Pathogenesis strategies and regulation of ginsenosides by two species of Ilyonectria in Panax ginseng: power of speciation

Comparative analysis of microbial community structure in different times of Panax ginseng Rhizosphere microbiome and soil properties under larch forest

BACKGROUND

Panax ginseng cultivated under the forest is popular because its shape and effective ingredients are similar to wild ginseng. The growth of P. ginseng in the larch forest is generally better than in the broad-leaved forest, and the incidence rate of diseases is low. Therefore, the selection of forest species is one of the basic factors in the successful cropping of P. ginseng.

METHODS

Illumina HiSeq high-throughput sequencing was used to analyze the 16S rRNA/ITS gene sequence of P. ginseng rhizosphere soil under larch forest to study the rhizosphere microbiome's diversity and community composition structure.

RESULTS

The species classification and richness of rhizosphere bacterial and fungal communities in the same-aged P. ginseng were similar. Consistent with the soil system of commonly cultivated crops, Proteobacteria, Actinobacteriota, Acidobacteriota, Verrucomicrobiota, Chloroflexi, and Basidiomycota, Ascomycota were the dominant phylum of bacteria and fungi, respectively. Compared with the soil without planting P. ginseng, the diversity of microorganisms and community structure of continuous planting for 2 years, 5 years, and 18 years of P. ginseng rhizosphere soil had little change. The accumulation levels of Ilyonectria, Fusarium, Gibberella, and Cylindrocarpon were not significantly increased with planting P. ginseng and the increased age of cropping P. ginseng.

CONCLUSIONS

The results of this study showed that the soil function of the larch forest was good, which provided a theoretical basis for the land selection and soil improvement of cultivating P. ginseng under the larch forest.

Comparative transcriptome analysis on wild-simulated ginseng of different age revealed possible mechanism of ginsenoside accumulation

Panax ginseng is one of the most famous pharmaceutical plants in Asia. Ginseng plants grown in mountain have longer longevity which ensures higher accumulation of ginsenoside components than those grown in farms. However, wild-simulated ginseng over certain age cannot be easily distinguished in morphology. To identify transcriptomic mechanism of ginsenoside accumulation in older wild-simulated ginseng without large phenotype change, we performed comparative transcriptome analysis for leaf, shoot, and root tissues of 7-yr-old and 13yr-old wild-simulated ginseng. Of 559 differentially expressed genes (DEGs) in comparison between 7-yr-old and 13yr-old wild-simulated ginseng, 280 leaf-, 103 shoot-, and 164 root-mainly expressing genes were found to be changed in transcript level according to age. Functional analysis revealed that pentose-phosphate shunt and abscisic acid responsive genes were up-regulated in leaf tissues of 7-yr-old ginseng while defense responsive genes were up-regulated in root tissues of 13-yr-old ginseng. Quantitative real-time PCR revealed that jasmonic acid responsive genes, ERDL6, and some UGTs were up-regulated in 13-yr-old ginseng in higher order lateral root tissues. These data suggest that bacterial stimulation in mountain region can enhance the expression of several genes which might support minor ginsenoside biosynthesis.

Effect of Soil and Root Extracts on the Innate Immune Response of American Ginseng (Panax quinquefolius) to Root Rot Caused by Ilyonectria mors-panacis

Panax quinquefolius shows much higher mortality to Ilyonectria mors-panacis root rot when grown in soil previously planted with ginseng than in soil not previously planted with ginseng, which is known as ginseng replant disease. Treatment of ginseng roots with methanol extracts of previous ginseng soils significantly increased root lesion sizes due to I. mors-panacis compared to roots treated with water or methanol extracts of ginseng roots or non-ginseng soils. Inoculation of water-treated roots with I. mors-panacis increased expression of a basic chitinase 1 gene (PqChi-1), neutral pathogenesis-related protein 5 gene (PqPR5) and pathogenesis-related protein 10-2 gene (PqPR10-2), which are related to jasmonic acid (JA), ethylene (ET) or necrotrophic infection, and also increased expression of an acidic β-1-3-glucanase gene (PqGlu), which is related to salicylic acid (SA). Infection did not affect expression of a cysteine protease inhibitor gene (PqCPI). Following infection, roots treated with ginseng root extract mostly showed similar expression patterns as roots treated with water, but roots treated with previous ginseng soil extract showed reduced expression of PqChi-1, PqPR5, PqPR10-2 and PqCPI, but increased expression of PqGlu. Methanol-soluble compound(s) in soil previously planted with ginseng are able to increase root lesion size, suppress JA/ET-related gene expression and trigger SA-related gene expression in ginseng roots during I. mors-panacis infection, and may be a factor contributing to ginseng replant disease.

