Search Results (2,151)

Background/Objectives: Rheumatoid arthritis (RA) is a chronic autoimmune disease marked by sustained synovial inflammation and systemic immune activation. Genetic polymorphisms in key immune-regulatory pathways are thought to influence both disease susceptibility and progression. This study aimed to characterize sequence variation within selected coding regions of TNFAIP3 and CTLA4 in Kurdish patients with RA and to evaluate circulating TNF-α and soluble CTLA-4 (sCTLA-4) levels in the same cohort. Methods: Eighty-seven participants (67 RA patients, 20 controls) were enrolled. Serum TNF-α and sCTLA-4 concentrations were quantified by ELISA. Genomic DNA was extracted and targeted Sanger sequencing of selected coding regions of TNFAIP3 and CTLA4 was performed in RA patients. Variant identification was conducted relative to GRCh38 and annotated using dbSNP and Genome Aggregation Database (gnomAD). GeneMANIA was used for network-based contextualization. Results: In the 218-bp targeted region of TNFAIP3, 103 sequence-level variant occurrences were identified in RA patients, including substitutions and insertion/deletion events. In the 136-bp targeted region of CTLA4, 33 sequence-level variant occurrences were identified, also including substitutions and insertion/deletion events. RA patients exhibited significantly elevated serum TNF-α levels compared with controls (p = 0.025), whereas sCTLA-4 levels did not differ significantly. Conclusions: This study provides the first targeted characterization of TNFAIP3 and CTLA4 genetic variation in Kurdish RA patients and integrates these findings with circulating inflammatory biomarkers. Although not designed to assess disease susceptibility, the study provides a valuable descriptive genetic resource for this population and complements existing evidence implicating NF-κB regulation and immune checkpoint signaling in RA. These findings establish a strong foundation for future case–control, genotype–phenotype, and functional investigations. Full article

This study aimed to investigate the accumulation of aboveground biomass, organ allocation patterns, and their driving mechanisms in Moso bamboo (Phyllostachys edulis) forests along different elevational gradients and to compare regional differences in growth processes. A total of 54 sample plots were established along an elevational gradient from 50 to 550 m across three different regions, with 100 m elevational intervals. Two-way ANOVA, regression analysis, Tukey’s HSD multiple comparisons, and generalized additive models (GAMs) were used to examine distribution patterns. (1) Individual bamboo biomass followed a unimodal pattern with increasing elevation, peaking at 150 m (16.20 ± 3.88 kg culm⁻¹), which was significantly higher than at other elevations (p = 0.048). Allometric covariance analysis showed that the b value did not differ significantly among elevations (p = 0.882), indicating a stable diameter at breast height (DBH)-biomass relationship. (2) Stand biomass was highest at 50 m (34.75 ± 10.97 t·ha⁻¹) and declined with elevation to 18.54 ± 7.13 t·ha⁻¹ at 550 m, revealing a decoupling from the elevational trend of individual biomass. (3) Branch and leaf dry mass allocation exhibited a “higher at both ends, lower in the middle” pattern. Culm allocation was highest at 150 m (80.3%), though differences among elevations were not statistically significant (p = 0.591). (4) Stand density decreased with elevation, while mean DBH first increased and then decreased, reaching a maximum at 450 m (9.77 cm). Differences in stand density and DBH among elevations were highly significant (p < 0.001). (5) ANCOVA showed that after controlling for mean DBH, the effect of elevation on individual biomass was substantially weakened (p = 0.051), with partial η² declining from 0.48 to 0.21 (a 56% reduction), indicating that DBH accounted for a substantial portion of the elevation effect on individual biomass.The individual biomass of Moso bamboo in central-southern Jiangxi peaked at approximately 150 m elevation. Elevation was associated with biomass mainly through its association with DBH (a size effect), rather than through changes in allocation ratios or allometric relationships. The pathway “elevation→DBH→individual biomass” appears to be the primary mediating pathway explaining the decoupling, although a causal interpretation requires further experimental validation. These findings provide a theoretical basis for elevation-differentiated management of Moso bamboo forests. Full article

