Alkaline Stress Research Articles

Characterization and In-silico toxicity prediction of degradation products of felbamate

BackgroundThe objective of the work carried out was to assess the toxicity of the degradation products (DPs) for the drug felbamate. Stress studies were performed in the condition specified in the international council of harmonization (ICH) guideline Q1A (R2).ResultsThe drug degraded under the alkaline stress conditions to generate two degradation products (DPs). They were separated on a Phenomenex C8 column (250 mm × 4.6 mm, 5 µm); mobile phase composition was 10 mM ammonium formate (pH adjusted to 3.7 with formic acid) and acetonitrile (80:20, v/v); flow rate and wavelength for recording absorbance were 1.0 ml/min and 206 nm, respectively. The structures of the degradation products were characterized by LC–MS/MS analysis.ConclusionThe drug was prone to hydrolysis in the presence of alkali. It was found to be stable under other stress conditions, viz., acidic, neutral, thermal, photolytic and oxidative. The structures of the impurities were characterized by LC–MS/MS. The drug and the DPs were screened through ADME and toxicity prediction software’s like pkCSM, Toxtree and OSIRIS property explorer. Felbamate was flagged for possible hepatotoxicity.

VP19.11: Evaluation of the relationship between salivary alkaline phosphatase activity and stress in pregnant women

VP19.11: Evaluation of the relationship between salivary alkaline phosphatase activity and stress in pregnant women

Stress survival islets contribute to clonal and serotype-specific differences in L. monocytogenes

Listeria monocytogenes is an important opportunistic foodborne pathogen causing listeriosis, an often fatal infection leading to meningitis, sepsis, or infection of the fetus and abortion in susceptible individuals. Diverse ready-to-eat food (RTE) like dairy, meat, fish, vegetables, and complex foods are often linked with listeriosis outbreaks. L. monocytogenes is capable of surviving in stressful environmental conditions and grow in refrigerated foods. Regarding stress-related genes, SSI-1 contributes to the survival of cells under suboptimal conditions, such as high salt content and acidic environment. At the same time, SSI-2 is responsible for persistence under alkaline and oxidative stresses.

Growth Response and Recovery of Corynebacterium glutamicum Colonies on Single-Cell Level Upon Defined pH Stress Pulses.

Bacteria respond to pH changes in their environment and use pH homeostasis to keep the intracellular pH as constant as possible and within a small range. A change in intracellular pH influences enzyme activity, protein stability, trace element solubilities and proton motive force. Here, the species Corynebacterium glutamicum was chosen as a neutralophilic and moderately alkali-tolerant bacterium capable of maintaining an internal pH of 7.5 ± 0.5 in environments with external pH values ranging between 5.5 and 9. In recent years, the phenotypic response of C. glutamicum to pH changes has been systematically investigated at the bulk population level. A detailed understanding of the C. glutamicum cell response to defined short-term pH perturbations/pulses is missing. In this study, dynamic microfluidic single-cell cultivation (dMSCC) was applied to analyze the physiological growth response of C. glutamicum to precise pH stress pulses at the single-cell level. Analysis by dMSCC of the growth behavior of colonies exposed to single pH stress pulses (pH = 4, 5, 10, 11) revealed a decrease in viability with increasing stress duration w. Colony regrowth was possible for all tested pH values after increasing lag phases for which stress durations w were increased from 5 min to 9 h. Furthermore, single-cell analyses revealed heterogeneous regrowth of cells after pH stress, which can be categorized into three physiological states. Cells in the first physiological state continued to grow without interruption after pH stress pulse. Cells in the second physiological state rested for several hours after pH stress pulse before they started to grow again after this lag phase, and cells in the third physiological state did not divide after the pH stress pulse. This study provides the first insights into single-cell responses to acidic and alkaline pH stress by C. glutamicum.

