Search Results (391)

Copper (Cu) is an essential micronutrient for plants, playing a crucial role in various physiological and molecular processes. Excess Cu induces oxidative stress and disrupts cellular functions, while Cu deficiency causes chlorosis and poor pollen development, thereby reducing crop yields. However, the molecular and evolutionary mechanisms of Cu tolerance and homeostasis remain unclear in the plant kingdom. In this review, we discuss the uptake, transport, and detoxification of Cu through high-affinity Cu transporters (COPTs). Additionally, we update recent studies on maintaining Cu balance by mediating the root exudation of organic acids (e.g., citrate and proline), xylem/phloem loading, cell wall binding, vacuolar sequestration, redistribution, and the activity of antioxidant enzymes (e.g., SOD, CAT, and APX). Furthermore, tissue-specific expression analyses reveal that COPT genes exhibit distinct spatial regulation in the roots and leaves, which are the primary sites of Cu transport and detoxification. Overall, our review highlights the critical roles of COPT gene families and detoxification pathways in maintaining Cu homeostasis in plants. Future research should focus on genetic engineering approaches to enhance Cu tolerance, optimize Cu distribution in grains, and mitigate soil contamination risks. By clarifying these mechanisms, we can develop strategies to sustain crop production under increasing Cu stress, thereby ensuring food security and human health. Full article

Constrained by site conditions and water resources, pear tree cultivation faces increasing drought stress. Paecilomyces variotii extract (PVE), a novel biostimulant extracted from wild sea buckthorn root-isolated strains and containing chitin, humic/fulvic acids, and beneficial microbes, has gained attention due to its high activity and efficacy in alleviating plant stresses (e.g., drought). In this study, Pyrus pyrifolia ‘Qiu Yue’ was used as the experimental material, and pot experiments were conducted to examine the drought-mitigating effects of different PVE concentrations. Drought stress was achieved by maintaining soil water content at 35–45% of water holding capacity for 45 days under natural evaporation conditions in rain shelters. The growth status of pear trees, soil enzyme activity, and metabolite levels were analyzed. The results showed that the application of 5 ng/mL PVE promoted pear tree growth, enhanced leaf antioxidant enzyme activity, and improved photosynthetic capacity and soil enzyme activity. Under normal water conditions, the shoot growth length, plant height, stem diameter, and root system activity of the 5 ng/mL PVE group were 31.91%, 12.05%, 3.54%, and 10.94% higher than those of the control group, respectively. Under drought stress, these values increased by 25.12%, 8.87%, 12.21%, and 16.98%, respectively. The addition of 5 ng/mL PVE facilitates trehalose release and upregulates starch-sucrose, glycerophospholipid, and galactose metabolic pathways, thereby potentiating drought stress tolerance in pear trees. However, at 20 ng/mL, reductions were observed in pear tree growth indicators, leaf antioxidant enzyme activity, soil enzyme activity, and trehalose content in root exudates compared to the 5 ng/mL PVE treatment. Overall, 5 ng/mL PVE effectively promotes pear tree growth and enhances drought resistance, making it suitable for broader use in pear cultivation practices. Full article

Continuous cropping poses a significant threat to sustainable pepper production by triggering soil degradation and growth inhibition, yet the role of root exudates in this process remains unclear. This study aimed to elucidate how continuous cropping duration (0, 1, 2, and 6 years) alters root exudate composition and drives rhizosphere feedback in green pepper. Pot experiments revealed that long-term continuous cropping (6 years) severely inhibited pepper growth, reducing photosynthetic rate (32.02%), chlorophyll content (12.26%), plant height (23.89%), and yield (42.37%). Critically, the relative abundance of 3,4-dimethylbenzaldehyde in root exudates increased progressively with cropping duration. Exogenous application of this compound or long-term monoculture extracts reduced soil pH and increased electrical conductivity, altered the rhizosphere microbial community (notably decreasing Proteobacteria abundance and fungal diversity while increasing Bacteroidota and Firmicutes), and significantly inhibited root development and vitality. Correlation analysis indicated that fungal communities were more responsive to soil property changes, while bacterial communities correlated more closely with root traits. This study demonstrates that the accumulation of specific root exudates, particularly 3,4-dimethylbenzaldehyde, is a key driver of continuous cropping obstacles in green pepper by disrupting rhizosphere microbial community structure and soil properties. This highlights the importance of managing root exudate dynamics, potentially through crop rotation or soil amendments, to mitigate these obstacles. Full article

