Isoquinoline alkaloid biosynthesis is regulated by a unique bHLH-type transcription factor in Coptis japonica

Multiomics Combined with Expression Pattern Analysis Reveals the Regulatory Response of Key Genes in Potato Jasmonic Acid Signaling Pathways to Cadmium Stress

Jasmonic acid (JA) is an endogenous phytohormone that regulates plant physiological metabolism and stress response processes, either independently or through hormone crosstalk. Our phytohormone assay and transcriptome-metabolome analysis revealed the key genes and metabolites involved in the JA pathway in response to 0-250 μM cadmium (Cd) in potato seedlings. Transcriptome gene set enrichment and gene ontology analysis indicated that JA-related genes were significantly enriched. Specifically, members from the StOPR and StJAZ gene families showed pronounced responses to Cd stress and methyl jasmonate treatment. As a negative regulatory transcription factor of the JA signaling pathway, StJAZ14 exhibited a decreasing trend under Cd stress. Yeast two-hybrid assay identified an interaction between StJAZ14 and StBZR1, which is located on the brassinolide pathway. In addition to unveiling the critical role of the JA pathway in regulating potato response to Cd stress, the functional mechanism was preliminarily explored.

Molecular regulation of the key specialized metabolism pathways in medicinal plants

The basis of modern pharmacology is the human ability to exploit the production of specialized metabolites from medical plants, for example, terpenoids, alkaloids, and phenolic acids. However, in most cases, the availability of these valuable compounds is limited by cellular or organelle barriers or spatio-temporal accumulation patterns within different plant tissues. Transcription factors (TFs) regulate biosynthesis of these specialized metabolites by tightly controlling the expression of biosynthetic genes. Cutting-edge technologies and/or combining multiple strategies and approaches have been applied to elucidate the role of TFs. In this review, we focus on recent progress in the transcription regulation mechanism of representative high-value products and describe the transcriptional regulatory network, and future perspectives are discussed, which will help develop high-yield plant resources.

Diversely functionalized isoquinolines and their core-embedded heterocyclic frameworks: a privileged scaffold for medicinal chemistry

Isoquinoline-enrooted organic small-molecules represent a challenging molecular target in the organic synthesis arsenal attributed to their structural diversity and therapeutic importance. Into the bargain, isoquinolines are significant structural frameworks in modern medicinal chemistry and drug development. Consequently, synthetic organic and medicinal chemists have been intensely interested in efficient synthetic tactics for the sustainable construction of isoquinoline frameworks and their derivatives in enantiopure or racemic forms. This review accentuates an overview of the literature on the modern synthetic approaches exploited in synthesising isoquinolines and their core embedded heterocyclic skeletons from 2021 to 2022. In detail, the methodologies and inspected pharmacological studies for the array of diversely functionalized isoquinolines or their core-embedded heterocyclic/carbocyclic structures involving the introduction of substituents at C-1, C-3, and C-4 carbon and N-2 atom, bond constructions at the C1-N2 atom and C3-N2 atom, and structural scaffolding within isoquinoline compounds have been reviewed. This intensive study highlights the need for and relevance of relatively unexplored bioisosterism employing isoquinoline-based small-molecules in drug design.

Genome Assembly of Cordia subcordata, a Coastal Protection Species in Tropical Coral Islands

Cordia subcordata trees or shrubs, belonging to the Boraginaceae family, have strong resistance and have adapted to their habitat on a tropical coral island in China, but the lack of genome information regarding its genetic background is unclear. In this study, the genome was assembled using both short/long whole genome sequencing reads and Hi-C reads. The assembled genome was 475.3 Mb, with 468.7 Mb (99.22%) of the sequences assembled into 16 chromosomes. Repeat sequences accounted for 54.41% of the assembled genome. A total of 26,615 genes were predicted, and 25,730 genes were functionally annotated using different annotation databases. Based on its genome and the other 17 species, phylogenetic analysis using 336 single-copy genes obtained from ortholog analysis showed that C. subcordata was a sister to Coffea eugenioides, and the divergence time was estimated to be 77 MYA between the two species. Gene family evolution analysis indicated that the significantly expanded gene families were functionally related to chemical defenses against diseases. These results can provide a reference to a deeper understanding of the genetic background of C. subcordata and can be helpful in exploring its adaptation mechanism on tropical coral islands in the future.

The association between circulatory, local pancreatic PCSK9 and type 2 diabetes mellitus: The effects of antidiabetic drugs on PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent modulator of cholesterol metabolism and plays a crucial role in the normal functioning of pancreatic islets and the progression of diabetes. Islet autocrine PCSK9 deficiency can lead to the enrichment of low-density lipoprotein (LDL) receptor (LDLR) and excessive LDL cholesterol (LDL-C) uptake, subsequently impairing the insulin secretion in β-cells. Circulatory PCSK9 levels are primarily attributed to hepatocyte secretion. Notably, anti-PCSK9 strategies proposed for individuals with hypercholesterolemia chiefly target liver-derived PCSK9; however, these anti-PCSK9 strategies have been associated with the risk of new-onset diabetes mellitus (NODM). In the current review, we highlight a new direction in PCSK9 inhibition therapy strategies: screening candidates for anti-PCSK9 from the drugs used in type 2 diabetes mellitus (T2DM) treatment. We explored the association between circulating, local pancreatic PCSK9 and T2DM, as well as the relationship between PCSK9 monoclonal antibodies and NODM. We discussed the emergence of artificial and natural drugs in recent years, exhibiting dual benefits of antidiabetic activity and PCSK9 reduction, confirming that the diverse effects of these drugs may potentially impact the progression of diabetes and associated disorders, thereby introducing novel avenues and methodologies to enhance disease prognosis.

Genome-wide analysis of bHLH gene family in Coptis chinensis provides insights into the regulatory role in benzylisoquinoline alkaloid biosynthesis

Coptis chinensis Franch is a perennial species with high medical value. The rhizome of C. chinensis is a traditional Chinese medicine widely used for more than 2000 years in China. Its principal active ingredients are benzylisoquinoline alkaloids (BIAs). The basic helix-loop-helix (bHLH) transcription factors play an important regulatory role in the biosynthesis of plant secondary metabolites. However, the bHLH genes in C. chinensis have not been described, and little is known about their roles in alkaloid biosynthesis. In this study, a total of 143 CcbHLH genes (CcbHLHs) were identified and unevenly distributed on nine chromosomes. Phylogenetic analysis divided the 143 CcbHLH proteins into 26 subfamilies by comparison with Arabidopsis thaliana bHLH proteins. The majority CcbHLHs in each subgroup had similar gene structures and conserved motifs. Furthermore, the physicochemical properties, conserved motif, intron/exon composition, and cis-acting elements of CcbHLHs were analyzed. Transcriptome analysis revealed that 30 CcbHLHs were significantly expressed in the rhizomes of C. chinensis. Co-expression analysis revealed that 11 CcbHLHs were highly positively correlated with contents of various alkaloids of C. chinensis. Moreover, yeast one-hybrid experiments verified that CcbHLH001 and CcbHLH0002 could interact with the promoters of berberine biosynthesis pathway genes CcBBE and CcCAS, suggesting their regulatory roles in BIA biosynthesis. This study provides comprehensive insights into the bHLH gene family in C. chinensis and will support in-depth functional characterization of CcbHLHs involved in the regulation of protoberberine-type alkaloid biosynthesis.

Multilayered regulation of secondary metabolism in medicinal plants

Medicinal plants represent a huge reservoir of secondary metabolites (SMs), substances with significant pharmaceutical and industrial potential. However, obtaining secondary metabolites remains a challenge due to their low-yield accumulation in medicinal plants; moreover, these secondary metabolites are produced through tightly coordinated pathways involving many spatiotemporally and environmentally regulated steps. The first regulatory layer involves a complex network of transcription factors; a second, more recently discovered layer of complexity in the regulation of SMs is epigenetic modification, such as DNA methylation, histone modification and small RNA-based mechanisms, which can jointly or separately influence secondary metabolites by regulating gene expression. Here, we summarize the findings in the fields of genetic and epigenetic regulation with a special emphasis on SMs in medicinal plants, providing a new perspective on the multiple layers of regulation of gene expression.

