Metabolites In Roots Research Articles

Exploring the synergistic effects of soil nutrients, rhizosphere fungi, and endophytic fungi on the shaping of root metabolites in Angelica sinensis (Oliv.) Diels.

The root of Angelica sinensis (Oliv.) Diels (Ang) is a bulk Chinese herbal medicine, and the microecological regulation is a sustainable means to enhance its quality. In this study, Angs at five bases (LZ, XZ, QS, PM, MZC) in Minxian County, Gansu Province were taken as the research objects. These bases locate in the typical spatial spans of the Ang authentic area, and are important planting bases. The Angs from production bases were systematically compared with respect to soil physicochemical properties, rhizosphere fungi, endophytic fungi, and metabolic profiles. Typically, LZ showed low levels of available nitrogen (AN), available phosphorus (AP), available potassium (AK), and soil enzyme activities, while QS had the highest AN, AP, AK, and cellulase activity. Although XZ exhibits moderate nutrient contents, its sucrase activity was highest. Based on microbiome sequencing, rhizosphere fungal communities responded these physicochemical differences, with XZ harboring more probiotics, including Tetracladium, Itersonilia, and Vishniacozyma, compared to LZ, which showed the lowest abundance of these microorganisms. Differential patterns were presented among their endophytic fungal communities. Through LC-MS detection, it was revealed that Angs in QS synthesized more short peptides, organic acids and phenylpropanoid ingredients. Upregulated metabolites with plant defense efficacy are mostly found in LZ's Angs. Whereas XZ's Angs had a moderate abundance of bioactive ingredients. Structural equation fitting further highlighted the synergistic effects of soil nutrients (AN, AP, AK) with key fungal genera (Tetracladium, Itersonilia, Paecilomyces, Aspergillus) and their potential shaping effects on amino acids, short peptides, organic acids, and phenylpropanoids such as L-phenylalanine, acetyl-L-tyrosine, Ile-His-Met-Thr, caffeic aldehyde, L-pipecolic acid, and 4-methoxycinnamic acid. This study further refined the potential action modes of these key microecological factors shaping the accumulation of main types of active ingredients. These results are expected to provide an important reference for the development of quality regulation strategies in Ang ecological cultivation.

Visualizing the Spatial Distribution of Metabolites in Angelica sinensis Roots by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging.

Angelica sinensis is one of the most popular traditional Chinese medicines (TCM) and has been extensively used to treat various diseases. Hundreds of endogenous ingredients have been isolated and identified from this herb, but their spatial distribution within the plant root is largely unknown. In this study, we tried to investigate and map within-tissue spatial distribution of metabolites in Angelica sinensis roots. After optimization of experiment conditions, the 1,5-diaminonaphthalene (1,5-DAN) was chosen as the matrix and was sprayed on the surface of root sections. Then matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was employed to perform insitu detection and obtain detail spatial distribution information of metabolites in Angelica sinensis roots. The spatial distributions of a wide range of metabolites including organic acids, amino acids, oligosaccharides, and phospholipids were characterized and visualized in Angelica sinensis roots. Majority of these metabolites were located in the phloem and xylem, while ferulic acid was mainly present in the cork layer. The results revealed a dramatic metabolic heterogeneity among different regions of the roots and distinct spatial distribution patterns of different metabolites. Additionally, the metabolic pathways involved in the biosynthesis of choline were also successfully localized and visualized. This study comprehensively characterized the spatial distribution of metabolites in Angelica sinensis roots, which would prompt the understanding of its chemical separation, biosynthesis, and pharmacological activities.