In this work, TiO₂/LaFeO₃ nanocomposites with varying lanthanum ferrite content were synthesized and comprehensively characterized to enhance the efficiency of photocatalytic processes under solar irradiation. The structural, morphological, and textural properties of the samples were investigated by SEM, TEM, HRTEM, XPS, Raman spectroscopy, and BET analysis. The incorporation of LaFeO₃ was found to extend the light absorption range of TiO₂ into the visible region and to modify the surface textural characteristics while preserving the mesoporous structure of the composites. Photoelectrochemical measurements and electrochemical impedance spectroscopy revealed that the formation of a p–n heterojunction between n-TiO₂ and p-LaFeO₃ promotes more efficient separation of photogenerated charge carriers and significantly reduces the charge-transfer resistance. The best performance was achieved for the TLFO_2.0 sample, which exhibited the highest photocurrent density (51.85 μA/cm²) and the highest photocatalytic activity toward the degradation of MB, RhB, and CR. After 240 min of irradiation, the degradation efficiencies reached 57.3% for MB, 90% for RhB, and 33.8% for CR. These results demonstrate that optimizing the LaFeO₃ content is an effective strategy for enhancing the photoelectrochemical and photocatalytic performance of TiO₂/LaFeO₃ nanocomposites, highlighting their promise for applications in wastewater treatment and solar energy conversion systems. Full article

Background/Objectives: Cortical morphology around the screw fixation level may influence screw purchase in Weber B lateral malleolar fractures. This study compared anterior and posterior cortical thickness of the distal fibula around the interfragmentary screw fixation level using preoperative computed tomography (CT) images matched with postoperative radiographs. Methods: This retrospective radiographic study included 155 patients who underwent operative treatment for Weber B lateral malleolar fractures using an interfragmentary screw between 2019 and 2023. Patients with Weber A or C fractures, no preoperative CT, fixation without an interfragmentary screw, previous ipsilateral lateral malleolar fracture or surgery, or unreliable CT measurement were excluded. The levels at which the screw crossed the anterior and posterior cortices were identified on postoperative radiographs and transferred to sagittal CT images. Results: The anterior cortex was significantly thicker than the posterior cortex (2.44 ± 0.82 mm vs. 1.39 ± 0.66 mm; mean difference, 1.05 mm; 95% confidence interval, 0.94–1.17; p < 0.001). This anterior cortical predominance was observed across all sex- and age-based subgroups. Men had greater anterior and mean cortical hickness than women, while patients aged <60 years had greater cortical thickness than those aged ≥60 years. Conclusions: Around the interfragmentary screw fixation level in Weber B lateral malleolar fractures, the anterior cortex was consistently thicker than the posterior cortex. Given the limitations of radiograph-to-CT matching, the results should be interpreted as demonstrating a relative regional pattern rather than exact absolute cortical thickness values. This pattern may provide useful reference information when planning screw fixation. Full article