Ginsenosides and Biotic Stress Responses of Ginseng

Ginsenosides are saponins that possess a sugar moiety attached to a hydrophobic aglycone triterpenoid. They have been widely studied for their various medicinal benefits, such as their neuroprotective and anti-cancer activities, but their role in the biology of ginseng plants has been much less widely documented. In the wild, ginsengs are slow-growing perennials with roots that can survive for approximately 30 years; thus, they need to defend themselves against many potential biotic stresses over many decades. Biotic stresses would be a major natural selection pressure and may at least partially explain why ginseng roots expend considerable resources in order to accumulate relatively large amounts of ginsenosides. Ginsenosides may provide ginseng with antimicrobial activity against pathogens, antifeedant activity against insects and other herbivores, and allelopathic activity against other plants. In addition, the interaction of ginseng with pathogenic and non-pathogenic microorganisms and their elicitors may trigger increases in different root ginsenosides and associated gene expression, although some pathogens may be able to suppress this behavior. While not covered in this review, ginsenosides also have roles in ginseng development and abiotic stress tolerance. This review shows that there is considerable evidence supporting ginsenosides as important elements of ginseng's defense against a variety of biotic stresses.

Interaction of Ginseng with Ilyonectria Root Rot Pathogens

The Ilyonectria radicicola species complex (A.A. Hildebr.) A. Cabral and Crous 2011 contains species of soilborne necrotrophic plant pathogens. The most aggressive to ginseng roots is I. mors-panacis, whereas I. robusta, I. crassa, I. panacis and I. radicicola are less aggressive. Infected ginseng roots show orange-red to black-brown lesions that can expand into a severe root rot, known as disappearing root rot, where only epidermal root tissue remains. Leaves become red-brown with wilting, and stems can have vascular discoloration with black-brown lesions at the base. Less aggressive Ilyonectria species trigger jasmonic acid (JA)-related defenses inducing host ginsenosides, pathogenesis-related (PR) proteins, wound periderm, and cell wall thickening. In contrast, I. mors-panacis triggers reactive oxygen species (ROS) and salicylic acid (SA) production but suppresses JA-related defenses and ginsenoside accumulation. It is also able to suppress SA-related PR protein production. Virulence factors include potential effectors that may suppress PAMP (Pathogen Associated Molecular Patterns) triggered immunity (PTI), polyphenoloxidases, Hsp90 inhibitors, siderophores and cell-wall-degrading enzymes, such as pectinases. Overall, I. mors-panacis appears to be more aggressive because it can suppress JA and SA-related PTI allowing for more extensive colonization of ginseng roots. While many possible mechanisms of host resistance and pathogen virulence mechanisms have been examined, there is a need for using genetic approaches, such as RNAi silencing of genes of Panax or Ilyonectria, to determine their importance in the interaction.

Genetic Diversity and Population Structure of Cylindrocarpon-like Fungi Infecting Ginseng Roots in Northeast China

