The genomes of chicory, endive, great burdock and yacon provide insights into Asteraceae palaeo-polyploidization history and plant inulin production

AMIR: a multi-omics data platform for Asteraceae plants genetics and breeding research

As the largest family of dicotyledon, the Asteraceae family comprises a variety of economically important crops, ornamental plants and numerous medicinal herbs. Advancements in genomics and transcriptomic have revolutionized research in Asteraceae species, generating extensive omics data that necessitate an efficient platform for data integration and analysis. However, existing databases face challenges in mining genes with specific functions and supporting cross-species studies. To address these gaps, we introduce the Asteraceae Multi-omics Information Resource (AMIR; https://yanglab.hzau.edu.cn/AMIR/), a multi-omics hub for the Asteraceae plant community. AMIR integrates diverse omics data from 74 species, encompassing 132 genomes, 4 408 432 genes annotated across seven different perspectives, 3897 transcriptome sequencing samples spanning 131 organs, tissues and stimuli, 42 765 290 unique variants and 15 662 metabolites genes. Leveraging these data, AMIR establishes the first pan-genome, comparative genomics and transcriptome system for the Asteraceae family. Furthermore, AMIR offers user-friendly tools designed to facilitate extensive customized bioinformatics analyses. Two case studies demonstrate AMIR's capability to provide rapid, reproducible and reliable analysis results. In summary, by integrating multi-omics data of Asteraceae species and developing powerful analytical tools, AMIR significantly advances functional genomics research and contributes to breeding practices of Asteraceae.

Modeling Substitution Rate Evolution across Lineages and Relaxing the Molecular Clock

Relaxing the molecular clock using models of how substitution rates change across lineages has become essential for addressing evolutionary problems. The diversity of rate evolution models and their implementations are substantial, and studies have demonstrated their impact on divergence time estimates can be as significant as that of calibration information. In this review, we trace the development of rate evolution models from the proposal of the molecular clock concept to the development of sophisticated Bayesian and non-Bayesian methods that handle rate variation in phylogenies. We discuss the various approaches to modeling rate evolution, provide a comprehensive list of available software, and examine the challenges and advancements of the prevalent Bayesian framework, contrasting them to faster non-Bayesian methods. Lastly, we offer insights into potential advancements in the field in the era of big data.

Asteraceae genome database: a comprehensive platform for Asteraceae genomics

Asteraceae, the largest family of angiosperms, has attracted widespread attention for its exceptional medicinal, horticultural, and ornamental value. However, researches on Asteraceae plants face challenges due to their intricate genetic background. With the continuous advancement of sequencing technology, a vast number of genomes and genetic resources from Asteraceae species have been accumulated. This has spurred a demand for comprehensive genomic analysis within this diverse plant group. To meet this need, we developed the Asteraceae Genomics Database (AGD; http://cbcb.cdutcm.edu.cn/AGD/). The AGD serves as a centralized and systematic resource, empowering researchers in various fields such as gene annotation, gene family analysis, evolutionary biology, and genetic breeding. AGD not only encompasses high-quality genomic sequences, and organelle genome data, but also provides a wide range of analytical tools, including BLAST, JBrowse, SSR Finder, HmmSearch, Heatmap, Primer3, PlantiSMASH, and CRISPRCasFinder. These tools enable users to conveniently query, analyze, and compare genomic information across various Asteraceae species. The establishment of AGD holds great significance in advancing Asteraceae genomics, promoting genetic breeding, and safeguarding biodiversity by providing researchers with a comprehensive and user-friendly genomics resource platform.

Production, modification and degradation of fructans and fructooligosacharides by enzymes originated from plants

Non-starch polysaccharides exhibit numerous beneficial health effects but compounds belonging to FODMAP (Fermentable Oligo- Di- and Monosaccharides and Polyols) has been recently connected to several gastrointestinal disorders. This review presents integrated literature data on the occurrence and types of fructans and fructooligosaccharids (classified as FODMAPs) as well as their degrading enzymes present in plants. Plants from the family Asteraceae and many monocotyledones, including families Poaceae and Liliaceae, are the most abundant sources of both fructans and fructan-degrading enzymes. So far, vast majority of publications concerning the application of these specific plants in production of bakery products is related to increase of dietary fibre content in these products. However, there is limited research on their effect on FODMAP content and fibre balance. The authors emphasize the possibility of application of enzyme rich plant extract in food production casting light on the new scientific approach to fibre modification.