Background: This study aimed to assess cone-beam computed tomography (CBCT) knowledge, adherence to justification criteria, field-of-view (FOV) selection practices, and awareness of radiation protection guidelines among dental practitioners in the Asir region. In Saudi Arabia, the Saudi Food and Drug Authority (SFDA) and the Nuclear and Radiological Regulatory Commission are the regulatory bodies responsible for radiation protection and the safe use of dental imaging; limited awareness of their roles may undermine regulatory compliance and patient safety. Accordingly, the specific objectives of this study were: (i) to assess knowledge of CBCT justification criteria and radiation-dose magnitudes; (ii) to evaluate adherence to the requirement for a prior 2D radiograph; (iii) to examine FOV selection across standardized clinical vignettes; (iv) to explore factors associated with knowledge scores; and (v) to identify perceived barriers to appropriate CBCT prescribing. Methods: A cross-sectional descriptive-analytical survey targeted 73 dental practitioners in Abha, Saudi Arabia. A validated 30-item questionnaire was distributed via Google Forms using snowball convenience sampling. The effective target population comprised dental practitioners and interns working in Abha during the study period. Because recruitment used open snowball distribution without a fixed sampling frame, a formal response rate could not be calculated. Results: The mean knowledge score was 5.47/10 (standard deviation: 1.86). Item-level correct rates were 82.2% for caries detection, 80.8% for the requirement for a prior 2D radiograph, and 58.9% for paediatric CBCT justification. FOV selection across four clinical vignettes ranged from 27.4% to 68.5% correct, with the lower-left-molar implant vignette showing the lowest rate (27.4%) and the six-unit anterior implant bridge vignette also poorly answered (37.0%), reflecting a frequent tendency to select an inappropriately large FOV. Guideline awareness was low: 65.8% were completely unaware of the Safety and Efficacy of a New and Emerging Dental X-ray Modality Computed Tomography (SEDENTEX CT) 2012 guidelines, while 54.8% did not know that the American Dental Association publishes specific radiation guidelines. In an exploratory multivariable model, no factor was a statistically significant predictor of the knowledge score; formal CBCT training showed a small, non-significant association (B = 0.585; 95% confidence interval [−0.27, 1.44]; p = 0.175). Conclusions: In this preliminary survey, CBCT knowledge among dental practitioners in Abha was moderate but suboptimal, with almost half of respondents scoring below the satisfactory threshold and with significant gaps in FOV optimisation and guideline awareness. Given the small, non-probability sample, these findings should be regarded as preliminary and hypothesis-generating. Full article

Methylmercury (MeHg) accumulation in rice is a major source of human MeHg exposure in some inland areas, yet the mechanism controlling mercury (Hg) accumulation in high geological background (HGB) regions remains poorly understood. Here, a field-scale remediation experiment was conducted in a karst HGB region of Guizhou, China, using a synergistic strategy combining selenium foliar spraying and calcium oxide-based soil conditioner. The combined treatment reduced total Hg and MeHg concentrations in rice grains by 63.0% and 80.0%, respectively. The root uptake from the soil–water system was found to be the primary pathway controlling Hg transfer into rice grain. Mechanistically, the soil conditioner increased soil pH and reduced bioavailable Hg, porewater Hg, and soil MeHg by 53.6%, 59.8%, and 62.6%, respectively, whereas selenium foliar spraying promoted Hg–Se complexation and reduced Hg mobility in the paddy system. In parallel, the combined treatment suppressed Hg-methylating microorganism (e.g., Geobacter decreased by 65%) and hgcAB gene (hgcA: −65%; hgcB: −58%), while enriching Hg-resistant taxa and merA-mediated detoxification pathway. These coupled physicochemical and microbial processes substantially reduced Hg bioavailability, MeHg production, and Hg bioaccumulation in rice grain of the paddy ecosystem, providing an effective strategy for mitigating Hg-related food safety risk in the karst HGB region. Full article

Background: Tertiary lymphoid structures (TLSs) are spatial immune niches in solid tumors, but their relationship to mature regulatory dendritic-cell (mregDC) states in ovarian cancer remains incompletely resolved. Methods: We integrated public gynecological-tumor single-cell RNA sequencing, representative CD11C/HLA-DRA/LAMP3/CCR7 multiplex immunofluorescence, public Xenium and multi-sample spatial transcriptomics, TCGA-OV immune deconvolution and exploratory prognostic modeling, scTenifoldKnk and CellOracle perturbation analyses, and supplementary computational drug prioritization. Results: A $LAMP{3}^{+}CCR{7}^{+}$ dendritic-cell state showed mature migratory, antigen-presentation, checkpoint, and NF-$\kappa$B/TNF-associated programs. Spatial analyses linked TLS-score-defined regions to mregDC, antigen-presentation/MHC-II proxy, and interferon-associated signals, with distance-gradient analyses supporting TLS-proximal enrichment. Immune deconvolution associated the TLS/mregDC axis with an immune-infiltrated TCGA-OV contexture, whereas adjusted analyses emphasized dependence on broader immune-program richness. Perturbation analyses nominated candidate regulatory axes for experimental testing, and the supplementary drug-prioritization layer was retained only as target-class hypothesis support. Conclusions: These data support a hypothesis-generating model of a TLS-associated $LAMP{3}^{+}CCR{7}^{+}$ mregDC antigen-presentation program in ovarian cancer, while requiring raw-channel tissue validation, functional perturbation, and independent clinical testing. Full article

