical compound. The purified recombinant enzyme was physico-kinetically characterized for its catalysis. The analysis of tissue-wide expression of NCOMT gene revealed interesting pattern of transcript abundance reflecting its role in the development of fruit tissues. Further, NCOMT was heterologously overexpressed in Withania somnifera and Ocimum species, to analyze its role in ferulic acid biosynthesis in planta. Thus, the study provides insight for the endogenous role of NCOMT in ferulic acid biosynthesis en route to lignin, an important structural component. To the best of our knowledge, NCOMT pertains to be the first enzyme of the secondary metabolism that has been purified and kinetically characterized from Neem. This study may also have important prospects of applications as the observation on heterologous expression of NCOMT showed its involvement in the maintenance of the in vivo pool of ferulic acid in the plants. Thus, the study involving NCOMT opens up new dimensions of metabolic engineering approaches for the biosynthesis of potential therapeutically important phytomolecules in heterologous systems.

Overexpression of Key Sterol Pathway Enzymes in Two Model Marine Diatoms Alters Sterol Profiles in Phaeodactylum tricornutum

Sterols are a class of triterpenoid molecules with diverse functional roles in eukaryotic cells, including intracellular signaling and regulation of cell membrane fluidity. Diatoms are a dominant eukaryotic phytoplankton group that produce a wide diversity of sterol compounds. The enzymes 3-hydroxy-3-methyl glutaryl CoA reductase (HMGR) and squalene epoxidase (SQE) have been reported to be rate-limiting steps in sterol biosynthesis in other model eukaryotes; however, the extent to which these enzymes regulate triterpenoid production in diatoms is not known. To probe the role of these two metabolic nodes in the regulation of sterol metabolic flux in diatoms, we independently over-expressed two versions of the native HMGR and a conventional, heterologous SQE gene in the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum. Overexpression of these key enzymes resulted in significant differential accumulation of downstream sterol pathway intermediates in P. tricornutum. HMGR-mVenus overexpression resulted in the accumulation of squalene, cycloartenol, and obtusifoliol, while cycloartenol and obtusifoliol accumulated in response to heterologous NoSQE-mVenus overexpression. In addition, accumulation of the end-point sterol 24-methylenecholesta-5,24(24’)-dien-3β-ol was observed in all P. tricornutum overexpression lines, and campesterol increased three-fold in P. tricornutum lines expressing NoSQE-mVenus. Minor differences in end-point sterol composition were also found in T. pseudonana, but no accumulation of sterol pathway intermediates was observed. Despite the successful manipulation of pathway intermediates and individual sterols in P. tricornutum, total sterol levels did not change significantly in transformed lines, suggesting the existence of tight pathway regulation to maintain total sterol content.

Comparative transcriptome analysis to identify putative genes related to trichome development in Ocimum species

Genus Ocimum is known to have species possessing important therapeutic essential oil. The major phytoconstituents of essential oil in Ocimum species are phenylpropanoids and terpenoids. The essential oil is accumulated in the trichomes; the specialized structures predominantly found on leaves and other tissues. The development of trichome is integrated with development of plant and leaf and also tightly coordinated with the primary and secondary metabolic pathways producing essential oil constituents. In continuation to our studies on elucidating/understanding the mechanism of biosynthesis of  essential oil pathways in Ocimum species, we have performed comparative transcriptome analysis to investigate the role of trichome-related gene expression in the regulation of biosynthetic pathways of essential oil. The essential oil biogenesis is tightly integrated with primary metabolic activities, the analysis for the expression pattern of genes related to primary metabolism and its relationship with secondary metabolism was evaluated in comparative manner. Physiological parameters in relation to primary metabolism such as photosynthetic pigment content, soluble sugar content, and invertase enzymes along with morphological parameters were analysed in O. basilicum and O. sanctum. Differential expression profiling uncovered about 8116 and 2810 differentially expressed transcripts in O. basilicum and O. sanctum, respectively. Enrichment of differentially expressed genes were analysed in relation to metabolic pathways, primary metabolism and secondary metabolism. Trichome related genes identified from the Ocimum species vis-à-vis their expression profiles suggested higher expression in O. basilicum. The findings in this study provide interesting insights into the role of trichome-related transcripts in relation to essential oil content in Ocimum species. The study is valuable as this is the first study on revealing the transcripts and their role in trichome development and essential oil biogenesis in two major species of Ocimum.

