Soil potassium is correlated with root secondary metabolites and root-associated core bacteria in licorice of different ages

Insight into farming native microbiome by bioinoculant in soil-plant system

Applying beneficial microorganisms (BM) as bioinoculants presents a promising soil-amendment strategy while impacting the native microbiome, which jointly alters soil-plant performance. Leveraging the untapped potential of native microbiomes alongside bioinoculants may enable farmers to sustainably regulate soil-plant systems via natural bioresources. This review synthesizes literature on native microbiome responses to BMs and their interactive effects on soil and plant performance. We highlight that native microbiomes harbor both microbial "helpers" that can improve soil fertility and plant productivity, as well as "inhibitors" that hinder these benefits. To harness the full potential of resident microbiome, it is crucial to elucidate their intricate synergistic and antagonistic interplays with introduced BMs and clarify the conditions that facilitate durable BM-microbiome synergies. Hence, we indicate current challenges in predicting these complex microbial interactions and propose corresponding strategies for microbiome breeding via BM bioinoculant. Overall, fully realizing the potential of BMs requires clarifying their interactions with native soil microbiomes and judiciously engineering microbiome to harness helpful microbes already present within agroecosystems.

Metabolites of blueberry roots at different developmental stages strongly shape microbial community structure and intra-kingdom interactions at the root-soil interface

The rhizosphere microorganisms of blueberry plants have long coexisted with their hosts under distinctively acidic soil conditions, exerting a profound influence on host performance through mutualistic symbiotic interactions. Meanwhile, plants can regulate rhizosphere microorganisms by exerting host effects to meet the functional requirements of plant growth and development. However, it remains unknown how the developmental stages of blueberry plants affect the structure, function, and interactions of the rhizosphere microbial communities. Here, we examined bacterial communities and root metabolites at three developmental stages (flower and leaf bud development stage, fruit growth and development stage, and fruit maturation stage) of blueberry plants. The results revealed that the Shannon and Chao 1 indices as well as community composition varied significantly across all three developmental stages. The relative abundance of Actinobacteria significantly increased by 10 % (p < 0.05) from stage 1 to stage 2, whereas that of Proteobacteria decreased significantly. The co-occurrence network analysis revealed a relatively complex network with 1179 edges and 365 nodes in the stage 2. Niche breadth was highest at stage 2, while niche overlap tended to increase as the plant developed. Furthermore, the untargeted metabolome analysis revealed that the number of differential metabolites of vitamins, nucleic acids, steroids, and lipids increased between stage 1 to stage2 and stage 2 to stage 3, while those for differential metabolites of carbohydrates and peptides decreased. Significant changes in expression levels of levan, L-glutamic acid, indoleacrylic acid, oleoside 11-methyl ester, threo-syringoylglycerol, gingerglycolipid B, and bovinic acid were highly correlated with the bacterial community structure. Collectively, our study reveals that significant alterations in dominant bacterial taxa are strongly correlated with the dynamics of root metabolites. These findings lay the groundwork for developing prebiotic products to enhance the beneficial effects of root microorganisms and boosting blueberry productivity via a sustainable approach.

A Comprehensive Review of Licorice: The Preparation, Chemical Composition, Bioactivities and Its Applications

Licorice (Glycyrrhiza) is a medicinal and food homologue of perennial plants derived from the dried roots and rhizomes of the genus Glycyrrhiza in the legume family. In recent years, the comprehensive utilization of licorice resources has attracted people's attention. It is widely utilized to treat diseases, health food products, food production, and other industrial applications. Furthermore, numerous bioactive components of licorice are found using advanced extraction processes, which mainly include polyphenols (flavonoids, dihydrostilbenes, benzofurans, and coumarin), triterpenoids, polysaccharides, alkaloids, and volatile oils, all of which have been reported to possess a variety of pharmacological characteristics, including anti-oxidant, anti-inflammatory, antibacterial, antiviral, anticancer, neuroprotective, antidepressive, antidiabetic, antiparasitic, antisex hormone, skin effects, anticariogenic, antitussive, and expectorant activities. Thereby, all of these compounds promote the development of novel and more effective licorice-derived products. This paper reviews the progress of research on extraction techniques, chemical composition, bioactivities, and applications of licorice to provide a reference for further development and application of licorice in different areas.

