Education Department of Heilongjiang Province

This study investigates the effects of exogenous abscisic acid in improving cold resistance in two medicinal Astragalus species, A. membranaceus and A. mongholicus, respectively. ABA was applied via foliar spraying at six concentrations (0, 5, 10, 15, 20, and 30 mg/L), after which plants were subjected to 4°C for 72 h. A series of physiological parameters were measured, including relative electrolyte leakage, MDA content, osmotic regulators (soluble sugars, soluble proteins, proline), antioxidant enzyme activities (superoxide dismutase, peroxidase and catalase), and total chlorophyll content. The results indicate that 15 mg/L ABA most effectively alleviated membrane damage and oxidative stress, while also enhancing osmotic adjustment and antioxidant enzyme activities. Both principal component analysis and membership function evaluation consistently identified 15 mg/L as the optimal ABA concentration, with significantly higher comprehensive scores and average membership values compared to other treatments. Interspecific differences were observed between the two species. A. membranaceus exhibited a stronger response in membrane protection and antioxidant enzyme activation, whereas A. mongholicus relied more on osmotic regulation for cold tolerance. These findings demonstrate that 15 mg/L ABA significantly enhances cold resistance in both species and provides a practical and effective strategy for mitigating cold stress in Astragalus cultivation.

Faeces serve as a widely used non-invasive material in wildlife studies, from which host DNA can be enriched for high-throughput sequencing. However, the characteristics of faecal DNA sequencing, particularly the relationship between sequencing volume and genotyping accuracy or genomic coverage, have remained unclear. This knowledge gap makes it challenging to pre-estimate the required sequencing depth to ensure data quality while controlling costs. In this study, we used host-enriched faecal DNA obtained via peri-extraction enrichment by SDS (PEERS) to perform comparative analyses of whole-genome sequencing data from paired faecal and blood samples of 11 captive Amur tigers. We systematically evaluated how data volume affects genomic coverage and genotyping accuracy. Our results revealed that faecal sequencing reads cover the genome unevenly, which may compromise the reliability of underrepresented allele identification and subsequent genomic analyses. Specifically, genomic coverage and genotyping accuracy, including precision, error rate, recall and F1-score, improved with increasing sequencing depth in both blood and faecal DNA. For reliable genotyping (values > 0.95), a minimum average depth of 20× was required for blood-derived DNA, whereas faecal DNA needed up to 50× depth when the nuclear DNA enrichment efficiency (EEN, defined as the ratio of nuclear to bacterial DNA copy number) reached 5E-5. At this sequencing volume, population-level indices, such as nucleotide diversity (π), polymorphism information content (PIC), the distribution of π in 500-kb sliding windows and SNP density, as well as individual-level indices, including heterozygosity, kinship coefficients, inbreeding coefficient (FROH) and genetic load, were highly consistent between faecal and blood samples. Only observed heterozygosity (Ho) and kernel density distributions of minor allele frequency (MAF) showed slight discrepancies. These findings underscore that effective host DNA enrichment using PEERS combined with deep sequencing is essential to achieve adequate genomic coverage and accurate genotyping when utilising faecal samples. Monitoring enrichment efficiency can help determine the necessary sequencing depth, facilitating cost-effective experimental design. This study offers practical guidance for the application of faecal DNA in genomic research and supports the broader use of this non-invasive material in future wildlife studies.

The Paenibacillus polymyxa group is potentially useful for regulating plant growth and controlling plant diseases. We previously isolated a novel P. polymyxa strain (X-11) that can promote plant growth. However, its antagonistic effects on plant pathogenic fungi and the underlying mechanisms therein remain unclear. To promote its utility for controlling plant diseases, strain X-11 was characterized in terms of its antagonistic effects on plant pathogenic fungi, genome sequence, genes related to antimicrobial activities, and extracellular antifungal proteins. Strain X-11 had significant antagonistic effects on several plant pathogenic fungi: Fusarium fujikuroi, Fusarium oxysporum, Magnaporthe oryzae, Botrytis cinerea, and Exserohilum turcicum. Its genome was revealed to contain 5,014 protein-coding genes as well as 49 tRNA and 10 rRNA sequences. The genome was most similar to that of P. polymyxa SC2, with 68.80% of its unique genes homologous to sequences in strain SC2. Furthermore, 85 genes related to antimicrobial activities were identified in the strain X-11 genome, including glycosyl hydrolase genes (20), serine protease genes (8), metalloproteinase genes (23), lanthionine antibiotic biosynthesis-related genes (6), and non-lanthionine antibiotic biosynthesis-related genes (2). Additionally, 14 nonribosomal peptide synthetase genes and 12 polyketide synthase genes were detected. Proteins with antifungal activities were identified in the inhibition zone between strain X-11 and Fusarium proliferatum (rice pathogen), including serine protease, lysophospholipase, metalloproteinase, glycoside hydrolase, β-glucosidase, peptidase M24, and amidase. Notably, bacillopeptidase F and bacillolysin were the most abundant antifungal proteins, suggesting that they may be the main contributors to strain X-11’s antifungal effects. An adenylation domain-containing protein involved in non-ribosomal peptide synthesis was also identified. The genomic characterization of strain X-11, coupled with experimental confirmation of its broad-spectrum antifungal activity, provides a strong genetic and functional basis for its development as a promising biocontrol agent against plant fungal diseases.

