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Senna tora is a widely used medicinal plant. Its health benefits have been attributed to the large quantity of anthraquinones, but how they are made in plants remains a mystery. To identify the genes responsible for plant anthraquinone biosynthesis, we reveal the genome sequence of S. tora at the chromosome level with 526 Mb (96%) assembled into 13 chromosomes. Comparison among related plant species shows that a chalcone synthase-like (CHS-L) gene family has lineage-specifically and rapidly expanded in S. tora . Combining genomics, transcriptomics, metabolomics, and biochemistry, we identify a CHS-L gene contributing to the biosynthesis of anthraquinones. The S. tora reference genome will accelerate the discovery of biologically active anthraquinone biosynthesis pathways in medicinal plants. Anthraquinones are aromatic polyketides and have been used for treating various diseases, but the biosynthetic pathway is unclear. Here, the authors assemble the genome of an anthraquinone-producing medicinal plant Senna tora and show the evidences that CHS-like genes may be involved in anthraquinone biosynthesis.

Tandem repeats can occupy a large portion of plant genomes and can either cause or result from chromosomal rearrangements, which are important drivers of dysploidy-mediated karyotype evolution and speciation. To understand the contribution of tandem repeats in shaping the extant Senna tora dysploid karyotype, we analyzed the composition and abundance of tandem repeats in the S. tora genome and compared the chromosomal distribution of these repeats between S. tora and a closely related euploid, Senna occidentalis . Using a read clustering algorithm, we identified the major S. tora tandem repeats and visualized their chromosomal distribution by fluorescence in situ hybridization. We identified eight independent repeats covering ~85 Mb or ~12% of the S. tora genome. The unit lengths and copy numbers had ranges of 7–5,833 bp and 325–2.89 × 10 6 , respectively. Three short duplicated sequences were found in the 45S rDNA intergenic spacer, one of which was also detected at an extra-NOR locus. The canonical plant telomeric repeat (TTTAGGG) n was also detected as very intense signals in numerous pericentromeric and interstitial loci. StoTR05_180, which showed subtelomeric distribution in Senna occidentalis , was predominantly pericentromeric in S. tora . The unusual chromosomal distribution of tandem repeats in S. tora not only enabled easy identification of individual chromosomes but also revealed the massive chromosomal rearrangements that have likely played important roles in shaping its dysploid karyotype.

Background Schisandra chinensis , an ancient member of the most basal angiosperm lineage which is known as the ANITA, is a fruit-bearing vine with the pharmacological effects of a multidrug system, such as antioxidant, anti-inflammatory, cardioprotective, neuroprotective, anti-osteoporosis effects. Its major bioactive compound is represented by lignans such as schisandrin. Molecular characterization of lignan biosynthesis in S. chinensis is of great importance for improving the production of this class of active compound. However, the biosynthetic mechanism of schisandrin remains largely unknown. Results To understand the potential key catalytic steps and their regulation of schisandrin biosynthesis, we generated genome-wide transcriptome data from three different tissues of S. chinensis cultivar Cheongsoon, including leaf, root, and fruit, via long- and short-read sequencing technologies. A total of 132,856 assembled transcripts were generated with an average length of 1.9 kb and high assembly completeness. Overall, our data presented effective, accurate gene annotation in the prediction of functional pathways. In particular, the annotation revealed the abundance of transcripts related to phenylpropanoid biosynthesis. Remarkably, transcriptome profiling during fruit development of S. chinensis cultivar Cheongsoon revealed that the phenylpropanoid biosynthetic pathway, specific to coniferyl alcohol biosynthesis, showed a tendency to be upregulated at the postfruit development stage. Further the analysis also revealed that the pathway forms a transcriptional network with fruit ripening-related genes, especially the ABA signaling-related pathway. Finally, candidate unigenes homologous to isoeugenol synthase 1 ( IGS1 ) and dirigent-like protein ( DIR ), which are subsequently activated by phenylpropanoid biosynthesis and thus catalyze key upstream steps in schisandrin biosynthesis, were identified. Their expression was increased at the postfruit development stage, suggesting that they may be involved in the regulation of schisandrin biosynthesis in S. chinensis . Conclusions Our results provide new insights into the production and accumulation of schisandrin in S. chinensis berries and will be utilized as a valuable transcriptomic resource for improving the schisandrin content.