Trophic relationships between protists and bacteria and fungi drive the biogeography of rhizosphere soil microbial community and impact plant physiological and ecological functions

Rhizosphere microorganisms play a vital role in enhancing plant health, productivity, and the accumulation of secondary metabolites. Currently, there is a limited understanding of the ecological processes that control the assembly of community. To address the role of microbial interactions in assembly and for functioning of the rhizosphere soil microbiota, we collected rhizosphere soil samples from Anisodus tanguticus on the Tibetan Plateau spanning 1500 kilometers, and sequenced the bacteria, fungi, archaea, and protist communities. We observed a significant but weak distance-decay relationship in the microbial communities of rhizosphere soil. Our comprehensive analysis of spatial, abiotic, and biotic factors showed that trophic relationships between protists and bacteria and fungi predominantly influenced the alpha and beta diversity of bacterial, fungal, and protistan communities, while abiotic factors had a greater impact on archaeal communities, including soil pH, available phosphorus, total phosphorus and mean annual temperature. Importantly, microbial interactions had a more significant influence on Anisodus tanguticus physiological and ecological functions compared to individual microorganisms. Network analyses revealed that bacteria occupy a central position of the co-occurrence network and play a crucial role of connector within this community. The addition of protists increased the stability of bacterial, fungal, and archaeal networks. Overall, our findings indicate that trophic relationships play an important role in assembly and for functioning of the rhizosphere soil microbiota. Bacterial communities serve as a crucial link between different kingdoms of microorganisms in the rhizosphere community. These findings help us to fully harness the beneficial functions of rhizosphere microorganisms for plants and achieve sustainable use of biological resources.

Plant secondary metabolites involved in the stress tolerance of long-lived trees

Ancient trees are natural wonders because of their longevity, having lived for hundreds or thousands of years, and their ability to withstand changing environments and a variety of stresses. These long-lived trees have sophisticated defense mechanisms, such as the production of specialized plant metabolites (SPMs). In this review, we provide an overview of the major biotic and abiotic stresses that long-lived trees often face, as well as an analysis of renowned ancient tree species and their unique protective SPMs against environmental stressors. We also discuss the synthesis and accumulation of defensive SPMs induced by environmental factors and endophytes in these trees. Furthermore, we conducted a comparative genomic analysis of 17 long-lived tree species and discovered significant expansions of SPM biosynthesis gene families in these species. Our comprehensive review reveals the crucial role of SPMs in high resistance in long-lived trees, providing a novel natural resource for plant defense, crop improvement and even the pharmaceutical industry.

Soil bacterial succession with different land uses along a millennial chronosequence derived from the Yangtze River flood plain

Wetlands reclamation has been a traditional and effective practice for obtaining new land to alleviate the pressure induced by population growth. However, the evolution of soil-dwelling microorganisms along with reclamation and the potential influence of land-use patterns on them remain unclear. In this study, a soil chronosequence derived from Yangtze River sediments was established, comprising of circa 0, 60, 160, 280, 2000, and 3000 years, to examine the succession of soil bacterial communities across different land uses. Our analysis revealed obvious development in soil properties and orderly bacterial succession along reclamation gradients. Over time, reclaimed land suffered from varying degrees of abundance loss and biodiversity simplification, with dryland being the most sensitive to reclamation duration changes, whereas woodland and paddies showed slight reductions. Bacterial communities tended to shift from oligotrophs (K-strategist) to copiotrophs (r-strategist) at the phylum level as reclamation proceeded for all land use types. The relative abundance of certain bacterial functional groups associated with the carbon (C) and nitrogen (N) cycles were significantly increased, including those involved in Aerobic chemoheterotrophy, Chitinolysis, Nitrate reduction, Nitrate respiration, and Ureolysis, while other groups, such as those related to Fermentation, Methylotrophy, Nitrification, and Hydrocarbon degradation, exhibited decreased expression. Notably, prolonged reclamation can also trigger ecological issues in soil, including a continuous increase of predatory/exoparasitic bacteria in dryland and woodland, as well as a significant increase in pathogenic bacteria during the later stages in paddy fields. Overall, our study identified the impact of long-term reclamation on soil bacterial communities and functional groups, providing insight into the development of land-use-oriented ecological protection strategies.

