Transcriptome profiling of khat (Catha edulis) and Ephedra sinica reveals gene candidates potentially involved in amphetamine-type alkaloid biosynthesis

Ephedrae Herba: A Review of Its Phytochemistry, Pharmacology, Clinical Application, and Alkaloid Toxicity

Ephedrae Herba (Ephedra), known as "MaHuang" in China, is the dried straw stem that is associated with the lung and urinary bladder meridians. At present, more than 60 species of Ephedra plants have been identified, which contain more than 100 compounds, including alkaloids, flavonoids, tannins, sugars, and organic phenolic acids. This herb has long been used to treat asthma, liver disease, skin disease, and other diseases, and has shown unique efficacy in the treatment of COVID-19 infection. Because alkaloids are the main components causing toxicity, the safety of Ephedra must be considered. However, the nonalkaloid components of Ephedra can be effectively used to replace ephedrine extracts to treat some diseases, and reasonable use can ensure the safety of Ephedra. We reviewed the phytochemistry, pharmacology, clinical application, and alkaloid toxicity of Ephedra, and describe prospects for its future development to facilitate the development of Ephedra.

Evaluation of the Influence of Genetic and Environmental Factors on the Ephedrine Alkaloids Content of Ephedra sinica

Ephedra herb, a dried terrestrial stem of Ephedra sinica, is used in traditional Japanese medicine (Kampo) and Chinese medicine to treat the common cold, headaches, bronchial asthma, and nasal inflammation. E. sinica predominantly contains two ephedrine alkaloids-(-)-ephedrine and (+)-pseudoephedrine-which are crucial for its medicinal effects. This study aimed to reveal the influence of genetic and environmental factors on ephedrine alkaloids content using statistical genetic analyses. To evaluate the influence of genetic factors on ephedrine alkaloids content, 25 clonal lines were cultivated in Ibaraki and the broad-sense heritability of the traits was estimated. The heritabilities of (-)-ephedrine, (+)-pseudoephedrine, and "total alkaloids" (TA) content were 0.871, 0.969, and 0.865, respectively. The heritabilities of ephedrine alkaloids content were high. To evaluate the influence of environmental factors on ephedrine alkaloids content, four clonal lines which have different genotypes were cultivated in three locations (Ibaraki, Shizuoka, and Yamanashi prefectures). The effects of genotype (G), location (L), and genotype by environment (G × E) interactions on ephedrine alkaloids content were found to be significant (p < 0.05) by two-way ANOVA, and, in particular, the genotypic effects were found to be the largest. Our results indicate that the ephedrine alkaloids content in E. sinica is under relatively strong genetic control and remains stable under various environments. These findings suggest that E. sinica with a higher and stable ephedrine alkaloids content could be cultivated in different locations through selective breeding.

Transcriptome Analysis Reveals an Essential Role of Exogenous Brassinolide on the Alkaloid Biosynthesis Pathway in Pinellia Ternata

Pinellia ternata (Thunb.) Druce is a traditional medicinal plant containing a variety of alkaloids, which are important active ingredients. Brassinolide (BR) is a plant hormone that regulates plant response to environmental stress and promotes the accumulation of secondary metabolites in plants. However, the regulatory mechanism of BR-induced alkaloid accumulation in P. ternata is not clear. In this study, we investigated the effects of BR and BR biosynthesis inhibitor (propiconazole, Pcz) treatments on alkaloid biosynthesis in the bulbil of P. ternata. The results showed that total alkaloid content and bulbil yield was enhanced by 90.87% and 29.67% under BR treatment, respectively, compared to the control. We identified 818 (476 up-regulated and 342 down-regulated) and 697 (389 up-regulated and 308 down-regulated) DEGs in the BR-treated and Pcz-treated groups, respectively. Through this annotated data and the Kyoto encyclopedia of genes and genomes (KEGG), the expression patterns of unigenes involved in the ephedrine alkaloid, tropane, piperidine, pyridine alkaloid, indole alkaloid, and isoquinoline alkaloid biosynthesis were observed under BR and Pcz treatments. We identified 11, 8, 2, and 13 unigenes in the ephedrine alkaloid, tropane, piperidine, and pyridine alkaloid, indole alkaloid, and isoquinoline alkaloid biosynthesis, respectively. The expression levels of these unigenes were increased by BR treatment and were decreased by Pcz treatment, compared to the control. The results provided molecular insight into the study of the molecular mechanism of BR-promoted alkaloid biosynthesis.

