Effects of artificially-simulated acidification on potential soil nitrification activity and ammonia oxidizing microbial communities in greenhouse conditions.

Background: Nitrification can lead to large quantities of nitrate leaching into the soil during vegetable production, which may result in soil acidification in a greenhouse system. A better understanding is needed of the nitrification process and its microbial mechanisms in soil acidification. Materials and Methods: A simulated acidification experiment with an artificially manipulated pH environment (T1: pH 7.0; T2: pH 6.5; T3: pH 6.0; T4: pH 5.5; T5: pH 4.5) was conducted in potted tomatoes grown in greenhouse conditions. The abundance and community structures of ammonia oxidizers under different pH environment were analyzed using q-PCR and high-throughput sequencing methods, respectively. Results and discussions: Soil acidification was accompanied by a reduction of soil organic matter (SOM), total nitrogen (TN), NH3 concentration, and enzyme activities. The abundance of ammonia-oxidizing archaea (AOA) in the soil was higher than that of ammonia-oxidizing bacteria (AOB) in soils with a pH of 6.93 to 5.33. The opposite trend was observed when soil pH was 4.21. In acidified soils, the dominant strain of AOB was Nitrosospira, while the dominant strain of AOA was Nitrososphaera. The abundance and community structure of ammonia oxidizers were mainly affected by soil pH, NH4 + content, and microbial biomass. Soil nitrification activity (PNA) has a relationship with both AOA and AOB, in which the abundance of AOA was the crucial factor affecting PNA. Conclusions: PNA was co-dominated by AOA and AOB in soils with simulated acidification. Changes of soil pH, NH4 +, and microbial biomass caused by acidification were the main factors for the differences in the ammonia-oxidizing microbial community in greenhouse soils. Under acidic conditions (pH < 5), the pH significantly inhibited nitrification and had a strong negative effect on the production of tomatoes in greenhouse conditions.

Co-analysis of cucumber rhizosphere metabolites and microbial PLFAs under excessive fertilization in solar greenhouse.

Fertilizer application is the most common measure in agricultural production, which can promote the productivity of crops such as cucumbers, but the problem of excessive fertilization occurs frequently in solar greenhouses. However, the effects of fertilization levels on cucumber rhizosphere soil microbes and metabolites and their relationships are still unclear. In order to determine how fertilization levels affect the rhizosphere microenvironment, we set up four treatments in the solar greenhouse: no-fertilization (N0P0K0), normal fertilization (N1P1K1), slight excessive fertilization (N2P2K2), and extreme excessive fertilization (N3P3K3). The results showed that fertilization treatments significantly increased cucumber yield compared to no-fertilization, but, the yield of N3P3K3 was significantly lower than that of N1P1K1 and N2P2K2. Fertilization levels had significant effects on rhizosphere microorganisms, and pH, NH4 +-N and AP were the main environmental factors that affected the changes in microbial communities. The total PLFAs, the percentages of fungi and arbuscular mycorrhizal fungi (AMF) were significantly reduced and bacteria percentage was significantly increased in N3P3K3 compared to other fertilization treatments. Differential metabolites under different fertilization levels were mainly organic acids, esters and sugars. Soil phenols with autotoxic effect under fertilization treatments were higher than that of N0P0K0. In addition, compared with soil organic acids and alkanes of N0P0K0, N2P2K2 was significantly increased, and N3P3K3 was not significantly different. This suggested that cucumber could maintain microbial communities by secreting beneficial metabolites under slight excessive fertilization (N2P2K2). But under extremely excessive fertilization (N3P3K3), the self-regulating ability of cucumber plants and rhizosphere soil was insufficient to cope with high salt stress. Furthermore, co-occurrence network showed that 16:1ω5c (AMF) was positively correlated with 2-palmitoylglycerol, hentriacontane, 11-octadecenoic acid, decane,4-methyl- and d-trehalose, and negatively correlated with 9-octadecenoic acid at different fertilization levels. This indicated that the beneficial microorganisms in the cucumber rhizosphere soil promoted with beneficial metabolites and antagonized with harmful metabolites. But with the deepening of overfertilization, the content of beneficial microorganisms and metabolites decreased. The study provided new insights into the interaction of plant rhizosphere soil metabolites and soil microbiomes under the different fertilization levels.