A core root bacteria contribute to plant growth and anisodine accumulation of Anisodus tanguticus

BACKGROUND

Although it is well recognized that core root microorganisms contribute to plant health and productivity, little is known about their role to the accumulation of secondary metabolites. The roots of Anisodus tanguticus, a traditional herbal medication utilized by Tibetan medicine, are rich in tropane alkaloids. We collected wild A. tanguticus populations throughout a 1500 km transect on the Qinghai-Tibetan Plateau.

RESULTS

Our results showed that despite sampling at a distance of 1500 km, the root of A. tanguticus selectively recruits core root bacteria. We obtained 102 root bacterial core OTUs, and although their number only accounted for 2.99% of the total, their relative abundance accounted for 73% of the total. Spearman correlation and random forest analyses revealed that the composition of core root microbiomes was related to anisodine contents, aboveground biomass and nitrogen contents of Anisodus tanguticus. Among them, the main role is played by Rhizobacter, Variovorax, Polaromonas, and Mycobacterium genus that are significantly enriched in roots. Functional prediction by FAPROTAX showed that nitrogen-cycling microorganisms and pathogenic bacteria are strongly associated with anisodine contents, aboveground biomass and nitrogen contents of Anisodus tanguticus.

CONCLUSIONS

Our findings show that the root selectively recruits core root bacteria and revealed that the core microbiomes and microbial functions potentially contributed to the anisodine contents, aboveground biomass and nitrogen contents of the plant. This work may increase our understanding of the interactions between microorganisms and plants and improve our ability to manage root microbiota to promote sustainable production of herbal medicines.

Geographical equations of Swertia mussotii bioactivities: evidence from the western Sichuan region of China

Swertia mussotii is the most authentic raw material used in Tibetan medicine in China for its various bioactivities. This natural medicine resource is at risk of being exhausted due to the double interference of climate change and anthropogenic over-collection. Little is known about habitat characteristics and the crucial environmental factors that influence the levels of active ingredients. The goal of this study is to understand the variability in the bioactive compound content of a wide range of wild S. mussotii as it adapts to changing environmental conditions. The target compound content of the whole plant material was analyzed with the environmental explanatory variables of the field sample sites using a constrained ordination method for their correlation analysis. The results show that 16.3 percent of the sampled wild S. mussotii populations with the highest bioactive content can be grouped into the elite type. The most prominent environmental variables affecting the content of major bioactive products include altitude, aspect, soil TK content, Fe content, and C/N and N/P ratios. Altitude and aspect put indirect effects that are mediated by plant height and density, N/P ratio puts a direct effect, while soil TK content, Fe content and C/N ratio have both direct and indirect effects on the bioactivity of S. mussotii. In addition to the total negative effects of altitude and C/N ratio, the remaining factors play a driving role. These findings demonstrate variation by geographical conditions across S. mussotii accessions for physiologic responses and secondary compounds in wild populations. The knowledge gained from this study can be used for environmental and plant physiology research, efficient collection of naturally active compounds, and conservation strategies for rare natural plant resources.

Metagenomics insights into responses of rhizobacteria and their alleviation role in licorice allelopathy

BACKGROUND

Allelopathy is closely associated with rhizosphere biological processes, and rhizosphere microbial communities are essential for plant development. However, our understanding of rhizobacterial communities under influence of allelochemicals in licorice remains limited. In the present study, the responses and effects of rhizobacterial communities on licorice allelopathy were investigated using a combination of multi-omics sequencing and pot experiments, under allelochemical addition and rhizobacterial inoculation treatments.

RESULTS

Here, we demonstrated that exogenous glycyrrhizin inhibits licorice development, and reshapes and enriches specific rhizobacteria and corresponding functions related to glycyrrhizin degradation. Moreover, the Novosphingobium genus accounted for a relatively high proportion of the enriched taxa and appeared in metagenomic assembly genomes. We further characterized the different capacities of single and synthetic inoculants to degrade glycyrrhizin and elucidated their distinct potency for alleviating licorice allelopathy. Notably, the single replenished N (Novosphingobium resinovorum) inoculant had the greatest allelopathy alleviation effects in licorice seedlings.

