Arbuscular mycorrhizal fungi and phosphorus supply accelerate main medicinal component production of Polygonum cuspidatum

Combined metabolome and transcriptome analyses reveal the pivotal role of mycorrhizal fungi Tulasnella sp. BJ1 in the growth and accumulation of secondary metabolites in Bletilla striata (Thunb.) Reiehb.f

The orchids usually coexist with mycorrhizal fungi during their growth and development. Numerous studies have substantiated the pivotal regulatory role of Tulasnella sp. mycorrhizal fungi in the germination and growth of orchid seeds. However, there remains a dearth of research elucidating the effects and underlying mechanisms of Tulasnella sp. on the growth, development, and metabolite accumulation in Bletilla striata seedlings. In the current study, metabolomics and transcriptomic analysis were used to reveal the key role of the mycorrhizal fungus Tulasnella sp.BJ1 in the growth and accumulation of secondary metabolites in B. striata. The results demonstrated that the application of BJ1 significantly enhanced the growth and development of B. striata seedlings. In September, the plant weight, tuber diameter, and tuber weight in the BJ1 treatment group reached 44.27 ± 6.79 g, 6.13 ± 0.53 cm, and 23.35 ± 3.06 g, respectively, surpassing those in the control group. The polysaccharide content in the BJ1 treatment group and control group peaked in June, reaching 14.91 ± 2.26 % and 14.38 ± 0.25 %, respectively. Total phenol content in both groups decreased in May and June, and the total phenol content in BJ1 treatment group was significantly lower than that in control group. The significant decrease observed in total phenol content during May and June may be attributed to an increase in proportion of polysaccharides promoted by BJ1. The transcriptome results showed that BJ1 upregulated polysaccharide biosynthesis-related genes, such as mannose phosphatase, transferase, mannose 6-phosphate isomerase, hexokinase, fructose kinase, and glucose 6-phosphate isomerase, as well as genes involved in stilbenes biosynthesis, including hydroxycinnamyltransferase and transcinnamate 4-monooxygenase. Metabolomics data indicated that the content of mannose and seven stilbene compounds in the tubers increased significantly after BJ1 treatment. Interestingly, the accumulation of these compounds corresponds to the pathway of upregulated genes. These findings suggest that an upregulation in mannose synthesis may facilitate the accumulation of polysaccharides in B. striata. Therefore, the current study uncovered that the mycorrhizal fungus Tulasnella sp. BJ1 can not only promote the growth and development of B. striata seedlings and increase tuber yield but also promote the accumulation of polysaccharides and stilbenes.

Analysis of Phenolic Compounds of Reynoutria sachalinensis and Reynoutria japonica Growing in the Russian Far East

The Russian Far East is a region of unique biodiversity, with numerous plant species, including Reynoutria japonica and Reynoutria sachalinensis. These plants are considered a serious threat to biodiversity and are classified as threatened species. However, Reynoutria plants synthesize and accumulate a variety of metabolites that are valued for their positive effects on human health. The main objective of this study is to quantitatively and qualitatively evaluate the content of secondary metabolites in different parts of R. japonica and R. sachalinensis plants. In this study, the results of phylogenetic analysis of the ITS2, matK, and rps16 genes showed that samples collected in the Sakhalin region were closest to R. sachalinensis, while samples collected in Primorsky krai were closer to R. japonica. The high-performance chromatography and mass spectrometry (HPLC-MS/MS) method was used to identify the compounds. As a result of the identification of metabolites in the leaves, stem, and roots of R. japonica and R. sachalinensis, we showed the presence of a total of 31 compounds, including stilbenes, phenolic acids, flavan-3-ols, flavones and flavonols, naphthalene derivatives, anthraquinones and derivatives, and phenylpropanoid disaccharide esters. The root of R. japonica was shown to be a rich source of stilbenes (up to 229.17 mg/g DW), which was 8.5 times higher than that of R. sachalinensis root (up to 27.04 mg/g DW). The root also contained high amounts of emodin derivatives and vanicoside B. Quercetin and its derivatives were the major metabolites in the leaves and stems of both Reynoutria species. In R. japonica leaves, quercetin-3-O-pentoside was the major compound, reaching a total of 7 mg/g DW, accounting for 34% of all compounds analyzed. In contrast, in R. sachalinensis leaves, quercitrin was the major compound (up to 13.96 mg/g DW), accounting for 62% of all compounds and 12.7 times higher than in R. japonica leaves. In turn, R. japonica leaves also contained high amounts of phenolic acids (up to 10 mg/g DW). Thus, the obtained results showed significant differences in the qualitative and quantitative composition of metabolites between R. japonica and R. sachalinensis plants. Additionally, in this work, a cell culture of R. japonica was obtained and tested for its ability to synthesize and accumulate stilbenes.