Signal Molecules Regulate the Synthesis of Secondary Metabolites in the Interaction between Endophytes and Medicinal Plants

Signaling molecules act as the links and bridges between endophytes and host plants. The recognition of endophytes and host plants, the regulation of host plant growth and development, and the synthesis of secondary metabolites are not separated by the participation of signaling molecules. In this review, we summarized the types and characteristics of signaling molecules in medicinal plants and the recent processes in intracellular conduction and multi-molecular crosstalk of signaling molecules during interactions between endophytic bacteria and medicinal plants. In addition, we overviewed the molecular mechanism of signals in medical metabolite accumulation and regulation. This work provides a reference for using endophytic bacteria and medicinal plants to synthesize pharmaceutical active ingredients in a bioreactor.

Unique gene duplications and conserved microsynteny potentially associated with resistance to wood decay in the Lauraceae

Wood decay resistance (WDR) is marking the value of wood utilization. Many trees of the Lauraceae have exceptional WDR, as evidenced by their use in ancient royal palace buildings in China. However, the genetics of WDR remain elusive. Here, through comparative genomics, we revealed the unique characteristics related to the high WDR in Lauraceae trees. We present a 1.27-Gb chromosome-level assembly for Lindera megaphylla (Lauraceae). Comparative genomics integrating major groups of angiosperm revealed Lauraceae species have extensively shared gene microsynteny associated with the biosynthesis of specialized metabolites such as isoquinoline alkaloids, flavonoid, lignins and terpenoid, which play significant roles in WDR. In Lauraceae genomes, tandem and proximal duplications (TD/PD) significantly expanded the coding space of key enzymes of biosynthesis pathways related to WDR, which may enhance the decay resistance of wood by increasing the accumulation of these compounds. Among Lauraceae species, genes of WDR-related biosynthesis pathways showed remarkable expansion by TD/PD and conveyed unique and conserved motifs in their promoter and protein sequences, suggesting conserved gene collinearity, gene expansion and gene regulation supporting the high WDR. Our study thus reveals genomic profiles related to biochemical transitions among major plant groups and the genomic basis of WDR in the Lauraceae.

California poppy (Eschscholzia californica), the Papaveraceae golden girl model organism for evodevo and specialized metabolism

California poppy or golden poppy (Eschscholzia californica) is the iconic state flower of California, with native ranges from Northern California to Southwestern Mexico. It grows well as an ornamental plant in Mediterranean climates, but it might be invasive in many parts of the world. California poppy was also highly prized by Native Americans for its medicinal value, mainly due to its various specialized metabolites, especially benzylisoquinoline alkaloids (BIAs). As a member of the Ranunculales, the sister lineage of core eudicots it occupies an interesting phylogenetic position. California poppy has a short-lived life cycle but can be maintained as a perennial. It has a comparatively simple floral and vegetative morphology. Several genetic resources, including options for genetic manipulation and a draft genome sequence have been established already with many more to come. Efficient cell and tissue culture protocols are established to study secondary metabolite biosynthesis and its regulation. Here, we review the use of California poppy as a model organism for plant genetics, with particular emphasis on the evolution of development and BIA biosynthesis. In the future, California poppy may serve as a model organism to combine two formerly separated lines of research: the regulation of morphogenesis and the regulation of secondary metabolism. This can provide insights into how these two integral aspects of plant biology interact with each other.

PeCLH2 Gene Positively Regulate Salt Tolerance in Transgenic Populus alba × Populus glandulosa

Salt is an important environmental stress factor, which seriously affects the growth, development and distribution of plants. Chlorophyllase plays an important role in stress response. Nevertheless, little is known about the physiological and molecular mechanism of chlorophyll (Chlase, CLH) genes in plants. We cloned PeCLH2 from Populus euphratica and found that PeCLH2 was differentially expressed in different tissues, especially in the leaves of P. euphratica. To further study the role of PeCLH2 in salt tolerance, PeCLH2 overexpression and RNA interference transgenic lines were established in Populus alba × Populus glandulosa and used for salt stress treatment and physiologic indexes studies. Overexpressing lines significantly improved tolerance to salt treatment and reduced reactive oxygen species production. RNA interference lines showed the opposite. Transcriptome analysis was performed on leaves of control and transgenic lines under normal growth conditions and salt stress to predict genes regulated during salt stress. This provides a basis for elucidating the molecular regulation mechanism of PeCLH2 in response to salt stress and improving the tolerance of poplar under salt stress.

Transcriptome and metabolome profiling of the medicinal plant Veratrum mengtzeanum reveal key components of the alkaloid biosynthesis

Veratrum mengtzeanum is the main ingredient for Chinese folk medicine known as "Pimacao" due to its unique alkaloids. A diverse class of plant-specific metabolites having key pharmacological activities. There are limited studies on alkaloid synthesis and its metabolic pathways in plants. To elucidate the alkaloid pathway and identify novel biosynthetic enzymes and compounds in V. mengtzeanum, transcriptome and metabolome profiling has been conducted in leaves and roots. The transcriptome of V. mengtzeanum leaves and roots yielded 190,161 unigenes, of which 33,942 genes expressed differentially (DEGs) in both tissues. Three enriched regulatory pathways (isoquinoline alkaloid biosynthesis, indole alkaloid biosynthesis and tropane, piperidine and pyridine alkaloid biosynthesis) and a considerable number of genes such as AED3-like, A4U43, 21 kDa protein-like, 3-O-glycotransferase 2-like, AtDIR19, MST4, CASP-like protein 1D1 were discovered in association with the biosynthesis of alkaloids in leaves and roots. Some transcription factor families, i.e., AP2/ERF, GRAS, NAC, bHLH, MYB-related, C3H, FARI, WRKY, HB-HD-ZIP, C2H2, and bZIP were also found to have a prominent role in regulating the synthesis of alkaloids and steroidal alkaloids in the leaves and roots of V. mengtzeanum. The metabolome analysis revealed 74 significantly accumulated metabolites, with 55 differentially accumulated in leaves compared to root tissues. Out of 74 metabolites, 18 alkaloids were highly accumulated in the roots. A novel alkaloid compound viz; 3-Vanilloylygadenine was discovered in root samples. Conjoint analysis of transcriptome and metabolome studies has also highlighted potential genes involved in regulation and transport of alkaloid compounds. Here, we have presented a comprehensive metabolic and transcriptome profiling of V. mengtzeanum tissues. In earlier reports, only the roots were reported as a rich source of alkaloid biosynthesis, but the current findings revealed both leaves and roots as significant manufacturing factories for alkaloid biosynthesis.

Dissection of transcriptome and metabolome insights into the isoquinoline alkaloid biosynthesis during stem development in Phellodendron amurense (Rupr.)

Phellodendron amurense (Rupr.) is a well-known medicinal plant with high medicinal value, and its various tissues are enriched in various active pharmaceutical ingredients. Isoquinoline alkaloids are the primary medicinal component of P. amurense and have multiple effects, such as anti-inflammation, antihypertension, and antitumor effects. However, the potential regulatory mechanism of isoquinoline alkaloid biosynthesis during stem development in P. amurense is still poorly understood. In the present study, a total of eight plant hormones for each stem development stage were detected; of those, auxin, gibberellins and brassinosteroids were significantly highly increased in perennial stems and played key roles during stem development in P. amurense. We also investigated the content and change pattern of secondary metabolites and comprehensively identified some key structural genes involved in the isoquinoline alkaloid biosynthesis pathway by combining the transcriptome and metabolomics. A total of 39,978 DEGs were identified in the present study, and six of those had candidate structural genes (NCS, GOT2, TYNA, CODM, TYR, TAT and PSOMT1) that were specifically related to isoquinoline alkaloid biosynthesis in P. amurense. Corydalmine, cyclanoline, dehydroyanhunine, (S)-canadine and corybulbine were the most significantly upregulated metabolites among the different comparative groups. Three differentially expressed metabolites, dopamine, (S)-corytuberine and (S)-canadine, were enriched in the isoquinoline alkaloid biosynthesis pathway. Furthermore, bHLH and WRKY transcription factors play key roles in the isoquinoline alkaloid biosynthesis pathway in P. amurense. The results not only provide comprehensive genetic information for understanding the molecular mechanisms of isoquinoline alkaloid biosynthesis but also lay a foundation for the combinatory usage of the medicinal active ingredient of P. amurense.