Overfertilization reduces tomato yield under long-term continuous cropping system via regulation of soil microbial community composition.

Long-term monoculture cropping and overfertilization degrade soil fertility, which reduces crop growth and promotes the development of soil-borne diseases. However, it remains unclear what the temporal effects of the above factors are on the tomato yield and microbial community structure. Thus, a greenhouse experiment with different amounts of fertilization [2,196 kg ha-1 (control) and 6,588 kg ha-1 (overfertilization) of inorganic fertilizers (NPK)] was carried out with the soils used previously for 1, 2, and 12 years under monoculture of tomato. A 12-year overfertilization decreased soil pH by 1.37 units. Soil electrical conductivity (EC) and concentrations of soil nutrients are enhanced with the increase in tomato cropping duration. Higher content of soil nutrients was found under overfertilization compared to the control in the 12-year soil. Overfertilization decreased the activity of ß-1,4-glucosidase (BG) and oxidase compared to the control in the 12-year soil. Bacterial diversity and richness decreased by 6 and 31%, respectively, under overfertilization in 12-year soil compared to the control. The relative abundance of Gemmatimonas and Gp6 in 12-year soil under overfertilization was 17 and 78%, respectively, lower than in control soil. Soil pH and total carbon (TC) were the major factors explaining changes in microbial composition. A 38% decrease in yield was caused by overfertilization in 12-year soil compared to the control. Microbial community composition was the main factor that moderated tomato yield. In addition, fertilization rather than cropping duration had a greater impact on tomato yield. Therefore, our results suggest that long-term overfertilization influenced soil pH, soil TC, and soil microbial community composition to regulate tomato yield.

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In this study, we investigated the effects of long-term continuous cucumber cropping on phenolic acids in rhizosphere soil, as well as their link to soil chemical characteristics, enzyme activities, and microbiological activities, using rhizosphere soil from the 2nd, 6th, 10th, 14th, 18th, 20th, 24th, and 26th round of cucumber cultivation in solar greenhouse. The results showed that contents of phenolic acids increased significantly with increasing continuous cropping rounds. The increase amount per round of total phenolic acid was significantly higher in the early stage (0-2 rounds) and late stage (20-26 rounds) than middle stage (10-14 rounds) of continuous cropping. Soil nutrient contents were enriched, while invertase enzyme activity and microbial activities were decreased. Redundancy analysis showed that organic matter, total phosphorus, total nitrogen, available nitrogen, microbial biomass carbon and microbial metabolic entropy were main soil fertility factors correlating with the accumulation of phenolic acids. Results of structural equation model showed that soil phosphorus enrichment directly led to the accumulation of phenolic acids, and that nitrogen enrichment indirectly facilitated the accumulation of phenolic acids by altering the activity of microorganisms. As a result, proper nitrogen and phosphorus fertilizers application would reduce the accumulation of phenolic acids and alleviate the cucumber continuous cropping obstacles.

FOXD3 inhibits cell proliferation, migration, and invasion in nasopharyngeal carcinoma through regulation of the PI3K-Akt pathway.