Although the upper nodal roots are vital for resource uptake in late-stage maize, their anatomical and physiological responses to varying nitrogen and light regimes remain unclear. In a field experiment, maize was grown under three nitrogen levels (0, 192, and 240 kg·ha⁻¹) and two light regimes (normal light and 50% shading). At flowering (R1), we selected the number, diameter, anatomy of nodal roots, root-bleeding sap composition, and grain yield. Sample sizes ranged from three to twelve replicates per treatment, depending on the trait measured. Data were analyzed using ANOVA and Duncan’s test (p < 0.05). Under normal light, N₁₉₂ and N₂₄₀ significantly enhanced stele and vessel diameters in the sixth and seventh nodal root whorls, vessel number and cortical cell layers in the fifth and seventh whorls, root-bleeding intensity, exudation rates of sucrose, abscisic acid, key free amino acids (Asn, Asp, Glu), and grain yield, compared to N₀. Shading markedly suppressed the nodal root anatomical structure, reducing root-bleeding intensity by 18.2–26.6% and yield by 30.6–40.8%; especially under SS-N0, which also notably increased the exudation of stress-related amino acids (particularly Asp and Glu). Correlation analysis revealed positive relationships of root-bleeding intensity with vessel area and grain yield, indicating that impaired root anatomy restricts resource transport under shading. Sufficient nitrogen partially alleviated these adverse effects. This study demonstrates that light and nitrogen synergistically regulate the upper nodal root anatomy, thereby modulating root-bleeding sap and ultimately influencing grain yield. These results provide a theoretical basis for high-yield maize cultivation and precision nitrogen management under low-light stress. Full article

Disease caused by Plasmodiophora brassicae severely disrupts cruciferous crops by altering root physiology and rhizosphere ecology. While pathogen-induced shifts in rhizosphere microbiomes are documented, the mechanisms linking root exudate reprogramming to microbial community remodeling remain poorly understood. Here, we integrated untargeted metabolomics and 16S rRNA sequencing to investigate how root exudates reshape the rhizosphere microbiome of tumorous stem mustard (Brassica juncea var. tumida) through P. brassicae infection. Metabolomic profiling identified 1718 root exudate metabolites, with flavones (e.g., apigenin 7-O-β-D-rutinoside, VIP > 1.5) and phenolic derivatives (e.g., gastrodin) being selectively enriched in infected plants. P. brassicae infection significantly increased rhizobacterial richness (ACE index, p < 0.05) and restructured the community composition, marked by enrichment of Paenibacillus (LDA score > 3.0). Procrustes analysis revealed tight coupling between microbial community shifts and metabolic reprogramming (M² = 0.446, p = 0.005), while Spearman correlations implicated pathogen-induced metabolites like geniposidic acid in recruiting beneficial Paenibacillus. Our results reveal that plant hosts dynamically secrete defense-related root metabolites to remodel the rhizosphere microbiome in response to P. brassicae infection. This dual-omics approach elucidates a chemical dialogue mediating plant–microbe–pathogen interactions, offering novel insights for engineering disease-suppressive microbiomes through root exudate manipulation. Full article

Zinc (Zn) deficiency poses a major global health challenge, and wheat grains generally contain low Zn concentrations. In this study, the wheat cultivar ‘Zhongmai 175’ was identified as zinc-efficient. Hydroponic experiments demonstrated that Zn deficiency induced the secretion of oxalic acid and malic acid in root exudates and significantly increased total root length in ‘Zhongmai 175’. To elucidate the underlying regulatory mechanisms, transcriptome profiling via RNA sequencing was conducted under Zn-deficient conditions. A total of 2287 and 1935 differentially expressed genes (DEGs) were identified in roots and shoots, respectively. Gene Ontology enrichment analysis revealed that these DEGs were primarily associated with Zn ion transport, homeostasis, transmembrane transport, and hormone signaling. Key DEGs belonged to gene families including VIT, NAS, DMAS, ZIP, tDT, HMA, and NAAT. KEGG pathway analysis indicated that phenylpropanoid biosynthesis, particularly lignin synthesis genes, was significantly downregulated in Zn-deficient roots. In shoots, cysteine and methionine metabolism, along with plant hormone signal transduction, were the most enriched pathways. Notably, most DEGs in shoots were associated with the biosynthesis of phytosiderophores (MAs, NA) and ethylene. Overall, genes involved in Zn ion transport, phytosiderophore biosynthesis, dicarboxylate transport, and ethylene biosynthesis appear to play central roles in wheat’s adaptive response to Zn deficiency. These findings provide a valuable foundation for understanding the molecular basis of Zn efficiency in wheat and for breeding Zn-enriched varieties. Full article