Interplay of transcription factors orchestrating the biosynthesis of plant alkaloids

Plants produce a range of secondary metabolites primarily as defence molecules. A plant has to invest considerable energy to synthesise alkaloids, and sometimes they are even toxic to themselves. Hence, the biosynthesis of alkaloids is a spatiotemporally regulated process under quantitative feedback regulation which is accomplished by the signal reception, transcriptional/translational regulation, transport, storage and accumulation. The transcription factors (TFs) initiate the biosynthesis of alkaloids after appropriate cues. The present study recapitulates last decade understanding of the role of TFs in alkaloid biosynthesis. The present review discusses TF families, viz. AP2/ERF, bHLH, WRKY, MYB involved in the biosynthesis of various types of alkaloids. It also highlights the role of the jasmonic acid cascade and post-translational modifications of TF proteins. A thorough understanding of TFs will help us to decide a strategy to facilitate successful pathway manipulation and in vitro production.

Natural products of medicinal plants: biosynthesis and bioengineering in post-genomic era

Globally, medicinal plant natural products (PNPs) are a major source of substances used in traditional and modern medicine. As we human race face the tremendous public health challenge posed by emerging infectious diseases, antibiotic resistance and surging drug prices etc., harnessing the healing power of medicinal plants gifted from mother nature is more urgent than ever in helping us survive future challenge in a sustainable way. PNP research efforts in the pre-genomic era focus on discovering bioactive molecules with pharmaceutical activities, and identifying individual genes responsible for biosynthesis. Critically, systemic biological, multi- and inter-disciplinary approaches integrating and interrogating all accessible data from genomics, metabolomics, structural biology, and chemical informatics are necessary to accelerate the full characterization of biosynthetic and regulatory circuitry for producing PNPs in medicinal plants. In this review, we attempt to provide a brief update on the current research of PNPs in medicinal plants by focusing on how different state-of-the-art biotechnologies facilitate their discovery, the molecular basis of their biosynthesis, as well as synthetic biology. Finally, we humbly provide a foresight of the research trend for understanding the biology of medicinal plants in the coming decades.

Environmental and Genetic Factors Involved in Plant Protection-Associated Secondary Metabolite Biosynthesis Pathways

Plant specialized metabolites (PSMs) play essential roles in the adaptation to harsh environments and function in plant defense responses. PSMs act as key components of defense-related signaling pathways and trigger the extensive expression of defense-related genes. In addition, PSMs serve as antioxidants, participating in the scavenging of rapidly rising reactive oxygen species, and as chelators, participating in the chelation of toxins under stress conditions. PSMs include nitrogen-containing chemical compounds, terpenoids/isoprenoids, and phenolics. Each category of secondary metabolites has a specific biosynthetic pathway, including precursors, intermediates, and end products. The basic biosynthetic pathways of representative PSMs are summarized, providing potential target enzymes of stress-mediated regulation and responses. Multiple metabolic pathways share the same origin, and the common enzymes are frequently to be the targets of metabolic regulation. Most biosynthetic pathways are controlled by different environmental and genetic factors. Here, we summarized the effects of environmental factors, including abiotic and biotic stresses, on PSM biosynthesis in various plants. We also discuss the positive and negative transcription factors involved in various PSM biosynthetic pathways. The potential target genes of the stress-related transcription factors were also summarized. We further found that the downstream targets of these Transcription factors (TFs) are frequently enriched in the synthesis pathway of precursors, suggesting an effective role of precursors in enhancing of terminal products. The present review provides valuable insights regarding screening targets and regulators involved in PSM-mediated plant protection in non-model plants.

Transcriptome Analysis of Stephania tetrandra and Characterization of Norcoclaurine-6-O-Methyltransferase Involved in Benzylisoquinoline Alkaloid Biosynthesis

Stephania tetrandra (S. Moore) is a source of traditional Chinese medicine that is widely used to treat rheumatism, rheumatoid arthritis, edema, and hypertension. Benzylisoquinoline alkaloids (BIAs) are the main bioactive compounds. However, the current understanding of the biosynthesis of BIAs in S. tetrandra is poor. Metabolite and transcriptomic analyses of the stem, leaf, xylem, and epidermis of S. tetrandra were performed to identify candidate genes associated with BIAs biosynthesis. According to the metabolite analysis, the majority of the BIAs accumulated in the root, especially in the epidermis. Transcriptome sequencing revealed a total of 113,338 unigenes that were generated by de novo assembly. Among them, 79,638 unigenes were successfully annotated, and 42 candidate structural genes associated with 15 steps of BIA biosynthesis identified. Additionally, a new (S)-norcoclaurine-6-O-methyltransferase (6OMT) gene was identified in S. tetrandra, named St6OMT2. Recombinant St6OMT2 catalyzed (S)-norcoclaurine methylation to form (S)-coclaurine in vitro. Maximum activity of St6OMT2 was determined at 30°C and pH 6.0 in NaAc-HAc buffer. Its half-life at 50°C was 22 min with the K_m and k_cat of 28.2 μM and 1.5 s^-1, respectively. Our results provide crucial transcriptome information for S. tetrandra, shedding light on the understanding of BIAs biosynthesis and further gene functional characterization.

Berberine as a Potential Anticancer Agent: A Comprehensive Review

Berberine (BBR), a potential bioactive agent, has remarkable health benefits. A substantial amount of research has been conducted to date to establish the anticancer potential of BBR. The present review consolidates salient information concerning the promising anticancer activity of this compound. The therapeutic efficacy of BBR has been reported in several studies regarding colon, breast, pancreatic, liver, oral, bone, cutaneous, prostate, intestine, and thyroid cancers. BBR prevents cancer cell proliferation by inducing apoptosis and controlling the cell cycle as well as autophagy. BBR also hinders tumor cell invasion and metastasis by down-regulating metastasis-related proteins. Moreover, BBR is also beneficial in the early stages of cancer development by lowering epithelial–mesenchymal transition protein expression. Despite its significance as a potentially promising drug candidate, there are currently no pure berberine preparations approved to treat specific ailments. Hence, this review highlights our current comprehensive knowledge of sources, extraction methods, pharmacokinetic, and pharmacodynamic profiles of berberine, as well as the proposed mechanisms of action associated with its anticancer potential. The information presented here will help provide a baseline for researchers, scientists, and drug developers regarding the use of berberine as a promising candidate in treating different types of cancers.

Transcription Factors in Alkaloid Engineering

Plants produce a large variety of low-molecular-weight and specialized secondary compounds. Among them, nitrogen-containing alkaloids are the most biologically active and are often used in the pharmaceutical industry. Although alkaloid chemistry has been intensively investigated, characterization of alkaloid biosynthesis, including biosynthetic enzyme genes and their regulation, especially the transcription factors involved, has been relatively delayed, since only a limited number of plant species produce these specific types of alkaloids in a tissue/cell-specific or developmental-specific manner. Recent advances in molecular biology technologies, such as RNA sequencing, co-expression analysis of transcripts and metabolites, and functional characterization of genes using recombinant technology and cutting-edge technology for metabolite identification, have enabled a more detailed characterization of alkaloid pathways. Thus, transcriptional regulation of alkaloid biosynthesis by transcription factors, such as basic helix-loop-helix (bHLH), APETALA2/ethylene-responsive factor (AP2/ERF), and WRKY, is well elucidated. In addition, jasmonate signaling, an important cue in alkaloid biosynthesis, and its cascade, interaction of transcription factors, and post-transcriptional regulation are also characterized and show cell/tissue-specific or developmental regulation. Furthermore, current sequencing technology provides more information on the genome structure of alkaloid-producing plants with large and complex genomes, for genome-wide characterization. Based on the latest information, we discuss the application of transcription factors in alkaloid engineering.

Plant isoquinoline alkaloids: Advances in the chemistry and biology of berberine

Alkaloids are one of the most important classes of plant bioactives. Among these isoquinoline alkaloids possess varied structures and exhibit numerous biological activities. Basically these are biosynthetically produced via phenylpropanoid pathway. However, occasionally some mixed pathways may also occur to provide structural divergence. Among the various biological activities anticancer, antidiabetic, antiinflammatory, and antimicrobial are important. A few notable bioactive isoquinoline alkaloids are antidiabetic berberine, anti-tussive codeine, analgesic morphine, and muscle relaxant papaverine etc. Berberine is one of the most discussed bioactives from this class possessing broad-spectrum pharmacological activities. Present review aims at recent updates of isoquinoline alkaloids with major emphasis on berberine, its detailed chemistry, important biological activities, structure activity relationship and implementation in future research.