CONCLUSIONS

Altogether, the findings highlight that exogenous glycyrrhizin simulates the allelopathic autotoxicity effects of licorice, and indigenous single rhizobacteria had greater effects than synthetic inoculants in protecting licorice growth from allelopathy. The results of the present study enhance our understanding of rhizobacterial community dynamics during licorice allelopathy, with potential implications for resolving continuous cropping obstacle in medicinal plant agriculture using rhizobacterial biofertilizers. Video Abstract.

Effects of time-space conversion on microflora structure, secondary metabolites composition and antioxidant capacity of Codonopsis pilosula root

In order to study the relationship between medicinal plant Codonopsis pilosula phenotype, secondary metabolites, antioxidant capacity and its rhizosphere soil nutrients, root-related microorganisms under seasonal and geographical changes, high-throughput sequencing technology was used to explore the bacterial community structure and variation in rhizosphere soil and root endosphere from six regions of Dingxi City, Gansu Province during four seasons. Secondary metabolites composition and antioxidant capacities of C. pilosula root collected successively from four seasons were determined. The chemical properties, nutrient content and enzyme activities of rhizosphere of C. pilosula were significantly different under different temporal and spatial conditions. All soil samples were alkaline (pH 7.64-8.42), with water content ranging from 9.53% to 19.95%, and electrical conductivity varied widely, showing obvious time-scale effects. Different time scales were the main reasons for the diversity and structure of rhizosphere bacterial community of C. pilosula. The diversity and richness of rhizosphere bacterial community in autumn and winter were higher than those in spring and summer, and bacterial community structure in spring and summer was more similar to that in autumn and winter. The root length and diameter of C. pilosula showed significant time gradient difference under different spatiotemporal conditions. Nutrition and niche competition lead to significant synergistic or antagonistic interactions between rhizosphere bacteria and endophytic bacteria, which invisibly affect soil properties, abundance of functional bacteria and even yield and quality of C. pilosula. Soil properties, rhizosphere bacteria and endophytic bacteria directly promoted root phenotype, stress resistance and polysaccharide accumulation of C. pilosula.

Responses of rhizosphere bacterial communities in newly reclaimed mudflat paddies to rice genotype and nitrogen fertilizer rate

The rhizosphere microbiome plays a vital role in crop growth and adaptation. However, the effects of rice genotype, nitrogen (N) fertilization, and their interactions on the rhizosphere bacterial communities in low fertility soil remain poorly understood. In this study, a two-factor field experiment was performed in newly reclaimed mudflat paddies characterized by poor fertility to analyze bacterial communities in the rhizosphere of Yongyou 2640 (japonica/indica hybrid rice, JIH) and Huaidao No.5 (japonica conventional rice, JC) under different N fertilizer rates. Results showed that genotype, followed by N fertilizer rate, was the primary factor affecting rhizobacteria diversity. Rhizobacteria diversity was higher in JIH than in JC and that of JIH and JC did not significantly change overall as N fertilizer rates but increased and decreased at N fertilizer rates of over 300 kg N ha^-1, respectively. The inconsistent response was probably attributed to the difference in the increase of ammonium and/or nitrate in the rhizosphere of JIH and JC. Genotype explained approximately 26% of the variation in rhizosphere bacterial communities. Rhizosphere bacterial communities with N fertilizer rates of over 300 kg N ha^-1 were more dissimilar to those without N fertilization relative to those with N fertilizer rates of below 300 kg N ha^-1, which was mainly attributed to changes in the concentration of ammonium and/or nitrate. The relative abundances of some potential beneficial genera such as Salinimicrobium, Salegentibacter, Gillisia, and Anaerolinea in the rhizosphere of JC and Salegentibacter, Lysobacter, Nocardioides, and Pontibacter in the rhizosphere of JIH were increased under N fertilizer rates of less than 300 kg N ha^-1 and positively correlated with rice yields, which indicate that changes in bacterial communities caused by N fertilization might be strongly associated with the improvement of rice yield. Overall, rhizosphere bacterial communities were more sensitive to genotype in newly reclaimed mudflat paddies and showed a consistent response to N fertilizer rates.

