Effective prediction of biosynthetic pathway genes involved in bioactive polyphyllins in Paris polyphylla

The biosynthesis of trillin 6'-O-glucoside: A low-abundance yet pharmacologically active polyphyllin from Paris polyphylla

Natural products from medicinal plants serve as an invaluable resource for drug discovery and development. However, low-abundance natural products are often understudied due to the challenges of obtaining sufficient quantities for pharmacological testing in cells or animals. Additionally, their complex stereochemistry and functional groups make chemical synthesis and purification difficult. In this study, we showcased the power of biosynthetic approaches to explore these underexplored compounds, using the low-abundance polyphyllin trillin 6'-O-glucoside from Paris polyphylla as an example. We identified two trillin 6'-O-glucosyltransferases required for its biosynthesis and successfully reconstructed the entire pathway in Nicotiana benthamiana. We demonstrated that trillin 6'-O-glucoside exhibits anti-bacterial activity comparable to major polyphyllins like polyphyllins I, II, and VII. Notably, it also showed much lower hemolytic activity, a common side effect of those major polyphyllins. Together, our study underscores the advantages of employing biosynthetic approaches to explore natural products that exist in low or trace abundances yet possess equally important pharmacological activities.

Two rhamnosyltransferases for de novo biosynthesis of polyphyllins in Nicotiana benthamiana

Polyphyllins, a prominent class of steroidal saponins in Paris species, owe their diverse bioactivities to their sugar unit configurations, though their glycosylation pathways remain poorly understood. Here, we identified and characterized two UDP-rhamnosyltransferases, PpUGT73YD1 and PpUGT738A2, using heterologous expression systems. These enzymes sequentially catalyze the conversion of polyphyllin V and VI into trisaccharide and tetrasaccharide derivatives, respectively. While PpUGT73YD1 accommodates both spiro and furo saponins, PpUGT738A2 specifically recognizes spiro saponins. Both enzymes exhibit strict specificity for UDP-l-Rha as a sugar donor. Structural modeling and site-directed mutagenesis of PpUGT73YD1 revealed that mutations at T149M and L283A shifted sugar donor preference toward UDP-d-Glc and UDP-d-Xyl. Furthermore, co-expression of PpUGT genes with upstream biosynthetic genes in Nicotiana benthamiana enabled de novo synthesis of polyphyllins III and II, achieving yields of 93.64 and 68.39 μg g-1 dry weight in leaves, respectively. This study elucidates the roles of two key rhamnosyltransferases in polyphyllin biosynthesis and demonstrates their involvement in steroidal saponin production through an engineered plant chassis.

Comparative transcriptome analysis reveals key genes responsible for the differences in polyphyllin composition in two Paris polyphylla species

Paris polyphylla biosynthesizes significant quantities of polyphyllins, which exhibit numerous pharmacological activities and have become vital components in many patented drugs. However, only two species in this genus are officially recognized as medicinal sources due to their high levels of bioactive compounds. In this study, we measured and compared the total saponin content in Paris forrestii and Paris polyphylla var. yunnanensis The content in Paris forrestii was nearly double that in Paris polyphylla var. yunnanensis, and polyphyllin V and gracillin, hardly detectable in Paris polyphylla var. yunnanensis, were the primary saponins in Paris forrestii. To elucidate the genetic mechanisms underlying the differences in saponin content between the two species, transcriptome sequencing was conducted, and the correlation between saponin content and the expression of genes involved in polyphyllin biosynthesis was analyzed. Differential expression of functional genes associated with terpenoid backbone biosynthesis and steroid biosynthesis was identified as a potential cause of the variation in polyphyllin V and gracillin levels. Screening the transcriptomics data led to the identification of two rhamnolipid glycosyltransferases, PpUGT91T1 and PpUGT91T2, whose expression levels were found to be highly correlated with polyphyllin II content. Subsequent functional validation demonstrated that PpUGTs catalyze the conversion of polyphyllin V to polyphyllin III, acting as polyphyllin V C'-4-O-rhamnosyltransferases. Additionally, polyphyllin II was derived from the extension of the polyphyllin III sugar chain with rhamnose. Key amino acid residues involved in sugar donor and acceptor recognition were predicted using molecular docking, providing a theoretical framework for the biosynthesis of polyphyllins.

Steroidal compounds in Paris polyphylla:structure, biological activities, and biosynthesis

Steroidal compounds are chemical constituents found in the traditional medicinal plant Paris polyphylla, known for their significant pharmacological activities. Due to their complex structures, the biosynthetic pathways of these compounds have garnered considerable attention. In recent years, substantial progress has been made in elucidating the biosynthetic pathways of steroidal compounds from P. polyphylla, with several complete biosynthetic routes being fully characterized. The de novo synthesis of diosgenin has been successfully achieved in both Saccharomyces cerevisiae and Nicotiana benthamiana using various metabolic engineering techniques. Herein, we summarize the latest research progress regarding the structural classification, biological activities, and biosynthesis studies of steroidal compounds from P. polyphylla.