Scientometric Analysis of Medicinal and Edible Plant Coptis

Objective: A scientometric analysis to obtain knowledge mapping of Coptis revealed the current research situation, knowledge base and research hotspots in Coptis research.

Methods:Coptis-related documents published from 1987 to 2020 were selected through the Web of Science Core Collection. CiteSpace, VOSviewer and Microsoft Excel were used to construct knowledge maps of the Coptis research field.

Results: A total of 367 documents and their references were analyzed. These papers were primarily published in mainland China (214), followed by Japan (57) and South Korea (52), and they each formed respective cooperation networks. The document co-citation analysis suggested that the identification of Coptis Salisb. species, the production of alkaloids, and the mechanisms of action of these alkaloids formed the knowledge bases in this field. A keyword analysis further revealed that the research hotspots were primarily concentrated in three fields of research involving berberine, Coptis chinensis Franch, and Coptis japonica (Thunb) Makino. Oxidative stress, rat plasma (for the determination of plasma alkaloid contents), and Alzheimer’s disease are recent research hotspots associated with Coptis.

Conclusion:Coptis research was mainly distributed in three countries: China, Japan, and South Korea. Researchers were concerned with the identification of Coptis species, the production of Coptis alkaloids, and the efficacy and pharmacological mechanism of the constituent alkaloids. In addition, the anti-oxidative stress, pharmacokinetics, and Alzheimer’s disease treatment of Coptis are new hotspots in this field. This study provides a reference for Coptis researchers.

Analysis of the Coptis chinensis genome reveals the diversification of protoberberine-type alkaloids

Chinese goldthread (Coptis chinensis Franch.), a member of the Ranunculales, represents an important early-diverging eudicot lineage with diverse medicinal applications. Here, we present a high-quality chromosome-scale genome assembly and annotation of C. chinensis. Phylogenetic and comparative genomic analyses reveal the phylogenetic placement of this species and identify a single round of ancient whole-genome duplication (WGD) shared by the Ranunculaceae. We characterize genes involved in the biosynthesis of protoberberine-type alkaloids in C. chinensis. In particular, local genomic tandem duplications contribute to member amplification of a Ranunculales clade-specific gene family of the cytochrome P450 (CYP) 719. The functional versatility of a key CYP719 gene that encodes the (S)-canadine synthase enzyme involved in the berberine biosynthesis pathway may play critical roles in the diversification of other berberine-related alkaloids in C. chinensis. Our study provides insights into the genomic landscape of early-diverging eudicots and provides a valuable model genome for genetic and applied studies of Ranunculales.

MYC2 Transcription Factors TwMYC2a and TwMYC2b Negatively Regulate Triptolide Biosynthesis in Tripterygium wilfordii Hairy Roots

Triptolide, an important bioactive diterpenoid extracted from the plant Tripterygium wilfordii, exhibits many pharmacological activities. MYC2 transcription factor (TF) plays an important role in the regulation of various secondary metabolites in plants. However, whether MYC2 TF could regulate the biosynthesis of triptolide in T. wilfordii is still unknown. In this study, two homologous MYC2 TF genes, TwMYC2a and TwMYC2b, were isolated from T. wilfordii hairy roots and functionally characterized. The analyses of the phylogenetic tree and subcellular localization showed that they were grouped into the IIIe clade of the bHLH superfamily with other functional MYC2 proteins and localized in the nucleus. Furthermore, yeast one-hybrid and GUS transactivation assays suggested that TwMYC2a and TwMYC2b inhibited the promoter activity of the miltiradiene synthase genes, TwTPS27a and TwTPS27b, by binding to the E-box (CACATG) and T/G-box (CACGTT) motifs in their promoters. Transgenic results revealed that RNA interference of TwMYC2a/b significantly enhanced the triptolide accumulation in hairy roots and liquid medium by upregulating the expression of several key biosynthetic genes, including TwMS (TwTPS27a/b), TwCPS (TwTPS7/9), TwDXR, and TwHMGR1. In summary, our findings show that TwMYC2a and TwMYC2b act as two negative regulators of triptolide biosynthesis in T. wilfordii hairy roots and also provide new insights on metabolic engineering of triptolide in the future.

MaMAPK3-MaICE1-MaPOD P7 pathway, a positive regulator of cold tolerance in banana

BACKGROUND

Banana is a tropical fruit with a high economic impact worldwide. Cold stress greatly affects the development and production of banana.

RESULTS

In the present study, we investigated the functions of MaMAPK3 and MaICE1 involved in cold tolerance of banana. The effect of RNAi of MaMAPK3 on Dajiao (Musa spp. 'Dajiao'; ABB Group) cold tolerance was evaluated. The leaves of the MaMAPK3 RNAi transgenic plants showed wilting and severe necrotic symptoms, while the wide-type (WT) plants remained normal after cold exposure. RNAi of MaMAPK3 significantly changed the expressions of the cold-responsive genes, and the oxidoreductase activity was significantly changed in WT plants, while no changes in transgenic plants were observed. MaICE1 interacted with MaMAPK3, and the expression level of MaICE1 was significantly decreased in MaMAPK3 RNAi transgenic plants. Over-expression of MaICE1 in Cavendish banana (Musa spp. AAA group) indicated that the cold resistance of transgenic plants was superior to that of the WT plants. The POD P7 gene was significantly up-regulated in MaICE1-overexpressing transgenic plants compared with WT plants, and the POD P7 was proved to interact with MaICE1.

CONCLUSIONS

Taken together, our work provided new and solid evidence that MaMAPK3-MaICE1-MaPOD P7 pathway positively improved the cold tolerance in monocotyledon banana, shedding light on molecular breeding for the cold-tolerant banana or other agricultural species.

Comparative analysis using the draft genome sequence of California poppy (Eschscholzia californica) for exploring the candidate genes involved in benzylisoquinoline alkaloid biosynthesis

Genome characterization of California poppy (Eschscholzia californica cv. “Hitoezaki”), which produces pharmaceutically important benzylisoquinoline alkaloids (BIAs), was carried out using the draft genome sequence. The numbers of tRNA and rRNA genes were close to those of the other plant species tested, whereas the frequency of repetitive sequences was distinct from those species. Comparison of the predicted genes with those of Amborella trichopoda, Nelumbo nucifera, Solanum lycopersicum, and Arabidopsis thaliana, and analyses of gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway indicated that the enzyme genes involved in BIA biosynthesis were highly enriched in the California poppy genome. Further comparative analysis using the genome information of Papaver somniferum and Aquilegia coerulea, both BIA-producing plants, revealed that many genes encoding BIA biosynthetic enzymes, transcription factors, transporters, and candidate proteins, possibly related to BIA biosynthesis, were specifically distributed in these plant species.

High-Quality Genome of the Medicinal Plant Strobilanthes cusia Provides Insights Into the Biosynthesis of Indole Alkaloids

Strobilanthes cusia (Nees) Kuntze is an important plant used to process the traditional Chinese herbal medicines "Qingdai" and "Nanbanlangen". The key active ingredients are indole alkaloids (IAs) that exert antibacterial, antiviral, and antitumor pharmacological activities and serve as natural dyes. We assembled the S. cusia genome at the chromosome level through combined PacBio circular consensus sequencing (CCS) and Hi-C sequencing data. Hi-C data revealed a draft genome size of 913.74 Mb, with 904.18 Mb contigs anchored into 16 pseudo-chromosomes. Contig N50 and scaffold N50 were 35.59 and 68.44 Mb, respectively. Of the 32,974 predicted protein-coding genes, 96.52% were functionally annotated in public databases. We predicted 675.66 Mb repetitive sequences, 47.08% of sequences were long terminal repeat (LTR) retrotransposons. Moreover, 983 Strobilanthes-specific genes (SSGs) were identified for the first time, accounting for ~2.98% of all protein-coding genes. Further, 245 putative centromeric and 29 putative telomeric fragments were identified. The transcriptome analysis identified 2,975 differentially expressed genes (DEGs) enriched in phenylpropanoid, flavonoid, and triterpenoid biosynthesis. This systematic characterization of key enzyme-coding genes associated with the IA pathway and basic helix-loop-helix (bHLH) transcription factor family formed a network from the shikimate pathway to the indole alkaloid synthesis pathway in S. cusia. The high-quality S. cusia genome presented herein is an essential resource for the traditional Chinese medicine genomics studies and understanding the genetic underpinning of IA biosynthesis.