Moringa (Moringa oleifera Lam.) is widely recognised as a multipurpose crop suitable for human and animal consumption, medicinal, and industrial purposes, making it attractive for introduction into new ranges. Its extracts have been found to have beneficial impacts on various crop species and biological activity against multiple weeds, making their use in agriculture promising. However, concerns have also been raised about moringa’s potential to negatively impact the growth and development of other cultivated and non-cultivated plant species, especially in areas where it has been introduced outside its native range. To understand the positive and negative interactions between moringa and other plants, it is essential to investigate its allelopathic potential. Allelopathy is a biological activity by which one plant species produces and releases chemical compounds that influence the reproduction, growth, survival, or behaviour of other plants with either beneficial or detrimental effects on the receiver. Plants produce and release allelochemicals by leaching, volatilisation, or through root exudation. These biochemical compounds can affect critical biological processes such as seed germination, root and shoot elongation, photosynthesis, enzymatic activities, and hormonal balance in neighboring plants. Therefore, allelopathy is an important driver of plant composition and ecological interactions in an ecosystem. This review explores the positive and negative allelopathic effects of moringa extracts on other plant species, which may help to inform decisions regarding its introduction into new biogeographical regions and incorporation into existing farming systems, as well as the use of moringa plant extracts in agriculture. Full article

Drought is a serious environmental problem that limits the yield of wheat around the world. Using biochemical and microscopy methods, it was shown that methyl jasmonate (MeJA) has the ability to induce the oxidative stress tolerance in roots of wheat plants due to the regulation of antioxidant enzymes activity, proline (Pro), and wheat germ agglutinin (WGA) accumulation. During the first hours of 12% polyethylene glycol (PEG) exposure, stress increased the superoxide radical (O₂^•−) and the hydrogen peroxide (H₂O₂) accumulation, the activity of superoxide dismutase (SOD), total peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), the percent of dead cells (PDC), malondialdehyde accumulation (MDA), and electrolyte leakage (EL) of wheat roots as compared to the control. Stress enhanced proline (Pro) and wheat germ agglutinin (WGA) contents in roots and the plant’s nutrient medium, as well as decreased the mitotic index (MI) of cells of root tips in comparison to the control. During PEG exposure, 10⁻⁷ M MeJA pretreatment increased the parameter of MI, declined O₂^•− and H₂O₂ generation, PDC, MDA, and EL parameters as compared to MeJA-untreated stressed seedlings. During 1 day of drought, MeJA pretreatment additionally increased the activity of SOD, total POD, APX, CAT, Pro, and WGA accumulation in wheat roots in comparison to MeJA-untreated stressed plants. During stress, MeJA pretreatment caused a decrease in Pro exudation into the growth medium, while WGA content in the medium was at the control level. Full article

Urine-derived and plant-derived benzoic acid can accumulate within soil, and it likely changes the soil microbial community as well as N₂O emissions; however, its mechanism is not clear. This study conducted an incubation experiment to monitor N₂O emissions under low moisture (40% water-filled pore space (WFPS)) and high moisture (85% WFPS) conditions. Metagenomic sequencing and q-PCR methods were used to determine the link between N₂O emissions and the composition and functions of soil microbiota. Benzoic acid (BA) was found to significantly, yet dose-dependently, impact N₂O emissions; that is, low BA concentrations increased N₂O, whereas high BA decreased N₂O. However, this was only found under high moisture conditions. In contrast, BA had little impact on N₂O emissions under low moisture conditions. Under high moisture conditions, BA increased the gene copy number of bacteria and fungi, and decreased the ratio of bacteria to fungi. Similarly, BA significantly increased the abundance of denitrification functional genes, but reduced the (NirS + NirK)-to-NosZ ratio at the peak of emission. This is in agreement with the observation of the increased relative abundance of genes encoding N₂O reductase (EC 1.7.2.4) and NO₃⁻ heterotrophic reductase (EC 1.7.1.15, EC 1.7.2.2) in the metagenomic analysis. In summary, high concentrations of benzoic acid reduce N₂O emissions by promoting the reduction of N₂O. This study revealed the impact of BA on soil microbiota and highlighted the favorable conditions and underlying mechanism behind BA’s significant impact on soil N₂O emissions. This study’s novelty lies in the fact that it deepens our understanding of the complicated role of root exudates and metabolites of animals and plants in soil. Full article