Humic acid (HA) is composed of a complex supramolecular association and is produced by humification of organic matters in soil environments. HA not only improves soil fertility, but also stimulates plant growth. Although numerous bioactivities of HA have been reported, the molecular evidences have not yet been elucidated. Here, we performed transcriptomic analysis to identify the HA-prompted molecular mechanisms in Arabidopsis. Gene ontology enrichment analysis revealed that HA up-regulates diverse genes involved in the response to stress, especially to heat. Heat stress causes dramatic induction in unique gene families such as Heat-Shock Protein ( HSP ) coding genes including HSP101 , HSP81.1 , HSP26.5 , HSP23.6 , and HSP17.6A . HSPs mainly function as molecular chaperones to protect against thermal denaturation of substrates and facilitate refolding of denatured substrates. Interestingly, wild-type plants grown in HA were heat-tolerant compared to those grown in the absence of HA, whereas Arabidopsis HSP101 null mutant ( hot1 ) was insensitive to HA. We also validated that HA accelerates the transcriptional expression of HSPs. Overall, these results suggest that HSP101 is a molecular target of HA promoting heat-stress tolerance in Arabidopsis. Our transcriptome information contributes to understanding the acquired genetic and agronomic traits by HA conferring tolerance to environmental stresses in plants.

Senna tora is an annual herb with rich source of anthraquinones that have tremendous pharmacological properties. However, there is little mention of genetic information for this species, especially regarding the biosynthetic pathways of anthraquinones. To understand the key genes and regulatory mechanism of anthraquinone biosynthesis pathways, we performed spatial and temporal transcriptome sequencing of S. tora using short RNA sequencing (RNA-Seq) and long-read isoform sequencing (Iso-Seq) technologies, and generated two unigene sets composed of 118,635 and 39,364, respectively. A comprehensive functional annotation and classification with multiple public databases identified array of genes involved in major secondary metabolite biosynthesis pathways and important transcription factor (TF) families (MYB, MYB-related, AP2/ERF, C2C2-YABBY, and bHLH). Differential expression analysis indicated that the expression level of genes involved in anthraquinone biosynthetic pathway regulates differently depending on the degree of tissues and seeds development. Furthermore, we identified that the amount of anthraquinone compounds were greater in late seeds than early ones. In conclusion, these results provide a rich resource for understanding the anthraquinone metabolism in S. tora.

The family Schisandraceae is a basal angiosperm plant group distributed in East and Southeast Asia and includes many medicinal plant species such as Schisandra chinensis . In this study, mitochondrial genomes (mitogenomes) of two species, Schisandra repanda and Kadsura japonica , in the family were characterized through de novo assembly using sequencing data obtained with Oxford Nanopore and Illumina sequencing technologies. The mitogenomes of S. repanda were assembled into one circular contig (571,107 bp) and four linear contigs (10,898–607,430 bp), with a total of 60 genes: 38 protein-coding genes (PCGs), 19 tRNA genes, and 3 rRNA genes. The mitogenomes of K. japonica were assembled into five circular contigs (211,474–973,503 bp) and three linear contigs (8,010–72,712 bp), with a total of 66 genes: 44 PCGs, 19 tRNA genes, and 3 rRNA genes. The mitogenomes of the two species had complex structural features with high repeat numbers and chloroplast-derived sequences, as observed in other plant mitogenomes. Phylogenetic analysis based on PCGs revealed the taxonomical relationships of S. repanda and K. japonica with other species from Schisandraceae. Finally, molecular markers were developed to distinguish between S. repanda , K. japonica , and S. chinensis on the basis of InDel polymorphisms present in the mitogenomes. The mitogenomes of S. repanda and K. japonica will be valuable resources for molecular and taxonomic studies of plant species that belong to the family Schisandraceae.