Analysis of the Synergistic Effect of Endophytic Bacteria and Metabolites on Yield in Soybean Roots Under Biochar with Nitrogen Fertilization

The appropriate application of nitrogen fertilizers and biochar to the soil is beneficial for soybean growth, and a combination of biochar and nitrogen can improve low-nitrogen fertilizer utilization efficiency. However, the effect of the combination of biochar and nitrogen fertilizer on soybean roots is still unclear. Therefore, in this study, we investigate the changes in endophytic bacterial communities and metabolites in soybean roots under different combinations of biochar and nitrogen fertilizer treatments by setting different fertilization levels and using high-throughput sequencing and non-targeted metabolomics techniques. The results showed that applying 20 t/ha of biochar and 180 kg/ha of nitrogen fertilizer (C2N1) resulted in the highest soybean yield. By studying the endophytic bacterial community in soybean roots, it was observed that the dominant phyla were Proteobacteria, Bacteroidota, and Actinobacteriota, and the dominant genera were Bradyrhizobium, Streptomyces, and Rhizobacter. Moreover, a metabolic pathway analysis revealed that glycosylphosphatidylinositol (GPI)-anchor biosynthesis was the most significant metabolic pathway in the C0N1 vs. C0N0 comparison group, and glycerophospholipid metabolism was the most significant metabolic pathway in the C2N1 vs. C1N1 comparison group; they were both associated with regulatory mechanisms such as plant growth promotion and nutrient cycling. Structural equation modeling indicates that both endophytic bacteria and metabolites have a significant positive impact on yield. Bradyrhizobium and Rhizobium are observable variables with significant positive effects on endophytic bacteria, while Phe-Thr and 7-allyloxycoumarin are observable variables with significant positive effects on metabolites. Endophytic bacteria not only have a direct impact on crop yield, but also indirectly affect crop yield through their effects on metabolites. This study has important scientific value and guiding significance for improving soybean yields.

Chemotaxis of rhizosphere Pseudomonas sp. induced by foliar spraying of lanthanum reduces cadmium uptake by pakchoi.

Foliar application of rare earth micronutrient of lanthanum (La) exhibits great potential in reducing cadmium (Cd) uptake in crops, the underlying mechanisms controlling the interaction between Cd toxicity-relieved crops and soil microbiota are poorly understood. In this study, LaCl3 with the concentrations of 10 and 30μM was sprayed on pakchoi (Brassica chinensis L.) planting on Cd contaminated solution and soil to determine the changes of root metabolites and rhizosphere bacterial communities. Compared to the control, Cd concentration in pakchoi leaves was significantly decreased by 30.9% and 22.6% with the high group under both hydroponic and pot culture by applying 30μM LaCl3. Herein, the concrete evidence is provided that pakchoi plants in response to foliar-spraying La under soil or solution Cd toxicity can promote the root secretion of amino acids, resulting in a strong enrichment of nitrogen-related microorganisms. To probe this linkage, a Pseudomonas representative specie was isolated that had the ability of consuming alanine, the most oversecreted root exudate due to La application. Further results demonstrated that this strain had the capacities for alleviating Cd toxicity and enhancing crop growth by immobilizing Cd and secreting plant-beneficial metabolites. This study reveals a plant-extrudate-microbiome feedback loop for responding to La-relieved Cd toxicity in crops by the chemotaxis of rhizosphere Pseudomonas toward alanine secreted by pakchoi.

Green Synthesized Silver Nanoparticles Induced Accumulation of Biomass and Secondary Metabolites in Hairy Roots of Rehmannia glutinosa.

The hairy roots of Rehmannia glutinosa (Gaertn.) Libosch. ex Fisch. & C. A. Mey. are capable of producing active compounds such as iridoid glycoside, and phenylethanoid glycosides, which have potential applications in the pharmaceutical industry. Silver nanoparticles (AgNPs) have been used as novel elicitors in the induced cultivation of hairy roots, but there is a lack of research regarding their effects on R. glutinosa hairy roots. In the present study, silver nanoparticles (Pp-AgNPs) synthesized by the endophytic fungus Penicillium polandii PG21 were adopted to elicit hairy roots of R. glutinosa, to investigate their influences on the biomass, color, secondary metabolites, antioxidant activity, sucrose metabolism, and phytohormone-related gene expression. The results revealed that the dry weight and fresh weight of R. glutinosa hairy roots were both higher in the treated group than in the control group after addition of 2 mg/L Pp-AgNPs for 20 d. The content of verbascoside, total phenylethanol glycosides and total cycloartenoid in the treatment group reached the highest level at 20 d, which were 1.75, 1.51, 1.44 times more than those in the control group, respectively. Pp-AgNPs significantly stimulated the enzyme activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). The growth-promoting effect of Pp-AgNPs may be accomplished by increasing sucrose metabolism, and regulating the synthesis and signal transduction of gibberellin (GA) and indoleacetic acid (IAA). Moreover, expressed sequence tags-simple sequence repeat (EST-SSR)-based genetic diversity analyses indicated that there was little possibility of genetic variation among samples under different treatment conditions. In conclusion, the appropriate concentration of Pp-AgNPs can be used as an effective elicitor to improve the biomass and secondary metabolites content in R. glutinosa hairy roots.