Northeast China is well known for cultivating ginseng (Panax ginseng and P. quinquefolius). Ginseng roots are threatened by the infection of the most notorious Cylindrocarpon-like fungi (CLF), which are a complex containing important soilborne pathogens. Although the disease is economically important, little is known about the genetic diversity and population structure of the pathogenic CLF complex. This knowledge will help in developing effective disease management strategies. To conduct this study, diseased ginseng roots were collected from 12 regions representing the main ginseng-growing areas in Northeast China, and CLF were isolated. A total of 169 isolates with CLF anamorph were identified in two Dactylonectria species and six Ilyonectria species using morphological and molecular methods. Cross pathogenicity tests showed that all species were pathogenic to both P. ginseng and P. quinquefolius, and most of them had slightly stronger aggressiveness in P. ginseng. The analysis of partial sequences of the Histone H3 gene generated a high level of genetic diversity and geographic differentiation. A total of 132 variable sites were detected in 169 sequences, which formed 20 haplotypes with a haplotype diversity of 0.824. Genetic differentiation was positively correlated with geographic distance. The geographic populations in the range of Changbai Mountain were distinctly discriminated from those in other non-Changbai Mountain populations. No significant genetic differentiation was found between ginseng hosts. Cylindrocarpon-like fungi causing ginseng root diseases are geographically correlated in the genetic distance in Northeast China and should be managed correspondingly.

Untargeted Metabolomic Approach to Determine the Regulatory Pathways on Salicylic Acid-Mediated Stress Response in Aphanamixis polystachya Seedlings

Plants thrive under abiotic and biotic stress conditions with the changes in phytohormones like salicylic acid (SA), resulting in the synthesis of secondary metabolites. The present study determines the response of plants in producing secondary metabolites towards different SA concentrations at varying time intervals. Liquid chromatography-mass spectrometry-based metabolomics studies in Aphanamixis polystachya (Wall.) Parker seedlings are grown at 10 mM, 50 mM, and 100 mM SA concentrations, showed the differential expression of metabolites towards the stress. Alkaloids like amaranthin showed a 15-fold increase on the second day, and analog of androvinblastin showed a 20-fold increase on the sixth day in 10 mM SA compared with other groups. Flavanoid cyanidin 3-3 glucosyl was found to be with a 22-fold increment along with terpenoids betavulgaroside (18-fold), asiaticoside (17-fold), mubenin B (20-fold), and deslanoside (22-fold) increment in 50 mM SA on the sixth day. The shock exerted by 100 mM was too harsh, and the lowered metabolite production level was insufficient for the seedlings to survive at this higher SA condition. Arrangement of stressed groups using Pearson correlation studies, principal component analysis, and partial least square analysis placed 10 mM SA and controlled group closer and 50 mM SA and 100 mM SA groups closer to each other. The study observed that SA regulates metabolites that mediate biotic stress responses at low concentrations, and higher concentrations regulate abiotic stress regulating metabolites.

Structure and Function of Rhizosphere Soil and Root Endophytic Microbial Communities Associated With Root Rot of Panax notoginseng

Panax notoginseng (Burk.) F. H. Chen is a Chinese medicinal plant of the Araliaceae family used for the treatment of cardiovascular and cerebrovascular diseases in Asia. P. notoginseng is vulnerable to root rot disease, which reduces the yield of P. notoginseng. In this study, we analyzed the rhizosphere soil and root endophyte microbial communities of P. notoginseng from different geographical locations using high-throughput sequencing. Our results revealed that the P. notoginseng rhizosphere soil microbial community was more diverse than the root endophyte community. Rhodopseudomonas, Actinoplanes, Burkholderia, and Variovorax paradoxus can help P. notoginseng resist the invasion of root rot disease. Ilyonectria mors-panacis, Pseudomonas fluorescens, and Pseudopyrenochaeta lycopersici are pathogenic bacteria of P. notoginseng. The upregulation of amino acid transport and metabolism in the soil would help to resist pathogens and improve the resistance of P. notoginseng. The ABC transporter and gene modulating resistance genes can improve the disease resistance of P. notoginseng, and the increase in the number of GTs (glycosyltransferases) and GHs (glycoside hydrolases) families may be a molecular manifestation of P. notoginseng root rot. In addition, the complete genomes of two Flavobacteriaceae species and one Bacteroides species were obtained. This study demonstrated the microbial and functional diversity in the rhizosphere and root microbial community of P. notoginseng and provided useful information for a better understanding of the microbial community in P. notoginseng root rot. Our results provide insights into the molecular mechanism underlying P. notoginseng root rot and other plant rhizosphere microbial communities.