Wounds in tissues provide a pathway of entry for pathogenic fungi and bacteria in plants. Plants respond to wounding by regulating the expression of genes involved in their defense mechanisms. To analyze this response, we investigated the defense-related genes induced by wounding in the leaves of Senna tora using RNA sequencing. The genes involved in jasmonate and ethylene biosynthesis were strongly induced by wounding, as were a large number of genes encoding transcription factors such as ERFs, WRKYs, MYBs, bHLHs, and NACs. Wounding induced the expression of genes encoding pathogenesis-related (PR) proteins, such as PR-1, chitinase, thaumatin-like protein, cysteine proteinase inhibitor, PR-10, and plant defensin. Furthermore, wounding led to the induction of genes involved in flavonoid biosynthesis and the accumulation of kaempferol and quercetin in S. tora leaves. All these genes were expressed systemically in leaves distant from the wound site. These results demonstrate that mechanical wounding can lead to a systemic defense response in the Caesalpinioideae, a subfamily of the Leguminosae. In addition, a co-expression analysis of genes induced by wounding provides important information about the interactions between genes involved in plant defense responses.

Bellflower is an edible ornamental gardening plant in Asia. For predicting the flower color in bellflower plants, a transcriptome-wide approach based on machine learning, transcriptome, and genotyping chip analyses was used to identify SNP markers. Six machine learning methods were deployed to explore the classification potential of the selected SNPs as features in two datasets, namely training (60 RNA-Seq samples) and validation (480 Fluidigm chip samples). SNP selection was performed in sequential order. Firstly, 96 SNPs were selected from the transcriptome-wide SNPs using the principal compound analysis (PCA). Then, 9 among 96 SNPs were later identified using the Random forest based feature selection method from the Fluidigm chip dataset. Among six machines, the random forest (RF) model produced higher classification performance than the other models. The 9 SNP marker candidates selected for classifying the flower color classification were verified using the genomic DNA PCR with Sanger sequencing. Our results suggest that this methodology could be used for future selection of breeding traits even though the plant accessions are highly heterogeneous.

Adlay (Coix lacryma-jobi) is a tropical grass that has long been used in traditional Chinese medicine and is known for its nutritional benefits. Recent studies have shown that vitamin E compounds in adlay protect against chronic diseases such as cancer and heart disease. However, the molecular basis of adlay's health benefits remains unknown. Here, we generated adlay gene sets by de novo transcriptome assembly using long-read isoform sequencing (Iso-Seq) and short-read RNA-Sequencing (RNA-Seq). The gene sets obtained from Iso-seq and RNA-seq contained 31,177 genes and 57,901 genes, respectively. We confirmed the validity of the assembled gene sets by experimentally analyzing the levels of prolamin and vitamin E biosynthesis-associated proteins in adlay plant tissues and seeds. We compared the screened adlay genes with known gene families from closely related plant species, such as rice, sorghum and maize. We also identified tissue-specific genes from the adlay leaf, root, and young and mature seed, and experimentally validated the differential expression of 12 randomly-selected genes. Our study of the adlay transcriptome will provide a valuable resource for genetic studies that can enhance adlay breeding programs in the future.

, also called adlay or Job's tears, is an annual herbal plant belonging to the Poaceae family that has been cultivated as a cereal and medicinal crop in Asia. Despite its importance, however, genomic resources for better understanding this plant species at the molecular level and informing improved breeding strategies remain limited. To address this, we generated a draft genome of the variety (soft-shelled adlay) Korean cultivar, Johyun, by assembly, using PacBio and Illumina sequencing data. A total of 3,362 scaffold sequences, 1.28 Gb in length, were assembled, representing 82.1% of the estimated genome size (1.56 Gb). Genome completeness was confirmed by the presence of 91.4% of the BUSCO angiosperm genes and mapping ratio of 98.3% of Illumina paired-end reads. We found that approximately 77.0% of the genome is occupied by repeat sequences, most of which are and -type retrotransposons, and evidence-based genome annotation predicts 39,574 protein-coding genes, 85.5% of which were functionally annotated. We further predict that soft-shelled adlay diverged from a common ancestor with sorghum 9.0-11.2 MYA. Transcriptome profiling revealed 3,988 genes that are differentially expressed in seeds relative to other tissues, of which 1,470 genes were strongly up-regulated in seeds and the most enriched Gene Ontology terms were assigned to carbohydrate and protein metabolism. In addition, we identified 76 storage protein genes including 18 seed-specific coixin genes and 13 candidate genes involved in biosynthesis of benzoxazinoids (BXs) including coixol, a unique BX compound found in species. The characterization of those genes can further our understanding of unique traits of soft-shelled adlay, such as high seed protein content and medicinal compound biosynthesis. Taken together, our genome sequence data will provide a valuable resource for molecular breeding and pharmacological study of this plant species.