Cross-Species Annotation of Expressed Genes and Detection of Different Functional Gene Modules Between 10 Cold- and 10 Hot-Propertied Chinese Herbal Medicines

According to the traditional Chinese medicine (TCM) system, Chinese herbal medicines (HMs) can be divided into four categories: hot, warm, cold, and cool. A cool nature usually is categorized as a cold nature, and a warm nature is classified as a hot nature. However, the detectable characteristics of the gene expression profile associated with the cold and hot properties have not been studied. To address this question, a strategy for the cross-species annotation of conserved genes was established in the present study by using transcriptome data of 20 HMs with cold and hot properties. Functional enrichment analysis was performed on group-specific expressed genes inferred from the functional genome of the reference species (i.e., Arabidopsis). Results showed that metabolic pathways relevant to chrysoeriol, luteolin, paniculatin, and wogonin were enriched for cold-specific genes, and pathways of inositol, heptadecane, lauric acid, octanoic acid, hexadecanoic acid, and pentadecanoic acid were enriched for hot-specific genes. Six functional modules were identified in the HMs with the cold property: nucleotide biosynthetic process, peptidy-L-cysteine S-palmitoylation, lipid modification, base-excision repair, dipeptide transport, and response to endoplasmic reticulum stress. For the hot HMs, another six functional modules were identified: embryonic meristem development, embryonic pattern specification, axis specification, regulation of RNA polymerase II transcriptional preinitiation complex assembly, mitochondrial RNA modification, and cell redox homeostasis. The research provided a new insight into HMs’ cold and hot properties from the perspective of the gene expression profile of plants.

Psychoactive plant- and mushroom-associated alkaloids from two behavior modifying cicada pathogens

Entomopathogenic fungi routinely kill their hosts before releasing infectious spores, but a few species keep insects alive while sporulating, which enhances dispersal. Transcriptomics- and metabolomics-based studies of entomopathogens with post-mortem dissemination from their parasitized hosts have unraveled infection processes and host responses. However, the mechanisms underlying active spore transmission by Entomophthoralean fungi in living insects remain elusive. Here we report the discovery, through metabolomics, of the plant-associated amphetamine, cathinone, in four Massospora cicadina-infected periodical cicada populations, and the mushroom-associated tryptamine, psilocybin, in annual cicadas infected with Massospora platypediae or Massospora levispora, which likely represent a single fungal species. The absence of some fungal enzymes necessary for cathinone and psilocybin biosynthesis along with the inability to detect intermediate metabolites or gene orthologs are consistent with possibly novel biosynthesis pathways in Massospora. The neurogenic activities of these compounds suggest the extended phenotype of Massospora that modifies cicada behavior to maximize dissemination is chemically-induced.

Phytochemistry and pharmacology of genus Ephedra

The genus Ephedra of the Ephedraceae family contains more than 60 species of nonflowering seed plants distributed throughout Asia, America, Europe, and North Africa. These Ephedra species have medicinal, ecological, and economic value. This review aims to summarize the chemical constituents and pharmacological activities of the Ephedra species to unveil opportunities for future research. Comprehensive information on the Ephedra species was collected by electronic search (e.g., GoogleScholar, Pubmed, SciFinder, and Web of Science) and phytochemical books. The chemical compounds isolated from the Ephedra species include alkaloids, flavonoids, tannins, polysaccharides, and others. The in vitro and in vivo pharmacological studies on the crude extracts, fractions and few isolated compounds of Ephedra species showed anti-inflammatory, anticancer, antibacterial, antioxidant, hepatoprotective, anti-obesity, antiviral, and diuretic activities. After chemical and pharmacological profiling, current research is focused on the antibacterial and antifungal effects of the phenolic acid compounds, the immunosuppressive activity of the polysaccharides, and the antitumor activity of flavonoids.

