The first high-quality chromosomal genome assembly of a medicinal and edible plant Arctium lappa

Whole genome sequencing data of greater burdock (Arctium lappa) naturalized in the United States of America

This dataset comprises whole genome sequencing burdock (Arctium lappa) naturalized in a residential yard in Rochester, New York, USA. Total DNA was extracted from a leaf sample and processed using the Illumina Nextera XT DNA library preparation kit. Sequencing on the NextSeq 2000 platform produced 127.4 GB of raw data, yielding 125.8 GB of high-quality reads after filtering, with an average genome coverage of 75x. The genome was assembled de novo into 792,817 contigs, achieving a total genome length of 1,075,454,921 base pairs with a GC content of 37.03 %. Scaffolding against a Chinese A. lappa reference genome improved genome completeness from 49.1 % to 94.93 %, successfully recovering the majority of protein-coding genes. Variant analysis identified approximately 20.8 million Single Nucleotide Polymorphisms (SNPs) and 1.3 million indels, including functionally significant mutations. The Internal Transcribed Spacer 2 (ITS2) ribosomal region was isolated and compared with global references, revealing significant genetic differentiation between the U.S.A and Chinese populations. This comprehensive genomic dataset has been deposited in publicly accessible repositories, including National Center for Biotechnology Information (NC and Zenodo. The sequencing of this sample provides a valuable resource for comparative genomics, population genetics, and investigations into bioactive compounds with antimicrobial properties, supporting agricultural and pharmaceutical applications. Direct access to the dataset is available at 10.5281/zenodo.14607136.

The chromosome-scale genomes of two cultivated safflowers (Carthamus tinctorius) provide insights into the genetic diversity resulting from domestication

KEY MESSAGE

Two cultivated safflowers from distinct areas elucidate the genetic diversity present in the linoleic acid biosynthesis, flowering time and flavonoid biosynthesis. The process of domestication facilitates the adaptation of crops to agricultural environments. In this study, we selected two representative safflower cultivars that has been domesticated in two distinct areas in China as samples to investigate their genetic diversity due to local environmental adaption. Yunhong-7 is a locally bred safflower (Carthamus tinctorius) cultivar, that has been currently widely cultivated in Yunnan Province, Southwest China, and Anhui-1 is a safflower cultivar that was locally bred in Anhui Province, East China. We firstly generated the chromosome-scale genome assembly for yunhong-7 cultivar by combining PacBio and Hi-C technologies. Through comparative genomic analysis, we identified structural variations (SVs) between yunhong-7 and anhui-1, which revealed their genetic differences in the pathways of fatty acid biosynthesis, circadian rhythm and flavonoid biosynthesis. Subsequently, a total of 40 non-redundant fatty acid desaturase 2 (FAD2) genes (39 for yunhong-7 and 20 for anhui-1) were identified, revealing the presence of copy-number variation and major genes change between yunhong-7 and anhui-1. The presented results suggested that changes in SVs may induce alterations in the expression of flowering-related genes, which could explain the observed early flowering phenotype in yunhong-7 compared to anhui-1. We identified a total of 197 non-redundant UDP-glucuronosyltransferases (UGT) genes. Based on prokaryotic expression system, we investigated the catalytic functions of two unique UGT genes (CtUGT.18 and CtUGT.191). The current study increases our knowledge of genetic diversity among crop cultivars resulting from distinct domestication processes and thus could contribute to the advancement of traits research and the safflower breeding.

SSR markers development and their application in genetic diversity of burdock (Arctium lappa L.) germplasm

BACKGROUND

Arctium lappa L. is a medicinal edible homologous plant, commonly known as burdock or bardana, which belongs to the Asteraceae family and is abundant all over the world. Genetic diversity assessment is essential for A. lappa germplasm resource conservation and breeding. The assessment techniques include morphological, biochemical, and DNA marker analysis. However, the limited number of available DNA markers is insufficient to conduct related genetic diversity assessment studies.