Strain-specific evolution and host-specific regulation of transposable elements in the model plant symbiont Rhizophagus irregularis

Transposable elements (TEs) are repetitive DNA that can create genome structure and regulation variability. The genome of Rhizophagus irregularis, a widely studied arbuscular mycorrhizal fungus (AMF), comprises ∼50% repetitive sequences that include TEs. Despite their abundance, two-thirds of TEs remain unclassified, and their regulation among AMF life stages remains unknown. Here, we aimed to improve our understanding of TE diversity and regulation in this model species by curating repeat datasets obtained from chromosome-level assemblies and by investigating their expression across multiple conditions. Our analyses uncovered new TE superfamilies and families in this model symbiont and revealed significant differences in how these sequences evolve both within and between R. irregularis strains. With this curated TE annotation, we also found that the number of upregulated TE families in colonized roots is 4 times higher than in the extraradical mycelium, and their overall expression differs depending on the plant host. This work provides a fine-scale view of TE diversity and evolution in model plant symbionts and highlights their transcriptional dynamism and specificity during host-microbe interactions. We also provide Hidden Markov Model profiles of TE domains for future manual curation of uncharacterized sequences (https://github.com/jordana-olive/TE-manual-curation/tree/main).

Metabolism of Inulin via Difructose Anhydride I Pathway in Microbacterium flavum

Difructose anhydride I (DFA-I) can be produced from inulin, with DFA-I-forming inulin fructotransferase (IFTase-I). However, the metabolism of inulin through DFA-I remains unclear. To clarify this pathway, several genes of enzymes related to this pathway in the genome of Microbacterium flavum DSM 18909 were synthesized, and the corresponding enzymes were encoded, purified, and investigated in vitro. After inulin is decomposed to DFA-I by IFTase-I, DFA-I is hydrolyzed to inulobiose by DFA-I hydrolase. Inulobiose is then hydrolyzed by β-fructofuranosidase to form fructose. Finally, fructose enters glycolysis through fructokinase. A β-fructofuranosidase (MfFFase1) clears the byproducts (sucrose and fructo-oligosaccharides), which might be partially hydrolyzed by fructan β-(2,1)-fructosidase/1-exohydrolase and another fructofuranosidase (MfFFase2). Exploring the DFA-I pathway of inulin and well-studied enzymes in vitro extends our basic scientific knowledge of the energy-providing way of inulin, thereby paving the way for further investigations in vivo and offering a reference for further nutritional investigation of inulin and DFA-I in the future.

Haplotype-resolved chromosome-level genome of hexaploid Jerusalem artichoke provides insights into its origin, evolution, and inulin metabolism

Jerusalem artichoke (Helianthus tuberosus) is a global multifunctional crop. It has wide applications in the food, health, feed, and biofuel industries and in ecological protection; it also serves as a germplasm pool for breeding of the global oil crop common sunflower (Helianthus annuus). However, biological studies of Jerusalem artichoke have been hindered by a lack of genome sequences, and its high polyploidy and large genome size have posed challenges to genome assembly. Here, we report a 21-Gb chromosome-level assembly of the hexaploid Jerusalem artichoke genome, which comprises 17 homologous groups, each with 6 pseudochromosomes. We found multiple large-scale chromosome rearrangements between Jerusalem artichoke and common sunflower, and our results show that the hexaploid genome of Jerusalem artichoke was formed by a hybridization event between a tetraploid and a diploid Helianthus species, followed by chromosome doubling of the hybrid, which occurred approximately 2 million years ago. Moreover, we identified more copies of actively expressed genes involved in inulin metabolism and showed that these genes may still be undergoing loss of function or sub- or neofunctionalization. These genomic resources will promote further biological studies, breeding improvement, and industrial utilization of Helianthus crops.

The genomes of Dahlia pinnata, Cosmos bipinnatus, and Bidens alba in tribe Coreopsideae provide insights into polyploid evolution and inulin biosynthesis

BACKGROUND

The Coreopsideae tribe, a subset of the Asteraceae family, encompasses economically vital genera like Dahlia, Cosmos, and Bidens, which are widely employed in medicine, horticulture, ecology, and food applications. Nevertheless, the lack of reference genomes hinders evolutionary and biological investigations in this tribe.