Genomics of sterols biosynthesis in plants: Current status and future prospects

Sterols produced by bacteria and all eukaryotic organisms are essential for membrane functionality and stability. They play a vital role in growth, development and in abiotic stress tolerance. They are involved in diverse responses to biotic and abiotic stresses that lead to providing resistance against multiple diseases. Additionally, sterols serve as defensive compounds against herbivorous insects and animals. Phytosterols derived from plants, improve human nutrition and health and cure different ailments. The biosynthetic pathways for sterols and triterpenes exhibit similarities until the synthesis of 2,3-oxidosqualene. The complexity of sterol pathways increases during the advanced stages of polycyclic structure synthesis, and remain poorly comprehended in plants. This review explores the various omics techniques used to unveil the functions of genes associated with the phytosterol pathways. The study investigates the biosynthetic gene clusters to clarify the structural arrangements of genes linked to metabolic pathways. Both the upstream and downstream genes associated with these pathways, as well as their evolutionary connections and interrelations within the pathways were brought to the forefront. Moreover, developing strategies to unravel the biosynthesis completely and their multi-layered regulation are crucial to comprehend the global roles that sterols play in plant growth, development, stress tolerance and in imparting defence against pathogens.

UDP-glucosyltransferases from UGT73 family catalyze 3-O-glucosylation of isosteroidal and steroidal alkaloids in Fritillaria unibracteata var. wabuensis

Fritillaria unibracteata var. wabuensis is an important resource plant for the famous traditional Chinese medicine Fritillariae cirrhosae bulbus ("Chuanbeimu" in Chinese). F. cirrhosae bulbus is the dried bulbs of several species from Fritillaria genus, with isosteroidal alkaloids components assumed as the bioactive ingredients. However, the biosynthesis pathway of isosteroidal alkaloids remains elusive. Here, we adopted F. unibracteata var. wabuensis as a material to identify genes involved in the biosynthesis of isosteroidal alkaloids. We first constructed the multi-tissue metabolome and transcriptome dataset of F. unibracteata var. wabuensis. Interestingly, imperialine-3-β-d-glucoside, an isosteroidal glycoalkaloid, was found to be the major tissue-specific accumulated alkaloid. Through phylogenetic and co-expression analysis, we identified two UDP-glucosyltransferases from UGT73 family catalyzing 3-O-glucosylation of isosteroidal and steroidal alkaloids: imperialine 3-O-glucosyltransferase (FuwI3GT) can use both isosteroidal alkaloid imperialine and steroidal alkaloid solanidine as substrates, while solanidine 3-O-glucosyltransferase (FuwS3GT) can only use steroidal alkaloid solanidine as a substrate. We further approved that the W201 residue of FuwI3GT determined its substrate preference of isosteroidal alkaloids. Overall, our results identified enzymes involved in 3-O-glucosylation of isosteroidal and steroidal alkaloids in F. unibracteata var. wabuensis and paved the way to fully elucidate the isosteroidal alkaloid biosynthesis pathway in Fritillaria species.

The genus Paris: a fascinating resource for medicinal and botanical studies

The genus Paris, comprising a series of distinctive medicinal plants, has been utilized globally for its therapeutic properties over centuries. Modern pharmacological studies have demonstrated that secondary metabolites from Paris species exhibit significant pharmacological activities, including anticancer, hemostatic, anti-inflammatory, antimicrobial, and other effects. Additionally, the unique morphological traits and large genome size of Paris species have continuously captured the interest of botanists and horticulturalists. Nonetheless, the conservation of wild Paris populations is threatened due to the lengthy reproductive cycle and overexploitation, posing considerable challenges to their development and sustainable use. This review provides a comprehensive overview of the botanical characteristics, historical medicinal uses, pharmacological effects, and toxicity evaluation of secondary metabolites in Paris species. It also covers the molecular biological research conducted on the genus Paris and proposes key research questions and important directions for future solutions. We advocate the expansion and implementation of multi-omics approaches, as well as molecular and genetic technologies recently advanced in model plant research, to intensively study Paris species. This will facilitate the comprehensive understanding of gene function and molecular mechanisms underlying specialized metabolite formation in Paris.