RESULTS

In this study, we conducted RNA sequencing of the A. lappa cultivar 'Yanagikawa Ideal' and developed SSR markers to characterize the genetic diversity and population structure of 56 A. lappa accessions and 8 wild relative accessions. A total of 4,851 simple sequence repeats (SSRs) loci were identified. The proportions of mono-, di- and tri-nucleotide repeat motifs were 30.40%, 21.50% and 33.10%, respectively. We developed and verified the reliability of 28 SSR core primer pairs through electronic polymerase chain reaction (ePCR) and the PCR amplification process. The polymorphism information content (PIC) values of the 28 SSR core primer pairs ranged from 0.246 to 0.848, with 14 pairs of SSR primers displaying high polymorphism (PIC > 0.5). The 28 SSR core primer pairs showed 100% mobility in Arctium tomentosum Miller and 96.43% mobility in Synurus deltoides (Aiton) Nakai, indicating their high versatility. The average Shannon information index (I) was 1.231, and the average observed heterozygosity (Ho) was 0.132, the average expected heterozygosity (He) was 0.564. The 64 accessions were divided into three clusters at a genetic distance of 0.558. AMOVA analysis shows 83% genetic variation within populations and 17% among populations, highlighting implications for conservation and breeding strategies.

CONCLUSION

Our study provides 28 newly high-quality SSR markers to enhance genetic resource conservation and breeding programs for A. lappa, as well as to support comparative genomics and cross-species breeding strategies for related species.

The haplotype-resolved genome of diploid Chrysanthemum indicum unveils new acacetin synthases genes and their evolutionary history

Acacetin, a flavonoid compound, possesses a wide range of pharmacological effects, including antimicrobial, immune regulation, and anticancer effects. Some key steps in its biosynthetic pathway were largely unknown in flowering plants. Here, we present the first haplotype-resolved genome of Chrysanthemum indicum, whose dried flowers contain abundant flavonoids and have been utilized as traditional Chinese medicine. Various phylogenetic analyses revealed almost equal proportion of three tree topologies among three Chrysanthemum species (C. indicum, C. nankingense, and C. lavandulifolium), indicating that frequent gene flow among Chrysanthemum species or incomplete lineage sorting due to rapid speciation might contribute to conflict topologies. The expanded gene families in C. indicum were associated with oxidative functions. Through comprehensive candidate gene screening, we identified five flavonoid O-methyltransferase (FOMT) candidates, which were highly expressed in flowers and whose expressional levels were significantly correlated with the content of acacetin. Further experiments validated two FOMTs (CI02A009970 and CI03A006662) were capable of catalyzing the conversion of apigenin into acacetin, and these two genes are possibly responsible acacetin accumulation in disc florets and young leaves, respectively. Furthermore, combined analyses of ancestral chromosome reconstruction and phylogenetic trees revealed the distinct evolutionary fates of the two validated FOMT genes. Our study provides new insights into the biosynthetic pathway of flavonoid compounds in the Asteraceae family and offers a model for tracing the origin and evolutionary routes of single genes. These findings will facilitate in vitro biosynthetic production of flavonoid compounds through cellular and metabolic engineering and expedite molecular breeding of C. indicum cultivars.

The conversion of monolignans to sesquilignans and dilignans is closely correlated to the regulation of Arctium lappa seed germination

MAIN CONCLUSION

The secondary metabolic conversion of monolignans to sesquilignans/dilignans was closely related to seed germination and seedling establishment in Arctium lappa. Arctium lappa plants are used as a kind of traditional Chinese medicines for nearly 1500 years, and so far, only a few studies have put focus on the key secondary metabolic changes during seed germination and seedling establishment. In the current study, a combined approach was used to investigate the correlation among secondary metabolites, plant hormone signaling, and transcriptional profiles at the early critical stages of A. lappa seed germination and seedling establishment. Of 50 metabolites in methonolic extracts of A. lappa samples, 35 metabolites were identified with LC-MS/MS and 15 metabolites were identified with GC-MS. Their qualitative properties were examined according to the predicted chemical structures. The quantitative analysis was performed for deciphering their metabolic profiles, discovering that the secondary metabolic conversion from monolignans to sesquilignans/dilignans was closely correlated to the initiation of A. lappa seed germination and seedling establishment. Furthermore, the critical transcriptional changes in primary metabolisms, translational regulation at different cellular compartments, and multiple plant hormone signaling pathways were revealed. In addition, the combined approach provides unprecedented insights into key regulatory mechanisms in both gene transcription and secondary metabolites besides many known primary metabolites during seed germination of an important traditional Chinese medicinal plant species. The results not only provide new insights to understand the regulation of key medicinal components of 'ARCTII FRUCTUS', arctiin and arctigenin at the stages of seed germination and seedling establishment, but also potentially spur the development of seed-based cultivation in A. lappa plants.