A Novel Analysis Method for Simultaneous Determination of 31 Pesticides by High-Performance Liquid Chromatography-Tandem Mass Spectrometry in Ginseng

Ginseng is a perennial herb with a long growth cycle and is known to easily accumulate pesticides during its growth process, seriously threatening people's health. Therefore, to ensure safe consumption, it is necessary to detect and monitor pesticide residues in ginseng. In this study, a novel analysis method was established for simultaneous determination of 31 pesticides in ginseng by high-performance liquid chromatography-mass spectrometry. Ginseng samples were extracted using acetonitrile, cleaned up by primary secondary amine (PSA) solid-phase extraction column eluted with acetonitrile-toluene, and then detected in multiple reaction mode (MRM). The calibration curves of target compounds were linear in the range of 0.005-1.0 mg/L, with correlation coefficients greater than 0.9921. The limits of detection of all the pesticides in ginseng were between 4.4×10^-5 and 1.6 × 10^-2 mg/kg. For fresh ginseng, the average recoveries ranged from 72.1 to 111.6%, and the relative standard deviations were 1.3-12.2%. For dry ginseng, the average recoveries were 74.3-108.3%, and the relative standard deviations were 0.9-14.9%. The residual concentrations of some pesticides in real samples were greater than the maximum residue limit (MRL) for European Union (EU). The method established here is rapid and simple with high sensitivity and good reproducibility, which is sensitive in the residue analysis of many pesticides in ginseng.

Ginsenosides Conversion and Anti-Oxidant Activities in Puffed Cultured Roots of Mountain Ginseng

CRMG (Cultured Roots of Mountain Ginseng) have the advantages in scale-up production, safety, and pharmacological efficacies. Though several methods are available for the conversion of major to minor ginsenosides, which has more pharmacological activities, a single step process with high temperature and pressure as a puffing method took place in this study to gain and produce more pharmacologically active compounds. Puffed CRMG exhibited an acceleration of major ginsenosides to minor ginsenosides conversions, and released more phenolic and flavonoid compounds. HPLC analysis was used to detect a steep decrease in the contents of major ginsenosides (Re, Rf, Rg1, Rg2, Rb1, Rb2, Rb3, Rc and Rd) with increasing pressure; on the contrary, the minor ginsenosides (20 (S, R)-Rg3, Rg5, Rk1, Rh1, Rh2, Rg6, F4 and Rk3) contents increased. Minor ginsenosides, such as Rg6, F4 and Rk3, were firstly reported to be produced from puffed CRMG. After the puffing process, phenolics, flavonoids, and minor ginsenoside contents were increased, and also, the antioxidant properties, such as DPPH inhibition and reducing the power of puffed CRMG, were significantly enhanced. Puffed CRMG at 490.3 kPa and 588.4 kPa had a low toxicity on HaCaT (immortalized human epidermal keratinocyte) cells at 200 μg/mL, and could significantly reduce ROS by an average of 60%, compared to the group treated with H2O2. Therefore, single step puffing of CRMG has the potential to be utilized for functional food and cosmeceuticals.

Phytochemistry of ginsenosides: Recent advancements and emerging roles

Ginsenosides, a group of tetracyclic saponins, accounts for the nutraceutical and pharmaceutical relevance of the ginseng (Panax sp.) herb. Owing to the associated therapeutic potential of ginsenosides, their demand has been increased significantly in the last two decades. However, a slow growth cycle, low seed production, and long generation time of ginseng have created a gap between the demand and supply of ginsenosides. The biosynthesis of ginsenosides involves an intricate network of pathways with multiple oxidation and glycosylation reactions. However, the exact functions of some of the associated genes/proteins are still not completely deciphered. Moreover, ginsenoside estimation and extraction using analytical techniques are not feasible with high efficiency. The present review is a step forward in recapitulating the comprehensive aspects of ginsenosides including their distribution, structural diversity, biotransformation, and functional attributes in both plants and animals including humans. Moreover, ginsenoside biosynthesis in the potential plant sources and their metabolism in the human body along with major regulators and stimulators affecting ginsenoside biosynthesis have also been discussed. Furthermore, this review consolidates biotechnological interventions to enhance the biosynthesis of ginsenosides in their potential sources and advancements in the development of synthetic biosystems for efficient ginsenoside biosynthesis to meet their rising industrial demands.