RESULTS

Here, we present 3 haplotype-resolved chromosome-level reference genomes of the tribe Coreopsideae, including 2 popular flowering plants (Dahlia pinnata and Cosmos bipinnatus) and 1 invasive weed plant (Bidens alba), with assembled genome sizes 3.93 G, 1.02 G, and 1.87 G, respectively. We found that Gypsy transposable elements contribute mostly to the larger genome size of D. pinnata, and multiple chromosome rearrangements have occurred in tribe Coreopsideae. Besides the shared whole-genome duplication (WGD-2) in the Heliantheae alliance, our analyses showed that D. pinnata and B. alba each underwent an independent recent WGD-3 event: in D. pinnata, it is more likely to be a self-WGD, while in B. alba, it is from the hybridization of 2 ancestor species. Further, we identified key genes in the inulin metabolic pathway and found that the pseudogenization of 1-FEH1 and 1-FEH2 genes in D. pinnata and the deletion of 3 key residues of 1-FFT proteins in C. bipinnatus and B. alba may probably explain why D. pinnata produces much more inulin than the other 2 plants.

CONCLUSIONS

Collectively, the genomic resources for the Coreopsideae tribe will promote phylogenomics in Asteraceae plants, facilitate ornamental molecular breeding improvements and inulin production, and help prevent invasive weeds.

Unlocking secrets of nature's chemists: Potential of CRISPR/Cas-based tools in plant metabolic engineering for customized nutraceutical and medicinal profiles

Plant species have evolved diverse metabolic pathways to effectively respond to internal and external signals throughout their life cycle, allowing adaptation to their sessile and phototropic nature. These pathways selectively activate specific metabolic processes, producing plant secondary metabolites (PSMs) governed by genetic and environmental factors. Humans have utilized PSM-enriched plant sources for millennia in medicine and nutraceuticals. Recent technological advances have significantly contributed to discovering metabolic pathways and related genes involved in the biosynthesis of specific PSM in different food crops and medicinal plants. Consequently, there is a growing demand for plant materials rich in nutrients and bioactive compounds, marketed as "superfoods". To meet the industrial demand for superfoods and therapeutic PSMs, modern methods such as system biology, omics, synthetic biology, and genome editing (GE) play a crucial role in identifying the molecular players, limiting steps, and regulatory circuitry involved in PSM production. Among these methods, clustered regularly interspaced short palindromic repeats-CRISPR associated protein (CRISPR/Cas) is the most widely used system for plant GE due to its simple design, flexibility, precision, and multiplexing capabilities. Utilizing the CRISPR-based toolbox for metabolic engineering (ME) offers an ideal solution for developing plants with tailored preventive (nutraceuticals) and curative (therapeutic) metabolic profiles in an ecofriendly way. This review discusses recent advances in understanding the multifactorial regulation of metabolic pathways, the application of CRISPR-based tools for plant ME, and the potential research areas for enhancing plant metabolic profiles.

Complete chloroplast genome and phylogenetic analysis of Smallanthus sonchifolius (Asteraceae)

Smallanthus sonchifolius (Asteraceae), is an important food plant in the world. There is no systematic report on the chloroplast genome of S. sonchifolius. Here we reported its complete chloroplast genome and analyzed the basic characteristics. The chloroplast genome was 152,301 bp in length, had a GC content of 37.55%, and encoded 113 unique genes, including 79 protein-coding genes, 4 ribosomal RNA genes, and 30 transfer RNA genes. Phylogenetic analysis showed that the tribe Millerieae and the tribe Madieae are closely related in the Asteraceae family. In the tribe Millerieae, Smallanthus was more closely related to Guizotia and Sigesbeckia. This chloroplast genome not only enriches the genome information of Smallanthus, but also lays the foundation for understanding the phylogeny within the genus Smallanthus.

Chromosome-level reference genome of stinkwort, Dittrichia graveolens (L.) Greuter: A resource for studies on invasion, range expansion, and evolutionary adaptation under global change

Dittrichia graveolens (L.) Greuter, or stinkwort, is a weedy annual plant within the family Asteraceae. The species is recognized for the rapid expansion of both its native and introduced ranges: in Europe, it has expanded its native distribution northward from the Mediterranean basin by nearly 7 °C latitude since the mid-20th century, while in California and Australia the plant is an invasive weed of concern. Here, we present the first de novo D. graveolens genome assembly (1N = 9 chromosomes), including complete chloroplast (151,013 bp) and partial mitochondrial genomes (22,084 bp), created using Pacific Biosciences HiFi reads and Dovetail Omni-C data. The final primary assembly is 835 Mbp in length, of which 98.1% are represented by 9 scaffolds ranging from 66 to 119 Mbp. The contig N50 is 74.9 Mbp and the scaffold N50 is 96.9 Mbp, which, together with a 98.8% completeness based on the BUSCO embryophyta10 database containing 1,614 orthologs, underscores the high quality of this assembly. This pseudo-molecule-scale genome assembly is a valuable resource for our fundamental understanding of the genomic consequences of range expansion under global change, as well as comparative genomic studies in the Asteraceae.

