Characterization of root-associated microbiota in medicinal plants Astragalus membranaceus and Astragalus mongholicus

Arbuscular mycorrhizal fungal communities in soils where astragalus had grown for 2 years were similar to those in the abandoned farmland

Purpose

Astragalus-cultivated soils are enriched in arbuscular mycorrhizal fungi (AMF); however, the community changes of AMF between years in stragalus-cultivated soils are still unclear.

Methods

To illustrate this, using high-throughput amplicon sequencing and quantitative real-time PCR, we analyzed the AMF communities of the abandoned farmlands and interannual astragalus-cultivated soils for 1-, 2-, 3-, and 4-years, including community composition, dominant, core, specific and significantly fluctuating AMF, co-occurrence network, alpha diversity, and beta diversity.

Results

A total of 74 OTUs were classified into one phylum, Glomeromycota; one class, Glomeromycetes; four orders; four families; and six genera. The 2-year soil had the highest number of reads among the interannual soils. Only one OTU was shared among all interannual soils. The treatments significantly affected the Ace, Shannoneven, and Shannon estimators of the communities. The 2-year soil had the highest richness, evenness, and diversity among all interannual soils and was the closest to the abandoned farmland in terms of alpha diversity. Glomus of the family Glomeraceae was the dominant genus present in all treatments, and the composition of the dominant genus in interannual soils was different. Both Glomus and Diversispora were the core AMF in interannual soils, and specific AMF existed in different interannual soils. Glomus is a genus that exhibits significant interannual variation. The interannual time significantly affected the network connectivity. The results of the principal coordinate analysis showed that the community composition of the interannual soils was close to each other and separated from the abandoned farmland, and that the interannual time significantly affected the community composition.

Conclusion

Among the interannual soils, the 2-year soil may be more suitable for A. sinensis seedling rotation.

Panax notoginseng-microbiota interactions: From plant cultivation to medicinal application

BACKGROUND

Microbiomes and their host plants are closely linked with each other; for example, the microbiome affects plant growth, fitness, nutrient uptake, stress tolerance and pathogen resistance, whereas the host plant supports the photosynthetically carbon-rich nutrition of the microbiome. The importance of the microbiome in plant‒soil ecosystems is unquestioned and has expanded to influence the medicinal application of some herbal plants via the gut microbiota.

PURPOSE

Herbal plant-microbiome interactions may provide novel knowledge to enhance the robustness of herbal plant crop performance and medicinal applications, which requires a systematic review and preceding discussion.

STUDY DESIGN AND METHODS

The interactions between Panax notoginseng and microorganisms (from soil to host) were reviewed from the literature. The terms "Panax notoginseng" and "microbiota" were used in combination with the keywords "microbiota/microbes", "bacteria/bacterium" or "fungi/fungus" or "endophyte", as well as our targeted bioactive phytochemicals, including saponins and ginsenosides.

RESULT

Our study focuses on the famous medicinal herb Panax notoginseng F. H. Chen and proposes that the microbiota is a crucial participant not only in the cultivation of this herbal plant but also in its medicinal application. We also summarize and discuss how these plant‒microbe co-associations shape the assembly of plant-related microbiomes and produce bioactive phytochemicals, as well as influence beneficial herbal traits, such as herbal plant health and pharmacology. In addition, we also highlight future directions.

CONCLUSION

The rhizosphere and endophytic microbiome of Panax notoginseng are indirectly or directly involved in plant health, biomass production, and the synthesis/biotransformation of plant secondary metabolites. Harnessing the microbiome to improve the quality of traditional Chinese medicine and improve the value of medicinal plants for human health is highly promising.

Root endophytic bacterial community composition of Aconitum carmichaelii debx. from three main producing areas in China

Aconitum carmichaelii Debx. is famous for the bioactive aconitum alkaloids as traditional Chinese medicine. Endophytic bacteria play vital roles in plant growth, health, and the production of secondary metabolites such as alkaloids. In this study, we employed 16 S rRNA amplicon high-throughput sequencing to determine the root endophytic bacterial community of A. carmichaelii Debx. collected from three main producing areas including the geo-authentic area in China, high performance liquid chromatography to measure the contents of six bioactive alkaloids and correlation analysis to explore the relationship among environmental factors, alkaloids contents, and endophytic bacterial community. The results indicated that the root core microbiota of A. carmichaelii Debx. was dominated by Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. Root endophytic bacterial community in the geo-authentic area was distinct from the other two regions. Soil nitrogen contents, organic matter, and temperature were the main factors contributing to the endophytic bacterial community structure. Significant correlation was found between alkaloids contents and some bacterial genera. Particularly, the abundance of Lactobacillus was positively correlated with the contents of benzoyl-mesaconitine and benzoyl-aconine. This study provided the first insight into the root endophytic bacterial community composition of A. carmichaelii Debx., and can direct further isolation of functional bacterial strains.