Identification and characterization of PpUGT91BP1 as a trillin synthase from Paris polyphylla

Polyphyllins are the active ingredients of the medicinal plant Paris polyphylla. The biosynthesis of different types of polyphyllins all requires the catalysis of glycosyltransferases. Even though significant efforts have been made to identify PpUGTs capable of catalyzing the initial glycosylation reaction, the specific glycosyltransferases responsible for the synthesis of trillin have not been reported in P. polyphylla. Here, we identified a new trillin synthase, named PpUGT91BP1, which was highly expressed in the rhizome. Importantly, PpUGT91BP1 could specifically glycosylate diosgenin but not pennogenin. To improve its catalytic efficiency, we introduced random mutations through error-prone PCR and conducted an activity-based screening. Three mutants with significantly enhanced trillin synthase activity were identified. Finally, we successfully reconstituted trillin biosynthesis in Nicotiana benthamiana, achieving a yield of 3.69 mg/g of plant dry weight using the mutant PpUGT91BP1. Taken together, our results deepen the understanding of the PpUGT91 family's role in polyphyllin biosynthesis in P. polyphylla, facilitating rational selection of better P. polyphylla cultivars and guiding future studies in the metabolic engineering of polyphllins.

Dissection of transcriptome and metabolome insights into the polyphyllin biosynthesis in Paris

BACKGROUND

Polyphyllins are significant medicinal compounds found in Paris species, with different polyphyllins fulfilling distinct medicinal roles. Although some genes involved in polyphyllin synthesis have been identified, further exploration of the genes in the polyphyllin synthesis pathway is necessary due to the extensive genome of Paris species. The content and composition of polyphyllins vary among different Paris species, and the variations in specific polyphyllin levels across these plants make them promising candidates for identifying metabolites and genes associated with the biosynthesis of specific polyphyllins.

RESULTS

In this study, we investigate the global metabolic and transcriptomic profiles of three types of Paris polyphylla var. yunnanensis (Franch.) Hand.-Mazz, one Paris fargesii Franch, and one Paris forrestii (Takht.) H. Li. The rhizome of P. polyphylla is rich in polyphyllin I and II, while P. forrestii is abundant in polyphyllin III, and P. fargesii contains high levels of polyphyllin VI, VII and H. The three Paris species exhibit distinct metabolomic and transcriptomic profiles. Through an integrated analysis of metabolic and transcriptomic data, along with a phylogenetic analysis of genes related to polyphyllin synthesis in Paris, we annotated a total of six 2,3-oxidosqualene cyclases (OSCs), 120 cytochrome P450s (CYPs), and 138 UDP glycosyltransferases (UGTs). Phylogenetic tree analysis of the obtained data assisted in refining the candidate gene pool for OSC, CYP, and UGT. Subsequently, we identified 6, 12, and 26 candidate genes for OSC, CYP, and UGT, respectively. Finally, by combining the analyses of metabolic and genetic differences, we identified a total of 17 candidate genes, including 2 CAS, 4 CYP, and 11 UGT.

CONCLUSIONS

P. fargesii and P. forrestii are candidate medicinal plants for the development and application of specific polyphyllins. Transcripts from the UGT91 subfamily in Paris may play dual roles, contributing to both the synthesis of polyphyllin II and the catabolism of polyphyllin V and VI. The homologous genes of PpUGT73CE1 may regulate the synthesis of polyphyllin VI in P. fargesii. This study provides new insights into the investigation of biosynthetic pathways in medicinal plants that lack gene clusters.

Haplotype-resolved genome and population genomics provide insights into dioscin biosynthesis and evolutionary history of the medicinal species Dioscorea nipponica

Dioscorea nipponica, a perennial herb widely distributed in the Sino-Japanese Floristic Region, is renowned for its medicinal properties, particularly its ability to produce dioscin. Here, we present a haplotype-resolved genome assembly of the diploid D. nipponica, comprising 511.41 Mb for Haplotype A and 498.29 Mb for Haplotype B, each organized into 10 chromosomes. The two haplotypes exhibited high similarity, with only 2.75% of the allelic genes exhibiting specific expression. Key genes in the dioscin biosynthesis pathway were identified, and expression analysis revealed that the majority (16/21) of genes involved in the first two stages were highly expressed in rhizomes. Notably, significant expansion of the CYP90, CYP94, and UGT73 gene families was observed in dioscin-producing species, highlighting their critical roles in dioscin biosynthesis. Additionally, genome size estimation and population genomic analyses of diverse D. nipponica accessions identified four principal clades in D. nipponica, corresponding to diploid, di-tetra-octoploid, tetraploid, and hexaploid accessions from various geographic regions, with clade A (diploids) further divided into five subclades. Demographic analysis of the diploid D. nipponica revealed a prolonged decline in effective population size from the Pleistocene to the Last Glacial Maximum, with population splits occurring during the mid-to-late Pleistocene. Selective sweep analysis identified key genes, including HD-Zip I, ADH1, SMT1, and CYPs that may contribute to adaptation to high-latitude environments and the geographical variations in dioscin content. Overall, this study enhances our understanding of the genomic architecture, biosynthetic pathways, and evolutionary dynamics of D. nipponica, providing valuable insights into its medicinal potential and evolution.