Genome-Wide Datasets of Chicories (Cichorium intybus L.) for Marker-Assisted Crop Breeding Applications: A Systematic Review and Meta-Analysis

Cichorium intybus L. is the most economically important species of its genus and among the most important of the Asteraceae family. In chicory, many linkage maps have been produced, several sets of mapped and unmapped markers have been developed, and dozens of genes linked to traits of agronomic interest have been investigated. This treasure trove of information, properly cataloged and organized, is of pivotal importance for the development of superior commercial products with valuable agronomic potential in terms of yield and quality, including reduced bitter taste and increased inulin production, as well as resistance or tolerance to pathogens and resilience to environmental stresses. For this reason, a systematic review was conducted based on the scientific literature published in chicory during 1980-2023. Based on the results obtained from the meta-analysis, we created two consensus maps capable of supporting marker-assisted breeding (MAB) and marker-assisted selection (MAS) programs. By taking advantage of the recently released genome of C. intybus, we built a 639 molecular marker-based consensus map collecting all the available mapped and unmapped SNP and SSR loci available for this species. In the following section, after summarizing and discussing all the genes investigated in chicory and related to traits of interest such as reproductive barriers, sesquiterpene lactone biosynthesis, inulin metabolism and stress response, we produced a second map encompassing 64 loci that could be useful for MAS purposes. With the advent of omics technologies, molecular data chaos (namely, the situation where the amount of molecular data is so complex and unmanageable that their use becomes challenging) is becoming far from a negligible issue. In this review, we have therefore tried to contribute by standardizing and organizing the molecular data produced thus far in chicory to facilitate the work of breeders.

Industrial chicory genome gives insights into the molecular timetable of anther development and male sterility

Industrial chicory (Cichorium intybus var. sativum) is a biannual crop mostly cultivated for extraction of inulin, a fructose polymer used as a dietary fiber. F1 hybrid breeding is a promising breeding strategy in chicory but relies on stable male sterile lines to prevent self-pollination. Here, we report the assembly and annotation of a new industrial chicory reference genome. Additionally, we performed RNA-Seq on subsequent stages of flower bud development of a fertile line and two cytoplasmic male sterile (CMS) clones. Comparison of fertile and CMS flower bud transcriptomes combined with morphological microscopic analysis of anthers, provided a molecular understanding of anther development and identified key genes in a range of underlying processes, including tapetum development, sink establishment, pollen wall development and anther dehiscence. We also described the role of phytohormones in the regulation of these processes under normal fertile flower bud development. In parallel, we evaluated which processes are disturbed in CMS clones and could contribute to the male sterile phenotype. Taken together, this study provides a state-of-the-art industrial chicory reference genome, an annotated and curated candidate gene set related to anther development and male sterility as well as a detailed molecular timetable of flower bud development in fertile and CMS lines.

MIK2 is a candidate gene of the S-locus for sporophytic self-incompatibility in chicory (Cichorium intybus, Asteraceae)