Soil salinization poses a critical threat to global agriculture, necessitating innovative strategies for sustainable remediation. This review synthesizes advances in leveraging plant–microbe interactions to remediate saline–alkali soils, focusing on oilseed crops—Brassica napus, Glycine max, Arachis hypogaea, Helianthus annuus, and Sesamum indicum—as keystone species for ecosystem restoration. These crops exhibit unique adaptive strategies, including root architectural plasticity and exudate-mediated recruitment of stress-resilient microbiomes (Proteobacteria, Actinobacteria, and Ascomycota), which collectively stabilize soil structure and enhance nutrient cycling, ion homeostasis, and soil aggregation to mitigate soil salinity and alkalinity. Emerging technologies further amplify these natural synergies: nanomaterials optimize nutrient delivery and microbial colonization, while artificial intelligence (AI) models predict optimal plant growth-promoting rhizobacteria (PGPR) combinations and simulate remediation outcomes. This integration establishes a roadmap for precision microbiome engineering, offering scalable strategies to restore soil health and ensure food security in saline–alkali ecosystems. Full article

This study evaluated the effects of different types and rates of locally produced organic residues on soil organic matter (SOM) and soil health in highly degraded loamy soils of olive orchards in arid southern Tunisia. Three residues were tested: poultry manure, raw date palm waste, and composted date palm waste mixed with manure. A randomised field trial was conducted over three years. Two years after application, soil samples were analysed for physical and chemical properties, basal respiration, nitrogen mineralisation, microbial biomass, enzyme activities (dehydrogenase, phosphomonoesterase, β-glucosidase, urease, arylsulphatase), and community-level physiological profiles. All residues increased SOM and available phosphorus (Pi), with dose-dependent effects sustained over time, though significant increases were only observed at the highest application rates. The most notable improvements occurred in soils amended with composted date palm waste. In contrast, biological and biochemical parameters showed little response, even after remoistening to stimulate microbial activity. This limited response was attributed to the absence of vegetation and, consequently, of root exudates and plant residues. This will be further investigated by assessing changes in the same biological and biochemical properties following the implementation of an intercropping system, which is expected to enhance both SOM content and microbial activity in these soils. Full article

Cereal/legume intercropping enhances legume nodulation and improves nitrogen use efficiency (NUE) in cereal crops. This facilitation of symbiotic nitrogen fixation (SNF) in intercropped legumes involves a complex eco-physiological mechanism driven by multiple factors. Among them, interspecific root interactions (IRIs) are a key factor influencing SNF in intercropped legumes. Currently, it remains unclear whether and how IRIs modulate SNF to affect NUE and yield formation in legume species. In this study, maize/pea intercropping with different types of root separation [no barrier (NB) and plastic barrier (PB)] and pea monocropping (IP) were simulated in a nitrogen (N)-free nutrient matrix in pots, and the SNF, N metabolism, and N partitioning were investigated. We demonstrated that IRIs optimize SNF performance. N assimilation is positively regulated following increases in enzyme activity and gene expression in intercropped roots and nodules. Furthermore, IRIs facilitate amino acid (AA) export from nodules to roots and shoots, which is followed by an increase in AA levels in leaves (source) and leaf exudates (sink). Overall, intensive SNF drives N metabolism and alters source-to-sink N partitioning, thereby increasing NUE (by 23%) and yield (by 15%) in intercropped pea. This study reveals the positive roles of IRIs to the NUE and yield and provides useful reference material for increasing N contents derived from SNF to maximize NUE and crop yields in intercropped legumes. Full article