Comparative Transcriptome Analysis Reveals Candidate Genes Involved in Isoquinoline Alkaloid Biosynthesis in Stephania tetrandra

The roots of Stephania tetrandra are used as a traditional Chinese medicine. Isoquinoline alkaloids are considered to be the most important and effective components in this herb, but little is known about the molecular mechanism underlying their biosynthesis. In this context, this study aimed to reveal candidate genes related to isoquinoline alkaloid biosynthesis in S. tetrandra. Determination of tetrandrine and fangchinoline in the roots and leaves of S. tetrandra by HPLC showed that the roots had much higher contents of the two isoquinoline alkaloids than the leaves. Thus, a comparative transcriptome analysis of the two tissues was performed to uncover candidate genes involved in isoquinoline alkaloid biosynthesis. A total of 71 674 unigenes was obtained and 31 994 of these were assigned putative functions based on BLAST searches against 6 annotation databases. Among the 79 isoquinoline alkaloid-related unigenes, 51 were differentially expressed, with 42 and 9 genes upregulated and downregulated, respectively, when the roots were compared with the leaves. The upregulated differentially expressed genes were consistent with isoquinoline alkaloid accumulation in roots and thus were deemed key candidate genes for isoquinoline alkaloid biosynthesis in the roots. Moreover, the expression profiles of 10 isoquinoline alkaloid-related differentially expressed genes between roots and leaves were validated by quantitative real-time polymerase chain reaction, which indicated that our transcriptome and gene expression profiles were reliable. This study not only provides a valuable genomic resource for S. tetrandra but also proposes candidate genes involved in isoquinoline alkaloid biosynthesis and transcription factors related to the regulation of isoquinoline alkaloid biosynthesis. The results lay a foundation for further studies on isoquinoline alkaloid biosynthesis in this medicinal plant.

Genome-wide identification of AP2/ERF transcription factor-encoding genes in California poppy (Eschscholzia californica) and their expression profiles in response to methyl jasmonate

With respect to the biosynthesis of plant alkaloids, that of benzylisoquinoline alkaloids (BIAs) has been the most investigated at the molecular level. Previous investigations have shown that the biosynthesis of BIAs is comprehensively regulated by WRKY and bHLH transcription factors, while promoter analyses of biosynthesis enzyme-encoding genes have also implicated the involvement of members of the APETALA2/ethylene responsive factor (AP2/ERF) superfamily. To investigate the physiological roles of AP2/ERF transcription factors in BIA biosynthesis, 134 AP2/ERF genes were annotated using the draft genome sequence data of Eschscholzia californica (California poppy) together with transcriptomic data. Phylogenetic analysis revealed that these genes could be classified into 20 AP2, 5 RAV, 47 DREB, 60 ERF and 2 Soloist family members. Gene structure, conserved motif and orthologous analyses were also carried out. Gene expression profiling via RNA sequencing in response to methyl jasmonate (MeJA) indicated that approximately 20 EcAP2/ERF genes, including 10 group IX genes, were upregulated by MeJA, with an increase in the expression of the transcription factor-encoding gene EcbHLH1 and the biosynthesis enzyme-encoding genes Ec6OMT and EcCYP719A5. Further quantitative RT-PCR confirmed the MeJA responsiveness of the EcAP2/ERF genes, i.e., the increased expression of 9 group IX, 2 group X and 2 group III ERF subfamily genes. Transactivation activity of group IX EcAP2/ERFs was also confirmed by a luciferase reporter assay in conjunction with the promoters of the Ec6OMT and EcCYP719A5 genes. The physiological roles of AP2/ERF genes in BIA biosynthesis and their evolution in the regulation of alkaloid biosynthesis are discussed.

Mining lycodine-type alkaloid biosynthetic genes and genetic markers from transcriptome of Lycopodiastrum casuarinoides

Objective

Lycopodiastrum casuarinoides, a fern of the Lycopodiaceae family, is a traditional Chinese medicine, which has similar efficacy to that of Huperzia serrata in treating rheumatoid arthritis (RA). However, they are different in the contents and compositions of lycopodium alkaloids. In this study, the biosynthesis related genes of lycopodium alkaloids and genetic markers are discovered in L. casuarinoides transcriptome.

Methods

The plant of L. casuarinoides was collected and was subjected to the RNA isolation, cDNA library construction, high throughput RNA sequencing and bioinformatics analysis.

Results

Totally 124, 524 high-quality unigenes were assembled from RNA sequencing reads, with an average sequence length of 601 bp. Among the L. casuarinoides transcripts, 61,304 shared the significant similarity (E-value < 10⁻⁵) with existing protein sequences in the public databases. From 124,524 unigenes, 47,538 open reading frames (ORFs) were predicted. Based on the bioinformatics analysis, all possible enzyme genes involved in the lycodine-type alkaloids biosynthetic pathway of L. casuarinoides were identified, including lysine decarboxylase (LDC), primary amine oxidase (PAO), malonyl-CoA decarboxylase, etc. Sixty-four putative cytochrome p450 (CYP) and 827 putative transcription factors were selected from the transcriptome unigenes as the candidates of lycodine-type alkaloids biosynthesis modifiers. Furthermore, 13,352 simple sequence repeats (SSRs) were identified from 124,524 unigenes, of which dinucleotide motifs AG/CT were the most abundant (50.1%). Meanwhile, we confirmed the amplification effectiveness of 25 PCR primer pairs for randomly selected SSRs.

Conclusion

We obtained the comprehensive transcriptomic information from the high throughput RNA sequencing and bioinformatics analysis, which provided a valuable resource of transcript sequences of L. casuarinoides in public databases.

Full-length transcriptome analysis of Coptis deltoidea and identification of putative genes involved in benzylisoquinoline alkaloids biosynthesis based on combined sequencing platforms

The study carry out comprehensive transcriptome analysis of C. deltoidea and exploration of BIAs biosynthesis and accumulation based on UHPLC-MS/MS and combined sequencing platforms. Coptis deltoidea is an important medicinal plant with a long history of medicinal use, which is rich in benzylisoquinoline alkaloids (BIAs). In this study, Ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) and combined sequencing platforms were performed for exploration of BIAs biosynthesis, accumulation and comprehensive transcriptome analysis of C. deltoidea. By metabolism profiling, the accumulation of ten BIAs was analyzed using UHPLC-MS/MS and different contents were observed in different organs. From transcriptome sequencing result, we applied single-molecule real-time (SMRT) sequencing to C. deltoidea and generated a total of 75,438 full-length transcripts. We proposed the candidate biosynthetic pathway of tyrosine, precursor of BIAs, and identified 64 full length-transcripts encoding enzymes putatively involved in BIAs biosynthesis. RNA-Seq data indicated that the majority of genes exhibited relatively high expression level in roots. Transport of BIAs was also important for their accumulation. Here, 9 ABC transporters and 2 MATE transporters highly homologous to known alkaloid transporters related with BIAs transport in roots and rhizomes were identified. These findings based on the combined sequencing platforms provide valuable genetic information for C. deltoidea and the results of transcriptome combined with metabolome analysis can help us better understand BIAs biosynthesis and transport in this medicinal plant. The information will be critical for further characterization of C. deltoidea transcriptome and molecular-assisted breeding for this medicinal plant with scarce resources.

