Phytotherapeutic potential against MRSA: mechanisms, synergy, and therapeutic prospects.

BACKGROUND: Rising resistance to antimicrobials, particularly in the case of methicillin-resistant Staphylococcus aureus (MRSA), represents a formidable global health challenge. Consequently, it is imperative to develop new antimicrobial solutions. This study evaluated 68 Chinese medicinal plants renowned for their historical applications in treating infectious diseases. METHODS: The antimicrobial efficacy of medicinal plants were evaluated by determining their minimum inhibitory concentration (MIC) against MRSA. Safety profiles were assessed on human colorectal adenocarcinoma (Caco-2) and hepatocellular carcinoma (HepG2) cells. Mechanistic insights were obtained through fluorescence and transmission electron microscopy (FM and TEM). Synergistic effects with vancomycin were investigated using the Fractional Inhibitory Concentration Index (FICI). RESULTS: Rheum palmatum L., Arctium lappa L. and Paeonia suffructicosaas Andr. have emerged as potential candidates with potent anti-MRSA properties, with an impressive low MIC of 7.8 µg/mL, comparable to the 2 µg/mL MIC of vancomycin served as the antibiotic control. Crucially, these candidates demonstrated significant safety profiles when evaluated on Caco-2 and HepG2 cells. Even at 16 times the MIC, the cell viability ranged from 83.3% to 95.7%, highlighting their potential safety. FM and TEM revealed a diverse array of actions against MRSA, such as disrupting the cell wall and membrane, interference with nucleoids, and inducing morphological alterations resembling pseudo-multicellular structures in MRSA. Additionally, the synergy between vancomycin and these three plant extracts was evident against MRSA (FICI < 0.5). Notably, aqueous extract of R. palmatum at 1/4 MIC significantly reduced the vancomycin MIC from 2 µg/mL to 0.03 µg/mL, making a remarkable 67-fold decrease. CONCLUSIONS: This study unveil new insights into the mechanistic actions and pleiotropic antibacterial effectiveness of these medicinal plants against resistant bacteria, providing robust evidence for their potential use as standalone or in conjunction with antibiotics, to effectively combat antimicrobial resistance, particularly against MRSA.

A chromosome-level genome reveals genome evolution and molecular basis of anthraquinone biosynthesis in Rheum palmatum.

BACKGROUND: Rhubarb is one of common traditional Chinese medicine with a diverse array of therapeutic efficacies. Despite its widespread use, molecular research into rhubarb remains limited, constraining our comprehension of the geoherbalism. RESULTS: We assembled the genome of Rheum palmatum L., one of the source plants of rhubarb, to elucidate its genome evolution and unpack the biosynthetic pathways of its bioactive compounds using a combination of PacBio HiFi, Oxford Nanopore, Illumina, and Hi-C scaffolding approaches. Around 2.8 Gb genome was obtained after assembly with more than 99.9% sequences anchored to 11 pseudochromosomes (scaffold N50 = 259.19 Mb). Transposable elements (TE) with a continuous expansion of long terminal repeat retrotransposons (LTRs) is predominant in genome size, contributing to the genome expansion of R. palmatum. Totally 30,480 genes were predicted to be protein-coding genes with 473 significantly expanded gene families enriched in diverse pathways associated with high-altitude adaptation for this species. Two successive rounds of whole genome duplication event (WGD) shared by Fagopyrum tataricum and R. palmatum were confirmed. We also identified 54 genes involved in anthraquinone biosynthesis and other 97 genes entangled in flavonoid biosynthesis. Notably, RpALS emerged as a compelling candidate gene for the octaketide biosynthesis after the key residual screening. CONCLUSION: Overall, our findings offer not only an enhanced understanding of this remarkable medicinal plant but also pave the way for future innovations in its genetic breeding, molecular design, and functional genomic studies.

Transcriptomic divergence of the Rheum palmatum complex derived from top-geoherb and non-geoherb areas provides the insights into geoherbalism properties of rhubarb.