Response of soybean root exudates and related metabolic pathways to low phosphorus stress.

Phosphorus (P) is an essential elemental nutrient required in high abundance for robust soybean growth and development. Low P stress negatively impacts plant physiological and biochemical processes, such as photosynthesis, respiration, and energy transfer. Soybean roots play key roles in plant adaptive responses to P stress and other soil-related environmental stressors. Study the changes in soybean root exudates and differences in related metabolic pathways under low phosphorus stress, analyzing the response mechanism of soybean roots to phosphorus stress from the perspective of root exudates, which provide a theoretical basis for further analyzing the physiological mechanism of phosphorus stress on soybean. In this study, soybean roots were exposed to three phosphate levels: 1 mg/L (P stress), 11 mg/L (P stress) and 31 mg/L (Normal P) for 10 days and 20 days, then root exudates were analyzed via ultra-high-performance liquid chromatography-mass spectrometry to identify effects of P stress on root metabolite profiles and associated metabolic pathways. Our results revealed that with increasing P stress severity and/or duration, soybean roots produced altered types, quantities, and increased numbers of exudate metabolites (DMs in the P1 group were primarily upregulated, whereas those in the P11 group were predominately downregulated) caused by changes in regulation of activities of numerous metabolic pathways. These pathways had functions related to environmental adaptation, energy metabolism, and scavenging of reactive oxygen species and primarily included amino acid, flavonoid, and nicotinate and nicotinamide metabolic pathways and pathways related to isoquinoline alkaloid biosynthesis, sugar catabolism, and phospholipid metabolism. These metabolites and metabolic pathways lay a foundation to support further investigations of physiological mechanisms underlying the soybean root response to P deficiency.

Root metabolites regulated by FERONIA promote phosphorus-solubilizing rhizobacteria enrichment induced by Arabidopsis thaliana coping with phosphorus deficiency.

The recruitment of the phosphorus-solubilizing rhizobacteria plays an important role in response to phosphorus deficiency. Through the treatments of Arabidopsis thaliana (Col-0) and the FERONIA (FER) functional deficient mutants (fer-4 and fer-5) with the soil suspension in various phosphorus conditions, we discovered that FER could promote phosphorus-solubilizing rhizobacteria enrichment to rescue the defective plant during phosphorus deficiency. The amplicon sequencing data reflected that the phosphorus-solubilizing rhizobacterial genus Alcaligenes was significantly enriched of Col-0 than fer-4 in low phosphorus conditions. Metabolomics analysis revealed that there were more α-D-Glucose (α-D-Glc) and L-Leucine (L-Leu) in Col-0 roots than those in fer-4 roots. The alterations of α-D-Glc and L-Leu mediated by FER had high-positive correlations to the enrichment of Alcaligenes. We successfully isolated a phosphorus-solubilizing rhizobacteria strain identified as Alcaligenes faecalis PSB15. The α-D-Glc and L-Leu could promote the strain PSB15 growth on LB agar plates and assist fer-4 in recovering from phosphorus starvation in the low phosphorus (LP) liquid medium vermiculite with tricalcium phosphate (TCP). The α-D-Glc and L-Leu could be considered as promising compounds to enrich beneficial phosphorus-solubilizing rhizobacteria, such as Alcaligenes, and provide a reference for overcoming the plight of phosphorus deficiency in crops in the field of agricultural production in the future.

Effects of Sugarcane/Peanut Intercropping on Root Exudates and Rhizosphere Soil Nutrient.