Zoysia japonica MYC type transcription factor ZjICE1 regulates cold tolerance in transgenic Arabidopsis

ICE1 (Inducer of CBF Expression 1) is a regulator of cold-induced transcriptome, which plays an important role in plant cold response pathway. To enhance the cold tolerance of Zoysia japonica, one of the warm-season turfgrasses, it is helpful to understand the cold response mechanism in Zoysia japonica. We identified stress-responsive ZjICE1 from Zoysia japonica and characterized its function in cold stress. Our results showed that ZjICE1 shared the typical feature of ICE homolog proteins belonging to a nucleic protein. Transactivation activity assay revealed that ZjICE1 bound to the MYC cis-element in the ZjDREB1's promotor. The ZjICE1 overexpressed transgenic Arabidopsis showed enhanced tolerance to cold stress with an increases in SOD, POD, and free proline content and reduction in MDA content. They also induced the transcripts abundance of cold-responsive genes (CBF1, CBF2, CBF3, COR47A, KIN1, and RD29A) after cold treatment. These results suggest that ZjICE1 is a positive regulator in Zoysia japonica plant during cold stress and can be a useful gene for the molecular breeding program to develop the cold tolerant zoysiagrass. Furthermore, the ZjICE1 also conferred resistance to salt and drought stresses, providing the better understanding of the basic helix-loop-helix (bHLH) gene family in abiotic stress responses.

The cold-induced transcription factor bHLH112 promotes artemisinin biosynthesis indirectly via ERF1 in Artemisia annua

Basic helix-loop-helix (bHLH) proteins are the second largest family of transcription factors (TFs) involved in developmental and physiological processes in plants. In this study, 205 putative bHLH TF genes were identified in the genome of Artemisia annua and expression of 122 of these was determined from transcriptomes used to construct the genetic map of A. annua. Analysis of gene expression association allowed division of the 122 bHLH TFs into five groups. Group V, containing 15 members, was tightly associated with artemisinin biosynthesis genes. Phylogenetic analysis indicated that two bHLH TFs, AabHLH106 and AabHLH112, were clustered with Arabidopsis ICE proteins. AabHLH112 was induced by low temperature, while AabHLH106 was not. We therefore chose AabHLH112 for further examination. AabHLH112 was highly expressed in glandular secretory trichomes, flower buds, and leaves. Dual-luciferase assays demonstrated that AabHLH112 enhanced the promoter activity of artemisinin biosynthesis genes and AaERF1, an AP2/ERF TF that directly and positively regulates artemisinin biosynthesis genes. Yeast one-hybrid assays indicated that AabHLH112 could bind to the AaERF1 promoter, but not to the promoters of artemisinin biosynthesis genes. Overexpression of AabHLH112 significantly up-regulated the expression levels of AaERF1 and artemisinin biosynthesis genes and consequently promoted artemisinin production.

Comparative analysis of the root and leaf transcriptomes in Chelidonium majus L

Chelidonium majus is a traditional medicinal plant, which commonly known as a rich resource for the major benzylisoquinoline alkaloids (BIAs), including morphine, sanguinarine, and berberine. To understand the biosynthesis of C. majus BIAs, we performed de novo transcriptome sequencing of its leaf and root tissues using Illumina technology. Following comprehensive evaluation of de novo transcriptome assemblies produced with five programs including Trinity, Bridger, BinPacker, IDBA-tran, and Velvet/Oases using a series of k-mer sizes (from 25 to 91), BinPacker was found to produce the best assembly using a k-mer of 25. This study reports the results of differential gene expression (DGE), functional annotation, gene ontology (GO) analysis, classification of transcription factor (TF)s, and SSR and miRNA discovery. Our DGE analysis identified 6,028 transcripts that were up-regulated in the leaf, and 4,722 transcripts that were up-regulated in the root. Further investigations showed that most of the genes involved in the BIA biosynthetic pathway are significantly expressed in the root compared to the leaf. GO analysis showed that the predominant GO domain is "cellular component", while TF analysis found bHLH to be the most highly represented TF family. Our study further identified 10 SSRs, out of a total of 39,841, that showed linkage to five unigenes encoding enzymes in the BIA pathway, and 10 conserved miRNAs that were previously not detected in this plant. The comprehensive transcriptome information presented herein provides a foundation for further explorations on study of the molecular mechanisms of BIA synthesis in C. majus.

Harpin-inducible defense signaling components impair infection by the ascomycete Macrophomina phaseolina

Soybean (Glycine max) infection by the charcoal rot (CR) ascomycete Macrophomina phaseolina is enhanced by the soybean cyst nematode (SCN) Heterodera glycines. We hypothesized that G. max genetic lines impairing infection by M. phaseolina would also limit H. glycines parasitism, leading to resistance. As a part of this M. phaseolina resistance process, the genetic line would express defense genes already proven to impair nematode parasitism. Using G. max[DT97-4290/PI 642055], exhibiting partial resistance to M. phaseolina, experiments show the genetic line also impairs H. glycines parasitism. Furthermore, comparative studies show G. max[DT97-4290/PI 642055] exhibits induced expression of the effector triggered immunity (ETI) gene NON-RACE SPECIFIC DISEASE RESISTANCE 1/HARPIN INDUCED1 (NDR1/HIN1) that functions in defense to H. glycines as compared to the H. glycines and M. phaseolina susceptible line G. max[Williams 82/PI 518671]. Other defense genes that are induced in G. max[DT97-4290/PI 642055] include the pathogen associated molecular pattern (PAMP) triggered immunity (PTI) genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), NONEXPRESSOR OF PR1 (NPR1) and TGA2. These observations link G. max defense processes that impede H. glycines parasitism to also potentially function toward impairing M. phaseolina pathogenicity. Testing this hypothesis, G. max[Williams 82/PI 518671] genetically engineered to experimentally induce GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 expression leads to impaired M. phaseolina pathogenicity. In contrast, G. max[DT97-4290/PI 642055] engineered to experimentally suppress the expression of GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 by RNA interference (RNAi) enhances M. phaseolina pathogenicity. The results show components of PTI and ETI impair both nematode and M. phaseolina pathogenicity.

SmJAZ8 acts as a core repressor regulating JA-induced biosynthesis of salvianolic acids and tanshinones in Salvia miltiorrhiza hairy roots

Jasmonates (JAs) are important plant hormones that regulate a variety of plant development and defense processes, including biosynthesis of secondary metabolites. The JASMONATE ZIM DOMAIN (JAZ) proteins act as negative regulators in the JA signaling pathways of plants. We first verified that methyl jasmonate (MeJA) enhanced the accumulation of both salvianolic acids and tanshinones in Salvia miltiorrhiza (Danshen) hairy roots by inducing the expression of their biosynthetic pathway genes. Nine JAZ genes were cloned from Danshen and their expression levels in hairy roots were all increased by treatment with MeJA. When analyzed in detail, however, SmJAZ8 showed the strongest expression in the induced hairy roots. Overexpression or RNAi of SmJAZ8 deregulated or up-regulated the yields of salvianolic acids and tanshinones in the MeJA-induced transgenic hairy roots, respectively, and transcription factors and biosynthetic pathway genes showed an expression pattern that mirrored the production of the compounds. Genetic transformation of SmJAZ8 altered the expression of other SmJAZ genes, suggesting evidence of crosstalk occurring in JAZ-regulated secondary metabolism. Furthermore, the transcriptome analysis revealed a primary-secondary metabolism balance regulated by SmJAZ8. Altogether, we propose a novel role for SmJAZ8 as a negative feedback loop controller in the JA-induced biosynthesis of salvianolic acids and tanshinones.

Metabolic Profiling of Dendrobium officinale in Response to Precursors and Methyl Jasmonate

Alkaloids are the main active ingredients in the medicinal plant Dendrobium officinale. Based on the published genomic and transcriptomic data, a proposed terpenoid indole alkaloid (TIA) biosynthesis pathway may be present in D. officinale. In this study, protocorm-like bodies (PLBs) with a high-yielding production of alkaloids were obtained by the optimization of tryptophan, secologanin and methyl jasmonate (MeJA) treatment. The results showed that the total alkaloid content was 2.05 times greater than that of the control group when the PLBs were fed with 9 µM tryptophan, 6 µM secologanin and 100 µM MeJA after 36 days. HPLC analysis showed that strictosidine synthase (STR) activity also increased in the treated plants. A total of 78 metabolites were identified using gas chromatography-mass spectrometry (GC-MS) in combination with liquid chromatography-mass spectrometry (LC-MS) methods; 29 differential metabolites were identified according to the multivariate statistical analysis. Among them, carapanaubine, a kind of TIA, exhibited dramatically increased levels. In addition, a possible underlying process of the metabolic flux from related metabolism to the TIA biosynthetic pathway was enhanced. These results provide a comprehensive view of the metabolic changes related to alkaloid biosynthesis, especially TIA biosynthesis, in response to tryptophan, secologanin and MeJA treatment.