Saline and alkaline stresses alter soil properties and composition and structure of gene-based nitrifier and denitrifier communities in a calcareous desert soil

BackgroundSaline and alkaline stresses damages the health of soil systems. Meanwhile, little is known about how saline or alkaline stress affects soil nitrifier and denitrifier communities. Therefore, we compared the responses of gene-based nitrifier and denitrifier communities to chloride (CS), sulfate (SS), and alkaline (AS) stresses with those in a no-stress control (CK) in pots with a calcareous desert soil.ResultsCompared with CK, saline and alkaline stress decreased potential nitrification rate (PNR) and NO3-N; increased pH, salinity, water content, and NH4-N; and decreased copy numbers of amoA-AOA and amoA-AOB genes but increased those of denitrifier nirS and nosZ genes. Copies of nirK increased in SS and AS but decreased in CS. There were more copies of amoA-AOB than of amoA-AOA and of nirS than of nirK or nosZ. Compared with CK, SS and AS decreased operational taxonomic units (OTUs) of amoA-AOB but increased those of nirS and nosZ, whereas CS decreased nirK OTUs but increased those of nosZ. The numbers of OTUs and amoA-AOB genes were greater than those of amoA-AOA. There were positive linear relations between PNR and amoA-AOA and amoA-AOB copies. Compared with CK, the Chao 1 index of amoA-AOA and amoA-AOB decreased in AS, that of nirK increased in CS and SS, but that of nirS and nosZ increased in all treatments. The Shannon index of amoA-AOB decreased but that of nirS increased in CS and SS, whereas the index of nirK decreased in all treatments. Saline and alkaline stress greatly affected the structure of nitrifier and denitrifier communities and decreased potential biomarkers of nirS-type; however, AS increased those of nirK- and nosZ-type, and SS decreased those of nosZ-type. Soil water content, pH, and salinity were important in shaping amoA-AOA and denitrifier communities, whereas soil water and pH were important to amoA-AOB communities.ConclusionThese results indicate that the nitrifier and denitrifier communities respond to saline and alkaline stresses conditions. Communities of amoA-AOA and amoA-AOB contribute to nitrification in alluvial gray desert soil, and those of nirS are more important in denitrification than those of nirK or nosZ.

SET DOMAIN GROUP 721 protein functions in saline-alkaline stress tolerance in the model rice variety Kitaake.

To isolate the genetic locus responsible for saline–alkaline stress tolerance, we developed a high‐throughput activation tagging‐based T‐DNA insertion mutagenesis method using the model rice (Oryza sativa L.) variety Kitaake. One of the activation‐tagged insertion lines, activation tagging 7 (AC7), showed increased tolerance to saline–alkaline stress. This phenotype resulted from the overexpression of a gene that encodes a SET DOMAIN GROUP 721 protein with H3K4 methyltransferase activity. Transgenic plants overexpressing OsSDG721 showed saline–alkaline stress‐tolerant phenotypes, along with increased leaf angle, advanced heading and ripening dates. By contrast, ossdg721 loss‐of‐function mutants showed increased sensitivity to saline–alkaline stress characterized by decreased survival rates and reduction in plant height, grain size, grain weight and leaf angle. RNA sequencing (RNA‐seq) analysis of wild‐type Kitaake and ossdg721 mutants indicated that OsSDG721 positively regulates the expression level of HIGH‐AFFINITY POTASSIUM (K+ ) TRANSPORTER1;5 (OsHKT1;5), which encodes a Na+‐selective transporter that maintains K+/Na+ homeostasis under salt stress. Furthermore, we showed that OsSDG721 binds to and deposits the H3K4me3 mark in the promoter and coding region of OsHKT1;5, thereby upregulating OsHKT1;5 expression under saline–alkaline stress. Overall, by generating Kitaake activation‐tagging pools, we established that the H3K4 methyltransferase OsSDG721 enhances saline–alkaline stress tolerance in rice.

VALIDATED AND QUANTIFIED STABILITY INDICATING STRESS DEGRADATION STUDY OF ORAL ANTI-DIABETIC AGENT CANAGLIFLOZIN BY RP-HPLC METHOD