Intercropping can enable more efficient resource use and increase yield. Most current studies focus on the correlation between soil nutrients and crop yield under intercropping conditions. However, the mechanisms related to root exudates and soil nutrients remain unclear. Therefore, this study explored the correlation between rhizosphere soil nutrients and root exudates in sugarcane/peanut intercropping. Root extracts, root exudates, rhizosphere soil enzyme activities, and soil nutrients were analyzed and compared in monocultured and intercropped peanut and sugarcane at different growth stages. The root metabolites were annotated using the Kyoto Encyclopedia of Genes and Genomes pathways to further identify the connection between soil nutrients and root exudates. The effects of intercropping differed in peanut and sugarcane at different growth stages, and the difference between podding and pod-filling stages was significant. Intercropping generally had a great effect on peanut; it not only significantly increased the organic acid, soluble sugars, and phenolic acids in root exudates and extracts from peanuts, but also significantly increased rhizosphere soil enzyme activities and soil nutrient levels. Intercropping peanuts promoted fumaric acid secretion from roots and significantly affected the metabolic pathways of alanine, aspartate, and glutamate. Sugarcane/peanut intercropping can increase root exudates and effectively improve soil nutrients. The changes in soil nutrients are closely related to the effects of fumaric acid on alanine, aspartate, and glutamate metabolism.

Arsenic-induced enhancement of diazotrophic recruitment and nitrogen fixation in Pteris vittata rhizosphere.

Heavy metal contamination poses an escalating global challenge to soil ecosystems, with hyperaccumulators playing a crucial role in environmental remediation and resource recovery. The enrichment of diazotrophs and resulting nitrogen accumulation promoted hyperaccumulator growth and facilitated phytoremediation. Nonetheless, the regulatory mechanism of hyperaccumulator biological nitrogen fixation has remained elusive. Here, we report the mechanism by which arsenic regulates biological nitrogen fixation in the arsenic-hyperaccumulator Pteris vittata. Field investigations and greenhouse experiments, based on multi-omics approaches, reveal that elevated arsenic stress induces an enrichment of key diazotrophs, enhances plant nitrogen acquisition, and thus improves plant growth. Metabolomic analysis and microfluidic experiments further demonstrate that the upregulation of specific root metabolites plays a crucial role in recruiting key diazotrophic bacteria. These findings highlight the pivotal role of nitrogen-acquisition mechanisms in the arsenic hyperaccumulation of Pteris vittata, and provide valuable insights into the plant stress resistance.

Effect of Fluridone on Roots and Leaf Buds Development in Stem Cuttings of Salix babylonica (L.) 'Tortuosa' and Related Metabolic and Physiological Traits.

The herbicide fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl (phenyl)]-4(1H)-pyridone) interferes with carotenoid biosynthesis in plants by inhibiting the conversion of phytoene to phytofluene. Fluridone also indirectly inhibits the biosynthesis of abscisic acid and strigolactones, and therefore, our study indirectly addresses the effect of reduced ABA on the roots and leaf buds development in stem cuttings of Salix babylonica L. 'Tortuosa'. The stem cuttings were kept in distilled water (control) or in a solution of fluridone (10 mg/L) in natural greenhouse light and temperature conditions. During the experiments, morphological observations were carried out on developing roots and leaf buds, as well as their appearance and growth. After three weeks of continuous treatments, adventitious roots and leaf buds were collected and analysed. Identification and analysis of anthocyanins were carried out using micro-HPLC-MS/MS-TOF, while HPLC-MS/MS was used to analyse phenolic acids, flavonoids and salicinoids. The fluridone applied significantly inhibited root growth, but the number or density of roots was higher compared to the control. Contents of salicortin and salicin were several dozen times higher in leaf buds than in roots of willow. Fluridone increased the content of salicortin in roots and leaf buds and declined the level of salicin in buds. Fluridone also declined the content of most anthocyanins in roots but enhanced their content in buds, especially cyanidin glucoside, cyanidin galactoside and cyanidin rutinoside. Besides, fluridone markedly decreased the level of chlorophylls and carotenoids in the leaf buds. The results indicate that applied fluridone solution reduced root growth, caused bleaching of leaf buds, and markedly affected the content of secondary metabolites in the adventitious roots and leaf buds of S. babylonica stem cuttings. The paper presents and discusses in detail the significance of fluridone's effects on physiological processes and secondary metabolism.