Dociostaurus maroccanus is a major migratory pest first recorded in Xinjiang, China, in 2025 in the Ili River Valley and Tacheng City. This event represents a new situation of concern in the field of biological security along China’s northwestern border that warrants attention. This study investigated the genetic diversity and population structure of four populations from the China–Kazakhstan border region using combined mitochondrial cytochrome C oxidase subunit I (COI) and cytochrome B (Cytb) gene markers. A total of 41 haplotypes were identified from 74 individuals, with the shared haplotypes H3 and H6 being the most frequent. Haplotype network analysis revealed no clear geographic population structuring. Haplotype diversity was high (Hd = 0.957), whereas nucleotide diversity was low (π = 0.00212), indicating low overall genetic diversity. Frequent gene flow (Nm = 12.31–43.08) and minimal genetic differentiation (Fst = −0.0255 to 0.0199) were detected among populations. AMOVA indicated that genetic variation mainly occurred within populations (100.12%), with no significant differentiation among populations (−0.59%). Neutrality tests (Tajima’s D = −2.45136, p < 0.05; Fu’s Fs = −44.037, p < 0.001), the unimodal mismatch distribution, and goodness-of-fit test results for KZ1 population (SSD = 0.0028, p = 0.91; raggedness = 0.0225, p = 0.86), KZ2 population (SSD = 0.00846, p = 0.25; raggedness = 0.0650, p = 0.13) and YN population further support the expansion phenomenon. Mantel test (r = −0.5948, p = 0.9583) preliminarily indicated that population distribution was not correlated with geographic distance. Therefore, in the region covered by this study, the overall characteristics show recent population expansion features. The preliminary results of this study provide basic materials for understanding the genetic background of this species in China’s border regions and can serve as a reference for subsequent population dynamic monitoring and control work. Full article

The dried rhizome of Atractylodes lancea (RAL) is a widely used traditional Chinese medicine (TCM). Its quality evaluation and origin authentication have long relied on time-consuming chromatographic methods, which are poorly suited for rapid, on-site decisions in commercial supply chains, and existing studies generally focus on isolated morphological indicators without systematic digital characterization and practical on-site grading tools. Guided by the traditional empirical knowledge of “Bianzhuang Lunzhi”, which holds that external morphological traits can reflect the internal quality of TCM, this study presents the first systematic multi-dimensional digital characterization of RAL morphological traits using an integrated multi-sensor approach and quantitatively explores the underlying correlations between digital traits and key bioactive constituent contents. Nighty samples from three major producing regions were analyzed. Significant correlations were observed between odor indices, color parameters, density, oil cavity area ratio and bioactive component contents in the authentic Maoshan-sourced RAL (p < 0.01 or p < 0.05). Such associations were absent in the emerging regions (Dabie and Qin−Ba Mountains). A three-grade quality classification system based on density thresholds (Grade A: ≥0.73 g/cm³; B: 0.58–0.73 g/cm³; C: <0.58 g/cm³) was established specifically for Maoshan RAL. Additionally, an electronic nose-based classification model was constructed for geographical origin discrimination, which delivered reliable and robust classification performance in external validation with independent blind test samples. This work provides practical, low-cost tools for rapid quality grading and origin identification of RAL. The proposed trait-driven analytical strategy offers a generalizable framework for the quality control of other complex herbal medicines. Full article