Rhizoplane and Rhizosphere Fungal Communities of Geographically Isolated Korean Bellflower (Campanula takesimana Nakai)

Simple Summary

The current study reports fungal diversities in the rhizoplane (RP) and rhizosphere (RS) samples of the geographically isolated Korean bellflower (Campanulatakesimana) obtained from its original habitats of the eastern coast of the Korean Peninsula for the first time. The identification of specific taxa in each site may provide a better understanding of the interaction between the soil fungi and Korean bellflower.

Abstract

Fungal communities in the rhizoplane (RP) and rhizosphere (RS) of geographically isolated C. takesimana habitats in different environments such as oceanic (Seodo, the Dokdo Islands), coastline (Sadong, Ulleungdo Island), and inland (Taeha, Ulleungdo Island) regions were analyzed by MiSeq sequencing. In total, 1279 operational taxonomic units (OTUs) were obtained and they were further classified into 185 genera belonging to five phyla. The total number of fungal taxa in the RP samples was lower than those in the RS samples in all the sampled locations, providing an indication of the existence of a certain level of the selective pressures from the host plant. The richness of the RP in the Dokdo Islands was higher than that of Ulleungdo Island, but the richness of the RS in the Dokdo Islands was lower than that of Ulleungdo Island. These results suggest evidence for strong effects of a harsh geo-climate on the RP and RS fungal diversities in the Dokdo Islands. Additionally, a total of 82 fungal genera were identified in all three RP samples and 63 genera (77%) were uniquely found in each of the geographical regions and 43 genera (52.4%) showed high dependency on the C. takesimana vegetation. It was found that the genus Mortierella was the most dominant taxon in all the samples. The geo-ecological isolation of the Korean bellflower may have caused unique formation of the RP and RS fungal communities in the natural habitats.

Cumulative Production of Bioactive Rg3, Rg5, Rk1, and CK from Fermented Black Ginseng Using Novel Aspergillus niger KHNT-1 Strain Isolated from Korean Traditional Food

Ginseng is an ancient herb widely consumed due to its healing property of active ginsenosides. Recent researchers were explored to increase its absorption and bioavailability of ginsenosides at the metabolic sites, due to its pharmacological activity. The purpose of this study was to investigate the isolation and characteristics of components obtained by a shorter steaming cycle (seven cycles) of white ginseng to fermented black ginseng, using a novel strain of Aspergillus niger KHNT-1 isolated from fermented soybean. The degree of bioactive of Rg3 increased effectively during the steaming process, and biotransformation converted the color towards black along active ginsenosides. Glycol moiety associated with C-3, C-6, or C-20 underwent rapid biotransformation and hydrolysis, such as Rb1, Rb2, Rc, Rd → Rg3, F2, and was converted to CK. Dehydration produces Rg3 → Rk1, Rg5. Rh2 → Rk2; thus, converted fermented black ginseng was solvent-extracted, and the isolated components were identified by TLC, HPLC, and quantification by LCMS. The unique composition obtained during this process with Rk1, Rg3, Rg5, and CK is nontoxic to HaCaT cell line up to 200 ug/mL for 24 h and was found to be effective in B16BL6 cell lines, in a dose- and time-dependent manner. Thus, it is a suitable candidate for nutraceuticals and cosmeceuticals.

Implications of the Human Gut-Brain and Gut-Cancer Axes for Future Nanomedicine

Recent clinical and pathological evidence have implicated the gut microbiota as a nexus for modulating the homeostasis of the human body, impacting conditions from cancer and dementia to obesity and social behavior. The connections between microbiota and human diseases offer numerous opportunities in medicine, most of which have limited or no therapeutic solutions available. In light of this paradigm-setting trend in science, this review aims to provide a comprehensive and timely summary of the mechanistic pathways governing the gut microbiota and their implications for nanomedicines targeting cancer and neurodegenerative diseases. Specifically, we discuss in parallel the beneficial and pathogenic relationship of the gut microbiota along the gut-brain and gut-cancer axes, elaborate on the impact of dysbiosis and the gastrointestinal corona on the efficacy of nanomedicines, and highlight a molecular mimicry that manipulates the universal cross-β backbone of bacterial amyloid to accelerate neurological disorders. This review further offers a forward-looking section on the rational design of cancer and dementia nanomedicines exploiting the gut-brain and gut-cancer axes.