An N-methyltransferase from Ephedra sinica catalyzing the formation of ephedrine and pseudoephedrine enables microbial phenylalkylamine production

Phenylalkylamines, such as the plant compounds ephedrine and pseudoephedrine and the animal neurotransmitters dopamine and adrenaline, compose a large class of natural and synthetic molecules with important physiological functions and pharmaceutically valuable bioactivities. The final steps of ephedrine and pseudoephedrine biosynthesis in members of the plant genus Ephedra involve N-methylation of norephedrine and norpseudoephedrine, respectively. Here, using a plant transcriptome screen, we report the isolation and characterization of an N-methyltransferase (NMT) from Ephedra sinica able to catalyze the formation of (pseudo)ephedrine and other naturally occurring phenylalkylamines, including N-methylcathinone and N-methyl(pseudo)ephedrine. Phenylalkylamine N-methyltransferase (PaNMT) shares substantial amino acid sequence identity with enzymes of the NMT family involved in benzylisoquinoline alkaloid (BIA) metabolism in members of the higher plant order Ranunculales, which includes opium poppy (Papaver somniferum). PaNMT accepted a broad range of substrates with phenylalkylamine, tryptamine, β-carboline, tetrahydroisoquinoline, and BIA structural scaffolds, which is in contrast to the specificity for BIA substrates of NMT enzymes within the Ranunculales. PaNMT transcript levels were highest in young shoots of E. sinica, which corresponded to the location of NMT activity yielding (pseudo)ephedrine, N-methylcathinone, and N-methyl(pseudo)ephedrine, and with in planta accumulation of phenylalkylamines. Co-expression of recombinant genes encoding PaNMT and an ω-transaminase (PP2799) from Pseudomonas putida in Escherichia coli enabled the conversion of exogenous (R)-phenylacetylcarbinol (PAC) and (S)-PAC to ephedrine and pseudoephedrine, respectively. Our work further demonstrates the utility of plant biochemical genomics for the isolation of key enzymes that facilitate microbial engineering for the production of medicinally important metabolites.

Stabilization of Ephedrine Alkaloid Content in Ephedra sinica by Selective Breeding and Stolon Propagation

The Ephedra herb, which has been used in Kampo medicines, originates from terrestrial stems of Ephedra species. It is important to establish cultivation methods and cultivars to secure a stable supply of the Ephedra herb that would meet the quality standards for the ephedrine alkaloids content. In this study, we first grew Ephedra sinica plants derived from seeds in the field for 5 years. Then, for selective breeding of cultivars that could meet the quality standards for the ephedrine alkaloids content, we measured the content of total alkaloids (TAs), ephedrine (Eph), and pseudoephedrine (PEph) in individual plants derived from seedlings and grown for 4 years in the field. The range of the TA content in each individual plant was narrower than that among individual plants grown in the field. Therefore, individual plants were selected according to their TA content, Eph/PEph ratio, and stolon-formation capability. The selected individuals were propagated using stolons, and their TA content was studied for 2 years. In the second year, the TA content in terrestrial stems derived from stolons of the selected individuals was as high as that of their parents. Therefore, it was confirmed that the selected individuals that were propagated using stolons could produce TA reproducibly. This study suggested that selective breeding using stolon propagation is effective for stabilizing Ephedra herb TA content.

De novo Sequencing and Transcriptome Analysis of Pinellia ternata Identify the Candidate Genes Involved in the Biosynthesis of Benzoic Acid and Ephedrine

BACKGROUND

The medicinal herb, Pinellia ternata, is purported to be an anti-emetic with analgesic and sedative effects. Alkaloids are the main biologically active compounds in P. ternata, especially ephedrine that is a phenylpropylamino alkaloid specifically produced by Ephedra and Catha edulis. However, how ephedrine is synthesized in plants is uncertain. Only the phenylalanine ammonia lyase (PAL) and relevant genes in this pathway have been characterized. Genomic information of P. ternata is also unavailable.

RESULTS

We analyzed the transcriptome of the tuber of P. ternata with the Illumina HiSeq™ 2000 sequencing platform. 66,813,052 high-quality reads were generated, and these reads were assembled de novo into 89,068 unigenes. Most known genes involved in benzoic acid biosynthesis were identified in the unigene dataset of P. ternata, and the expression patterns of some ephedrine biosynthesis-related genes were analyzed by reverse transcription quantitative real-time PCR (RT-qPCR). Also, 14,468 simple sequence repeats (SSRs) were identified from 12,000 unigenes. Twenty primer pairs for SSRs were randomly selected for the validation of their amplification effect.