Metabolomics and transcriptomics profiling of three Paris species with varied polyphyllin compositions

Most of the species in Paris have important medicinal values in China. Polyphyllins are the key components in Paris, with varying levels and compositions among different species. This study investigated polyphyllin compositions of 206 Paris samples from 16 different producing areas. 9 Paris polyphylla var. yunnanensis, 3 Paris fargesii, and 3 Paris forrestii were selected based on polyphyllin levels and composition for metabolome and transcriptome analysis. A total of 1,243 metabolites were identified among these samples, along with 92.11 Gb of full-length transcriptome data. This study provides potential candidate genes involved in polyphyllins synthesis in Paris, aiming to facilitate the biosynthesis of different polyphyllins.

Integration of induction, system optimization and genetic transformation in Veratrum californicum var. vitro cultures to enhance the production of cyclopamine and veratramine

Cyclopamine, a compound found in wild Veratrum has shown promising potential as a lead anti-cancer drug by effectively blocking cancer signaling pathways. However, its complex chemical structure poses challenges for artificial synthesis, thus limiting its supply and downstream drug production. This study comprehensively utilizes induction, system optimization, and transgenic technologies to establish an efficient suspension culture system for the high-yield production of cyclopamine and its precursor, veratramine. Experimental results demonstrate that methyl jasmonate (MeJA) effectively promotes the content of veratramine and cyclopamine in Veratrum californicum var. callus tissue, while yeast extract (YE) addition significantly increases cell biomass. The total content of veratramine and cyclopamine reached 0.0638 mg after synergistic treatment of suspension system with these two elicitors. And the content of the two substances was further increased to 0.0827 mg after the optimization by response surface methodology. Subsequently, a genetic transformation system for V. californicum callus was established and a crucial enzyme gene VnOSC1, involved in the steroidal alkaloid biosynthesis pathway, was screened and identified for genetic transformation. Combined suspension culture and synergistic induction system, the total content of the two substances in transgenic suspension system was further increased to 0.1228 mg, representing a 276.69% improvement compared to the initial culture system. This study proposes a complete and effective genetic transformation and cultivation scheme for V. californicum tissue cells, achieving milligram-level production of the anticancer agent cyclopamine and its direct precursor veratramine for the first time. It provides a theoretical basis for the industrial-scale production of these substances.

Genomic insights into Aspergillus tamarii TPD11: enhancing polyphyllin production and uncovering potential therapeutic applications

BACKGROUND

The excavation and utilization of endophytic fungi from medicinal plants is highly important for the development of new drugs. The endophytic fungus Aspergillus tamarii TPD11, which was isolated and obtained by the authors in the previous stage, can produce a variety of polyphyllins with important potential applications in hemostasis, inflammation and antitumor activities; however, the genomic information of TPD11 is still unknown.

RESULTS

In this study, we sequenced and assembled the whole genome of the endophytic fungus A. tamarii TPD11, resolved the genome evolutionary relationships of 24 Aspergillus strains, and phylogenetic analysis of the genomes of 16 strains revealed the evolutionary differences between Aspergillus and Penicillium and the mechanisms of genome expansion and contraction. CAZy annotation analysis revealed that TPD11 obtains nutrients mainly by ingesting starch from the host plant. TPD11 has a biosynthesis-related gene cluster for the synthesis of squalestatin S1, and the silencing of this biosynthesis-related gene cluster might increase the content of polyphyllin. Annotation of 11 UDP-glycosyltransferase genes helps to further reveal the biosynthetic pathway of polyphyllin. In addition, secondary metabolism gene cluster and CAZy analyses confirmed the potential probiotic, insecticidal and antimicrobial activities of TPD11 on host plants.

CONCLUSIONS

This study reveals the intrinsic mechanism by which endophytic fungi increase the content of polyphyllin, which provides a basis for the synthetic synthesis of the natural product polyphyllin.

Development of a RNA-protein complex based smart drug delivery system for 9-hydroxycamptothecin

Camptothecin (CPT) is a monoterpenoid indole alkaloid with a wide spectrum of anticancer activity. However, its application is hindered by poor solubility, lack of targeting specificity, and severe side effects. Structural derivatization of CPT and the development of suitable drug delivery systems are potential strategies for addressing these issues. In this study, we discovered that the protein Cytochrome P450 Family 1 Subfamily A Member 1 (CYP1A1) from Homo sapiens catalyzes CPT to yield 9-hydroxycamptothecin (9-HCPT), which exhibits increased water solubility and cytotoxicity. We then created a RNA-protein complex based drug delivery system with enzyme and pH responsiveness and improved the targeting and stability of the nanomedicine through protein module assembly. The subcellular localization of nanoparticles can be visualized using fluorescent RNA probes. Our results not only identified the protein CYP1A1 responsible for the structural derivatization of CPT to synthesize 9-HCPT but also offered potential strategies for enhancing the utilization of silk-based drug delivery systems in tumor therapy.

