Phylogenomics, phylogeography and germplasms authentication of the Rheum palmatum complex based on complete chloroplast genomes.

As a traditional Chinese medicine, rhubarb is used to treat several diseases such as severe acute pancreatitis, sepsis and chronic renal failure. However, few studies focused on the authentication of germplasm for the Rheum palmatum complex, and no studies have been conducted to elucidate the evolutionary history of the R. palmatum complex using plastome datasets. Hence, we aim to develop the potential molecular markers to identify the elite germplasms of rhubarb and explore the divergence and biogeographic history of the R. palmatum complex based on the newly sequenced chloroplast genome datasets. Chloroplast genomes of thirty-five the R. palmatum complex germplasms were sequenced, and the length ranged from 160,858 to 161,204 bp. The structure, gene content and gene order were highly conserved across all genomes. Eight InDels and sixty-one SNPs loci could be used to authenticate the high-quality germplasms of rhubarb in specific areas. Phylogenetic analysis revealed that all rhubarb germplasms were clustered in the same clade with high bootstrap support values and Bayesian posterior probabilities. According to the molecular dating result, the intraspecific divergence of the complex occurred in the Quaternary, which might be affected by climatic fluctuation. The biogeography reconstruction indicated that the ancestor of the R. palmatum complex might originate from the Himalaya-Hengduan Mountains or/and Bashan-Qinling Mountains, and then spread to surrounding areas. Several useful molecular markers were developed to identify rhubarb germplasms, and our study will provide further understanding on speciation, divergence and biogeography of the R. palmatum complex.

Transcriptome profiles of yellowish-white and fuchsia colored flowers in the Rheum palmatum complex reveal genes related to color polymorphism.

Flower color variation is ubiquitous in many plant species, and several studies have been conducted to elucidate the underlying molecular mechanism. There are two flower color variants (yellowish-white and fuchsia) in the Rheum palmatum complex, however, few studies have investigated this phenomenon. Here, we used transcriptome sequencing of the two color variants to shed light on the molecular and biochemical basis for these color morphs. Comparison of the two transcriptomes identified 9641 differentially expressed unigenes (DEGs), including 6477 up-regulated and 3163 down-regulated genes. Functional analyses indicated that several DEGs were related to the anthocyanin biosynthesis pathway, and the expression profiles of these DEGs were coincident with the qRT-PCR validation results, indicating that expression levels of structural genes have a profound effect on the color variation in the R. palmatum complex. Our results suggested that the interaction of transcription factors (MYB, bHLH and WRKY) also regulated the anthocyanin biosynthesis in the R. palmatum complex. Estimation of selection pressures using the dN/dS ratio showed that 1106 pairs of orthologous genes have undergone positive selection. Of these positively selected genes, 21 were involved in the anthocyanin biosynthetic pathway, indicating that they may encode the proteins for structural alteration and affect flower color in the R. palmatum complex.

Comparative Transcriptome Analyses of Different Rheum officinale Tissues Reveal Differentially Expressed Genes Associated with Anthraquinone, Catechin, and Gallic Acid Biosynthesis.

Rheum officinale Baill. is an important traditional Chinese medicinal herb, its dried roots and rhizomes being widely utilized to cure diverse diseases. However, previous studies mainly focused on the active compounds and their pharmacological effects, and the molecular mechanism underlying the biosynthesis of these ingredients in R. officinale is still elusive. Here, we performed comparative transcriptome analyses to elucidate the differentially expressed genes (DEGs) in the root, stem, and leaf of R. officinale. A total of 236,031 unigenes with N50 of 769 bp was generated, 136,329 (57.76%) of which were annotated. A total of 5884 DEGs was identified after the comparative analyses of different tissues; 175 and 126 key enzyme genes with tissue-specific expression were found in the anthraquinone, catechin/gallic acid biosynthetic pathway, respectively, and some of these key enzyme genes were verified by qRT-PCR. The phylogeny of the PKS III family in Polygonaceae indicated that probably only PL_741 PKSIII1, PL_11549 PKSIII5, and PL_101745 PKSIII6 encoded PKSIII in the polyketide pathway. These results will shed light on the molecular basis of the tissue-specific accumulation and regulation of secondary metabolites in R. officinale, and lay a foundation for the future genetic diversity, molecular assisted breeding, and germplasm resource improvement of this essential medicinal plant.

Kinetic cellular phenotypic profiling: prediction, identification, and analysis of bioactive natural products.

Natural products have always been a major source of therapeutic agents; however, the development of traditional herbal products has been currently hampered by the lack of analytic methods suitable for both high-throughput screening and evaluating the mechanism of action. Cellular processes such as proliferation, apoptosis, and toxicity are well-orchestrated in real time. Monitoring these events and their perturbation by natural products can provide high-rich information about cell physiological relevancies being involved. Here, we report a novel cell-based phenotypic profiling strategy that uses electronic impedance readouts for real-time monitoring of cellular responses to traditional Chinese medicines (TCMs). The utility of this approach was used to screen natural herbs that have been historically documented to cure human diseases and that have been classified into seven clusters based on their mechanisms of action. The results suggest that herbal medicines with similar cellular mechanisms produce similar time/dose-dependent cell response profiles (TCRPs). By comparing the TCRPs produced by the Chinese medicinal Cordyceps sinensis with similar TCRPs of chemical compounds, we explored the potential use of herbal TCRPs for predicting cellular mechanisms of action, herbal authentications, and bioactive identification. Additionally, we further compared this novel TCRP technology with high-performance liquid chromatography (HPLC)-based methods for herbal origin-tracing authentication and identification of bioactive ingredients. Together, our findings suggest that using TCRP as an alternative to existing spectroscopic techniques can allow us to analyze natural products in a more convenient and physiologically relevant manner.