Panax notoginseng , a perennial herb of the genus Panax in the family Araliaceae, has played an important role in clinical treatment in China for thousands of years because of its extensive pharmacological effects. Here, we report a high-quality reference genome of P. notoginseng , with a genome size up to 2.66 Gb and a contig N50 of 1.12 Mb, produced with third-generation PacBio sequencing technology. This is the first chromosome-level genome assembly for the genus Panax . Through genome evolution analysis, we explored phylogenetic and whole-genome duplication events and examined their impact on saponin biosynthesis. We performed a detailed transcriptional analysis of P. notoginseng and explored gene-level mechanisms that regulate the formation of characteristic tubercles. Next, we studied the biosynthesis and regulation of saponins at temporal and spatial levels. We combined multi-omics data to identify genes that encode key enzymes in the P. notoginseng terpenoid biosynthetic pathway. Finally, we identified five glycosyltransferase genes whose products catalyzed the formation of different ginsenosides in P. notoginseng . The genetic information obtained in this study provides a resource for further exploration of the growth characteristics, cultivation, breeding, and saponin biosynthesis of P. notoginseng .
ApUGT, a diterpene glycosyltransferase from Andrographis paniculata, could transfer a glucose to the C-19 hydroxyl moiety of andrograpanin to form neoandrographolide. This glycosyltransferase has a broad substrate scope, and it can glycosylate 26 natural and unnatural compounds of different structural types. This study provides a basis for exploring the glycosylation mechanism of ent-labdane-type diterpenes and plays an important role in diversifying the structures used in drug discovery.
Tripterygium wilfordii (Celastraceae) is a traditional Chinese medicine; and the dried root and rhizome constitute the main officinal parts. Tripterygium wilfordii has been identified as a potential candidate for the treatment of systemic lupus erythematosus, rheumatoid arthritis, nephritis, asthma, leprosy, and cancer. The phylogenetic relationships within the Tripterygium genus are ambiguous; thus, our aim is to clarify the relationships within this genus using phylogeographic and phylogenetic analyses. Here, we first sequenced three plastid DNA regions (i.e., psbA‐trnH, rpl32‐trnL, and trnL‐trnF) and found that Tripterygium hypoglaucum and T. wilfordii were clustered together based on the strength of the topology in the phylogenetic analysis: T. hypoglaucum is polyphyletic, and T. wilfordii is paraphyletic. A spatial analysis of molecular variance showed that the best group value is 4, and the groups were almost consistent with the topology of in the phylogenetic analysis. The Mantel analyses of Tripterygium using IBD web showed statistically significant relationships between genetic and geographical distance distributions (r = .3479, p < .0001). The molecular dating using Fossil calibration indicated that the divergence in Tripterygium was approximately 8.13 Ma. Furthermore, we also analyzed four DNA regions (i.e., ITS2, psbA‐trnH, matK, and rbcL) that were obtained from the NCBI nucleotide database; these results showed that T. wilfordii and T. hypoglaucum clustered together, while Tripterygium regelii represented a separate cluster. Tripterygium hypoglaucum and T. wilfordii were never distinct lineages, and the species circumscriptions are artificial. We propose that T. wilfordii and T. hypoglaucum are conspecific, while T. regelii likely constitutes a separate species.
Tripterygium wilfordii produces not only ent-kaurene, which is an intermediate of gibberellin (GA) biosynthesis in flowering plants, but also 16α-hydroxy-ent-kaurane, whose physiological role has not been characterized. The two compounds are biosynthesized from the universal diterpenoid precursor (E,E,E)-geranylgeranyl diphosphate (GGPP) by diterpene synthases, which have been discovered and functionally characterized in T. wilfordii. Here, we described the functional characterization of four cytochrome P450 reductases (TwCPR) and one ent-kaurene oxidase (TwKO). Four TwCPRs were found to have relatively ubiquitous expression in T. wilfordii root, stem, leaf, and flower tissues. Co-expression of both a TwCPR and TwKO in yeast showed that TwCPR3 has a slightly better activity for providing the electrons required for these reactions, indicating that TwCPR3 is more suitable for use in the functional analysis of other cytochrome P450 monooxygenases. TwKO catalyzed the three-step oxidation of the C4α methyl of the tetracyclic diterpene intermediate ent-kaurene to form ent-kaurenoic acid as an early step in GA biosynthesis. Notably, TwKO could also convert 16α-hydroxy-ent-kaurane to 16α-hydroxy-ent-kaurenoic acid, indicating an important function of 16α-hydroxy-ent-kaurane in the anti-HIV principle tripterifordin biosynthetic pathway in planta. Homology modeling and molecular docking were used to investigate the unknown crucial active amino acid residue involved in the catalytic reaction of TwKO, and one key residue (Leu387) contributed to the formation of 16α-hydroxy-ent-kaurenoic acid, most likely by forming hydrogen bonds with the hydroxyl group (-OH) of 16α-hydroxy-ent-kaurane, which laid the basis for further investigation of the multifunctional nature of KO catalysis. Also, our findings paved the way for the complete biosynthesis of the anti-HIV principle tripterifordin.
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