Geoherb usually represents high-quality medicinal herbs with better clinical therapeutic effects, and elucidating the geoherbalism is essential for the quality improvement of traditional Chinese Medicine. However, few researches were conducted to clarify the geoherbalism based on a large scale of transcriptomics. In the present study, we compared the transcriptomes of Rheum palmatum complex derived from top-geoherb and non-geoherb areas to show the geoherbalism properties of rhubarb. A total of 412.32 Gb clean reads were obtained with unigene numbers of 100,615 after assembly. Based on the obtained transcriptome datasets, key enzyme-encoding genes involved in the anthraquinones biosynthesis were also obtained. We also found that 21 anthraquinone-related unigenes were differentially expressed between two different groups, and some of these DEGs were correlated to the content accumulation of five free anthraquinones, indicating that the gene expression profiles may promote the geoherbalism formation of rhubarb. In addition, the selective pressure analyses indicated that most paired orthologous genes between these two groups were subject to negative selection, and only a low proportion of orthologs under positive selection were detected. Functional annotation analyses indicated that these positive-selected genes related to the functions such as gene expression, substance transport, stress response and metabolism, indicating that discrepant environment also enhanced the formation of geoherbalism. Our study not only provided insights for the genetic mechanism of geoherbalism of rhubarb, but also laid more genetic cues for the future rhubarb germplasms improvement and utilization.

Application of two-dimensional reversed phase countercurrent chromatography × high-performance liquid chromatography to bioactivity-guided screening and isolation of α-glucosidase inhibitors from Rheum palmatum L.

In the present work, comprehensive two-dimensional reversed-phase countercurrent chromatography × reversed-phase liquid chromatography combined (2D RPCCC × RPLC) with 2D microfraction bioactive evaluation was employed to screen and isolate α-glucosidase inhibitors from Rheum palmatum L. Countercurrent chromatography was employed to improve 2D analysis and preparative separation. A selected biphasic solvent system composed of petroleum ether/ethyl acetate/methanol/water with gradient elution mode was used for the first dimension RPCCC separation (1D RPCCC). Solid-phase extraction was applied to eliminate interfering polar compounds before the second dimension analysis (2D RPLC). 76 components were shown in 2D contour plot in UV 280 nm. 11 Candidates were separated by a scaled-up CCC and identified by 1H NMR and 13C NMR, including anthraquinones, flavonoids, stilbenes, phenols, and glucoside derivatives. In addition, it was found that two components, resveratrol-4'-O-(6″-galloyl)glucoside (36) and lyciumaside (43) were identified as natural α-glucosidase inhibitors in Rheum palmatum L. for the first time.

Comparative transcriptome analysis and identification of candidate R2R3-MYB genes involved in anthraquinone biosynthesis in Rheum palmatum L.

BACKGROUND: Rheum palmatum L. has important medicinal value because it contains biologically active anthraquinones. However, the key genes and TFs involved in anthraquinone biosynthesis and regulation in R. palmatum remain unclear. METHODS: Based on full length transcriptome data, in this study, we screened the differentially expressed genes in the anthraquinone biosynthesis pathway. The R2R3-MYB family genes of R. palmatum were systematically identified based on full-length transcriptome sequencing followed by bioinformatics analyses. The correlation analysis was carried out by using co-expression analysis, protein interaction analysis, and real-time fluorescence quantitative analysis after MeJA treatment. The RpMYB81 and RpMYB98 genes were amplified by RT-PCR, and their subcellular localization and self-activation characteristics were analyzed. RESULTS: Comparative transcriptome analysis results revealed a total of 3525 upregulated and 6043 downregulated DEGs in the CK versus MeJA group; 28 DEGs were involved in the anthraquinone pathway. Eleven CHS genes that belonged to the PKS family were differentially expressed and involved in anthraquinone biosynthesis. Twelve differentially expressed MYBs genes were found to be co-expressed and interact with CHS genes. Furthermore, 52 MYB genes were identified as positive regulators of anthraquinone biosynthesis and were further characterized. Three MYB genes including RpMYB81, RpMYB98, and RpMYB100 responded to MeJA treatment in R. palmatum, and the levels of these genes were verified by qRT-PCR. RpMYB81 was related to anthraquinone biosynthesis. RpMYB98 had an interaction with genes in the anthraquinone biosynthesis pathway. RpMYB81 and RpMYB98 were mainly localized in the nucleus. RpMYB81 had self-activation activity, while RpMYB98 had no self-activation activity. CONCLUSION: RpMYB81, RpMYB98, and RpMYB100 were significantly induced by MeJA treatment. RpMYB81 and RpMYB98 are located in the nucleus, and RpMYB81 has transcriptional activity, suggesting that it might be involved in the transcriptional regulation of anthraquinone biosynthesis in R. palmatum.