Structural characteristics and diversity of the rhizosphere bacterial communities of wild Fritillaria przewalskii Maxim. in the northeastern Tibetan Plateau

Introduction

Fritillaria przewalskii Maxim. is a Chinese endemic species with high medicinal value distributed in the northeastern part of the Tibetan Plateau. F. przewalskii root-associated rhizosphere bacterial communities shaped by soil properties may maintain the stability of soil structure and regulate F. przewalskii growth, but the rhizosphere bacterial community structure of wild F. przewalskii from natural populations is not clear.

Methods

In the current study, soil samples from 12 sites within the natural range of wild F. przewalskii were collected to investigate the compositions of bacterial communities via high-throughput sequencing of 16S rRNA genes and multivariate statistical analysis combined with soil properties and plant phenotypic characteristics.

Results

Bacterial communities varied between rhizosphere and bulk soil, and also between sites. Co-occurrence networks were more complex in rhizosphere soil (1,169 edges) than in bulk soil (676 edges). There were differences in bacterial communities between regions, including diversity and composition. Proteobacteria (26.47-37.61%), Bacteroidetes (10.53-25.22%), and Acidobacteria (10.45-23.54%) were the dominant bacteria, and all are associated with nutrient cycling. In multivariate statistical analysis, both soil properties and plant phenotypic characteristics were significantly associated with the bacterial community (p < 0.05). Soil physicochemical properties accounted for most community differences, and pH was a key factor (p < 0.01). Interestingly, when the rhizosphere soil environment remained alkaline, the C and N contents were lowest, as was the biomass of the medicinal part bulb. This might relate to the specific distribution of genera, such as Pseudonocardia, Ohtaekwangia, Flavobacterium (relative abundance >0.01), which all have significantly correlated with the biomass of F. przewalskii (p < 0.05).

Discussion

F. przewalskii is evidently averse to alkaline soil with high potassium contents, but this requires future verification. The results of the present study may provide theoretical guidance and new insights for the cultivation and domestication of F. przewalskii.

Regulation of soil micro-foodwebs to root secondary metabolites in cultivated and wild licorice plants

The diversity of soil eukaryotes and micro-foodwebs are only partially understood. Moreover, how they affect secondary metabolites in plant roots under distinct soil environment is not well elucidated. By combining multiple statistical analyses and network constructions, variations in soil eukaryotic diversity, community assembly processes and potential associations of holistic microbiotas were investigated in the bulk and rhizosphere soils of cultivated and wild licorice, and their regulatory patterns for root secondary metabolites were elucidated. The protistan communities displayed lower alpha diversity, more varied beta diversity patterns, and higher stochastic processes, as compared with fungal communities. Soil fungi individually played a more essential role than soil protists in the regulation of root secondary metabolites. Furthermore, rhizosphere soil was associated with more complicated networks than bulk soil; and wild licorice was associated with more complicated networks than cultivated licorice. Specific responsive modules resulting from networks were essential for the regulation of root secondary metabolites and were mostly affected by edaphic properties. Moreover, these modules directly or indirectly regulated the root secondary metabolites to varying degrees in the presence of soil protists. This indicated that the secondary metabolites were affected by associations between protistan, fungal and bacterial groups, and not merely by individual types of microorganisms in agricultural ecosystems. This study provides insight into the responses of root secondary metabolites to different groups of soil eukaryotic diversity and micro-foodwebs. The results have implications for comprehensively understanding the characteristics of the separate and combined roles of microbiotas for environmental management of licorice plantation ecosystem.

Population Evolution, Genetic Diversity and Structure of the Medicinal Legume, Glycyrrhiza uralensis and the Effects of Geographical Distribution on Leaves Nutrient Elements and Photosynthesis