Chromosome-level genome assembly provides insights into the genome evolution and functional importance of the phenylpropanoid-flavonoid pathway in Thymus mongolicus

BACKGROUND

Thymus mongolicus (family Lamiaceae) is a Thyme subshrub with strong aroma and remarkable environmental adaptability. Limited genomic information limits the use of this plant.

RESULTS

Chromosome-level 605.2 Mb genome of T. mongolicus was generated, with 96.28% anchored to 12 pseudochromosomes. The repetitive sequences were dominant, accounting for 70.98%, and 32,593 protein-coding genes were predicted. Synteny analysis revealed that Lamiaceae species generally underwent two rounds of whole genome duplication; moreover, species-specific genome duplication was identified. A recent LTR retrotransposon burst and tandem duplication might play important roles in the formation of the Thymus genome. Using comparative genomic analysis, phylogenetic tree of seven Lamiaceae species was constructed, which revealed that Thyme plants evolved recently in the family. Under the phylogenetic framework, we performed functional enrichment analysis of the genes on nodes that contained the most gene duplication events (> 50% support) and of relevant significant expanded gene families. These genes were highly associated with environmental adaptation and biosynthesis of secondary metabolites. Combined transcriptome and metabolome analyses revealed that Peroxidases, Hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferases, and 4-coumarate-CoA ligases genes were the essential regulators of the phenylpropanoid-flavonoid pathway. Their catalytic products (e.g., apigenin, naringenin chalcone, and several apigenin-related compounds) might be responsible for the environmental tolerance and aromatic properties of T. mongolicus.

CONCLUSION

This study enhanced the understanding of the genomic evolution of T. mongolicus, enabling further exploration of its unique traits and applications, and contributed to the understanding of Lamiaceae genomics and evolutionary biology.

Applications of some advanced sequencing, analytical, and computational approaches in medicinal plant research: a review

The potential active chemicals found in medicinal plants, which have long been employed as natural medicines, are abundant. Exploring the genes responsible for producing these compounds has given new insights into medicinal plant research. Previously, the authentication of medicinal plants was done via DNA marker sequencing. With the advancement of sequencing technology, several new techniques like next-generation sequencing, single molecule sequencing, and fourth-generation sequencing have emerged. These techniques enshrined the role of molecular approaches for medicinal plants because all the genes involved in the biosynthesis of medicinal compound(s) could be identified through RNA-seq analysis. In several research insights, transcriptome data have also been used for the identification of biosynthesis pathways. miRNAs in several medicinal plants and their role in the biosynthesis pathway as well as regulation of the disease-causing genes were also identified. In several research articles, an in silico study was also found to be effective in identifying the inhibitory effect of medicinal plant-based compounds against virus' gene(s). The use of advanced analytical methods like spectroscopy and chromatography in metabolite proofing of secondary metabolites has also been reported in several recent research findings. Furthermore, advancement in molecular and analytic methods will give new insight into studying the traditionally important medicinal plants that are still unexplored.

Novel Tri-Segmented Rhabdoviruses: A Data Mining Expedition Unveils the Cryptic Diversity of Cytorhabdoviruses

Cytorhabdoviruses (genus Cytorhabdovirus, family Rhabdoviridae) are plant-infecting viruses with enveloped, bacilliform virions. Established members of the genus Cytorhabdovirus have unsegmented single-stranded negative-sense RNA genomes (ca. 10-16 kb) which encode four to ten proteins. Here, by exploring large publicly available metatranscriptomics datasets, we report the identification and genomic characterization of 93 novel viruses with genetic and evolutionary cues of cytorhabdoviruses. Strikingly, five unprecedented viruses with tri-segmented genomes were also identified. This finding represents the first tri-segmented viruses in the family Rhabdoviridae, and they should be classified in a novel genus within this family for which we suggest the name "Trirhavirus". Interestingly, the nucleocapsid and polymerase were the only typical rhabdoviral proteins encoded by those tri-segmented viruses, whereas in three of them, a protein similar to the emaravirus (family Fimoviridae) silencing suppressor was found, while the other predicted proteins had no matches in any sequence databases. Genetic distance and evolutionary insights suggest that all these novel viruses may represent members of novel species. Phylogenetic analyses, of both novel and previously classified plant rhabdoviruses, provide compelling support for the division of the genus Cytorhabdovirus into three distinct genera. This proposed reclassification not only enhances our understanding of the evolutionary dynamics within this group of plant rhabdoviruses but also illuminates the remarkable genomic diversity they encompass. This study not only represents a significant expansion of the genomics of cytorhabdoviruses that will enable future research on the evolutionary peculiarity of this genus but also shows the plasticity in the rhabdovirus genome organization with the discovery of tri-segmented members with a unique evolutionary trajectory.