Background and Aim: Mango (Mangifera indica) is a globally important fruit crop whose productivity is repeatedly threatened by foliar diseases such as anthracnose, bacterial canker, powdery mildew, die-back, and sooty mould. Although deep learning has rapidly advanced automated leaf-disease diagnosis, recently reported accuracies on the MangoLeafBD benchmark are approaching saturation, and many studies still rely on random data splits that may inflate performance through leakage of duplicate or near-duplicate images. This study aimed to develop and rigorously evaluate a leakage-aware, deployment-oriented deep learning framework for the complete eight-class MangoLeafBD task. Methods: Three modern transfer-learning backbones—EfficientNetB0, MobileNetV3Large, and ConvNeXtTiny—were fine-tuned using a two-stage training strategy on a group-aware data partition. Duplicate and near-duplicate images were detected with cleaned filename stems, average hashing (aHash), and difference hashing (dHash) and grouped before splitting to guarantee zero cross-partition overlap. The strongest models were combined through probability-level soft voting. Robustness was further assessed using 5-fold StratifiedGroupKFold cross-validation. Explainability was examined with Gradient-weighted Class Activation Mapping (Grad-CAM), deployment suitability was characterized through CPU latency benchmarking, and the framework was operationalized as a publicly accessible web-based diagnostic system. Results: EfficientNetB0 achieved the highest performance under the leakage-controlled protocol, reaching 99.50% accuracy and 99.50% weighted F1-score on the 599-image group-aware test set. The heterogeneous soft-voting ensemble matched EfficientNetB0 but did not exceed it, indicating that the ensemble gains reported in earlier studies may partly reflect optimistic split conditions. Five-fold grouped cross-validation confirmed stability, yielding a mean accuracy of 99.63% (SD = 0.20%) and a mean weighted F1 of 99.62% (SD = 0.20%). Grad-CAM visualizations showed that the model attended to biologically meaningful lesion regions across all eight classes, and CPU benchmarking produced a mean single-image latency of 25.3 ms (p95 = 27.6 ms) with batch throughput scaling up to 166.5 images per second. Conclusions: The proposed framework demonstrates that a compact, leakage-aware EfficientNetB0 model can match the accuracy of more complex hybrid CNN–transformer architectures while remaining interpretable and deployable on commodity CPU hardware. By coupling group-aware evaluation, explainable AI, latency benchmarking, and a publicly accessible web application, the study advances reproducible, deployment-ready precision agriculture research and offers a more rigorous benchmarking protocol for future mango leaf disease classification studies. Full article

Calcineurin B-like (CBL) proteins are plant-specific calcium sensors critical for ion homeostasis and stress tolerance. Here, seven MdCBL genes were genome-wide identified in apple (Malus domestica). We conducted systematic bioinformatic profiling of their physicochemical features, subcellular localization, cis-regulatory elements, phylogeny, secondary structures, phosphorylation sites, and functional annotations and further verified the salt-stress regulatory function of MdCBL5 via transgenic tests. MdCBL proteins contain 210–246 amino acids, with molecular weights of 24,196.73–28,283.39 Da, pI values of 4.63–4.97 and instability indices of 37.12–49.20. Localization prediction placed these proteins in nuclei, cytosol and chloroplasts. Their promoter regions are rich in hormone-responsive (auxin, ABA, salicylic acid) and stress-responsive (cold, drought, salt) cis-elements. Phylogenetic clustering divided MdCBLs into five subgroups (A–E) with high homology to Arabidopsis CBLs. Random coils and α-helices dominate their secondary structures, and serine residues constitute most phosphorylation sites. Functional annotation supports their involvement in calcium signaling, ion transport and diverse stress adaptation. Salt stress experiments have confirmed that MdCBL5 may enhance apple salt resistance by promoting MdSOS gene expression. Meanwhile, transient transformation in apple fruit showed that MdCBL5 can effectively enhance fruit quality traits. Collectively, this study establishes a theoretical foundation for further elucidating the biological functions of the apple MdCBL5 gene and provides valuable insights for genetically improving stress resistance and fruit quality in apple via molecular breeding strategies. Full article