Efficient screening of pancreatic lipase inhibitors from Rheum palmatum by affinity ultrafiltration-high-performance liquid chromatography combined with high-resolution inhibition profiling.

INTRODUCTION: Pancreatic lipase is one of the most important key targets in the treatment of obesity. Inhibition of pancreatic lipase can effectively reduce lipid absorption and treat obesity and other related metabolic disorders. OBJECTIVES: The goal of this study is the efficient screening of pancreatic lipase inhibitors in the root and rhizome of Rheum palmatum using affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) combined with high-resolution inhibition profiling (HRIP). METHODS: Potential pancreatic lipase ligands and pancreatic lipase inhibitors in ethyl acetate fraction of R. palmatum were screened using AUF-HPLC and HRIP, respectively. All screened compounds were identified by HPLC- quadrupole time-of-flight (Q-TOF)/MS. Eight compounds were screened out by both AUF-HPLC and HRIP, and six compounds were screened out by either AUF-HPLC or HRIP alone. The pancreatic lipase inhibitory activities of all screened compounds were verified by enzyme inhibition assay and molecular docking. RESULTS: Five new potent pancreatic lipase inhibitors were discovered, namely procyanidin B5 3,3'-di-O-gallate (IC50 = 0.06 ± 0.01 µM), 1,6-di-O-galloyl-2-O-cinnamoyl-ß-D-glucoside (IC50 = 12.83 ± 0.67 µM), 1-O-(1,3,5-trihydroxy)phenyl-2-O-galloyl-6-O-cinnamoyl-ß-D-glucoside (IC50 = 17.84 ± 1.33 µM), 1,2-di-O-galloyl-6-O-cinnamoyl-ß-D-glucoside (IC50 = 18.39 ± 1.52 µM), and 4-(4'-hydroxyphenyl)-2-butanone-4'-O-ß-D-(2"-O-galloyl-6"-O-cinnamoyl)-glucoside (IC50 = 2.91 ± 0.40 µM). It was found that procyanidin B5 3,3'-di-O-gallate showed higher pancreatic lipase inhibitory activity than the positive control orlistat (IC50 = 0.12 ± 0.02 µM). CONCLUSION: The combination of affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) and high-resolution inhibition profiling (HRIP) could reduce the risk of false-negative screening and missed screening and could achieve more efficient screening of bioactive compounds in complex natural products.

Rheum palmatum L. and Salvia miltiorrhiza Bge. Alleviates Acute Pancreatitis by Regulating Th17 Cell Differentiation: An Integrated Network Pharmacology Analysis, Molecular Dynamics Simulation and Experimental Validation.

OBJECTIVE: To identify the core targets of Rheum palmatum L. and Salvia miltiorrhiza Bge., (Dahuang-Danshen, DH-DS) and the mechanism underlying its therapeutic efficacy in acute pancreatitis (AP) using a network pharmacology approach and validate the findings in animal experiments. METHODS: Network pharmacology analysis was used to elucidate the mechanisms underlying the therapeutic effects of DH-DS in AP. The reliability of the results was verified by molecular docking simulation and molecular dynamics simulation. Finally, the results of network pharmacology enrichment analysis were verified by immunohistochemistry, Western blot analysis and real-time quantitative PCR, respectively. RESULTS: Sixty-seven common targets of DH-DS in AP were identified and mitogen-activated protein kinase 3 (MAPK3), Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), protein c-Fos (FOS) were identified as core targets in the protein interaction (PPI) network analysis. Gene ontology analysis showed that cellular response to organic substance was the main functions of DH-DS in AP, and Kyoto Encyclopedia of Genes and Genomes analysis showed that the main pathway included Th17 cell differentiation. Molecular docking simulation confirmed that DH-DS binds with strong affinity to MAPK3, STAT3 and FOS. Molecular dynamics simulation revealed that FOS-isotanshinone II and STAT3-dan-shexinkum d had good binding capacity. Animal experiments indicated that compared with the AP model group, DH-DS treatment effectively alleviated AP by inhibiting the expression of interleukin-1ß, interleukin-6 and tumor necrosis factor-α, and blocking the activation of Th17 cell differentiation (P<0.01). CONCLUSION: DH-DS could inhibit the expression of inflammatory factors and protect pancreatic tissues, which would be functioned by regulating Th17 cell differentiation-related mRNA and protein expressions.

Antiviral, antioxidant, and anti-inflammatory activities of rhein against white spot syndrome virus infection in red swamp crayfish (Procambarus clarkii).