Chlorogenic Acid from Burdock Roots Ameliorates Oleic Acid-Induced Steatosis in HepG2 Cells through AMPK/ACC/CPT-1 Pathway

Hepatic steatosis can cause liver dysfunction and cell injury, on which natural functional factors are expected to be an effective approach for long-term intervention. However, the cellular molecular mechanisms are unclear. Chlorogenic acid is a phenolic compound, which can regulate lipid metabolism and is abundant in burdock root. The aim of this study was to investigate the potential molecular mechanism of the effect of chlorogenic acid from burdock root (ACQA) on steatosis in HepG2 cells. In this study, we found that ACQA reduced the number of lipid droplets and lipid levels in oleic acid-treated HepG2 cells. Molecular mechanistic results showed that ACQA enhanced CPT-1 expression by activating AMPK-related signaling pathways, and the concentrations of Ca2+ and cAMP were increased with the intervention of ACQA. In addition, ACQA enhanced the β-oxidation of fatty acids, reduced alanine transaminase and aspartate transaminase, and inhibited apoptosis in oleic acid-treated HepG2 cells. Our studies elucidate a novel mechanism that ACQA enhances the β-oxidation of fatty acids through the AMPK/ACC/CPT-1 pathway to protect against steatosis in HepG2 cells, which provides insight into its molecular mechanism as well as intervention strategies for chlorogenic acid against fatty liver diseases.

Two-step model of paleohexaploidy, ancestral genome reshuffling and plasticity of heat shock response in Asteraceae

An ancient hexaploidization event in the most but not all Asteraceae plants, may have been responsible for shaping the genomes of many horticultural, ornamental, and medicinal plants that promoting the prosperity of the largest angiosperm family on the earth. However, the duplication process of this hexaploidy, as well as the genomic and phenotypic diversity of extant Asteraceae plants caused by paleogenome reorganization, are still poorly understood. We analyzed 11 genomes from 10 genera in Asteraceae, and redated the Asteraceae common hexaploidization (ACH) event ~70.7-78.6 million years ago (Mya) and the Asteroideae specific tetraploidization (AST) event ~41.6-46.2 Mya. Moreover, we identified the genomic homologies generated from the ACH, AST and speciation events, and constructed a multiple genome alignment framework for Asteraceae. Subsequently, we revealed biased fractionations between the paleopolyploidization produced subgenomes, suggesting the ACH and AST both are allopolyplodization events. Interestingly, the paleochromosome reshuffling traces provided clear evidence for the two-step duplications of ACH event in Asteraceae. Furthermore, we reconstructed ancestral Asteraceae karyotype (AAK) that has 9 paleochromosomes, and revealed a highly flexible reshuffling of Asteraceae paleogenome. Of specific significance, we explored the genetic diversity of Heat Shock Transcription Factors (Hsfs) associated with recursive whole-genome polyploidizations, gene duplications, and paleogenome reshuffling, and revealed that the expansion of Hsfs gene families enable heat shock plasticity during the genome evolution of Asteraceae. Our study provides insights on polyploidy and paleogenome remodeling for the successful establishment of Asteraceae, and is helpful for further communication and exploration of the diversification of plant families and phenotypes.

The burdock database: a multi-omic database for Arctium lappa, a food and medicinal plant

BACKGROUND

Burdock is a biennial herb of Asteraceae found in Northern Europe, Eurasia, Siberia, and China. Its mature dry fruits, called Niu Bang Zi, are recorded in various traditional Chinese medicine books. With the development of sequencing technology, the mitochondrial, chloroplast, and nuclear genomes, transcriptome, and sequence-related amplified polymorphism (SRAP) fingerprints of burdock have all been reported. To make better use of this data for further research and analysis, a burdock database was constructed.