Phyllanthus emblica is valued for its nutritional and medicinal properties, yet the genomic divergence between localized and widespread cultivars remains poorly understood. We investigated the genomes of two individuals from the endemic cultivar ‘Hongguang’ (HG), propagated via regional grafting, and the commercially widespread ‘Dongkeng’ (DK), known for its superior protein content. Using whole-genome sequencing, we reconstructed phylogenies from two nuclear markers, profiled genome-wide variations, assembled chloroplast genomes, and verified relative plastid copy numbers via real-time quantitative PCRs (qPCRs). Nuclear internal transcribed spacer (ITS) and phytochrome C (PHYC) phylogenies confirmed both samples belonged to the P. emblica lineage, while revealing a distinct genetic identity for the HG individual. Genome-wide variant profiling of the two individuals identified KEGG enrichment in plant hormone signaling pathways; DK variants mapped to the canonical auxin axis, while HG variants were annotated to reversible protein phosphorylation. Comparative chloroplast genomics demonstrated shared maternal inheritance and shared mutations in key photosynthetic genes (psaB, petA, and the ndh cluster) between the two genomes, though qPCR validation revealed a higher relative chloroplast DNA copy number in the DK sample. Despite the two-individual limitation, these findings revealed preliminary genomic variations, offering candidate molecular markers for future population studies and marker-assisted breeding. Full article

The canine supraspinatus insertion tendon (SIT) is frequently involved in shoulder disorders; however, objective ultrasonographic reference data remain limited. This study aimed to describe the ultrasonographic appearance of the SIT in clinically non-lame dogs and to develop a reproducible protocol for the quantitative analysis of tendon thickness and relative echogenicity. Thirty-five clinically non-lame dogs (70 shoulders) underwent prospective B-mode ultrasonography. On ultrasonographic examination, the SIT appeared as a structure composed of two clearly differentiated regions: a proximal region, which was thinner and more hyperechoic, and a distal region, which was thicker, relatively more hypoechoic, and attached to the bone surface. These findings were consistent with previous descriptions of the SIT ultrasonographic appearance reported in the literature. Tendon thickness and mean echogenicity were evaluated in both regions. Mean echogenicity was quantified using region-of-interest analysis and pixel intensity histograms, with trapezius muscle echogenicity used for background normalisation. Paired statistical tests and Pearson correlation analyses were performed. No significant differences were identified between the left and right SIT measurements for either thickness or relative echogenicity (p > 0.05). The distal region was significantly thicker than the proximal region (p < 0.001). Relative echogenicity also differed significantly between regions: the proximal region was more hyperechoic and heterogeneous, whereas the distal region was more homogeneous and hypoechoic (p < 0.001). Body weight and height were positively associated with tendon thickness, whereas associations with mean echogenicity were reduced after normalisation to trapezius muscle echogenicity. In conclusion, the canine SIT comprises two ultrasonographically distinct regions that differ in thickness and echogenicity. The proposed protocol provides an objective and standardized method for the quantitative ultrasonographic evaluation of tendon structure in dogs. However, this study represents a preliminary assessment of the SIT ultrasonography, and a larger sample size is required to confirm the statistical results obtained. Full article