Interactions between arbuscular mycorrhizal fungi and phosphate-soluble bacteria affect ginsenoside compositions by modulating the C:N:P stoichiometry in Panax ginseng

The biomass production as well as the accumulation of secondary metabolites of plant is highly determined by the absorption of nutritional elements, in particular nitrogen (N) and phosphorus (P). Arbuscular mycorrhizal fungi (AMF) can absorb soluble P and transport it to plants, while phosphate solubilizing bacteria (PSB) can increase the content of solubilizing P in soil. Previous studies have identified the effects of either AMF or PSB inoculation on altering plant C:N:P stoichiometry, whether AMF interact with PSB in promoting plant growth and changing elemental concentration and composition of secondary metabolites by altering plant C:N:P stoichiometry remains ambiguous. In this study, we investigated the effects of inoculation of AMF, PSB, and their co-inoculation AMP (AMF and PSB) on the biomass growth, the C:N:P stoichiometry, the core microorganisms of rhizosphere soil, and the ginsenoside compositions of ginseng (Panax ginseng). The results showed that compared to control or single inoculation of AMF or PSB, co-inoculation of AMF and PSB significantly increased the AMF colonization rate on ginseng roots, increased the biomass of both above and under-ground parts of ginseng. Similarly, co-inoculation of AMF and PSB substantially increased the concentrations of N and P, reduced the ratios of C:P and N:P in the above-ground part of ginseng. The co-inoculation of AMF and PSB also increased concentrations of total ginsenosides and altered the compositions of ginsenosides in both the above and under-ground parts of ginseng. Analysis the rhizosphere microorganism showed that the co-inoculation of AMF and PSB recruited distinct core microorganisms that differ from the control and treatments with single inoculation of AMF or PSB. Our results suggested that PSB inoculation enhanced the positive effect of AMF in improving the absorption of nutrimental elements, altered the C:N:P stoichiometry and, ginsenosides concentration and composition of ginseng, influenced the plant rhizosphere microbial community. These findings offer valuable insights into enhancing plant biomass production and promoting secondary metabolites by improving the plant-fungi-bacterial relationships.

Widely Targeted Metabolomic Analysis Reveals the Improvement in Panax notoginseng Triterpenoids Triggered by Arbuscular Mycorrhizal Fungi via UPLC-ESI-MS/MS

Panax notoginseng is a highly valued perennial medicinal herb in China and is widely used in clinical treatments. The main purpose of this study was to elucidate the changes in the composition of P. notoginseng saponins (PNSs), which are the main bioactive substances, triggered by arbuscular mycorrhizal fungi (AMF) via ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). A total of 202 putative terpenoid metabolites were detected, of which 150 triterpene glycosides were identified, accounting for 74.26% of the total. Correlation analysis, principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) of the metabolites revealed that the samples treated with AMF (group Ce) could be clearly separated from the CK samples. In total, 49 differential terpene metabolites were identified between the Ce and CK groups, of which 38 and 11 metabolites were upregulated and downregulated, respectively, and most of the upregulated differentially abundant metabolites were mainly triterpene glycosides. The relative abundances of the two major notoginsenosides (MNs), ginsenosides Rd and Re, and 13 rare notoginsenosides (RNs), significantly increased. The differential saponins, especially RNs, were more easily clustered into one branch and had a high positive correlation. It could be concluded that the biosynthesis and accumulation of some RNs share the same pathways as those triggered by AMF. This study provides a new way to obtain more notoginsenoside resources, particularly RNs, and sheds new light on the scientization and rationalization of the use of AMF agents in the ecological planting of medicinal plants.

Improvement of Panax notoginseng saponin accumulation triggered by methyl jasmonate under arbuscular mycorrhizal fungi

Panax notoginseng is a highly valued perennial medicinal herb plant in Yunnan Province, China, and the taproots are the main medicinal parts that are rich in active substances of P. notoginseng saponins. The main purpose of this study is to uncover the physiological and molecular mechanism of Panax notoginseng saponin accumulation triggered by methyl jasmonate (MeJA) under arbuscular mycorrhizal fungi (AMF) by determining physiological indices, high-throughput sequencing and correlation analysis. Physiological results showed that the biomass and saponin contents of P. notoginseng, the concentrations of jasmonic acids (JAs) and the key enzyme activities involved in notoginsenoside biosynthesis significantly increased under AMF or MeJA, but the interactive treatment of AMF and MeJA weakened the effect of AMF, suggesting that a high concentration of endogenous JA have inhibitory effect. Transcriptome sequencing results indicated that differential expressed genes (DEGs) involved in notoginsenoside and JA biosynthesis were significantly enriched in response to AMF induction, e.g., upregulated genes of diphosphocytidyl-2-C-methyl-d-erythritol kinases (ISPEs), cytochrome P450 monooxygenases (CYP450s)_and glycosyltransferases (GTs), while treatments AMF-MeJA and salicylhydroxamic acid (SHAM) decreased the abundance of these DEGs. Interestingly, a high correlation presented between any two of saponin contents, key enzyme activities and expression levels of DEGs. Taken together, the inoculation of AMF can improve the growth and saponin accumulation of P. notoginseng by strengthening the activities of key enzymes and the expression levels of encoding genes, in which the JA regulatory pathway is a key link. This study provides references for implementing ecological planting of P. notoginseng, improving saponin accumulation and illustrating the biosynthesis mechanism.