Objective: The present investigation is aimed to develop and validate, a simple, consistent and sensitive stability-indicating reverse phase-high performance liquid chromatography (RP-HPLC) method for the determination of oral anti-diabetic drug Canagliflozin in bulk and pharmaceutical dosage form as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH-Q2 (R1)). Methods: The chromatographic separation was achieved by using Reverse Phase-High Performance Liquid Chromatography (RP-HPLC) ZORBAX C18 (250 mm x 4.6 mm, 5μm particle size) with a mobile phase consisting of Acetonitrile: Water in a ratio of 53:47% v/v at a flow rate of 1 ml/min with an injection volume of 20 μl. Results: The Retention time of the drug Canagliflozin was found to be 2.36±0.05 min and detected at 214 nm UV wavelength. The linear regression equation was found to be y = 60702x–2156.2 with a correlation coefficient 0.9999. Stress degradation studies were performed by exposing the Canagliflozin into acidic, alkaline, oxidative, thermal and photolytic stress conditions with active samples withdrawn at different time intervals as per ICH guidelines. Conclusion: The proposed Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) method was found to be robust, precise and specific for estimation of Canagliflozin in pharmaceutical dosage forms.

Transcriptome analysis reveals the mechanism of alkalinity exposure on spleen oxidative stress, inflammation and immune function of Luciobarbus capito

Saline-alkali land is distributed all over the world, and it affects the economic development of fisheries. The alkalinity in water is related to the accumulation of carbonate, so the is generally higher. To understand how alkalinity impacts the immune response in Luciobarbus capito, we performed transcriptomic profiles for spleen, the immune organ of Luciobarbus capito which were underwent alkalinity exposure. Totally there are 47,727,954, 53,987,820 and 51,398,546 high quality clean reads obtained from the control groups, and 46,996,982, 49,650,460 and 45,964,986 clean reads from the alkalinity exposure groups. Among them, 611 genes were differently expressed, including 534 upregulated and 77 down-regulated genes. The identified genes were enriched using databases of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). It was found that differentially expressed genes in Luciobarbus capito spleen tissue were enriched into 14 GO pathways, and differentially expressed genes in Luciobarbus capito spleen were enriched into 25 corresponding KEGG pathways under alkalinity stress. Inflammation and immune function genes and pathways were identified and validated by quantitative real-time RT-PCR. Our results showed that alkalinity exposure leads to inflammation and immunoregulation in spleen of Luciobarbus capito. These results provide new insights for unveiling the biological effects of alkalinity in Luciobarbus capito.

Stability Indicating RP-HPLC Method For Determination Of Itraconazole In Bulk Drug And In Capsule Dosage Form

Stability Indicating RP HPLC method was developed for estimation of Itraconazole in bulk drug and in capsule dosage form. An isocratic separation was achieved using Phenomenex symmetry C8 (250 ×4.6 mm) 5?m [Part number - 00G-4249-E0] column with a flow rate of 1.0 ml/min and detection wavelength at 254 nm. The mobile phase consisted of 20 mM potassium dihydrogen orthophosphate buffer (pH=5.5): Acetonitrile: Methanol (20:40:40 % v/v). The method was rectilinear from 10-60 ?g/ml and displayed adequate precision (RSD < 2.0%) & accuracy (99.31-101.16%). The proposed method is found to be specific with respect to degradation product formed after Acidic hydrolysis, Oxidation, Thermal and Photolytic degradation. The Itracoazole was found to be stable under alkaline stress condition. Acidic, thermal, photolytic stress conditions showed moderate degradation whereas the oxidative stress condition showed severe degradation. The proposed chromatographic method can be used for estimation of drug during stress testing & formal stability studies.

The Alkali Tolerance of Broomcorn Millet (Panicum miliaceum L.) at the Germination and Seedling Stage: The Case of 296 Broomcorn Millet Genotypes.

Broomcorn millet (BM), one of the earliest domesticated cereal crops originating in northern China, can tolerate extreme conditions, such as drought and high temperatures, which are prevalent in saline-alkali, arid, and barren landscapes. However, its adaptive mechanism to alkali stress is yet to be comprehensively understood. In this study, 80 and 40 mM standard alkali stress concentrations were used to, respectively, evaluate the alkali tolerance at the germination and seedling stages of 296 BM genotypes. Principal component analysis (PCA), Pearson's correlation analysis, and F-value comprehensive analysis were performed on the germination parameters (germination potential, germination index, germination rate, vigor index, root length/weight, sprout length/weight, and alkali damage rate). Based on their respective F-values, the BM genotypes were divided into five categories ranging from highly alkali resistant to alkali sensitive. To study the response of seedlings to alkaline stress, we investigated the phenotypic parameters (plant height, green leaf area, biomass, and root structure) of 111 genotypes from the above five categories. Combining the parameters of alkali tolerance at the germination and seedling stages, these 111 genotypes were further subdivided into three groups with different alkali tolerances. Variations in physiological responses of the different alkali-tolerant genotypes were further investigated for antioxidant enzyme activity, soluble substances, malondialdehyde (MDA) content, electrolyte leakage rate, and leaf structure. Compared with alkali-sensitive genotypes, alkali-tolerant genotypes had high antioxidant enzyme activity and soluble osmolyte content, low MDA content and electrolyte leakage rate, and a more complete stomata structure. Taken together, this study provides a comprehensive and reliable method for evaluating alkali tolerance and will contribute to the improvement and restoration of saline-alkaline soils by BM.