Trans2express - de novo transcriptome assembly pipeline optimized for gene expression analysis

BACKGROUND

As genomes of many eukaryotic species, especially plants, are large and complex, their de novo sequencing and assembly is still a difficult task despite progress in sequencing technologies. An alternative to genome assembly is the assembly of transcriptome, the set of RNA products of the expressed genes. While a bunch of de novo transcriptome assemblers exists, the challenges of transcriptomes (the existence of isoforms, the uneven expression levels across genes) complicates the generation of high-quality assemblies suitable for downstream analyses.

RESULTS

We developed Trans2express - a web-based tool and a pipeline of de novo hybrid transcriptome assembly and postprocessing based on rnaSPAdes with a set of subsequent filtrations. The pipeline was tested on Arabidopsis thaliana cDNA sequencing data obtained using Illumina and Oxford Nanopore Technologies platforms and three non-model plant species. The comparison of structural characteristics of the transcriptome assembly with reference Arabidopsis genome revealed the high quality of assembled transcriptome with 86.1% of Arabidopsis expressed genes assembled as a single contig. We tested the applicability of the transcriptome assembly for gene expression analysis. For both Arabidopsis and non-model species the results showed high congruence of gene expression levels and sets of differentially expressed genes between analyses based on genome and based on the transcriptome assembly.

CONCLUSIONS

We present Trans2express - a protocol for de novo hybrid transcriptome assembly aimed at recovering of a single transcript per gene. We expect this protocol to promote the characterization of transcriptomes and gene expression analysis in non-model plants and web-based tool to be of use to a wide range of plant biologists.

Study on Synthesis and Regulation of PPVI and PPVII in Paris polyphylla with UV

Paris polyphylla Smith var. Chinensis (Franch.) Hara is a medicinal plant that belongs to the Liliaceae family. Its main components are parissaponins, which have excellent medicinal effects such as anti-inflammatory, anti-tumor, etc. Improving the quality of parissaponins through artificial directional regulation has emerged as a practice to meet medical demand and is a new research hotspot. In this paper, P. polyphylla plants were treated with UVA, UVB, and UVC, and the contents of PolyPhyllin VI (PPVI) and PolyPhyllin VII (PPVII), saponin synthase (squalene synthase, SS; cycloartenol synthase, CAS; cytochrome P450, CYP450; and glycosyl transferases, GT) activity, MDA, and the photosynthetic pigment indexes were measured and analyzed. The results showed that PPVII content increased by 32.43% with UVC treatment after 4 h (3.43 mg/g), but the PPVI and PPVII contents in the other groups decreased compared with CK (control group) and they did not return to the original level after 4 h. SS, CAS, CYP450, and GT synthases were activated in varying degrees via UV treatment and increased, respectively, by 22.93%, 10.83%, 20.15%, and 25.98%. Among them, GT, as the last of the synthetases, had a shorter response time to UVB (30 min) and UVC (15 min); the difference was sensible compared with CK. Moreover, UV had a stressing effect and promoted the rapid accumulation of MDA content (increased 17.66%, 34.53%, and 9.65%) and carotenoid (increased 7.58, 5.60, and 7.76 times) within 4 h compared to CK. UVB and UVC radiation visibly improved chlorophyll a content (42.56% and 35.45%), but UVA did not, and the change in chlorophyll b content showed no overt statistical difference. In addition, PPVI and PPVII were negatively correlated with SS, CAS, carotenoids, and MDA (p < 0.05) and positively correlated with CYP450, GT, and chlorophyll a (p < 0.05). This study provides a theoretical basis for using UV light to regulate secondary metabolism in P. polyphylla, which is of great value for production management.

Steroidal saponins from rhizome of Paris polyphylla var. chinensis and their anti-inflammatory, cytotoxic effects

Five undescribed compounds, including two cholestane glycosides parispolyosides A and E, and three spirostanol glycosides parispolyosides B-D, were isolated from rhizome of Paris polyphylla var. chinensis (Franch.) Hara, together with twenty-one known steroidal saponins. Their chemical structures were elucidated on the basis of comprehensive analysis of 1D and 2D NMR, as well as HR-ESI-MS spectroscopic data. Two of these compounds demonstrated potent inhibitory effect on NO production stimulated by lipopolysaccharide in raw 264.7 cells with IC50 values of 61.35 μM and 37.23 μM. Four compounds exhibited moderate inhibitory activity against HepG2 cells with IC50 values ranging from 9.43 to 24.54 μM. Molecular docking analysis revealed that the potential mechanism of NO inhibition by the active compounds was associated with the interactions with iNOS protein.