Exogenous Melatonin Regulates Physiological Responses and Active Ingredient Levels in Polygonum cuspidatum under Drought Stress

Polygonum cuspidatum, an important medicinal plant, is rich in resveratrol and polydatin, but it frequently suffers from drought stress in the nursery stage, which inhibits the plant's growth, active components concentrations, and the price of rhizome in the later stage. The purpose of this study was to analyze how exogenous 100 mM melatonin (MT) (an indole heterocyclic compound) affected biomass production, water potential, gas exchange, antioxidant enzyme activities, active components levels, and resveratrol synthase (RS) gene expression of P. cuspidatum seedlings growing under well-watered and drought stress conditions. The 12-week drought treatment negatively affected the shoot and root biomass, leaf water potential, and leaf gas exchange parameters (photosynthetic rate, stomatal conductance, and transpiration rate), whereas the application of exogenous MT significantly increased these variables of stressed and non-stressed seedlings, accompanied by higher increases in the biomass, photosynthetic rate, and stomatal conductance under drought versus well-watered conditions. Drought treatment raised the activities of superoxide dismutase, peroxidase, and catalase in the leaves, while the MT application increased the activities of the three antioxidant enzymes regardless of soil moistures. Drought treatment reduced root chrysophanol, emodin, physcion, and resveratrol levels, while it dramatically promoted root polydatin levels. At the same time, the application of exogenous MT significantly increased the levels of the five active components, regardless of soil moistures, with the exception of no change in the emodin under well-watered conditions. The MT treatment also up-regulated the relative expression of PcRS under both soil moistures, along with a significantly positive correlation between the relative expression of PcRS and resveratrol levels. In conclusion, exogenous MT can be employed as a biostimulant to enhance plant growth, leaf gas exchange, antioxidant enzyme activities, and active components of P. cuspidatum under drought stress conditions, which provides a reference for drought-resistant cultivation of P. cuspidatum.

Serendipita indica promotes P acquisition and growth in tea seedlings under P deficit conditions by increasing cytokinins and indoleacetic acid and phosphate transporter gene expression

The culturable endophytic fungus Serendipita indica has many beneficial effects on plants, but whether and how it affects physiological activities and phosphorus (P) acquisition of tea seedlings at low P levels is unclear. The objective of this study was to analyze the effects of inoculation with S. indica on growth, gas exchange, chlorophyll fluorescence, auxins, cytokinins, P levels, and expressions of two phosphate transporter (PT) genes in leaves of tea (Camellia sinensis L. cv. Fudingdabaicha) seedlings grown at 0.5 μM (P_0.5) and 50 μM (P₅₀) P levels. Sixteen weeks after the inoculation, S. indica colonized roots of tea seedlings, with root fungal colonization rates reaching 62.18% and 81.34% at P_0.5 and P₅₀ levels, respectively. Although plant growth behavior, leaf gas exchange, chlorophyll values, nitrogen balance index, and chlorophyll fluorescence parameters of tea seedlings were suppressed at P_0.5 versus P₅₀ levels, inoculation of S. indica mitigated the negative effects to some extent, along with more prominent promotion at P_0.5 levels. S. indica inoculation significantly increased leaf P and indoleacetic acid concentrations at P_0.5 and P₅₀ levels and leaf isopentenyladenine, dihydrozeatin, and transzeatin concentrations at P_0.5 levels, coupled with the reduction of indolebutyric acid at P₅₀ levels. Inoculation of S. indica up-regulated the relative expression of leaf CsPT1 at P_0.5 and P₅₀ levels and CsPT4 at P_0.5 levels. It is concluded that S. indica promoted P acquisition and growth in tea seedlings under P deficit conditions by increasing cytokinins and indoleacetic acid and CsPT1 and CsPT4 expression.

Research progress of rhizosphere microorganisms in Fritillaria L. medicinal plants

The soil's rhizosphere is a highly active place where the exchange of substances and information occurs among plants, soils, and microorganisms. The microorganisms involved are crucial to the activities of plant growth and development, metabolism, and reproduction. Fritillaria L. medicinal plants are unique Chinese medicinal ingredients, but the continuous cropping obstacles formed in the artificial planting process is severely harmful to the growth and development of these medicinal plants. In this review, we summarized the current species and distribution of Fritillaria L. in China, and analyzed the changes in microbial diversity (mainly among bacteria and fungi) in the rhizosphere of these plants under long-term continuous cropping. The fungi showed an increasing trend in the soil rhizosphere, resulting in the transition of the soil from the high-fertility "bacterial type" to the low-fertility "fungal type" as planting years increased. Furthermore, the interaction between Fritillaria L. medicinal plants and the rhizosphere microorganisms was reviewed, and promising applications for the rhizosphere microbiome in the cultivation of Fritillaria L. medicinal plants were suggested. It is expected that this review will facilitate the in-depth understanding of rhizosphere microorganisms in the growth, accumulation of active ingredients, and disease control of Fritillaria L.