IMPORTANCE: Aquaculture is essential for ensuring global food security by providing a significant source of animal protein. However, the spread of the white spot syndrome virus (WSSV) has resulted in considerable economic losses in crustacean industries. In this study, we evaluated the antiviral activity of rhein, the primary bioactive component of Rheum palmatum L., against WSSV infection, and many pathological aspects of WSSV were also described for the first time. Our mechanistic studies indicated that rhein effectively arrested the replication of WSSV in crayfish by modulating innate immunity to inhibit viral gene transcription. Furthermore, we observed that rhein attenuated WSSV-induced oxidative and inflammatory stresses by regulating the expression of antioxidant and anti-inflammatory-related genes while enhancing innate immunity by reducing total protein levels and increasing phosphatase activity. Our findings suggest that rhein holds great promise as a potent antiviral agent for the prevention and treatment of WSSV in aquaculture.

In Silico Neuroprotective Effects of Specific Rheum palmatum Metabolites on Parkinson's Disease Targets.

Parkinson's disease (PD) is one of the large-scale health issues detrimental to human quality of life, and current treatments are only focused on neuroprotection and easing symptoms. This study evaluated in silico binding activity and estimated the stability of major metabolites in the roots of R. palmatum (RP) with main protein targets in Parkinson's disease and their ADMET properties. The major metabolites of RP were subjected to molecular docking and QSAR with α-synuclein, monoamine oxidase isoform B, catechol o-methyltransferase, and A2A adenosine receptor. From this, emodin had the greatest binding activity with Parkinson's disease targets. The chemical stability of the selected compounds was estimated using density functional theory analyses. The docked compounds showed good stability for inhibitory action compared to dopamine and levodopa. According to their structure-activity relationship, aloe-emodin, chrysophanol, emodin, and rhein exhibited good inhibitory activity to specific targets. Finally, mediocre pharmacokinetic properties were observed due to unexceptional blood-brain barrier penetration and safety profile. It was revealed that the major metabolites of RP may have good neuroprotective activity as an additional hit for PD drug development. Also, an association between redox-mediating and activities with PD-relevant protein targets was observed, potentially opening discussion on electrochemical mechanisms with biological functions.

Inhibitory effect of Bofutsushosan (Fangfengtongshengsan) extract on the absorption of fructose in rats and mice.

Bofutsushosan (BTS; fangfengtongshengsan in Chinese) is a formula in traditional Japanese Kampo and Chinese medicine comprising 18 crude drugs and used to treat obesity and metabolic syndrome. In our previous study, BTS boiling water extract inhibited the uptake of fructose absorbed via glucose transporter 5 into cultured cells. In this study, the inhibitory effect of BTS extract on the absorption of fructose from the intestine was investigated in vivo. The extract of BTS was orally administered to rats at doses equivalent to 25-fold of the daily dose for humans. One minute after sample administration, fructose was orally administered and blood samples were collected from the jugular vein 0.5, 1, 1.5, 2, and 4 h after the administration of fructose. The absorption of fructose from the intestine was significantly reduced by treatment with BTS extract, and this in vivo study reproduced previous in vitro results. Subsequently, the blood samples were collected from the portal vein 30 min after the oral administration of fructose in mice. BTS extract significantly reduced fructose absorption in mice, and compared the effect of modified BTS samples by removing one to several crude drugs from BTS. We found that the dried rhizome of Rheum palmatum (RR) significantly contributed to the inhibitory effect of BTS on fructose absorption. We found sennoside A to be the active ingredient of RR for the inhibition of fructose absorption, and that its effect almost saturated at a dose of 3 mg/kg. These results support the action mechanisms of BTS when used for the treatment of obesity in clinics and drug stores.

Synergistic Inhibiting Effect of Phytochemicals in Rheum palmatum on Tyrosinase Based on Metabolomics and Isobologram Analyses.