Genome-Wide Comparative Profiles of Triterpenoid Biosynthesis Genes in Ginseng and Pseudo Ginseng Medicinal Plants

Saponin-rich medicinal plants, particularly ginseng and Pseudo ginseng, are valuable in traditional medical practice due to the presence of different saponins. These plants benefit from natural saponins/triterpenoids drugs, such as Ginsenosides, Gypenosides, Platycodins, and Lancemasides. Ginsenosides are highly required for research and functional materials preparation in industrial practices, and some compounds, like Compound-K, have been taken to human trials for various therapeutic applications. To elucidate the genes/transcripts profiles responsible for secondary metabolites and ginsenoside biosynthesis in Ginseng and Pseudo ginseng plant genomes, a comparative analysis was conducted in this study. Nine plant genomes with a 99% BUSCO completeness score were used, resulting in 49 KEGG secondary metabolite pathways, 571 cytochromes genes with 42 families, and 3529 carbohydrate genes with 103 superfamilies. The comparative analysis revealed 24 genes/transcripts belonging to the CYP716 family, which is involved in the ginsenoside biosynthesis pathway. Additionally, it found that various ginsenosides demonstrated strong binding affinity with twelve targets, with ginsenoside Rg3, Rg2, Rh1, Rh5, F3, Rh9, Panaxadione, Protopanaxatriol, Floral ginsenoside C, and Floral ginsenoside E exhibiting the highest binding affinities with the tested enzymes. Since these groups of enzymes are not yet fully characterized for Pseudo ginseng plants in the interconversion of triterpenoids, this comparative bioinformatics analysis could aid experimentalists in selecting and conducting characterization with practical knowledge.

The synthesis of Paris saponin VII mainly occurs in leaves and is promoted by light intensity

Unraveling the specific organs and tissues involved in saponin synthesis, as well as the light regulatory mechanisms, is crucial for improving the quality of artificially cultivated medicinal materials of Paris plants. Paris saponin VII (PS VII), a high-value active ingredient, is found in almost all organs of Paris plant species. In this study, we focused on Paris polyphylla var. yunnanensis (Franch.) Hand. - Mzt. (PPY) and found that PS VII synthesis predominantly occurs in leaves and is increased by high light intensity. This intriguing discovery has unveiled the potential for manipulating non-traditional medicinal organ leaves to improve the quality of medicinal organ rhizomes. The analysis of the impact of organ differences on saponin concentration in P. polyphylla var. chinensis (Franch.) Hara (PPC), P. fargesii Franch. (PF), and PPY revealed consistency among the three Paris species and was mainly dominated by PS VII. Notably, the leaves and stems exhibited much higher proportions of PS VII than other organs, accounting for 80-90% of the four main saponins. Among the three Paris species, PPY had the highest concentration of PS VII and was selected for subsequent experiments. Further investigations on saponin subcellular localization, temporal variation, and stem wound fluid composition demonstrated that PS VII is synthesized in mesophyll cells, released into the intercellular space through exocytosis, and then transported to the rhizome via vascular tissue. These findings confirm the significant role of leaves in PS VII synthesis. Additionally, a 13C-glucose feeding to trace PS VII biosynthesis revealed that only PS VII in the leaves exhibited incorporation of the labeled carbon, despite conducting 13C-glucose feeding in leaves, stems, rhizomes, and roots. Thus, the leaves are indeed the primary organ for PS VII synthesis in PPY. Furthermore, compared with plants under 100 μmol m-2 s-1, plants under 400 μmol m-2 s-1 exhibited a higher PS VII concentration, particularly in the upper epidermal cells of the leaves. We propose that high light intensity promotes PS VII synthesis in leaves through three mechanisms: (1) increased availability of substrates for saponin synthesis; (2) protection of leaves from high light damage through enhanced saponin synthesis; and (3) enhanced compartmentalization of saponins within the leaves, which in turn feedback regulates saponin synthesis.

Cytotoxic steroidal glycosides from the rhizomes of Paris polyphylla var. yunnanensis

Paris polyphylla var. yunnanensis (Franch.) Hand.-Mazz. (Melanthiaceae), an important specie of the genus Paris, has long been in a traditional Chinese medicine (TCM) for a long time. This study aimed to isolate and identify the structures of bioactive saponins from the rhizomes of P. polyphylla var. yunnanensis and evaluate their cytotoxicity against BxPC-3, HepG2, U373 and SGC-7901 carcinoma cell lines. Seven previously undescribed and seven known saponins were identified, and Paris saponins VII (PSVII) showed significant cytotoxicity against the BxPC-3 cell line with IC₅₀ values of 3.59 μM. Furthermore, flow cytometry, transmission electron microscopy and western-bolt analysis revealed that PSVII inhibited the proliferation of BxPC-3 cells and might be involved in inducing apoptosis and pyroptosis by activating caspase-3, -7 and caspase-1, respectively.