Breaking the Summer Dormancy of Pinellia ternata by Introducing a Heat Tolerance Receptor-Like Kinase ERECTA Gene

Pinellia ternata is a perennial traditional Chinese medicinal plant that undergoes different phenological patterns of dormancy depending on where it is growing. Plants grown in central and southern China typically display two growth cycles every year before and after hot summer days, exhibiting a summer dormancy. However, germplasms from these areas do not go into a dormancy phase in northern China where the summer monthly average temperatures range from 29-31°C. The northern China herbal growers prefer plant stocks from central China due to their longer growing quality and better tuber harvests. Here, we introduced a heat responsive receptor-like kinase ERECTA (ER) gene into P. ternata to explore changes in the growth cycle which were aimed at disrupting the summer dormancy. The 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene was also co-transformed with ER to improve the commercial trait. For the thermo-tolerance evaluation, all plants were treated with high temperatures (35°C/40°C) in a growth chamber or grown in natural field temperature in an isolated field before measurement of different agricultural, biochemical and physiological traits. The transgenics showed significantly (P < 0.05) higher heat tolerance, maintaining healthy vegetative growth unlike the empty vector (EV) harboring controls that became chlorotic and necrotic. Better performance in some of the monitored physiological traits was evident for overexpression lines exposed to the heat stress. In open isolated field trials, the transgenic genotypes did not show a summer dormancy but had a survival rate of 84-95%. The tuber biomasses were also significantly (P < 0.05) higher for the transgenic lines as compared to the EV controls, except for line ER118. Metabolites analysis indicated that the HMGR overexpressing lines (HMGR orHMGR + ER) exhibited significantly higher amounts of bioactive compounds including aromadendrene-4, 10-diol and 4, 8, 13-cyclotetradecatriene-1, 3-diol, 1, 5, 9-trimethyl-12-(1-methylethyl). Our findings show that the summer dormancy of P. ternata which is a naturally evolved trait, can be removed by a single heat responsive gene. The study contributes to generating heat tolerant new Pinellia varieties with enhanced commercially valuable chemicals.

Comparative temporal metabolomics studies to investigate interspecies variation in three Ocimum species

Ocimum is one of the most revered medicinally useful plants which have various species. Each of the species is distinct in terms of metabolite composition as well as the medicinal property. Some basil types are used more often as an aromatic and flavoring ingredient. It would be informative to know relatedness among the species which though belong to the same genera while exclusively different in terms of metabolic composition and the operating pathways. In the present investigation the similar effort has been made in order to differentiate three commonly occurring Ocimum species having the high medicinal value, these are Ocimum sanctum, O. gratissimum and O. kilimandscharicum. The parameters for the comparative analysis of these three Ocimum species comprised of temporal changes in number leaf trichomes, essential oil composition, phenylpropanoid pathway genes expression and the activity of important enzymes. O. gratissimum was found to be richest in phenylpropanoid accumulation as well as their gene expression when compared to O. sanctum while O. kilimandscharicum was found to be accumulating terpenoid. In order to get an overview of this qualitative and quantitative regulation of terpenes and phenylpropenes, the expression pattern of some important transcription factors involved in secondary metabolism were also studied.

Berry transcriptome: insights into a novel resource to understand development dependent secondary metabolism in Withania somnifera (Ashwagandha)

Withania somnifera (Ashwagandha) is considered as Rasayana in Indian systems of medicine. This study reports a novel transcriptome of W. somnifera berries, with high depth, quality and coverage. Assembled and annotated transcripts for nearly all genes related with the withanolide biosynthetic pathway were obtained. Tissue-wide gene expression analysis reflected almost similar definitions for the terpenoid pathway in leaf, root and berry tissues with relatively higher abundance of transcripts linked to steroid, phenylpropanoid metabolism as well as flavonoid metabolism in berries. The metabolome map generated from the data embodied transcripts from 143 metabolic pathways connected together and mediated collectively by about 1792 unique enzyme functions specific to berry, leaf and root tissues, respectively. Transcripts specific to cytochrome p450 (CYP450), methyltransferases and glycosyltransferases were distinctively located in a tissue specific manner and exhibited a complex network. Significant distribution of transcription factor genes such as MYB, early light inducible protein (ELI), minichromosome maintenance1, agamous, deficiens and serum response factor (MADS) and WRKY etc. was observed, as the major transcriptional regulators of secondary metabolism. Validation of the assembly was ascertained by cloning WsELI, which has a light dependent regulatory role in development. Quantitative expression of WsELI was observed to be considerably modulated upon exposure to abiotic stress and elicitors. Co-relation of over-expression of WsELI, may provide new aspects for the functional role of ELI proteins in plants linked to secondary metabolism. The study offers the first comprehensive and comparative evaluation of W. somnifera transcriptome data between the three tissues and across other members of Solanaceae (Nicotiana, Solanum and Capsicum) with respect to major pathways and their metabolome regulation.