ObjectivesTo explore the chain-mediating role of academic buoyancy and academic burnout between self-directed learning ability (SDLA) and learning engagement in undergraduate nursing students.DesignA cross-sectional survey.Setting and participantsThis study was conducted in December 2024, involving 239 nursing undergraduates from a university in Daqing city, Heilongjiang province.MethodsIndependent samples t-tests and analysis of variance were employed to examine the relationships between undergraduate nursing students’ characteristics and learning engagement. Pearson correlation analysis was used to analyse the correlations among the variables. Based on self-determination theory, the chain-mediating effects of academic buoyancy and academic burnout between self-directed learning ability and learning engagement were tested using Model 6 of the SPSS PROCESS macro (V.3.5), with bootstrap samples set to 5000.ResultsA total of 239 undergraduate nursing students were included in the analysis, of whom 84.94% were female. The sample comprised students from all academic years, including first-year (27.62%), second-year (33.47%), third-year (17.57%) and final-year students (21.34%). Most participants selected nursing as a voluntary major choice (62.34%), and 43.51% were from urban areas. The 239 undergraduate nursing students scored 72.26±10.26 on SDLA, 14.90±2.64 on academic buoyancy, 53.75±9.33 on academic burnout and 50.81±7.64 on learning engagement. SDLA and academic buoyancy were positively correlated with learning engagement (all p<0.05), while academic burnout was negatively correlated with learning engagement (p<0.05). The chain-mediating effect of academic buoyancy and academic burnout between SDLA and learning engagement was identified, with a total indirect effect of 0.255, accounting for 37.89% of the total effect. Notably, academic buoyancy served as a significant mediator between SDLA and learning engagement, whereas the mediating effect of academic burnout between SDLA and learning engagement was not statistically significant.ConclusionSDLA is associated with higher learning engagement among nursing students through academic buoyancy and reduced academic burnout. These findings highlight the importance of developing SDLA and clarify the mediating roles of academic buoyancy and burnout in this relationship, providing valuable insights for enhancing learning engagement in nursing education.

Mastitis seriously affects the mammary health of humans and animals. Studies have found that inflammation and oxidative stress play key roles in the occurrence and development of mastitis. Therefore, in-depth research on related molecular mechanisms is of great significance. Postpartum mice were anesthetized with pentobarbital and administered lipopolysaccharide to develop the mouse mastitis model. Proteomic analysis was performed to compare protein expression in mitochondria-associated endoplasmic reticulum membranes (MAM) from two mouse mammary gland groups. Western blot was used to detect the expression of MAM-related proteins in mitochondria. AlphaFold3 was used to predict the molecular structures of phosphofurin acidic cluster sorting protein 2 (PACS2) and mitofusin 2 (MFN2) and their interaction levels. The MFN2-PACS2 interaction was investigated using co-immunoprecipitation and small interfering RNA. The results showed that the inflammation level in the mammary gland tissue of mice with mastitis significantly increased, the total antioxidant capacity decreased, and the expression of MAM-related proteins MFN2 and PACS2 was significantly downregulated. In cell experiments, overexpression of MFN2 can inhibit inflammation and oxidative stress responses, and promote the interaction between MFN2 and PACS2 to affect the formation of MAMs. In summary, this study suggests that mastitis can alter the expression of MAM-related proteins in mouse breast tissue. The interaction between MFN2 and PACS2 regulates the formation of MAMs. Overexpression of MFN2 can promote the formation of MAMs and inhibit inflammation and oxidative stress response in mammary epithelial cells. Our results provided a new theoretical basis and potential therapeutic targets for the prevention and treatment of mastitis.