The Cichorium genus offers a unique opportunity to study the sporophytic self-incompatibility (SSI) system, being composed of species characterized by highly efficient self-incompatibility (e.g., C. intybus) and complete self-compatibility (e.g., C. endivia). To this end, the chicory genome was used to map seven previously identified SSI locus-associated markers. The region containing the S-locus was therefore restricted to an ~4 M bp window on chromosome 5. Among the genes predicted in this region, MDIS1 INTERACTING RECEPTOR LIKE KINASE 2 (ciMIK2) was particularly promising as a candidate for SSI. Its ortholog in Arabidopsis (atMIK2) is involved in pollen-stigma recognition reactions, and its protein structure is similar to that of S-receptor kinase (SRK), a key component of the SSI system in the Brassica genus. The amplification and sequencing of MIK2 in chicory and endive accessions revealed two contrasting scenarios. In C. endivia, MIK2 was fully conserved even when comparing different botanical varieties (i.e., smooth and curly endive). In C. intybus, 387 polymorphic positions and 3 INDELs were identified when comparing accessions of different biotypes all belonging to the same botanical variety (i.e., radicchio). The polymorphism distribution throughout the gene was uneven, with hypervariable domains preferentially localized in the LRR-rich extracellular region, putatively identified as the receptor domain. The gene was hypothesized to be under positive selection, as the nonsynonymous mutations were more than double the synonymous ones (dN/dS = 2.17). An analogous situation was observed when analyzing the first 500 bp of the MIK2 promoter: no SNPs were observed among the endive samples, whereas 44 SNPs and 6 INDELs were detected among the chicory samples. Further analyses are needed to confirm the role of MIK2 in SSI and to demonstrate whether the 23 species-specific nonsynonymous SNPs in the CDS and/or the species-specific 10 bp-INDEL found in a CCAAT box region of the promoter are responsible for the contrasting sexual behaviors of chicory and endive.

Insights into the convergent evolution of fructan biosynthesis in angiosperms from the highly characteristic chicory genome

Fructans in angiosperms play essential roles in physiological functions and environmental adaptations. As a major source of industrial fructans (especially inulin-type), chicory (Cichorium intybus L.) is a model species for studying fructan biosynthesis. However, the genes underlying this process and their evolutionary history in angiosperms remain elusive. We combined multiple sequencing technologies to assemble and annotate the chicory genome and scan its (epi)genomic features, such as genomic components, DNA methylation, and three-dimensional (3D) structure. We also performed a comparative genomics analysis to uncover the associations between key traits and gene families. We achieved a nearly complete chicory genome assembly and found that continuous bursts of a few highly active retrotransposon families largely shaped the (epi)genomic characteristics. The highly methylated genome with its unique 3D structure potentially influences critical biological processes. Our comprehensive comparative genomics analysis deciphered the genetic basis for the rich sesquiterpene content in chicory and indicated that the fructan-accumulating trait resulted from convergent evolution in angiosperms due to shifts in critical sites of fructan-active enzymes. The highly characterized chicory genome provides insight into Asteraceae evolution and fructan biosynthesis in angiosperms.

Pipeline to Design Inbred Lines and F1 Hybrids of Leaf Chicory (Radicchio) Using Male Sterility and Genotyping-by-Sequencing

Chicory, a horticultural crop cultivated worldwide, presents many botanical varieties and local biotypes. Among these, cultivars of the Italian radicchio group of the pure species Cichorium intybus L. and its interspecific hybrids with Cichorium endivia L.-as the "Red of Chioggia" biotype-includes several phenotypes. This study uses a pipeline to address the marker-assisted breeding of F1 hybrids: it presents the genotyping-by-sequencing results of four elite inbred lines using a RADseq approach and an original molecular assay based on CAPS markers for screening mutants with nuclear male sterility in the radicchio of Chioggia. A total of 2953 SNP-carrying RADtags were identified and used to compute the actual estimates of homozygosity and overall genetic similarity and uniformity of the populations, as well as to determine their genetic distinctiveness and differentiation. Molecular data were further used to investigate the genomic distribution of the RADtags among the two Cichorium species, allowing their mapping in 1131 and 1071 coding sequences in chicory and endive, respectively. Paralleling this, an assay to screen the genotype at the male sterility locus Cims-1 was developed to discriminate wild-type and mutant alleles of the causative gene myb80-like. Moreover, a RADtag mapped close to this genomic region proved the potential application of this method for future marker-assisted selection tools. Finally, after combining the genotype information of the core collection, the best 10 individuals from each inbred line were selected to compute the observed genetic similarity as a measure of uniformity as well as the expected homozygosity and heterozygosity estimates scorable by the putative progenies derived from selfing (pollen parent) and full-sibling (seed parent) or pair-wise crossing (F1 hybrids). This predictive approach was conducted as a pilot study to understand the potential application of RADseq in the fine tuning of molecular marker-assisted breeding strategies aimed at the development of inbred lines and F1 hybrids in leaf chicory.

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.