Mechanisms by Which Increased pH Ameliorates Copper Excess in Citrus sinensis Roots: Insight from a Combined Analysis of Physiology, Transcriptome, and Metabolome.

Limited data are available on copper (Cu)-pH interaction-responsive genes and/or metabolites in plant roots. Citrus sinensis seedlings were treated with 300 μM (Cu toxicity) or 0.5 μM (control) CuCl2 at pH 3.0 or 4.8 for 17 weeks. Thereafter, gene expression and metabolite profiles were obtained using RNA-Seq and widely targeted metabolome, respectively. Additionally, several related physiological parameters were measured in roots. The results indicated that elevating the pH decreased the toxic effects of Cu on the abundances of secondary metabolites and primary metabolites in roots. This difference was related to the following several factors: (a) elevating the pH increased the capacity of Cu-toxic roots to maintain Cu homeostasis by reducing Cu uptake and Cu translocation to young leaves; (b) elevating the pH alleviated Cu toxicity-triggered oxidative damage by decreasing reactive oxygen species (ROS) formation and free fatty acid abundances and increasing the ability to detoxify ROS and maintain cell redox homeostasis in roots; and (c) increasing the pH prevented root senescence and cell wall (CW) metabolism impairments caused by Cu toxicity by lowering Cu levels in roots and root CWs, thus improving root growth. There were some differences and similarities in Cu-pH interaction-responsive genes and metabolites between leaves and roots.

Phosphorus availability influences disease-suppressive soil microbiome through plant-microbe interactions.

Soil nutrient status and soil-borne diseases are pivotal factors impacting modern intensive agricultural production. The interplay among plants, soil microbiome, and nutrient regimes in agroecosystems is essential for developing effective disease management. However, the influence of nutrient availability on soil-borne disease suppression and associated plant-microbe interactions remains to be fully explored. This study aims to elucidate the mechanistic understanding of nutrient impacts on disease suppression, using phosphorous as a target nutrient. A 6-year field trial involving monocropping of tomatoes with varied fertilizer manipulations demonstrated that phosphorus availability is a key factor driving the control of bacterial wilt disease caused by Ralstonia solanacearum. Subsequent greenhouse experiments were then conducted to delve into the underlying mechanisms of this phenomenon by varying phosphorus availability for tomatoes challenged with the pathogen. Results showed that the alleviation of phosphorus stress promoted the disease-suppressive capacity of the rhizosphere microbiome, but not that of the bulk soil microbiome. This appears to be an extension of the plant trade-off between investment in disease defense mechanisms versus phosphorus acquisition. Adequate phosphorus levels were associated with elevated secretion of root metabolites such as L-tryptophan, methoxyindoleacetic acid, O-phosphorylethanolamine, or mangiferin, increasing the relative density of microbial biocontrol populations such as Chryseobacterium in the rhizosphere. On the other hand, phosphorus deficiency triggered an alternate defense strategy, via root metabolites like blumenol A or quercetin to form symbiosis with arbuscular mycorrhizal fungi, which facilitated phosphorus acquisition as well. Overall, our study shows how phosphorus availability can influence the disease suppression capability of the soil microbiome through plant-microbial interactions. These findings highlight the importance of optimizing nutrient regimes to enhance disease suppression, facilitating targeted crop management and boosting agricultural productivity. Video Abstract.

Profiling sorghum-microbe interactions with a specialized photoaffinity probe identifies key sorgoleone binders in Acinetobacter pittii.