CONCLUSION

RNA-seq data was used for the first time to provide a comprehensive gene information on P. ternata at the transcriptional level. These data will advance molecular genetics in this valuable medicinal plant.

Comparative analysis of transcriptomes in aerial stems and roots of Ephedra sinica based on high-throughput mRNA sequencing

Ephedra plants are taxonomically classified as gymnosperms, and are medicinally important as the botanical origin of crude drugs and as bioresources that contain pharmacologically active chemicals. Here we show a comparative analysis of the transcriptomes of aerial stems and roots of Ephedra sinica based on high-throughput mRNA sequencing by RNA-Seq. De novo assembly of short cDNA sequence reads generated 23,358, 13,373, and 28,579 contigs longer than 200 bases from aerial stems, roots, or both aerial stems and roots, respectively. The presumed functions encoded by these contig sequences were annotated by BLAST (blastx). Subsequently, these contigs were classified based on gene ontology slims, Enzyme Commission numbers, and the InterPro database. Furthermore, comparative gene expression analysis was performed between aerial stems and roots. These transcriptome analyses revealed differences and similarities between the transcriptomes of aerial stems and roots in E. sinica. Deep transcriptome sequencing of Ephedra should open the door to molecular biological studies based on the entire transcriptome, tissue- or organ-specific transcriptomes, or targeted genes of interest.

Transcriptome analysis and molecular marker discovery in Solanum incanum and S. aethiopicum, two close relatives of the common eggplant (Solanum melongena) with interest for breeding

Background

Solanum incanum is a close wild relative of S. melongena with high contents of bioactive phenolics and drought tolerance. S. aethiopicum is a cultivated African eggplant cross-compatible with S. melongena. Despite their great interest in S. melongena breeding programs, the genomic resources for these species are scarce.

Results

RNA-Seq was performed with NGS from pooled RNA of young leaf, floral bud and young fruit tissues, generating more than one hundred millions raw reads per species. The transcriptomes were assembled in 83,905 unigenes for S. incanum and in 87,084 unigenes for S. aethiopicum with an average length of 696 and 722 bp, respectively. The unigenes were structurally and functionally annotated based on comparison with public databases by using bioinformatic tools. The single nucleotide variant calling analysis (SNPs and INDELs) was performed by mapping our S. incanum and S. aethiopicum reads, as well as reads from S. melongena and S. torvum available on NCBI database (National Center for Biotechnology Information), against the eggplant genome. Both intraspecific and interspecific polymorphisms were identified and subsets of molecular markers were created for all species combinations. 36 SNVs were selected for validation in the S. incanum and S. aethiopicum accessions and 96 % were correctly amplified confirming the polymorphisms. In addition, 976 and 1,278 SSRs were identified in S. incanum and S. aethiopicum transcriptomes respectively, and a set of them were validated.

Conclusions

This work provides a broad insight into gene sequences and allelic variation in S. incanum and S. aethiopicum. This work is a first step toward better understanding of target genes involved in metabolic pathways relevant for eggplant breeding. The molecular markers detected in this study could be used across all the eggplant genepool, which is of interest for breeding programs as well as to perform marker-trait association and QTL analysis studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2631-4) contains supplementary material, which is available to authorized users.

Hepatotoxicity Induced by "the 3Ks": Kava, Kratom and Khat

The 3Ks (kava, kratom and khat) are herbals that can potentially induce liver injuries. On the one hand, growing controversial data have been reported about the hepatotoxicity of kratom, while, on the other hand, even though kava and khat hepatotoxicity has been investigated, the hepatotoxic effects are still not clear. Chronic recreational use of kratom has been associated with rare instances of acute liver injury. Several studies and case reports have suggested that khat is hepatotoxic, leading to deranged liver enzymes and also histopathological evidence of acute hepatocellular degeneration. Numerous reports of severe hepatotoxicity potentially induced by kava have also been highlighted, both in the USA and Europe. The aim of this review is to focus on the different patterns and the mechanisms of hepatotoxicity induced by “the 3Ks”, while trying to clarify the numerous aspects that still need to be addressed.