Tyrosinase (TYR) plays a key role in the enzymatic reaction that is responsible for a range of unwanted discoloration effects, such as food browning and skin hyperpigmentation. TYR inhibitors could, therefore, be candidates for skin care products that aim to repair pigmentation problems. In this study, we used a metabolomics approach combined with the isobologram analysis to identify anti-TYR compounds within natural resources, and evaluate their possible synergism with each other. Rheum palmatum was determined to be a model plant for observing the effect, of which seven extracts with diverse phytochemicals were prepared by way of pressurized solvent extraction. Each Rheum palmatum extract (RPE) was profiled using nuclear magnetic resonance spectroscopy and its activity of tyrosinase inhibition was evaluated. According to the orthogonal partial least square analysis used to correlate phytochemicals in RPE with the corresponding activity, the goodness of fit of the model (R2 = 0.838) and its predictive ability (Q2 = 0.711) were high. Gallic acid and catechin were identified as the active compounds most relevant to the anti-TYR effect of RPE. Subsequently, the activity of gallic acid and catechin were evaluated individually, and when combined in various ratios by using isobologram analysis. The results showed that gallic acid and catechin in the molar ratios of 9:5 and 9:1 exhibited a synergistic inhibition on TYR, with a combination index lower than 0.77, suggesting that certain combinations of these compounds may prove effective for use in cosmetic, pharmaceutical, and food industries.

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.

Rheum officinale and Salvia miltiorrhiza inhibit renal fibrosis via miR-21/PTEN/Akt signaling pathway in vitro and in vivo.

ETHNOPHARMACOLOGICAL RELEVANCE: As one of the main components of many famous Chinese herbal formulas, Rheum palmatum L. and Salvia miltiorhiza Bunge (RS) are extensively used to treat chronic kidney disease (CKD). RS has been proved to improve renal function and relieve renal fibrosis (RF), but the potential mechanism remains a mystery. AIM OF THE STUDY: The purpose of this study is to determine whether microRNA-21 (miR-21) is associated with RF progression, as well as whether RS protects against RF through miR-21/PTEN/AKT signaling. MATERIALS AND METHODS: (1) The rat model of RF was established using unilateral ureteral obstruction (UUO). After UUO surgery, miR-21 levels in plasma were detected by RT-PCR and RF scores were assessed by Masson's trichrome stain at days 3, 7, 14 and 21. The correlation analysis of the above two indexes was carried out by Spearman correlation analysis. (2) Human proximal tubular epithelial cells (HK-2) was transfected with miR-21 mimic and inhibitor, and then the levels of phosphatase and tensin homolog (PTEN) protein and mRNA were measured with Western blotting and RT-PCR, respectively. (3) TGF-ß (10 ng/mL) was added into HK-2 cells to induce fibrosis, followed by the intervention of RS-containing rat serum. PTEN and protein kinase-B (Akt) phosphorylation, as well as the expression of PTEN protein in HK-2 cells, were assessed by RT-PCR, Western blotting and immunofluorescence. (4) The rat models of RF were prepared by UUO and treated with RS. Serum creatinine and urea nitrogen levels were measured. RF score was determined by Masson's trichrome stain. RT-PCR was used to determine the expression of miR-21, PTEN, and Akt mRNA. Western blotting was used to determine the expression of PTEN and Akt proteins. RESULTS: A positive correlation was found between plasma miR-21 levels and RF scores of rats after UUO surgery at Days 3, 7, 14 and 21. It was confirmed that miR-21 targeted PTEN. RS drug-containing serum could rise the expression of PTEN and reduce Akt phosphorylation of HK-2 cells induced by TGF-ß. Moreover, RS drug-containing serum could increase PTEN expression and reduce Akt phosphorylation induced by miR-21 mimic in HK-2 cells. The rats treated with RS had significantly decreased serum creatinine and urea nitrogen levels and a lower RF score. RS also decreased miR-21 and Akt expressions, increased PTEN expression of UUO rats. CONCLUSION: There was a positive correlation between plasma miR-21 levels and RF scores. The inhibitory effect of RS on RF might be mediated by miR-21/PTEN/AKT signaling.

Integrated network pharmacology and DSS-induced colitis model to determine the anti-colitis effect of Rheum palmatum L. and Coptis chinensis Franch in granules.