The 3-hydroxy-3-methylglutaryl-coenzyme A reductase 5 gene from Malus domestica enhances oxidative stress tolerance in Arabidopsis thaliana

3-Hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) is the first rate-limiting enzyme regulating the synthesis of terpenoids upstream of the mevalonate (MVA) pathway. In higher plants, members of the HMGR genes families play an important role in plant growth and development and in response to various environmental stresses. In the present study, a novel HMGR gene, designated MdHMGR5, was isolated from apple (Malus domestica L.) and characterized. Expression of MdHMGR5 enhanced the activity of HMGR enzyme in transgenic Arabidopsis thaliana L. plants. Under oxidative stress, transgenic A. thaliana plants over-expressing MdHMGR5 had a higher germination rate, a longer main root length, higher chlorophyll and proline content, and higher activities of antioxidant enzymes. On the other hand, malondialdehyde (MDA) content, relative conductivity and reactive oxygen species (ROS) production rate were significantly lower than in wild type plants. These results indicated that over-expression of MdHMGR5 enhanced plant tolerance to oxidative stress by scavenging ROS in transgenic plants. Over-expression of MdHMGR5 also affected the expression levels of genes in mevalonic acid and 2C-methyl-D-erythritol 4-phosphate (MVA and MEP) pathways of A. thaliana plants. These results indicate that over-expression of MdHMGR5 enhances tolerance to oxidative stress by maintaining photosynthesis and scavenging ROS in transgenic A. thaliana plants.

Isolation, characterization and in silico analysis of 3-Hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) gene from Andrographis paniculata (Burm. f) Nees

3-Hydroxy-3-methylglutaryl-coenzymeA reductase (HMGR), the first rate-limiting enzyme of Mevalonate (MVA) pathway was isolated from Andrographis paniculata (ApHMGR) and expressed in bacterial cells. Full length ApHMGR (1937 bp) was submitted to NCBI with accession number MG271748.1. The open reading frame (ORF) was flanked by a 31-bp 5'-UTR, 118-bp 3'-UTR and ApHMGR contained a 1787 bp ORF encoding protein of 595 amino acids. ApHMGR protein was approximately 64 kDa, with isoelectric point of 5.75. Isolated ApHMGR was cloned into pET102 vector and expressed in E. coli BL21 (DE 3) cells, and characterized by SDS-PAGE. HPLC analysis for andrographolide content in leaf, stem and root of A. paniculata revealed highest in leaf tissue. The expression patterns of ApHMGR in different plant tissues using qRT-PCR revealed high in root tissue correlating with HPLC data. Three dimensional (3D) structural model of ApHMGR displayed 90% of the amino acids in most favored regions of the Ramachandran plot with 93% overall quality factor. ApHMGR was highly conserved with plant specific N-terminal membrane domains and C-terminal catalytic regions. Phylogenetic analysis showed A. paniculata sharing common ancestor with Handroanthus impetiginosus. 3D model of ApHMGR was screened for the interaction with substrates NADPH, HMG CoA and inhibitor using Auto Dock Vina. In silico analysis revealed that full length ApHMGR had extensive similarities to other plant HMGRs. The present communication reports the isolation of full length HMGR from A. paniculata, its heterologous expression in bacterial cells and in silico structural and functional characterization providing valuable genomic information for future molecular interventions.