A novel sterol glycosyltransferase catalyses steroidal sapogenin 3-O glucosylation from Paris polyphylla var. yunnanensis

BACKGROUND

Paris polyphylla var. yunnanensis is an important medicinal plant, and the main active ingredient of the plant is polyphyllin, which is a steroid saponin with pharmacological activities. The central enzyme genes participating in the biosynthesis of polyphyllin are increasingly being uncovered; however, UGTs are rarely illustrated.

METHODS AND RESULTS

In this study, we cloned a new sterol glycosyltransferase from Paris polyphylla var. yunnanensis and identified its catalytic function in vitro. PpUGT6 showed the ability to catalyse the C-3 glycosylation of pennogenin sapogenin of polyphyllin, and PpUGT6 showed catalytic promiscuity towards steroids at the C-17 position of testosterone and methyltestosterone and the triterpene at the C-3 position of glycyrrhetinic acid. Homology modelling of the PpUGT6 protein and virtual molecular docking of PpUGT6 with sugar acceptors and donors were performed, and we predicted the key residues interacting with ligands.

CONCLUSIONS

Here, PpUGT6, a novel sterol glycosyltransferase related to the biosynthesis of polyphyllin from P. polyphylla, was characterized. PpUGT6 catalysed C-3 glycosylation to pennogenin sapogenin of polyphyllin, which is the first glycosylation step of the biosynthetic pathway of polyphyllins. Interestingly, PpUGT6 demonstrated glycodiversification to testosterone and methyltestosterone at C-17 and triterpene of glycyrrhetinic acid at the C-3 position. The virtual molecular docking of PpUGT6 protein with ligands predicted the key residues interacting with them. This work characterized a novel SGT glycosylating pennogenin sapogenin at C-3 of polyphyllin from P. polyphylla and provided a reference for further elucidation of the phytosterol glycosyltransferases in catalytic promiscuity and key residues interacting with substrates.

Deciphering the network of cholesterol biosynthesis in Paris polyphylla laid a base for efficient diosgenin production in plant chassis

Cholesterol serves as a key precursor for many high-value chemicals such as plant-derived steroidal saponins and steroidal alkaloids, but a plant chassis for effective biosynthesis of high levels of cholesterol has not been established. Plant chassis have significant advantages over microbial chassis in terms of membrane protein expression, precursor supply, product tolerance, and regionalization synthesis. Here, using Agrobacterium tumefaciens-mediated transient expression technology, Nicotiana benthamiana, and a step-by-step screening approach, we identified nine enzymes (SSR1-3, SMO1-3, CPI-5, CYP51G, SMO2-2, C14-R-2, 8,7SI-4, C5-SD1, and 7-DR1-1) from the medicinal plant Paris polyphylla and established detailed biosynthetic routes from cycloartenol to cholesterol. Specfically, we optimized HMGR, a key gene of the mevalonate pathway, and co-expressed it with the PpOSC1 gene to achieve a high level of cycloartenol (28.79 mg/g dry weight, which is a sufficient amount of precursor for cholesterol biosynthesis) synthesis in the leaves of N. benthamiana. Subsequently, using a one-by-one elimination method we found that six of these enzymes (SSR1-3, SMO1-3, CPI-5, CYP51G, SMO2-2, and C5-SD1) were crucial for cholesterol production in N. benthamiana, and we establihed a high-efficiency cholesterol synthesis system with a yield of 5.63 mg/g dry weight. Using this strategy, we also discovered the biosynthetic metabolic network responsible for the synthesis of a common aglycon of steroidal saponin, diosgenin, using cholesterol as a substrate, obtaining a yield of 2.12 mg/g dry weight in N. benthamiana. Our study provides an effective strategy to characterize the metabolic pathways of medicinal plants that lack a system for in vivo functional verification, and also lays a foundation for the synthesis of active steroid saponins in plant chassis.

Illuminating the biosynthesis pathway genes involved in bioactive specific monoterpene glycosides in Paeonia veitchii Lynch by a combination of sequencing platforms

BACKGROUND

Paeonia veitchii Lynch, a well-known herb from the Qinghai-Tibet Plateau south of the Himalayas, can synthesize specific monoterpene glycosides (PMGs) with multiple pharmacological activities, and its rhizome has become an indispensable ingredient in many clinical drugs. However, little is known about the molecular background of P. veitchii, especially the genes involved in the biosynthetic pathway of PMGs.