The chromosome-level genome assembly of lance asiabell (Codonopsis lanceolata), a medicinal and vegetable plant of the Campanulaceae family

Codonopsis lanceolata (2n = 2x = 16) belongs to the Campanulaceae family and is a valuable medicinal and vegetable plant primarily found in East Asia. Several studies have demonstrated its excellent pharmacological effects, for example in bronchial treatment. However, genomic information of C. lanceolata is scarce, hindering studies on crop improvement of the species. Here, we report a high-quality chromosome-level genome assembly of C. lanceolata based on a hybrid method using Nanopore long-read, Illumina short-read, and Hi-C data. The assembled genome was completed as 1,273 Mb (84.5% of the estimated genome size), containing eight pseudo-chromosomes, ranging from 101.3 to 184.3 Mb. The genome comprised of 71.3% repeat sequences and 46,005 protein-coding genes, of which 85.7% genes were functionally annotated. Completeness of the assembled genome and genes was assessed to be 97.5% and 90.4%, respectively, by Benchmarking Universal Single-Copy Orthologs analysis. Phylogenetic and synteny analysis revealed that C. lanceolata was closely related to Platycodon grandiflorus in the Campanulaceae family. Gene family evolution revealed significant expansion of related genes involved in saponin biosynthesis in the C. lanceolata genome. This is the first reference genome reported for C. lanceolata. The genomic data produced in this study will provide essential information for further research to improve this medicinal plant and will broaden the understanding of the Campanulaceae family.

EndHiC: assemble large contigs into chromosome-level scaffolds using the Hi-C links from contig ends

BACKGROUND

The application of PacBio HiFi and ultra-long ONT reads have enabled huge progress in the contig-level assembly, but it is still challenging to assemble large contigs into chromosomes with available Hi-C scaffolding tools, which count Hi-C links between contigs using the whole or a large part of contig regions. As the Hi-C links of two adjacent contigs concentrate only at the neighbor ends of the contigs, larger contig size will reduce the power to differentiate adjacent (signal) and non-adjacent (noise) contig linkages, leading to a higher rate of mis-assembly.

RESULTS

We design and develop a novel Hi-C based scaffolding tool EndHiC, which is suitable to assemble large contigs into chromosomal-level scaffolds. The core idea behind EndHiC, which distinguishes it from other Hi-C scaffolding tools, is using Hi-C links only from the most effective regions of contig ends. By this way, the signal neighbor contig linkages and noise non-neighbor contig linkages are separated more clearly. Benefiting from the increased signal to noise ratio, the reciprocal best requirement, as well as the robustness evaluation, EndHiC achieves higher accuracy for scaffolding large contigs compared to existing tools. EndHiC has been successfully applied in the Hi-C scaffolding of simulated data from human, rice and Arabidopsis, and real data from human, great burdock, water spinach, chicory, endive, yacon, and Ipomoea cairica, suggesting that EndHiC can be applied to a broad range of plant and animal genomes.

CONCLUSIONS

EndHiC is a novel Hi-C scaffolding tool, which is suitable for scaffolding of contig assemblies with contig N50 size near or over 10 Mb and N90 size near or over 1 Mb. EndHiC is efficient both in time and memory, and it is interface-friendly to the users. As more genome projects have been launched and the contig continuity constantly improved, we believe EndHiC has the potential to make a great contribution to the genomics field and liberate the scientists from labor-intensive manual curation works.

Chromosome-level genome of a leaf vegetable Glebionis coronaria provides insights into the biosynthesis of monoterpenoids contributing to its special aroma

Glebionis coronaria is a popular vegetable with special aroma and a medical plant in East Asia and Mediterranean, but its biological studies and breeding have been hindered by the lack of reference genome. Here, we present a chromosome-level reference genome of G. coronaria, with assembled genome size of 6.8 Gb, which is the largest among all the published genomes of diploid Asteraceae species. The large genome size of G. coronaria is mainly caused by the recent widespread explosions of long-terminal-repeat retrotransposons. Analyses of macro-synteny and synonymous mutation rate distribution indicate that the G. coronaria genome experienced a whole-genome triplication at 40-45 million years ago, shared with all Asteraceae species. In subtribe Artemisiinae, Glebionis arose before the divergence of Chrysanthemum from Artemisia, and Glebionis species evolved much faster than Chrysanthemum and Artemisia species. In G. coronaria, the synthesis genes of monoterpenoids 8-oxocitronellyl enol and isopiperitenone were expanded, and the higher expressions of these expanded genes in leaves and stems may contribute to its special aroma. The G. coronaria genomic resources will promote the evolution studies of Asteraceae, the metabolism mechanism studies of bioactive compounds, and the breeding improvement of agronomic traits in G. coronaria.

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.