Glycyrrhiza uralensis is a valuable medicinal legume, which occurs widely in arid and semi-arid regions. G. uralensis demand has risen steeply due to its high medical and commercial value. Interpret genome-wide information can stimulate the G. uralensis development as far as its increased bioactive compound levels, and plant yield are concerned. In this study, leaf nutrient concentration and photosynthetic chlorophyll index of G. uralensis were evaluated to determine the G. uralensis growth physiology in three habitats. We observed that G. uralensis nutrient levels and photosynthesis differed significantly in three regions (p < 0.05). Whole-genome re-sequencing of the sixty G. uralensis populations samples from different habitats was performed using an Illumina HiSeq sequencing platform to elucidate the distribution patterns, population evolution, and genetic diversity of G. uralensis. 150.06 Gb high-quality clean data was obtained after strict filtering. The 895237686 reads were mapped against the reference genome, with an average 89.7% mapping rate and 87.02% average sample coverage rate. A total of 6985987 SNPs were identified, and 117970 high-quality SNPs were obtained after filtering, which were subjected to subsequent analysis. Principal component analysis (PCA) based on interindividual SNPs and phylogenetic analysis based on interindividual SNPs showed that the G. uralensis samples could be categorized into central, southern, and eastern populations, which reflected strong genetic differentiation due to long periods of geographic isolation. In this study, a total of 131 candidate regions were screened, and 145 candidate genes (such as Glyur001802s00036258, Glyur003702s00044485, Glyur001802s00036257, Glyur007364s00047495, Glyur000028s00003476, and Glyur000398s00034457) were identified by selective clearance analysis based on Fst and θπ values. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed significant enrichment of 110 GO terms including carbohydrate metabolic process, carbohydrate biosynthetic process, carbohydrate derivative biosynthetic process, and glucose catabolic process (p < 0.05). Alpha-linolenic acid metabolism, biosynthesis of unsaturated fatty acids, and fatty acid degradation pathways were significantly enriched (p < 0.05). This study provides information on the genetic diversity, genetic structure, and population adaptability of the medicinal legumes, G. uralensis. The data obtained in this study provide valuable information for plant development and future optimization of breeding programs for functional genes.

Regulation of root secondary metabolites by partial root-associated microbiotas under the shaping of licorice ecotypic differentiation in northwest China

Interactions between plant hosts and their microbiotas are becoming increasingly evident, while the effects of plant communities on microbial communities in different geographic environments are poorly understood. Here, the differentiation of licorice plant ecotypes and the distribution of root-associated microbiotas were investigated across five sampling sites in northwest China. The interactions between the environment, plant and microbial communities, and their effects on licorice root secondary metabolites, were elucidated. The plant community was clearly differentiated into distinct ecotypes based on genotyping-by-sequencing and was primarily driven by geographic distance and available soil nitrogen. The bulk soil and root-associated microbiotas (rhizosphere soil and root endosphere) partially correlated with plant community, but all were significantly discriminated by plant clade. Moreover, these microbiotas were explained to different extents by distinct combinations of environment, geography, and plant community. Similarly, three structural equation models showed that licorice root secondary metabolites were complicatedly modulated by multiple abiotic and biotic factors, and were mostly explained by these factors in the rhizosphere model. Collectively, the results provide novel insights into the role of environment-plant-microbiota interactions in regulating root secondary metabolites. That should be accounted for when selecting appropriate licorice planting sites and management measures.

Succession of endophytic fungi and arbuscular mycorrhizal fungi associated with the growth of plant and their correlation with secondary metabolites in the roots of plants

BACKGROUND

To decipher the root and microbial interaction, secondary metabolite accumulation in roots and the microbial community's succession model during the plant's growth period demands an in-depth investigation. However, till now, no comprehensive study is available on the succession of endophytic fungi and arbuscular mycorrhizal fungi (AMF) with roots of medicinal licorice plants and the effects of endophytic fungi and AMF on the secondary metabolite accumulation in licorice plant's root.

RESULTS

In the current study, interaction between root and microbes in 1-3 years old medicinal licorice plant's root and rhizospheric soil was investigated. Secondary metabolites content in licorice root was determined using high-performance liquid chromatography (HPLC). The composition and diversity of endophytic and AMF in the root and soil were deciphered using high-throughput sequencing technology. During the plant's growth period, as compared to AMF, time and species significantly affected the diversity and richness of endophytic fungi, such as Ascomycota, Basidiomycota, Fusarium, Cladosporium, Sarocladium. The growth period also influenced the AMF diversity, evident by the significant increase in the relative abundance of Glomus and the significant decrease in the relative abundance of Diversispora. It indicated a different succession pattern between the endophytic fungal and AMF communities. Meanwhile, distance-based redundancy analysis and Mantel tests revealed root's water content and secondary metabolites (glycyrrhizic acid, liquiritin, and total flavonoids), which conferred endophytic fungi and AMF diversity. Additionally, plant growth significantly altered soil's physicochemical properties, which influenced the distribution of endophytic fungal and AMF communities.