Interspecies comparative features of trichomes in Ocimum reveal insights for biosynthesis of specialized essential oil metabolites

Ocimum species commonly referred to as "Tulsi" are well-known for their distinct medicinal and aromatic properties. The characteristic aroma of Ocimum species and cultivars is attributed to their specific combination of volatile phytochemicals mainly belonging to terpenoid and/or phenylpropanoid classes in their essential oils. The essential oil constituents are synthesized and sequestered in specialized epidermal secretory structures called as glandular trichomes. In this comparative study, inter- and intra-species diversity in structural attributes and profiles of expression of selected genes related to terpenoid and phenylpropanoid biosynthetic pathways have been investigated. This is performed to seek relationship of variations in the yield and phytochemical composition of the essential oils. Microscopic analysis of trichomes of O. basilicum, O. gratissimum, O. kilimandscharicum, and O. tenuiflorum (green and purple cultivars) revealed substantial variations in density, size, and relative proportions of peltate and capitate trichomes among them. The essential oil yield has been observed to be controlled by the population, dominance, and size of peltate and capitate glandular trichomes. The essential oil sequestration in leaf is controlled by the dominance of peltate glandular trichome size over its number and is also affected by the capitate glandular trichome size/number with variations in leaf area albeit at lower proportions. Comprehension and comparison of results of GC-MS analysis of essential oils showed that most of the Ocimum (O. basilicum, O. tenuiflorum, and O. gratissimum) species produce phenylpropanoids (eugenol, methyl chavicol) as major volatiles except O. kilimandscharicum, which is discrete in being monoterpenoid-rich species. Among the phenylpropanoid-enriched Ocimum (O. basilicum, O. gratissimum, O. tenuiflorum purple, O. tenuiflorum green) as well, terpenoids were important constituents in imparting characteristic aroma. Further, comparative abundance of transcripts of key genes of phenylpropanoid (PAL, C4H, 4CL, CAD, COMT, and ES) and terpenoid (DXS and HMGR) biosynthetic pathways was evaluated vis-à-vis volatile oil constituents. Transcript abundance demonstrated that richness of their essential oils with specific constituent(s) of a chemical group/subgroup was manifested by the predominant upregulation of phenylpropanoid/terpenoid pathway genes. The study provides trichomes as well as biosynthetic pathway-based knowledge for genetic improvement in Ocimum species for essential oil yield and quality.

The jasmonate-responsive transcription factor CbWRKY24 regulates terpenoid biosynthetic genes to promote saponin biosynthesis in Conyza blinii H. Lév

Conyza blinii H. Lév., the most effective component is saponin, is a biennial medicinal material that needs to be overwintered. WRKY transcription factors family is a large protein superfamily that plays a predominant role in plant secondary metabolism, but their characteristics and functions have not been identified in C. blinii. The CbWRKY24 sequence was selectedfrom the transcriptome database of the C. blinii leaves constructed in our laboratory. Phylogenetic tree analysis revealed that it was associated with AaWRKY1 which can regulate artemisinin synthesis in Artemisia annua. Expression analysis in C. blinii revealed that CbWRKY24 was mainly induced by methyl jasmonate (MeJA) and cold treatments. Transcriptional activity assay showed that it had an independent biological activity. Overexpression of CbWRKY24 in transient transformed C. blinii resulted in improved totalsaponins content, which was attributed to upregulate the expression level of keys genes from mevalonate (MVA) pathway in transient transformed plants compared to wild type (WT) plants. Meanwhile, overexpression the CbWRKY24 in transient transformed tomato fruits showed that the transcript level of related genes in lycopene pathway decreased significantly when compared to WT tomatofruits. Additionally, the MeJA-response-element was found in the promoter regions of CbWRKY24 and the histochemical staining experiments showed that promoter had GUS activity in transiently transformed tobacco leaves. In summary, our results indicated that we may have found a transcription factor that can regulate the biosynthesis of terpenoids in C. blinii.

Ocimum Genome Sequencing—A Futuristic Therapeutic Mine

Next-generation sequencing (NGS) platforms from the past decade are in the continuous efforts of changing the impact of sequencing on our current knowledge about plant genes, genomes, and their regulation. Holy basil (Ocimum tenuiflorum L. or sanctum L.) genome sequencing has also paved the path for deeper exploration of the medicinal properties of this beneficial herb making it a true ‘elixir of life.’ The draft genome sequence of the holy basil has not only opened the avenues for the drug discovery but has also widened the prospects of the molecular breeding for development of new improved plant varieties.