Zinc finger transcription factor ZAT family genes confer multi-tolerances in Gossypium hirsutum L.

ZAT (Zinc Finger of Arabidopsis thaliana) proteins are composed of a plant-specific transcription factor family, which play an important role in plant growth, development, and stress resistance. To study the potential function of ZAT family in cotton, the whole genome identification, expression, and structure analysis of ZAT gene family were carried out. In this study, our analysis revealed the presence of 115, 56, 59, and 115 ZAT genes in Gossypium hirsutum, G. raimondii, G. arboreum and G. barbadense, respectively. According to the number of domains and phylogenetic characteristics, we divided ZAT genes of four Gossypium species into 4 different clades, and further divided them into 11 subfamilies. The results of collinearity analysis showed that segmental duplication was the main method to amplify the cotton ZAT genes family. Analysis of cis-elements of promoters indicated that most GhZAT genes contained cis-elements related to plant hormones and abiotic stress. According to heatmap analysis, the expression patterns of GhZAT genes under different stresses indicated that GhZAT genes were significantly involved in the response to cold, heat, salt, and PEG stress, possibly through different mechanisms. Among the highly expressed genes, we cloned a G. hirsutum gene GhZAT67. Through virus-induced gene silencing (VIGS), we found that its expression level decreased significantly after being silenced. Under alkaline treatment, the wilting degree of silenced plants was even greater than the wild type, which proved that GhZAT67 gene was involved in the response to alkaline stress.

RNAi-mediated suppression of the abscisic acid catabolism gene OsABA8ox1 increases abscisic acid content and tolerance to saline–alkaline stress in rice (Oryza sativa L.)

Saline–alkaline (SA) stress is characterized by high salinity and high alkalinity (high pH), which severely inhibit plant growth and cause huge losses in crop yields worldwide. Here we show that a moderate elevation of endogenous abscisic acid (ABA) levels by RNAi-mediated suppression of OsABA8ox1 (OsABA8ox1-kd), a key ABA catabolic gene, significantly increased tolerance to SA stress in rice plants. We produced OsABA8ox1-kd lines in two different japonica cultivars, Dongdao 4 and Nipponbare. Compared with non-transgenic control plants (WT), the OsABA8ox1-kd seedlings accumulated 25.9%–55.7% higher levels of endogenous ABA and exhibited reduced plasmalemma injury, ROS accumulation and Na+/K+ ratio, and higher survival rates, under hydroponic alkaline conditions simulated by 10, 15, and 20 mmol L−1 of Na2CO3. In pot trials using SA field soils of different alkali levels (pH 7.59, 8.86, and 9.29), OsABA8ox1–kd plants showed markedly higher seedling survival rates and more vigorous plant growth, resulting in significantly higher yield components including panicle number (85.7%–128.6%), spikelets per panicle (36.9%–61.9%), branches (153.9%–236.7%), 1000–kernel weight (20.0%–28.6%), and percentage of filled spikelets (96.6%–1340.8%) at harvest time. Under severe SA soil conditions (pH = 9.29, EC = 834.4 μS cm−1), OsABA8ox1-kd lines showed an 194.5%–1090.8% increase in grain yield per plant relative to WT plants. These results suggest that suppression of OsABA8ox1 to increase endogenous ABA levels provides a new molecular approach for improving rice yield in SA paddies.

Ion homeostasis and Na+ transport-related gene expression in two cotton (Gossypium hirsutum L.) varieties under saline, alkaline and saline-alkaline stresses.