RESULTS

This burdock multi-omics database contains two burdock genome datasets, two transcriptome datasets, eight burdock chloroplast genomes, one burdock mitochondrial genome, one A. tomentosum chloroplast genome, one A. tomentosum mitochondrial genome, 26 phenotypes of burdock varieties, burdock rhizosphere-associated microorganisms, and chemical constituents of burdock fruit, pericarp, and kernel at different growth stages (using UPLC-Q-TOF-MS). The wild and cultivation distribution of burdock in China was summarized, and the main active components and pharmacological effects of burdock currently reported were concluded. The database contains ten central functional modules: Home, Genome, Transcriptome, Jbrowse, Search, Tools, SRAP fingerprints, Associated microorganisms, Chemical, and Publications. Among these, the "Tools" module can be used to perform sequence homology alignment (Blast), multiple sequence alignment analysis (Muscle), homologous protein prediction (Genewise), primer design (Primer), large-scale genome analysis (Lastz), and GO and KEGG enrichment analyses (GO Enrichment and KEGG Enrichment).

CONCLUSIONS

The database URL is http://210.22.121.250:41352/ . This burdock database integrates molecular and chemical data to provide a comprehensive information and analysis platform for interested researchers and can be of immense help to the cultivation, breeding, and molecular pharmacognosy research of burdock.

Intraspecific variation in genome size in Artemisia argyi determined using flow cytometry and a genome survey

Different collections and accessions of Artemisia argyi (Chinese mugwort) harbour considerable diversity in morphology and bioactive compounds, but no mechanisms have been reported that explain these variations. We studied genome size in A. argyi accessions from different regions of China by flow cytometry. Genome size was significantly distinct among origins of these 42 Chinese mugwort accessions, ranging from 8.428 to 11.717 pg. There were no significant intraspecific differences among the 42 accessions from the five regions of China. The clustering analysis showed that these 42 A. argyi accessions could be divided into three groups, which had no significant relationship with geographical location. In a genome survey, the total genome size of A. argyi (A15) was estimated to be 7.852 Gb (or 8.029 pg) by K-mer analysis. This indicated that the results from the two independent methods are consistent, and that the genome survey can be used as an adjunct to flow cytometry to compensate for its deficiencies. In addition, genome survey can provide the information about heterozygosity, repeat sequences, GC content and ploidy of A. argyi genome. The nuclear DNA contents determined here provide a new reference for intraspecific variation in genome size in A. argyi, and may also be a potential resource for the study of genetic diversity and for breeding new cultivar.

Chromosome-level genome assembly and functional characterization of terpene synthases provide insights into the volatile terpenoid biosynthesis of Wurfbainia villosa

Wurfbainia villosa is a well-known medicinal and edible plant that is widely cultivated in the Lingnan region of China. Its dried fruits (called Fructus Amomi) are broadly used in traditional Chinese medicine for curing gastrointestinal diseases and are rich in volatile terpenoids. Here, we report a high-quality chromosome-level genome assembly of W. villosa with a total size of approximately 2.80 Gb, 42 588 protein-coding genes, and a very high percentage of repetitive sequences (87.23%). Genome analysis showed that W. villosa likely experienced a recent whole-genome duplication event prior to the W. villosa-Zingiber officinale divergence (approximately 11 million years ago), and a recent burst of long terminal repeat insertions afterward. The W. villosa genome enabled the identification of 17 genes involved in the terpenoid skeleton biosynthesis pathway and 66 terpene synthase (TPS) genes. We found that tandem duplication events have an important contribution to the expansion of WvTPSs, which likely drove the production of volatile terpenoids. In addition, functional characterization of 18 WvTPSs, focusing on the TPS-a and TPS-b subfamilies, showed that most of these WvTPSs are multi-product TPS and are predominantly expressed in seeds. The present study provides insights into the genome evolution and the molecular basis of the volatile terpenoids diversity in W. villosa. The genome sequence also represents valuable resources for the functional gene research and molecular breeding of W. villosa.

Application of High-Throughput Sequencing on the Chinese Herbal Medicine for the Data-Mining of the Bioactive Compounds

The Chinese Herbal Medicine (CHM) has been used worldwide in clinic to treat the vast majority of human diseases, and the healing effect is remarkable. However, the functional components and the corresponding pharmacological mechanism of the herbs are unclear. As one of the main means, the high-throughput sequencing (HTS) technologies have been employed to discover and parse the active ingredients of CHM. Moreover, a tremendous amount of effort is made to uncover the pharmacodynamic genes associated with the synthesis of active substances. Here, based on the genome-assembly and the downstream bioinformatics analysis, we present a comprehensive summary of the application of HTS on CHM for the synthesis pathways of active ingredients from two aspects: active ingredient properties and disease classification, which are important for pharmacological, herb molecular breeding, and synthetic biology studies.