RESULTS

A corrective full-length transcriptome with 30,827 unigenes was generated by combining next-generation sequencing (NGS) and single-molecule real-time sequencing (SMRT) of six tissues (leaf, stem, petal, ovary, phloem and xylem). The enzymes terpene synthase (TPS), cytochrome P450 (CYP), UDP-glycosyltransferase (UGT), and BAHD acyltransferase, which participate in the biosynthesis of PMGs, were systematically characterized, and their functions related to PMG biosynthesis were analysed. With further insight into TPSs, CYPs, UGTs and BAHDs involved in PMG biosynthesis, the weighted gene coexpression network analysis (WGCNA) method was used to identify the relationships between these genes and PMGs. Finally, 8 TPSs, 22 CYPs, 7 UGTs, and 2 BAHD genes were obtained, and these putative genes were very likely to be involved in the biosynthesis of PMGs. In addition, the expression patterns of the putative genes and the accumulation of PMGs in tissues suggested that all tissues are capable of biosynthesizing PMGs and that aerial plant parts could also be used to extract PMGs.

CONCLUSION

We generated a large-scale transcriptome database across the major tissues in P. veitchii, providing valuable support for further research investigating P. veitchii and understanding the genetic information of plants from the Qinghai-Tibet Plateau. TPSs, CYPs, UGTs and BAHDs further contribute to a better understanding of the biology and complexity of PMGs in P. veitchii. Our study will help reveal the mechanisms underlying the biosynthesis pathway of these specific monoterpene glycosides and aid in the comprehensive utilization of this multifunctional plant.

Transcriptome Analysis of CYP450 Family Members in Fritillaria cirrhosa D. Don and Profiling of Key CYP450s Related to Isosteroidal Alkaloid Biosynthesis

Fritillaria cirrhosa D. Don (known as Chuan-Bei-Mu in Chinese) can synthesize isosteroidal alkaloids (ISA) with excellent medicinal value, and its bulb has become an indispensable ingredient in many patented drugs. Members of the cytochrome P450 (CYP450) gene superfamily have been shown to play essential roles in regulating steroidal alkaloids biosynthesis. However, little information is available on the P450s in F. cirrhosa. Here, we performed full-length transcriptome analysis and discovered 48 CYP450 genes belonging to 10 clans, 25 families, and 46 subfamilies. By combining phylogenetic trees, gene expression, and key F. cirrhosa ISA content analysis, we presumably identify seven FcCYP candidate genes, which may be hydroxylases active at the C-22, C-23, or C-26 positions in the late stages of ISA biosynthesis. The transcript expression levels of seven FcCYP candidate genes were positively correlated with the accumulation of three major alkaloids in bulbs of different ages. These data suggest that the candidate genes are most likely to be associated with ISA biosynthesis. Finally, the subcellular localization prediction of FcCYPs and transient expression analysis within Nicotiana benthamiana showed that the FcCYPs were mainly localized in the chloroplast. This study presents a systematic analysis of the CYP450 gene family in F. cirrhosa and provides a foundation for further functional characterization of the CYPs involved in ISA biosynthesis.

Comparative transcriptome analysis reveals key genes for polyphyllin difference in five Paris species

Paris species accumulate a large amount of steroidal saponins, which have numerous pharmacological activities and have become an essential component in many patented drugs. However, only two among all Paris species. Paris are identified as official sources due to high level of bioactive compounds. To clarify the composition of steroidal saponins and the molecular basis behind the differences between species, we investigated transcriptome and metabolic profiles of leaves and rhizomes in Paris polyphylla var. chinensis (PPC), Paris polyphylla var. yunnanensis (PPY), Paris polyphylla var. stenophylla (PPS), Paris fargesii (PF), and Paris mairei (PM). Phytochemical results displayed that the accumulation of steroidal saponins was tissue- and species-specific. PF and PPS contained more steroidal saponins in leaves than rhizomes, while PPY accumulated more steroidal saponins in rhizomes than leaves. PPC and PM contained similar amounts of steroidal saponins in leaves and rhizomes. Transcriptome analysis illustrated that most differentially expressed genes related to the biosynthesis of steroidal saponins were abundantly expressed in rhizomes than leaves. Meanwhile, more biosynthetic genes had significant correlations with steroidal saponins in rhizomes than in leaves. The result of CCA indicated that ACAT, DXS, DWF1, and CYP90 constrained 97.35% of the variance in bioactive compounds in leaves, whereas CYP72, UGT73, ACAT, and GPPS constrained 98.61% of the variance in phytochemicals in rhizomes. This study provided critical information for enhancing the production of steroidal saponins by biotechnological approaches and methodologies.