The sensitivity of cotton to salt stress depends on the genotypes and salt types. Understanding the mechanism of ion homeostasis under different salt stresses is necessary to improve cotton performance under saline conditions. A pot experiment using three salt stresses saline stress (NaCl+Na2SO4), alkaline stress (Na2CO3+NaHCO3), and saline-alkaline stress (NaCl+Na2SO4+Na2CO3+NaHCO3) and two cotton varieties (salt-tolerant variety L24 and salt-sensitive variety G1) was conducted. The growth, ion concentrations, and Na+ transport-related gene expression in the cotton varieties were determined. The inhibitory effects of saline-alkaline stress on cotton growth were greater than that of either saline stress or alkaline stress alone. The root/shoot ratio under alkaline stress was significantly lower than that under saline stress. The salt-tolerant cotton variety had lower Na and higher K concentrations in the leaves, stems and roots than the salt-sensitive variety under different salt stresses. For the salt-sensitive cotton variety, saline stress significantly inhibited the absorption of P and the transport of P, K, and Mg, while alkaline stress and saline-alkaline stress significantly inhibited the uptake and transport of P, K, Ca, Mg, and Zn. Most of the elements in the salt-tolerant variety accumulated in the leaves and stems under different salt stresses. This indicated that the salt-tolerant variety had a stronger ion transport capacity than the salt-sensitive variety under saline conditions. Under alkaline stress and salt-alkaline stress, the relative expression levels of the genes GhSOS1, GhNHX1 and GhAKT1 in the salt-tolerant variety were significantly higher than that in the salt-sensitive variety. These results suggest that this salt-tolerant variety of cotton has an internal mechanism to maintain ionic homeostasis.

Accelerated stability study of the ester prodrug remdesivir: Recently FDA-approved Covid-19 antiviral using reversed-phase-HPLC with fluorimetric and diode array detection.

Remdesivir (RDV) is the first antiviral drug, approved by the Food and Drug Administration, to treat severe acute respiratory syndrome coronavirus 2. RDV is a relatively new chemical entity, 'ester prodrug', with no reported stability profile. Due to the urgency of its use and thus fast production, it is important to develop a stability-indicating method for its assay. Chromatographic separation was carried out on a C18 column (250 × 4.6 mm, 5 µm) with dual detection: diode array at 240 nm and fluorescence at λex/em 245/390 nm. Isocratic elution of acetonitrile and distilled water (acidified with phosphoric acid, pH 4) in the ratio of 55:45 (v/v), respectively, was used. The linearity range using HPLC-diode array detection was 0.1-15 μg/mL, whereas that using fluorimetric detection was 0.05-15 μg/mL. As per the International Conference on Harmonization guidelines, RDV has been degraded by accelerated alkaline, acidic, neutral hydrolysis, oxidative, heat, and photolytic stress conditions. Possible degradation hypothesis of the parent molecule has been suggested and illustrated. The proposed methods have achieved selective determination of the intact drug with no peaks overlapping in all assumptions. Extensive degradation confirms threatened drug stability at thermal and basic hydrolytic stressing. The developed methods were fully validated and proved suitable for quality control routine analysis of RDV in raw material and pharmaceutical dosage forms.

Structures of the TetR-like transcription regulator RcdA alone and in complexes with ligands.

RcdA is a helix-turn-helix (HTH) transcriptional regulator belonging to the TetR family. The protein regulates the transcription of curlin subunit gene D, the master regulator of biofilm formation. Moreover, it was predicted that it might be involved in the regulation of up to 27 different genes. However, an effector of RcdA and the environmental conditions which trigger RcdA action remain unknown. Herein, we report the first crystal structures of RcdA in complexes with ligands, trimethylamine N-oxide (TMAO) and tris(hydroxymethyl)aminomethane (Tris), which might serve as RcdA effectors. Based on these structures, the ligand-binding pocket of RcdA was characterized in detail. The conservation of the amino acid residues forming the ligand-binding cavity was analyzed and the comprehensive search for RcdA structural homologs was performed. This analysis indicated that RcdA is structurally similar to multidrug-binding TetR family members, however, its ligand-binding cavity differs significantly from the pockets of its structural homologs. The interaction of RcdA with TMAO and Tris indicates that the protein might be involved in alkaline stress response.