Interactions between plants and soil microbial communities that benefit plant growth and enhance nutrient acquisition are driven by the selective release of metabolites from plant roots, or root exudation. To investigate these plant-microbe interactions, we developed a photoaffinity probe based on sorgoleone (sorgoleone diazirine alkyne for photoaffinity labeling, SoDA-PAL), a hydrophobic secondary metabolite and allelochemical produced in Sorghum bicolor root exudates. We applied SoDA-PAL to the identification of sorgoleone-binding proteins in Acinetobacter pittii SO1, a potential plant growth-promoting microbe isolated from sorghum rhizosphere soil. Competitive photoaffinity labeling of A. pittii whole cell lysates with SoDA-PAL identified 137 statistically enriched proteins, including putative transporters, transcriptional regulators, and a subset of proteins with predicted enzymatic functions. We performed computational protein modeling and docking with sorgoleone to prioritize candidates for experimental validation and then confirmed binding of sorgoleone to four of these proteins in vitro: the α/β fold hydrolase SrgB (OH685_09420), a fumarylacetoacetase (OH685_02300), a lysophospholipase (OH685_14215), and an unannotated hypothetical protein (OH685_18625). Our application of this specialized sorgoleone-based probe coupled with structural bioinformatics streamlines the identification of microbial proteins involved in metabolite recognition, metabolism, and toxicity, widening our understanding of the range of cellular pathways that can be affected by a plant secondary metabolite.IMPORTANCEHere, we demonstrate that a photoaffinity-based chemical probe modeled after sorgoleone, an important secondary metabolite released by sorghum roots, can be used to identify microbial proteins that directly interact with sorgoleone. We applied this probe to the sorghum-associated bacterium Acinetobacter pittii and showed that probe labeling is dose-dependent and sensitive to competition with purified sorgoleone. Coupling the probe with proteomics and computational analysis facilitated the identification of putative sorgoleone binders, including a protein implicated in a conserved pathway essential for sorgoleone catabolism. We anticipate that discoveries seeded by this workflow will expand our understanding of the molecular mechanisms by which specific metabolites in root exudates shape the sorghum rhizosphere microbiome.

Comparison of transcriptome and metabolome analysis revealed cold-resistant metabolic pathways in cucumber roots under low-temperature stress in root zone.

Low ground temperature is a major factor limiting overwintering in cucumber cultivation facilities in northern alpine regions. Lower temperatures in the root zone directly affect the physiological function of the root system, which in turn affects the normal physiological activity of plants. However, the importance of the ground temperature in facilities has not attracted sufficient attention. Therefore, this study tested the cucumber variety Jinyou 35 under three root zone temperatures (room temperature, 20-22°C; suboptimal temperature, 13- 15°C; and low temperature, 8-10°C) to investigated possible cold resistance mechanisms in the root of cucumber seedlings through hormone, metabolomics, and transcriptomics analyses. The results showed that cucumber roots were subjected to chilling stress at different temperatures. Hormone analysis indicated that auxin content was highest in the roots. Jasmonic acid and strigolactone participated in the low-temperature stress response. Auxin and jasmonate are key hormones that regulate the response of cucumber roots to low temperatures. Phenolic acid was the most abundant metabolite in cucumber roots under chilling stress. Additionally, triterpenes may play an important role in chilling resistance. Differentially expressed genes and metabolites were significantly enriched in benzoxazinoid biosynthesis in the room temperature vs. suboptimal temperature groups and the room temperature vs. low temperature groups. Most differentially expressed transcription factor genes in AP2/ERF were strongly induced in cucumber roots by both suboptimal and low-temperature stress conditions. These results provide guidance for the cultivation of cucumber in facilities.

Enhancing olive tree (Olea europaea) rhizosphere dynamics: Co-inoculation effects of arbuscular mycorrhizal fungi and plant growth- promoting rhizobacteria in field experiments