FOXD3 has been found previously to positively regulate miR-26b, a tumor inhibitor of nasopharyngeal carcinoma (NPC). However, FOXD3's precise function and associated mechanism of action in NPC have not yet been investigated. In this study, the expression of FOXD3 mRNA and protein was evaluated using RT-qPCR, western blotting, and immunohistochemistry. Protein levels involved in the phosphoinositide 3-kinase - protein kinase B (PI3K-Akt) pathway were assessed by western blot, and cell proliferation was determined by MTT and colony forming assays. Additionally, cell apoptosis was assessed by flow cytometric assay. Finally, the migration and invasion capabilities of the NPC cells were determined using wound healing and Transwell assays. We found that FOXD3 levels were relatively low in NPC tissue and cells, while an increase caused the inhibition of the PI3K-Akt pathway. Functional experiments found that overexpression of FOXD3 suppressed cell proliferation, migration, and invasion and enhanced cell apoptosis in NPC C6661 cells. IGF-1, an activator of the PI3K-Akt pathway, reversed the inhibitory effect of FOXD3. Furthermore, we found upregulation of the PI3K-Akt pathway and upregulation of the inhibitory effects of FOXD3 on C6661 cellular activities. In conclusion, FOXD3 negatively affected the PI3K-Akt pathway to restrain the processes involved in C6661 cell pathology. These findings further exposed the function and downstream axis of FOXD3 in NPC and displayed a promising new target for NPC therapy.

BMP-7 accelerates the differentiation of rabbit mesenchymal stem cells into cartilage through the Wnt/ß-catenin pathway.

Mesenchymal stem cells (MSCs) are able to differentiate into adipocytes, chondroblasts or cartilage under different stimulation conditions. Identifying a mechanism that triggers the differentiation of MSCs into cartilage may help the development of novel therapeutic approaches for heterotopic ossification, the pathological formation of lamellar bone in soft tissue outside the skeleton that may lead to debilitating immobility. Bone morphogenetic proteins (BMPs), including BMP-7, are the most potent growth factors for enhancing bone formation. The current study aimed to understand the potential involvement of the Wnt/ß-catenin signaling pathway in the BMP-7-induced growth of rabbit MSCs (rMSCs). Different concentrations of BMP-7 were applied to cultured rMSCs, and proliferation was evaluated by MTT assay. Changes in the phosphorylation state of glycogen synthase kinase (GSK)-3ß, in addition to the expression levels of alkaline phosphatase, ß-catenin and runt-related transcription factor 2 were observed by western blot analysis. Following treatment with BMP-7, the phosphorylation of GSK-3ß was stimulated and the expression of ß-catenin, ALP and Runx2 was increased. Furthermore, inhibiting ß-catenin signaling with XAV-939 suppressed the BMP-7-mediated changes. The results indicated that the BMP-7-induced differentiation of rMSCs into cartilage was promoted primarily by the Wnt/ß-catenin pathway.

Decreased local and systematic matrix Gla protein (MGP) expression and its link to radiographic progression in ankylosing spondylitis patients.

BACKGROUND: Decreased serum levels of uncarboxylated matrix Gla-protein (ucMGP) have been detected in Ankylosing Spondylitis (AS) patients. The current study was to investigate the expression of MGP in AS tissues as well as the relationship between serum ucMGP (an inactive form of MGP) levels and radiographic severity in AS patients. METHODS: Local MGP expression were assessed by Western blot and RT-PCR in hip synovial tissues from patients with AS and control subjects. In addition, the serum level of ucMGP was assessed by enzyme-linked immunosorbent assay in 68 healthy subjects and 62 patients with AS. The radiographic progression of AS was classified according to the radiographic events of modified New York Criteria for sacroiliac joint evaluation and modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) system for spine assessment. RESULTS: MGP expression was downregulated in AS patients compared to controls in hip tissues. Decreased levels of ucMGP in serum were found in AS patients compared with healthy controls. ucMGP levels in serum of AS patients were significantly negatively correlated with the disease radiographic severity evaluated by modified New York grading criteria (r = -0.293, p = 0.045) and mSASSS system (r = -0.361, p = 0.03). CONCLUSIONS: MGP expression is impaired in patients with AS. A low serum level of ucMGP in the setting of AS is linked to increased structural damage, emphasizing the role of MGP in the suppression of new bone formation.