Comprehensive Genome Analysis on the Novel Species Sphingomonas panacis DCY99T Reveals Insights into Iron Tolerance of Ginseng

Plant growth-promoting rhizobacteria play vital roles not only in plant growth, but also in reducing biotic/abiotic stress. Sphingomonas panacis DCY99T is isolated from soil and root of Panax ginseng with rusty root disease, characterized by raised reddish-brown root and this is seriously affects ginseng cultivation. To investigate the relationship between 159 sequenced Sphingomonas strains, pan-genome analysis was carried out, which suggested genomic diversity of the Sphingomonas genus. Comparative analysis of S. panacis DCY99T with Sphingomonas sp. LK11 revealed plant growth-promoting potential of S. panacis DCY99T through indole acetic acid production, phosphate solubilizing, and antifungal abilities. Detailed genomic analysis has shown that S. panacis DCY99T contain various heavy metals resistance genes in its genome and the plasmid. Functional analysis with Sphingomonas paucimobilis EPA505 predicted that S. panacis DCY99T possess genes for degradation of polyaromatic hydrocarbon and phenolic compounds in rusty-ginseng root. Interestingly, when primed ginseng with S. panacis DCY99T during high concentration of iron exposure, iron stress of ginseng was suppressed. In order to detect S. panacis DCY99T in soil, biomarker was designed using spt gene. This study brings new insights into the role of S. panacis DCY99T as a microbial inoculant to protect ginseng plants against rusty root disease.

Silicon confers protective effect against ginseng root rot by regulating sugar efflux into apoplast

Root rot caused by Ilyonectria mors-panacis is a devastating fungal disease leading to defect in root quality and causes reduced yield during the perennial life cycle of Panax ginseng Meyer. This indicates the imperative need to understand the molecular basis of disease development and also to enhance tolerance against the fungus. With this idea, the protective effect of silicon (supplied as silica nanoparticles) in P. ginseng root rot pathosystem and its molecular mechanism was investigated in the current study. We have tested different concentrations of silicon (Si) to disease-infected ginseng and found that long term analysis (30 dpi) displayed a striking 50% reduction in disease severity index upon the treatment of Si. Expectedly, Si had no direct degradative effect against the pathogen. Instead, in infected roots it resulted in reduced expression of PgSWEET leading to regulated sugar efflux into apoplast and enhanced tolerance against I. mors-panacis. In addition, under diseased condition, both protopanaxadiol (PPD) and protopanaxatriol (PPT) type ginsenoside profile in roots were higher in Si treated plants. This is the first report indicating the protective role of Si in ginseng-root rot pathosystem, thereby uncovering novel features of ginseng mineral physiology and at the same time, enabling its usage to overcome root rot.

Deciphering Microbiome Related to Rusty Roots of Panax ginseng and Evaluation of Antagonists Against Pathogenic Ilyonectria

Plant roots host diverse microbes that are closely associated with root fitness. Currently, the relationship between microbes and rusty roots of Panax ginseng remains unclear. Here, we described the root-associated microbiome in rusty and healthy ginseng by metagenomic sequencing of 16S rRNA and ITS regions. Being enriched in Diseased-roots (Dr) of ginseng and their rhizosphere soil, the fungus of Ilyonectria, was identified as the most probable cause of the disease after ITS analysis. Meanwhile, an increase of Mortierella was observed in Healthy-roots (Hr). Surprisingly, an enriched Fusarium was found in both Hr and their rhizosphere soil. Besides, in comparison with Hr, decreased relative abundance of Actinomycetales and increased relative abundance of Pseudomonadales was observed in Dr after 16S rRNA analysis. What's more, we isolated several microorganisms as antagonists that showed strong inhibiting effects on Ilyonectria in plate assays. In field trials, inoculation of Bacillus sp. S-11 displayed apparent suppression effect against Ilyonectria and shifted microbial communities in rhizosphere soil. Our research identified key microbiota involved in rusty roots of P. ginseng and offered potential biocontrol solutions to rusty disease.