Modulation of benzylisoquinoline alkaloid biosynthesis by heterologous expression of CjWRKY1 in Eschscholzia californica cells

Transcription factors control many processes in plants and have high potentials to manipulate specialized metabolic pathways. Transcriptional regulation of the biosynthesis of monoterpenoid indole alkaloids (MIAs), nicotine alkaloids, and benzylisoquinoline alkaloids (BIAs) has been characterized using Catharanthus roseus, Nicotiana and Coptis plants. However, metabolic engineering in which specific transcription factors are used in alkaloid biosynthesis is limited. In this study, we characterized the effects of ectopic expression of CjWRKY1, which is a transcriptional activator with many targets in BIA biosynthesis in Coptis japonica (Ranunculaceae) and Eschscholzia californica (California poppy, Papaveraceae). Heterologous expression of CjWRKY1 in cultured California poppy cells induced increases in transcripts of several genes encoding BIA biosynthetic enzymes. Metabolite analyses indicated that the overexpression of the CjWRKY1 gene also induced increases in the accumulation of BIAs such as sanguinarine, chelerythrine, chelirubine, protopine, allocryptopine, and 10-hydroxychelerythrine in the culture medium. Previous characterization of EcbHLH1 and current results indicated that both transcription factors, WRKY1 and bHLH1, are substantially involved in the regulation of BIA biosynthesis. We discuss the function of CjWRKY1 in E. californica cells and its potential for metabolic engineering in BIA biosynthesis.

Identification of candidate genes involved in isoquinoline alkaloids biosynthesis in Dactylicapnos scandens by transcriptome analysis

Dactylicapnos scandens (D. Don) Hutch (Papaveraceae) is a well-known traditional Chinese herb used for treatment of hypertension, inflammation, bleeding and pain for centuries. Although the major bioactive components in this herb are considered as isoquinoline alkaloids (IQAs), little is known about molecular basis of their biosynthesis. Here, we carried out transcriptomic analysis of roots, leaves and stems of D. scandens, and obtained a total of 96,741 unigenes. Based on gene expression and phylogenetic relationship, we proposed the biosynthetic pathways of isocorydine, corydine, glaucine and sinomenine, and identified 67 unigenes encoding enzymes potentially involved in biosynthesis of IQAs in D. scandens. High performance liquid chromatography analysis demonstrated that while isocorydine is the most abundant IQA in D. scandens, the last O-methylation biosynthesis step remains unclear. Further enzyme activity assay, for the first time, characterized a gene encoding O- methyltransferase (DsOMT), which catalyzes O-methylation at C7 of (S)-corytuberine to form isocorydine. We also identified candidate transcription factor genes belonging to WRKY and bHLH families that may be involved in the regulation of IQAs biosynthesis. Taken together, we first provided valuable genetic information for D. scandens, shedding light on candidate genes involved in IQA biosynthesis, which will be critical for further gene functional characterization.

A multidrug and toxic compound extrusion transporter mediates berberine accumulation into vacuoles in Coptis japonica

Plants produce a large variety of alkaloids, which have diverse chemical structures and biological activities. Many of these alkaloids accumulate in vacuoles. Although some membrane proteins on tonoplasts have been identified as alkaloid uptake transporters, few have been characterized to date, and relatively little is known about the mechanisms underlying alkaloid transport and accumulation in plant cells. Berberine is a model alkaloid. Although all genes involved in berberine biosynthesis, as well as the master regulator, have been identified, the gene responsible for the final accumulation of berberine at tonoplasts has not been determined. This study showed that a multidrug and toxic compound extrusion protein 1 (CjMATE1) may act as a berberine transporter in cultured Coptis japonica cells. CjMATE1 was found to localize at tonoplasts in C. japonica cells and, in intact plants, to be expressed preferentially in rhizomes, the site of abundant berberine accumulation. Cellular transport analysis using a yeast expression system showed that CjMATE1 could transport berberine. Expression analysis showed that RNAi suppression of CjbHLH1, a master transcription factor of the berberine biosynthetic pathway, markedly reduced the expression of CjMATE1 in a manner similar to the suppression of berberine biosynthetic genes. These results strongly suggest that CjMATE1 is the transporter that mediates berberine accumulation in vacuoles.

Digital Gene Expression Analysis Provides Insight into the Transcript Profile of the Genes Involved in Aporphine Alkaloid Biosynthesis in Lotus (Nelumbo nucifera)

The predominant alkaloids in lotus leaves are aporphine alkaloids. These are the most important active components and have many pharmacological properties, but little is known about their biosynthesis. We used digital gene expression (DGE) technology to identify differentially-expressed genes (DEGs) between two lotus cultivars with different alkaloid contents at four leaf development stages. We also predicted potential genes involved in aporphine alkaloid biosynthesis by weighted gene co-expression network analysis (WGCNA). Approximately 335 billion nucleotides were generated; and 94% of which were aligned against the reference genome. Of 22 thousand expressed genes, 19,000 were differentially expressed between the two cultivars at the four stages. Gene Ontology (GO) enrichment analysis revealed that catalytic activity and oxidoreductase activity were enriched significantly in most pairwise comparisons. In Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, dozens of DEGs were assigned to the categories of biosynthesis of secondary metabolites, isoquinoline alkaloid biosynthesis, and flavonoid biosynthesis. The genes encoding norcoclaurine synthase (NCS), norcoclaurine 6-O-methyltransferase (6OMT), coclaurine N-methyltransferase (CNMT), N-methylcoclaurine 3'-hydroxylase (NMCH), and 3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (4'OMT) in the common pathways of benzylisoquinoline alkaloid biosynthesis and the ones encoding corytuberine synthase (CTS) in aporphine alkaloid biosynthetic pathway, which have been characterized in other plants, were identified in lotus. These genes had positive effects on alkaloid content, albeit with phenotypic lag. The WGCNA of DEGs revealed that one network module was associated with the dynamic change of alkaloid content. Eleven genes encoding proteins with methyltransferase, oxidoreductase and CYP450 activities were identified. These were surmised to be genes involved in aporphine alkaloid biosynthesis. This transcriptomic database provides new directions for future studies on clarifying the aporphine alkaloid pathway.

Tyrosine phosphorylation and protein degradation control the transcriptional activity of WRKY involved in benzylisoquinoline alkaloid biosynthesis

Benzylisoquinoline alkaloids (BIQ) are among the most structurally diverse and pharmaceutically valuable secondary metabolites. A plant-specific WRKY-type transcription factor, CjWRKY1, was isolated from Coptis japonica and identified as a transcriptional activator of BIQ biosynthesis. However, the expression of CjWRKY1 gene alone was not sufficient for the activation of genes encoding biosynthetic enzymes. Here, we report the importance of post-translational regulation of CjWRKY1 in BIQ biosynthesis. First, we detected the differential accumulation of CjWRKY1 protein in two cell lines with similar CjWRKY1 gene expression but different levels of accumulated alkaloids. Further investigation of the WRKY protein identified the phosphorylation of the WRKYGQK core domain at Y115. The CjWRKY^Y115E phosphorylation-mimic mutant showed loss of nuclear localization, DNA-binding activity, and transactivation activity compared to wild-type CjWRKY1. Rapid degradation of the CjWRKY1 protein was also confirmed following treatment with inhibitors of the 26S proteasome and protease inhibitors. The existence of two independent degradation pathways as well as protein phosphorylation suggests the fine-tuning of CjWRKY1 activities is involved in the regulation of biosynthesis of BIQs.

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.

De Novo Transcriptome Assembly and Annotation of the Leaves and Callus of Cyclocarya Paliurus (Bata1) Iljinskaja

Cyclocarya Paliurus (Bata1) Iljinskaja contains various bioactive secondary metabolites especially in leaves, such as triterpenes, flavonoids, polysaccharides and alkaloids, and its leaves are widely used as an hyperglycemic tea in China. In the present paper, we sequenced the transcriptome of the leaves and callus of Cyclocarya Paliurus using Illumina Hiseq 4000 platform. After sequencing and de novo assembly, a total of 65,654 unigenes were generated with an N50 length of 1,244bp. Among them, 35,041 (53.37%) unigenes were annotated in NCBI Non-Redundant database, 19,453 (29.63%) unigenes were classified into Gene Ontology (GO) database, and 7,259 (11.06%) unigenes were assigned to Clusters of Orthologous Group (COG) categories. Furthermore, 11,697 (17.81%) unigenes were mapped onto 335 pathways in Kyoto Encyclopedia of Genes and Genomes (KEGG), among which 1,312 unigenes were identified to be involved in biosynthesis of secondary metabolites. In addition, a total of 11,247 putative simple sequence repeats (SSRs) were detected. This transcriptome dataset provides a comprehensive sequence resource for gene expression profiling, genetic diversity, evolution and further molecular genetics research on Cyclocarya Paliurus.