Despite chemical exchange often serving as the first step in plant–microbe interactions, the specialized chemical metabolites produced by grass–Epichloë endophyte symbiosis as mediators of host growth, nutrient acquisition, and modulators of the rhizosphere community under low-nitrogen conditions are areas lacking in knowledge. In this study, we investigated the plant growth-promoting effects of the Epichloë endophyte strain and identified the growth of the Epichloë strain under different types of nitrogen source treatments. In addition to the in vitro test, we evaluated growth performance for Epichloë endophyte–infected plants (E+) and Epichloë endophyte–free plants (E−) in a pot trial under 0.01 mol/L urea treatment. Seedlings from E+ and E− groups were collected to analyze the plant bacterial microbiome and root metabolites. The E. gansuensis endophyte strain was found not to produce indoleacetic acid (IAA), pectinase, or contain ferritin. The nitrogenase gene, essential for nitrogen fixation, was also absent. These results suggest that E. gansuensis endophyte strains themselves do not contain attributes to promote plant growth. Concerning N fertilization, it was observed an increase in the colony diameter of E. gansuensis strain was observed only in the NO₃⁻-N (NN) treatment, while inhibition was observed in the urea-N (UN) treatment. E. gansuensis endophyte symbiosis significantly increased tiller number and plant dry weight. Overall, our results suggest that the E+ plants had more root forks and greater average root diameter compared to E− plants under the UN treatment. In a pot experiment using UN, data from 16S rRNA amplicon sequencing revealed that E. gansuensis endophyte infection significantly altered the bacterial community composition in shoot and root, and significantly increased Shannon (p < 0.001) and Chao 1 (p < 0.01) indexes. The relative abundance of Acidobacteriota, Actinomycetota, Cyanobacteriota, Fibrobacterota, Myxococcota, and Patescibacteria in the shoot, and Cyanobacteriota, Pseudomonadota, and Verrucomicrobiota in the root were significantly increased by E. gansuensis endophyte infection. Similarly, E. gansuensis endophyte symbiosis shifted the metabolite composition of the host plants, with the E+ plants showing a higher number of metabolites than the E− plants. In addition, co-metabolism network analysis revealed that the positive relevance between exudates and microorganisms in the root of the E+ plants is higher than that of the E− plants. These findings provide valuable insights into the knowledge of the effects of the symbiotic relationship between host plants and Epichloë endophyte on interspecific interactions of plant microbiome, beneficial for harnessing endophytic symbiosis, promoting plant growth. Full article

Microbial interactions within the rhizosphere are fundamental to plant health, influencing nutrient availability, stress tolerance, and pathogen resistance. Beneficial microbes, such as plant growth-promoting microbes (PGPMs), including bacteria and mycorrhizal fungi, enhance plant resilience through mechanisms like nutrient solubilization, phytohormone production, and pathogen suppression via antimicrobial compounds and siderophores. Root exudates, composed of sugars, organic acids, and secondary metabolites, act as chemoattractants that shape the rhizosphere microbiome by recruiting beneficial microbes. Microbial metabolites can, in turn, modulate plant physiology and exudate profiles, thereby reinforcing mutualistic interactions. Stress conditions alter exudate composition, enabling plants to attract specific microbes that aid in stress mitigation. Given the growing interest in microbiome-based agricultural solutions, this review aims to synthesize recent literature on plant–microbe interactions, with a focus on bidirectional signaling between plants and microbes. A structured literature search was conducted using databases such as PubMed, Scopus, and ScienceDirect to identify key studies on root exudation, microbial functions, and synthetic microbial communities (SynComs). We highlight major findings on how engineered microbiomes can enhance plant growth, resilience, and productivity, particularly under stress conditions. This review also explores how advances in SynCom design can promote sustainable agriculture by reducing reliance on chemical inputs. Full article

Understanding species-specific mechanisms governing symbiotic fungal responses to plant traits and soil factors is critical for optimizing urban tree “plant-soil-fungus” systems under pollution stress. To address this gap, we combined δ¹³C/δ¹⁵N isotope analysis and ITS sequencing for three common street trees in Beijing: Sophora japonica, Ginkgo biloba, and Populus tomentosa. In S. japonica, symbiotic fungal abundance was positively associated with leaf δ¹⁵N, indicating root exudate-mediated “plant-microbe” interactions during atmospheric NO_x assimilation. G. biloba, with weak NO_x assimilation, exhibited a negative correlation between fungal abundance and soil available N/P, suggesting mycorrhizal nutrient compensation under low fertility. P. tomentosa showed decreased fungal abundance with increasing soil N/P ratios and specific leaf area, reflecting carbon allocation trade-offs that limit mycorrhizal investment. These results demonstrate that symbiotic fungi respond to atmospheric and edaphic drivers in a tree species-dependent manner. Urban greening strategies should prioritize S. japonica for its NO_x mitigation potential and optimize fertilization for G. biloba (nutrient-sensitive fungi) and P. tomentosa (nutrient balance sensitivity). Strategic mixed planting of P. tomentosa with S. japonica could synergistically enhance ecosystem services through complementary resource acquisition patterns. This study provides mechanism-based strategies for optimizing urban tree management under atmospheric pollution stress. Full article