ETHNOPHARMACOLOGICAL RELEVANCE: Rheum palmatum L. (RP) and Coptis chinensis Franch. (CC), frequently used as herbal pair (HP) in clinical practicing of traditional Chinese medicine, exerted predominate efficacies in colitis treatment. However, the mechanism of their synergism lacks scientific explanation. AIM OF THE STUDY: By integrating network pharmacology and DSS-induced colitis model, the anti-colitis effects and synergistic molecular mechanisms of RP-CC combination was determined. MATERIALS AND METHODS: In vivo study, mice were divided into control, model, RP, CC and RP-CC (low, middle, high) groups, 2.5% DSS was administrated to induce colitis for consecutive 7 days, subsequently, the therapeutic effects were evaluated from body weight changes, disease activity index (DAI), and pathological conditions. After determining the shared and exclusive targets of RP and CC, respectively by network pharmacology, CETSA, WB, and qPCR were utilized to verify the action modes of RP and CC on specific targets. RESULTS: Compared to RP or CC used alone, RP-CC combination can significantly protect colon tissues from inflammatory damage in a dose-dependent manner via remarkably alleviating DAI and colon shortening. Network pharmacological analysis suggested that AKT1 would be the core target for RP-CC synergism since these two herbs could simultaneously but non-competitively bind to AKT1 at different sits. Furthermore, RP and CC could also influencing HIF and MAPK pathways, respectively, these additional actions attribute to more optimizing effectiveness towards colitis. CONCLUSION: In contrast to the mild therapeutic effects of RP or CC individually, RP-CC herb pair could exert strong and synergistic effects in treatment of colitis via non-competitive binding to AKT1 simultaneously, as well as exclusively influencing MAPK and HIF pathways. Our study not only provides the evidence for understanding the combined effect of RP and CC, but also brings up a new strategy and suggestive thoughts for the rationality of HP-based TCM formula.

Identification and analysis of R1-MYB gene family in Rheum palmatum L. based on full-length transcriptome sequencing / 药学学报

As one kind of v-myb avian myeloblastosis viral oncogene homolog (MYB) transcription factors, R1-MYB (MYB-related) family plays an important role in plant growth and development, as well as environmental stress and hormone signal transduction. In this study, R1-MYB family genes in Rheum palmatum L. were systematically screened based on full-length transcriptome sequencing analysis. Firstly, the physicochemical, protein domain and molecular evolution characteristics of the coding proteins were analyzed. Furthermore, the tissue expression levels of R1-MYB genes were analyzed by RNA-seq. We also investigated the expression pattern of RpMYB24 in response to various hormones and abiotic stresses. The results showed that a total of 49 R1-MYB genes were identified, which mainly encoded thermally stable hydrophilic proteins. Most of the deduced proteins were predicted to locate in nucleus. Each protein had a large proportion of random curl and α helix, and also had the W-type conserved amino acids which were the signature of MYB. R1-MYB family members were distributed in five subgroups, including circadian clock associated 1 (CCA1)-like, I-box (GATAAG)-like, CAPRICE (CPC)-like, telomere repeat binding factor (TRF)-like and TATA binding protein (TBP)-like, and the number of CCA1-like was the majority. RNA-seq revealed that 49 R1-MYB genes were differentially expressed in roots, rhizomes and leaves of R. palmatum, and the expression levels of 15 and 23 genes in roots and rhizomes were higher than those in leaves, respectively. RpMYB24 transcript was induced by abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA) treatment, and could also significantly respond to injury, low temperature and high temperature stresses except drought stress. This study systematically identified the R1-MYB family genes and their molecular characteristics, better for further gene functional validation, and then provide a scientific basis for the transcriptional regulation mechanism research into rhubarb quality formation.

Analysis of endophyte diversity of Rheum palmatum among different tissues and ages.

Rheum palmatum, a well-known Traditional Chinese Medicines (TCM), has been used for medical purposes for thousand years in China. However, endophyte diversity of R. palmatum among different tissues and ages is still not revealed. In this study, we used 16S and ITS amplicon sequencing and combined with PICRUSt and FUNGuild to compare endophyte diversity and ecological function among different tissues and ages of R. palmatum. The results showed that the diversity and OTUs (Operational taxonomic units) abundance of endophytic fungi and bacteria of R. palmatum differed among different tissues and ages. The predictive function analysis showed that metabolism was main function of endophytic bacteria in different tissue and year samples, while saprotroph was dominant trophic mode of endophytic fungi in different year samples. The dominant trophic modes of endophytic fungi were saprotroph, pathotroph-symbiotroph and symbiotroph, and relative abundances differed in the different tissue samples. Our results elucidated the comprehensive diversity and composition profiles of endophytes in different tissues and year of R. palmatum. Our data offered pivotal information to clarify the role of endophytes in the production of R. palmatum and its important metabolites.

Anti-Psoriatic Effect of Rheum palmatum L. and Its Underlying Molecular Mechanisms.