The Composition of Root-Associated Bacteria and Fungi of Astragalus mongholicus and Their Relationship With the Bioactive Ingredients

Astragalus membranaceus (Fisch.) Bge. var. mongholicus, which is used in traditional Chinese medicine, contains several bioactive ingredients. The root-associated microbial communities play a crucial role in the production of secondary metabolites in plants. However, the correlation of root-associated bacteria and fungi with the bioactive ingredients production in A. mongholicus has not been elucidated. This study aimed to examine the changes in soil properties, root bioactive ingredients, and microbial communities in different cultivation years. The root-associated bacterial and fungal composition was analyzed using high-throughput sequencing. The correlation between root-associated bacteria and fungi, soil properties, and six major bioactive ingredients were examined using multivariate correlation analysis. Results showed that soil properties and bioactive ingredients were distinct across different cultivation years. The composition of the rhizosphere microbiome was different from that of the root endosphere microbiome. The bacterial community structure was affected by the cultivation year and exhibited a time-decay pattern. Soil properties affected the fungal community composition. It was found that 18 root-associated bacterial operational taxonomic units (OTUs) and four fungal OTUs were positively and negatively correlated with bioactive ingredient content, respectively. The abundance of Stenotrophomonas in the rhizosphere was positively correlated with astragaloside content. Phyllobacterium and Inquilinus in the endosphere were positively correlated with the calycosin content. In summary, this study provided a new opportunity and theoretical reference for improving the production and quality of in A. mongholicus, which thus increase the pharmacological value of A. mongholicus.

Microplastic pollution alters forest soil microbiome

The impact of microplastic pollution on terrestrial biota is an emerging research area, and this is particularly so for soil biota. In this study, we addressed this knowledge gap by examining the impact of aged low-density polyethylene (LDPE) and polyester fibres (i.e. polyethylene terephthalate, PET) on a forest microbiome composition and activity. We also measured the corresponding physicochemical changes in the soil. We observed that bacteria community composition diverged in PET and LDPE treated soils from that of the control by day 42. These changes occurred at 0.2% and 0.4% (w/w) of PET and at 3% LDPE. Additionally, soil respiration was 8-fold higher in soil that received 3% LDPE compared to other treatments and control. There were no clear patterns linking these biological changes to physicochemical changes measured. Taken together, we concluded that microplastics aging in the environment may have evolutionary consequences for forest soil microbiome and there is immediate implication for climate change if the observed increase in soil respiration is reproducible in multiple ecosystems.

Repair Effects of Astragalus Polysaccharides with Different Molecular Weights on Oxidatively Damaged HK-2 Cells

This study investigated the repair effects of three Astragalus polysaccharides (APSs) with different molecular weights (Mws) on injured human renal proximal tubular epithelial (HK-2) cells to reveal the effect of Mw of polysaccharide on cell repair. A damage model was established by injuring HK-2 cells with 2.6 mM oxalate, and APS0, APS1, and APS2 with Mw of 11.03, 4.72, and 2.61 KDa were used to repair the damaged cells. After repair by APSs, the morphology of damaged HK-2 cells gradually returned to normal, the destruction of intercellular junctions recovered, intracellular reactive oxygen species production amount decreased, and their mitochondrial membrane potential increased. In addition, the cell cycle progression gradually normalized, lysosome integrity increased, and cell apoptotic rates obviously declined in the repaired cells. All three APSs could promote the expression of Keap1, Nrf2, SOD1, and CAT. In addition, the expression levels of inflammation markers containing MCP-1 and IL-6 decreased after APS repair. We deduced that APSs exert their repair function by activating the Nrf2-Keap1 signaling pathway and inhibiting inflammation. Among the APSs, APS1 with a moderate Mw provided the strongest repair effect. APSs may have a preventive effect on kidney stones.

Comparative analysis of twenty-five compounds in different parts of Astragalus membranaceus var. mongholicus and Astragalus membranaceus by UPLC-MS/MS

As a traditional Chinese medicine, the root of Astragalus membranaceus var. mongholicus (AMM) or A. membranaceus (AM) has been widely used in China and other Asian countries for thousands of years. Till now, the flavonoids, phenolic acids and saponins are considered as the main active components contributing to their therapeutic effect in these plants. In order to clarify the distribution and contents of these compounds in different organs of these plants, a rapid and sensitive analytical method for simultaneous determination of 25 active compounds including seven types (i.e. dihydroflavones, isoflavane, isoflavones, flavones, pterocarpans, phenolic acid and saponins) within 10 min was established using ultra-pressure liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). Then, the established method was fully validated and successfully applied to the determination of the contents of these analytes in different parts (root, rhizome, stem, leaf and flower) of AMM and AM. The results indicated that the contents of the same type of compounds in two different species plants were significantly different. Moreover, the obvious differences were also found for the distribution and contents of different type of compounds in five organs of the same species. The present study could provide necessary information for the rational development and utilization of AMM and AM resource.

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A sensitive UPLC–MS/MS method was established for analysis of Astragalus plants.

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Total 25 analytes such as flavonoids, phenolic acids and saponins were determined.

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The contents of these analytes in different parts of the two plants were compared.

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A scientific information for the utilization of two Astragalus plants was provided.