We investigated the outcome of the interaction between the arbuscular mycorrhizal fungus (AMF) Rhizophagus (R) irregularis DAOM 197198 and the Plant-Growth-Promoting Rhizobacteria (PGPR) (mix of Bacillus megaterium, Burkholdria cedrus and Streptomyces beta-vulgaris) by conducting an olive field experiment. Our data provide evidence that the co-inoculation of R. irregularis and PGPR has important effects on the rhizosphere microbial community. The largest proportional increase was found for the PLFA biomarkers indicative of Gram-negative bacteria (16:1ω9, 18:1ω7 and 18:1ω9), fungi (18:2ω6) and actinobacteria (10Me16:0 and 10Me18:0). Microbial inoculants application of all tested treatments caused a significant decrease in the level of trehalose in the olive rhizosphere. The most pronounced decrease was observed in the plant inoculated with R. intraradices only, suggesting that the presence of AMF may have relaxed the bacterial stress. Co-inoculation of PGPR and AMF significantly improved the nutritional status of olive roots. Specifically, the interaction of PGPR and R. intraradices led to an increase in N (26 %), P (60 %), Fe (25 %), Mn (18 %), Zn (26 %), B (22 %) and Cu (14 %) compared with the control. We also found that the co-inoculation of AMF with PGPR causes a shift in the accumulation of secondary metabolites in olive roots. In particular, the most important effect induced by AMF was an improvement of oleuropein concentration, while co-inoculation of R. irregularis and PGPR positively modulated verbascoside concentration. The novelty of the present work lies in the use of microbial inoculants in the field of olive trees. This approach provided direct information regarding the advantages of using AMF and PGPR inoculants, allowing the reduction of chemical inputs and positively influencing the olive tree performance.

Microbiology Combined with the Root Metabolome Reveals the Responses of Root Microorganisms to Maize Cultivars under Different Forms of Nitrogen Supply

Plant–microbe interactions are key to nutrient-use efficiency. Root microbes are influenced by rhizosphere soil and plant cultivars. The impact of cultivar-by-nitrogen (N) interactions on the maize-root microbiome remains unclear, yet it is crucial for understanding N use efficiency in maize. This study evaluated the effects of maize cultivars and N forms, along with their interactions, on the diversity and composition of root bacteria and fungi. Additionally, we examined correlations between soil microbes and root metabolites. The maize cultivar Zhengdan 958 (ZD958) showed a positive response to the mixture of nitrate and ammonium N, resulting in increased in biomass, grain yield, shoot N content, grain N content, and root area. In contrast, the cultivar Denghai605 (DH605) did not exhibit a similar response. The diversity and composition of root bacteria and fungi differed between ZD958 and DH605. The N form primarily affected the community structure of rhizospheric fungi in ZD958 and rhizospheric bacteria in DH605, rather than endophytic microbes. A mixed N supply increased the relative abundance of Basidiomycota, which was positively correlated with ZD958 yield. For DH605, a mixed N treatment enhanced nitrification functions involving Bacteroidetes and Proteobacteria, while it reduced the effects of ammonium N supply. The dominant rhizospheric microbes in DH605 showed a stronger response to changes in root metabolites compared to those in ZD958. A mixed N supply increased the content of palmitoleic acid in ZD958 root exudates, facilitating the recruitment of beneficial rhizospheric microbes, which promotes maize growth. In DH605, a mixed N supply decreased the concentration of sphinganine, which is significantly correlated with Acidobacteria (negatively), Proteobacteria (negatively), Bacteroidetes (positively), and TM7 (positively). Our findings suggest that different maize cultivars respond differently to N forms, causing distinct rhizospheric microbial effects, and that root metabolites send metabolic signals to regulate and recruit key bacterial and fungal communities.

Elicitor-enhanced steroidal sapogenin accumulation in hairy root cultures of Trigonella foenum-graecum

In current work, we studied hairy root induction in Trigonella foenum graecum, which is an important medicinal plant, and examined the impact of different elicitors on some phytochemical characteristics and metabolites production in hairy root cultures. Accordingly, some factors such as five strain types of Agrobacterium rhizogenes (1724, 15834, A4, A13 and MSU) and three different explants, namely leaf, cotyledon and hypocotyl were studied. The results showed that different A. rhizogenes strains exhibited different infection efficiency. MSU and 15834 had highest efficiency of hairy root induction than other strains. Also, hairy root induction frequency in leaf explants was higher than in other explants. Salicylic acid (SA), nitric oxide (NO), CaCl2 and penconazole (PEN) were used in elicitation process. Hairy roots were treated with SA (0.1 and 0.5 mM), NO (10 and 50 µM), CaCl2 (5 and 10 mM) and PEN (5 and 10 mg/L). Applied elicitors enhanced antioxidant enzymes activities and reduced oxidative stress markers; this observation might be ascribed to regulation of the oxidative status of the elicited cells. Significant increase of antioxidant metabolites (total phenol, flavonoid and anthocyanin) in PEN-treated hairy roots was associated to phenylalanine ammonia lyase activity, indicating an up-regulation of phenylpropanoid/flavonoid metabolism. PEN and CaCl2 treatment enhanced steroidal sapogenin in hairy root cultures. These results suggested that use of elicitors can enhance the production of secondary metabolites in transformed hairy roots. Among the elicitors applied, CaCl2 and PEN were the most effective in increasing secondary metabolite production in transformed hairy roots of T. foenum graecum.