Psoriasis is a chronic, immune-mediated inflammatory skin disorder. Rheum palmatum L. is a common traditional medicinal herb with anti-inflammatory and immunomodulatory activities. This study aimed to investigate the anti-psoriatic effects of the ethanolic extract from R. palmatum L. (RPE) and its chemical constituents, as well as the mechanisms underlying their therapeutic significance. An imiquimod (IMQ)-induced psoriasis-like mouse model was used to examine the anti-psoriatic effect of RPE in vivo. Network pharmacological analysis was performed to investigate the potential targets and related pathways of the RPE components, including rhein, emodin, chrysophanol, aloe-emodin, and physcion. The anti-inflammatory effects and underlying mechanisms of these components were examined using in vitro models. Topical application of RPE alleviated psoriasis-like symptoms and reduced levels of inflammatory cytokines and proliferation markers in the skin. Network pharmacological analysis revealed that RPE components target 20 genes that are linked to psoriasis-related pathways, such as IL-17, MAPK, and TNF signaling pathways. Among the five components of RPE, rhein and emodin showed inhibitory effects on TNF-α and IL-17 production in EL-4 cells, attenuated the production of CXCL8, CXCL10, CCL20, and MMP9, and reduced proliferation in HaCaT cells. Chrysophanol, aloe-emodin, and physcion were less effective than rhein and emodin in suppressing inflammatory responses and keratinocyte proliferation. The effects of these compounds might occur through the inhibition of the ERK, STAT3, and NF-κB signaling pathways. This study suggested the anti-psoriatic effect of RPE, with rhein and emodin as the main contributors that regulate multiple signaling pathways.

Molecular Traits Underlying the Growth Promotion and Metabolite Accumulation in Rheum palmatum Inoculated with Endophytic Trichoderma citrinoviride HT-1.

Trichoderma spp. are an important plant-growth-promoting fungi. Trichoderma citrinoviride HT-1 was isolated from Rheum palmatum root, which has beneficial effects on growth and metabolite accumulation. However, the improvement mechanisms for growth and metabolite accumulation of T. citrinoviride HT-1 are unclear. In this study, RNA sequencing (RNA-seq) and high-performance liquid chromatography (HPLC) were used to measure the effect of different concentrations of conidial suspension of the HT-1 strain on the growth promotion and metabolite accumulation of R. palmatum seedlings. The results showed that the highest biomass and metabolites of R. palmatum seedlings were obtained through treatment with the HT-1 strain at a final spore concentration of 107 spores/mL. RNA sequencing indicated that 1662 genes were upregulated and 2155 genes were downregulated after inoculation with 107 spores/mL of the HT-1 strain. This strain induced significant upregulation of related genes in the phenylpropanoid biosynthesis pathway, plant hormone signal transduction pathway, biosynthesis of secondary metabolites pathway, and plant-pathogen interaction pathway in R. palmatum. The gene expression trends were revealed through quantitative real-time polymerase chain reaction (qRT-PCR) and were consistent with those determined by RNA-seq. Our results will help us to understand the growth-promoting mechanisms of the HT-1 strain on R. palmatum and provide a theoretical basis for the application of T. citrinoviride HT-1 as a biological fertilizer.

Extracts of Rheum palmatum and Aloe vera Show Beneficial Properties for the Synergistic Improvement of Oral Wound Healing.

Various local and systemic factors compromise oral wound healing and may lead to wound dehiscence, inflammation, or ulcers. Currently, there is a lack of topical therapeutical options. Thus, this study aimed to investigate the effect of Aloe vera (AV) and Rheum palmatum root (RPR) on oral wound healing capacity in vitro. The effect of AV and RPR on human primary fibroblast viability and migration was studied by measuring metabolic activity and gap closure in a scratch assay. Furthermore, cell cycle distribution and cytoskeletal features were analyzed. Antimicrobial activity against the oral pathogen Porphyromonas gingivalis was evaluated by broth microdilution assay. AV and RPR increased fibroblast migration after single agent treatment. Synergistic effects of the plant extract combination were observed regarding cellular migration which were confirmed by calculation of the phenomenological combination index (pCI), whereas the cell cycle distribution was not influenced. Furthermore, the combination of AV and RPR showed synergistic antibacterial effects as determined by the fractional inhibitory concentration index. This study demonstrated that the combination of AV and RPR can promote the migration of human primary fibroblasts in vitro and exert antimicrobial efficacy against P. gingivalis, suggesting these compounds for the topical treatment of wound healing disorders.

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.