Jasmonates: signal transduction components and their roles in environmental stress responses

Jasmonates, oxylipin-type plant hormones, are implicated in diverse aspects of plant growth development and interaction with the environment. Following diverse developmental and environmental cues, jasmonate is produced, conjugated to the amino acid isoleucine and perceived by a co-receptor complex composed of the Jasmonate ZIM-domain (JAZ) repressor proteins and an E3 ubiquitin ligase complex containing the F-box CORONATINE INSENSITIVE 1 (COI1). This event triggers the degradation of the JAZ proteins and the release of numerous transcription factors, including MYC2 and its homologues, which are otherwise bound and inhibited by the JAZ repressors. Here, we will review the role of the COI1, JAZ and MYC2 proteins in the interaction of the plant with its environment, illustrating the significance of jasmonate signalling, and of the proteins involved, for responses to both biotic stresses caused by insects and numerous microbial pathogens and abiotic stresses caused by adverse climatic conditions. It has also become evident that crosstalk with other hormone signals, as well as light and clock signals, plays an important role in the control and fine-tuning of these stress responses. Finally, we will discuss how several pathogens exploit the jasmonate perception and early signalling machinery to decoy the plants defence systems.

Comparative analysis of transcription factor gene families from Papaver somniferum: identification of regulatory factors involved in benzylisoquinoline alkaloid biosynthesis

Opium poppy (Papaver somniferum L.), known for biosynthesis of several therapeutically important benzylisoquinoline alkaloids (BIAs), has emerged as the premier organism to study plant alkaloid metabolism. The most prominent molecules produced in opium poppy include narcotic analgesic morphine, the cough suppressant codeine, the muscle relaxant papaverine and the anti-microbial agent sanguinarine and berberine. Despite several health benefits, biosynthesis of some of these molecules is very low due to tight temporal and spatial regulation of the genes committed to their biosynthesis. Transcription factors, one of the prime regulators of secondary plant product biosynthesis, might be involved in controlled biosynthesis of BIAs in P. somniferum. In this study, identification of members of different transcription factor gene families using transcriptome datasets of 10 cultivars of P. somniferum with distinct chemoprofile has been carried out. Analysis suggests that most represented transcription factor gene family in all the poppy cultivars is WRKY. Comparative transcriptome analysis revealed differential expression pattern of the members of a set of transcription factor gene families among 10 cultivars. Through analysis, two members of WRKY and one member of C3H gene family were identified as potential candidates which might regulate thebaine and papaverine biosynthesis, respectively, in poppy.

GAME9 regulates the biosynthesis of steroidal alkaloids and upstream isoprenoids in the plant mevalonate pathway

Steroidal glycoalkaloids (SGAs) are cholesterol-derived molecules produced by solanaceous species. They contribute to pathogen defence but are toxic to humans and considered as anti-nutritional compounds. Here we show that GLYCOALKALOID METABOLISM 9 (GAME9), an APETALA2/Ethylene Response Factor, related to regulators of alkaloid production in tobacco and Catharanthus roseus, controls SGA biosynthesis. GAME9 knockdown and overexpression in tomato and potato alters expression of SGAs and upstream mevalonate pathway genes including the cholesterol biosynthesis gene STEROL SIDE CHAIN REDUCTASE 2 (SSR2). Levels of SGAs, C24-alkylsterols and the upstream mevalonate and cholesterol pathways intermediates are modified in these plants. Δ(7)-STEROL-C5(6)-DESATURASE (C5-SD) in the hitherto unresolved cholesterol pathway is a direct target of GAME9. Transactivation and promoter-binding assays show that GAME9 exerts its activity either directly or cooperatively with the SlMYC2 transcription factor as in the case of the C5-SD gene promoter. Our findings provide insight into the regulation of SGA biosynthesis and means for manipulating these metabolites in crops.

Jasmonate-responsive transcription factors regulating plant secondary metabolism

Plants produce a large variety of secondary metabolites including alkaloids, glucosinolates, terpenoids and phenylpropanoids. These compounds play key roles in plant-environment interactions and many of them have pharmacological activity in humans. Jasmonates (JAs) are plant hormones which induce biosynthesis of many secondary metabolites. JAs-responsive transcription factors (TFs) that regulate the JAs-induced accumulation of secondary metabolites belong to different families including AP2/ERF, bHLH, MYB and WRKY. Here, we give an overview of the types and functions of TFs that have been identified in JAs-induced secondary metabolite biosynthesis, and highlight their similarities and differences in regulating various biosynthetic pathways. We review major recent developments regarding JAs-responsive TFs mediating secondary metabolite biosynthesis, and provide suggestions for further studies.

Characterization of the Promoter Region of Biosynthetic Enzyme Genes Involved in Berberine Biosynthesis in Coptis japonica

The presence of alkaloids is rather specific to certain plant species. However, berberine, an isoquinoline alkaloid, is relatively broadly distributed in the plant kingdom. Thus, berberine biosynthesis has been intensively investigated, especially using Coptis japonica cell cultures. Almost all biosynthetic enzyme genes have already been characterized at the molecular level. Particularly, two transcription factors (TFs), a plant-specific WRKY-type TF, CjWRKY1, and a basic helix-loop-helix TF, CjbHLH1, were shown to comprehensively regulate berberine biosynthesis in C. japonica cells. In this study, we characterized the promoter region of some biosynthetic enzyme genes and associated cis-acting elements involved in the transcriptional regulation via two TFs. The promoter regions of three berberine biosynthetic enzyme genes (CYP80B2, 4'OMT and CYP719A1) were isolated, and their promoter activities were dissected by a transient assay involving the sequentially truncated promoter::luciferase (LUC) reporter constructs. Furthermore, transactivation activities of CjWRKY1 were determined using the truncated promoter::LUC reporter constructs or constructs with mutated cis-elements. These results suggest the involvement of a putative W-box in the regulation of biosynthetic enzyme genes. Direct binding of CjWRKY1 to the W-box DNA sequence was also confirmed by an electrophoresis mobility shift assay and by a chromatin immunoprecipitation assay. In addition, CjbHLH1 also activated transcription from truncated 4'OMT and CYP719A1 promoters independently of CjWRKY1, suggesting the involvement of a putative E-box. Unexpected transcriptional activation of biosynthetic enzyme genes via a non-W-box sequence and by CjWRKY1 as well as the possible involvement of a GCC-box in berberine biosynthesis in C. japonica are discussed.

ICE1 of Pyrus ussuriensis functions in cold tolerance by enhancing PuDREBa transcriptional levels through interacting with PuHHP1

ICE1 transcription factor plays an important role in plant cold stress via regulating the expression of stress-responsive genes. In this study, a PuICE1 gene isolated from Pyrus ussuriensis was characterized for its function in cold tolerance. The expression levels of the PuICE1 were induced by cold, dehydration and salt, with the greatest induction under cold conditions. PuICE1 was localized in the nucleus and could bind specifically to the MYC element in the PuDREBa promoter. The PuICE1 fused to the GAL4 DNA-binding domain to have transcriptional activation activity. Ectopic expression of the PuICE1 in tomato conferred enhanced tolerance to cold stress at cold temperatures, less electrolyte leakage, less MDA content, higher chlorophyll content, higher survival rate, higher proline content, higher activities of enzymes. In additon, steady-state mRNA levels of six stress-responsive genes coding for either functional or regulatory genes were induced to higher levels in the transgenic lines by cold stress. Yeast two-hybrid, transient assay, split luciferase complementation and BiFC assays all revealed that PuHHP1 protein can physically interact with PuICE1. Taken together, these results demonstrated that PuICE1 plays a positive role in cold tolerance, which may be due to enhancement of PuDREBa transcriptional levels through interacting with the PuHHP1.