The importation of hepatitis B virus (HBV) variants through migration challenges elimination efforts in low-endemicity countries. This study evaluated the seroprevalence, occult hepatitis B infection (OBI), and molecular signatures of HBV among 537 international migrants from 46 countries who arrived in St. Petersburg, Russia. HBsAg, anti-HBs, and anti-HBc were measured by ELISA. This was followed by nested real-time PCR targeting viral genes (S, X) and a human housekeeping gene (HPRT, internal control), amplification of overlapping fragments covering the complete HBV genome, and Sanger sequencing. HBsAg prevalence was 2.61% (95% CI: 1.43–4.34), while anti-HBc was detected in 16.39% (95% CI: 13.36–19.79). HBV DNA was found in 8.19% (44/537; 95% CI: 6.02–10.04) of migrants. Notably, OBI (HBsAg-negative/HBV DNA-positive) was identified in 33 individuals, yielding a prevalence of 6.15% (33/537; 95% CI: 4.27–8.52) in the entire cohort and 6.31% among HBsAg-negative subjects. The findings among OBI cases were as follows: the majority (54.5%) had no detectable anti-HBc or anti-HBs; 30.3% were positive for anti-HBs only; 6.06% were positive for anti-HBc IgG only; 9.09% of cases featured both anti-HBc and anti-HBs. Viral loads in OBI cases were uniformly low (14–53 IU/mL). Genotype D predominated (86.36%, 38/44). The distribution of subgenotypes among all sequenced isolates was as follows: D1 in 36.36% (16/44), D2 in 36.36% (16/44), D3 in 13.64% (6/44), while genotypes A2 (6.82%, 3/44), B4 (4.55%, 2/44), and C2 (2.27%, 1/44) were rare. In the major hydrophilic region (MHR), the most frequent amino acid substitutions were at positions T127P/I (61.4%) and T118R/M/V/A (45.5%). Immune escape mutations were significantly associated with OBI (81.82% of OBI cases versus 18.18% of HBsAg-positive cases; p = 0.003). Drug resistance mutations (L180M + M204V ± T184A) were detected in 11.4% of isolates (all genotype D2). In the precore region, stop codon mutation W28* was found in 31.82% of samples, and the A1762T/G1764A double substitution in the basal core promoter occurred in 25.0%. The high prevalence of OBI, coupled with the accumulation of escape and drug resistance mutations in imported HBV variants, highlights the urgent need to include molecular HBV screening in mandatory medical examinations for arriving migrants to prevent undetected transmission and inform clinical management in receiving countries. Full article

In modern livestock production, a reliable supply of high-quality forage is essential for sustaining animal productivity and product quality. Although nitrogen (N) fertilization can promote forage growth, excessive N inputs often result in low agronomic nitrogen use efficiency (NAUE) and increased environmental risks. Biochar, owing to its porous structure, high specific surface area, and physicochemical stability, can improve soil physical properties, enhance water and nutrient retention, and regulate soil N availability. However, the mechanisms by which biochar combined with reduced N rate fertilization affects NAUE in artificial grasslands remain insufficiently quantified. A two-year field experiment was conducted at the Grassland Science Experimental Station of Xinjiang Agricultural University on the northern slope of the Tianshan Mountains, Xinjiang, China. Eight treatments were established using a factorial design with two biochar rates (0 and 20 t·ha⁻¹; B0 and B20) and four N application rates (0, 75, 150, and 225 kg·ha⁻¹; N0, N75, N150, and N225). Results showed that biochar application significantly decreased soil bulk density and increased soil water content and electrical conductivity. It also elevated soil total carbon, total nitrogen, total phosphorus, NH₄⁺–N, and NO₃⁻–N concentrations, with B20N150 exhibiting the highest overall nutrient status. Plant community diversity indices did not differ significantly among treatments (p > 0.05), though B20 slightly enhanced Shannon–Wiener and Simpson indices under N0 and N75. Moderate N application significantly increased hay yield, whereas the highest N rate (225 kg·ha⁻¹) did not further improve yield and reduced NAUE. Biochar combined with N75 or N150 improved NAUE, and B20N150 achieved the best balance of high hay yield and high NAUE. Structural equation modeling revealed that soil water content (path coefficient = 0.45), NH₄⁺–N (0.27), and plant community diversity (0.20) were key positive drivers of NAUE, with biochar exerting indirect effects primarily via improving soil water and available N. Collectively, applying 20 t·ha⁻¹ biochar with 150 kg·ha⁻¹ N (B20N150) is recommended as an optimal strategy for N rate reduction and NAUE enhancement in artificial grasslands of arid and semiarid regions. Full article