Differences of endophytic microbial compositions and metabolites in roots between fusarium wilt resistant and susceptible melon varieties

BackgroundStudies have shown that plant endophytic microbial communities are ubiquitous and closely related to plant growth and health. To clarify the mechanism of the melon varieties with high resistant to wilt, the endophytic microbial compositions and metabolites in roots of melon varieties with high resistant ability to wilt were analyzed.ResultsThe results showed that the abundances of Firmicutes, Ascomycota, Bacillus, Bradyrhizobium, Amycolatopsis, Actinospica, and Catenulispora all increased in roots of wilt high resistant melon varieties (MT) which compared to wilt susceptible melon varieties (MS). Meanwhile, Ochrobactrum, Bordetella, Roseateles, Staphylococcus, Acidovorax, Amycolatopsis, Catenulispora, Promicromonospora, and Gymnopilus were the unique endophytic microbes in roots of MT. Moreover, in comparison with the MS varieties, the functions of Defense mechanisms, Secondary metabolites biosynthesis, transport and catabolism, Nucleotide transport and metabolism, Signal transduction mechanisms, Coenzyme transport and metabolism, Carbohydrate transport and metabolism and Amino acid transport and metabolism all increased in roots of MT varieties. Additionally, the nucleotide metabolism and biosynthesis of cofactors metabolic pathways were also significantly increased in roots of MT varieties. On the other hand, the untargeted metabolome results showed that Biosynthesis of various plant secondary metabolites, Nucleotide metabolism and Biosynthesis of cofactors metabolic pathways were significantly increased in the expression of MT varieties; and the content of metabolic compounds such as flavonoids, Cinnamic acid compounds, Organic acid compounds, and Nucleotides were increased. In addition, the correlation between microbiome and metabolome indicates a significant correlation between the two.ConclusionsAll above results suggested that higher abundant antagonistic microbes and metabolic functions of endophytes in roots of wilt high resistant melon varieties (MT) were the important mechanisms for their high resistance to wilt.Graphical

Root Exudates Promoted Microbial Diversity in the Sugar Beet Rhizosphere for Organic Nitrogen Mineralization

Rhizosphere environments play a vital role in the nutrient cycling of crops and soil organic nitrogen mineralization. Sugar beet is a highly nitrogen (N)-demanding crop, and it is necessary to explore the relationship between the sugar beet root exudates, the microbial community, and nitrogen utilization. In this study, a special separation method was employed to create rhizosphere (H3) and non-rhizosphere (H2 and H1) environments for sugar beet. After 50 d of cultivation in nearly inorganic-free soil, the microbial diversity and its correlation with root metabolites and N were examined. The results showed that in H3, the inorganic N content was over 23 times higher than in H1 and H2, with a 13.1% higher relative abundance of ammonia-oxidizing bacteria compared to H2 and a 32% higher abundance than H1. The relative abundance of nitrite-oxidizing bacteria was also 18.8% higher than in H1. Additionally, a significant positive correlation was observed between inorganic nitrogen content and serine (Ser) and isoleucine (Ile). The organic nitrogen content exhibited positive correlations with glycine (Gly), alanine (Ala), and tyrosine (Tyr) but displayed negative correlations with certain amino acids, organic acids, and glucose. The co-linearity network indicated that the microbial composition in H3 also exhibited higher node connectivity. It can be inferred that under the influence of sugar beet root exudates, the changes in the rhizosphere’s microbial diversity were more intricate, thereby benefiting soil nitrogen cycling and inorganic N accumulation. These findings provide profound insight into sugar beet soil organic nitrogen mineralization and contribute to the sustainable and environmentally friendly development of modern agriculture.

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.