CONCLUSIONS

This study indicated a different succession pattern between the endophytic fungal and AMF communities. During the plant's growth period, the contents of three secondary metabolites in roots increased per year, which contributed to the overall differences in composition and distribution of endophytic fungal and AMF communities. The endophytic fungal communities were more sensitive to secondary metabolites than AMF communities. The current study provides novel insights into the interaction between rhizospheric microbes and root exudates.

Differences in the endophytic fungal community and effective ingredients in root of three Glycyrrhiza species in Xinjiang, China

Background

Endophytic fungi influence the quality and quantity of the medicinal plant’s bioactive compounds through specific fungus-host interactions. Nevertheless, due to the paucity of information, the composition of endophytic fungal communities and the mechanism by which effective ingredients regulate endophytic fungal communities in roots remains unclear.

Methods

In this study, we collected root and soil samples (depth range: 0–20, 20–40, and 40–60 cm) of three Glycyrrhiza species (Glycyrrhiza uralensis, Glycyrrhiza inflata, and Glycyrrhiza glabra). Glycyrrhizic acid and liquiritin content were determined using high-performance liquid chromatography (HPLC), and total flavonoid content was determined using ultraviolet spectrophotometry. High-throughput sequencing technology was employed to explore the composition and diversity of the endophytic fungal community in different root segments of three Glycyrrhiza species. Furthermore, soil samples were subjected to physicochemical analyses.

Results

We observed that the liquiritin content was not affected by the root depth (0–20 cm, 20–40 cm, and 40–60 cm). Still, it was significantly affected by the Glycyrrhiza species (Glycyrrhiza uralensis, Glycyrrhiza inflata, Glycyrrhiza glabra) (P < 0.05). In Glycyrrhiza root, a total of eight phyla and 140 genera were annotated so far, out of which Ascomycota and Basidiomycota phyla, and the Fusarium, Paraphoma, and Helminthosporium genera were found to be significantly dominant. Spearman correlation analysis revealed that liquiritin content was accountable for the differences in the diversity of the endophytic fungal community. Furthermore, distance-based redundancy analysis (db-RDA) showed that physicochemical properties of the soil (available potassium and ammonium nitrogen) and the root factors (liquiritin and water content) were the main contributing factors for the variations in the overall structure of the endophytic fungal community. Our results showed that the effective ingredients of Glycyrrhiza root and physicochemical properties of the soil regulated the endophytic fungal community composition and medicinal licorice diversity.

Is a drought a drought in grasslands? Productivity responses to different types of drought

Drought, defined as a marked deficiency of precipitation relative to normal, occurs as periods of below-average precipitation or complete failure of precipitation inputs, and can be limited to a single season or prolonged over multiple years. Grasslands are typically quite sensitive to drought, but there can be substantial variability in the magnitude of loss of ecosystem function. We hypothesized that differences in how drought occurs may contribute to this variability. In four native Great Plains grasslands (three C₄- and one C₃-dominated) spanning a ~ 500-mm precipitation gradient, we imposed drought for four consecutive years by (1) reducing each rainfall event by 66% during the growing season (chronic drought) or (2) completely excluding rainfall during a shorter portion of the growing season (intense drought). The drought treatments were similar in magnitude but differed in the following characteristics: event number, event size and length of dry periods. We observed consistent drought-induced reductions (28-37%) in aboveground net primary production (ANPP) only in the C₄-dominated grasslands. In general, intense drought reduced ANPP more than chronic drought, with little evidence that drought duration altered this pattern. Conversely, belowground net primary production (BNPP) was reduced by drought in all grasslands (32-64%), with BNPP reductions greater in intense vs. chronic drought treatments in the most mesic grassland. We conclude that grassland productivity responses to drought did not strongly differ between these two types of drought, but when differences existed, intense drought consistently reduced function more than chronic drought.