Analytical Method Development and Validation of Etravirine by RP-UFLC

An ultra-fast liquid chromatography (RP-UFLC) approach was processed for the estimation of ETR, which is quick, responsive, reliable, and inexpensive. Work on the Phenomenex Kinetex C18 column (250x 4,6mm. 5μ) was carried out with MeOH and acetonitrile in the mobile phase ratio of (60:40v/v) at 1.0mL/min. With a PDA detection system, the eluent was tracked at 311nm. ETR elutes at a persistence time of 3.226 min. The proposed method gives linearity of concentration from 1 to 5μg/mL, with the value of R2 at 0.9942%. For the proposed method, LOD and LOQ are measured as 0.02 and 0.073μg/mL. The pharmaceutical drug included acidic, alkaline, corrosion, Ultraviolet, and heat stress stipulations. The deterioration material was nicely resolved from ETR peaks, which showed the reliability of the process. The approach has been tested with respect to process adequacy, linearity, reliability, and robustness, as per ICH guidelines.

A stability-indicating HPLC method for estimation of doxylamine succinate in tablets and characterization of its major alkaline stress degradation product

BackgroundA new selective rapid RP-HPLC-DAD method was developed and evaluated for the quantification of doxylamine succinate (DOX) in bulk and pharmaceutical dosage form. The separation of DOX at different degradation conditions was achieved with a Kromasil C18 (4.6 × 250 mm, 5-μm particle size). The mobile phase employed comprised of phosphate buffer (pH 3.5) and methanol in the ratio of 45:55 v/v. The flow rate was kept maintained at 1.0 ml/min and eluents were detected at 262 nm. The drug was subjected to different stress conditions like acid, base, neutral, hydrolysis, oxidation, photolysis, and thermal degradation. The analytical performance of the proposed HPLC method was thoroughly validated in terms of linearity, precision, accuracy, specificity, robustness, detection, and quantification limits.ResultsThe method produces linear responses that were found in the range of 10–50 μg/ml. The regression equation was found to be Y = 42984x − 10260. The correlation coefficient was found to be 0.9998. The LOD and LOQ for DOX were found to be 0.96 and 3.28 μg/ml, respectively. The short-term solution stability of DOX (100 μg/ml) was evaluated under (25 ± 2°C) storage condition and found to be 98.82 to 101%. The percentage recovery for DOX was in the range of 99.73 to 99.91%. The obtained results of the stress degradation study and peak purity data indicate the potential of the developed HPLC method to resolve degradants from DOX peak. The major alkaline degradation product was isolated using preparative chromatographic technique and extensive FT-IR was performed to ascertain the structure of the alkaline degradant.ConclusionIt was concluded that the proposed method was simple, sensitive, accurate, cost-effective, and less time-consuming for the quantification of DOX. This method was successfully utilized for stability testing of commercially available DOX tablets. Hence, the proposed method can be applied for routine quality control of DOX in bulk drug as well as in marketed formulations.

Carbonate alkalinity and dietary protein levels affected growth performance, intestinal immune responses and intestinal microflora in Songpu mirror carp (Cyprinus carpio Songpu)

An eight week 3 × 2 two-factorial experiment was conducted to investigate the interaction between carbonate alkalinity levels at 0 and 15 mmol/L, and dietary protein levels at 310, 340 and 370 g/kg on the growth rate, digestive ability and the intestinal immunity, physical barrier function and microflora of Songpu mirror carp (Cyprinus carpio songpu). Fish at an initial average weight of 17.86 ± 0.19 g were randomly allotted to 18 aquariums each with 30 fish. Results revealed that weight gain rate (WGR) significantly decreased as carbonate alkalinity levels increased (p < 0.05), whereas the feed conversion ratio (FCR) of fish significantly increased (p < 0.05). Amylase activity in the intestine significantly decreased with increasing carbonate alkalinity levels (p < 0.05). A carbonate alkalinity of 15 mmol/L significantly reduced the superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities, elevated the malondialdehyde (MDA) contents in the intestine and hepatopancreas and decreased the contents of Complement 3 (C3), Complement (C4) and Ig M (p < 0.05). The relative expressions of occludin, claudin3, claudin7, myosin light chain kinase (MLCK) and interleukin 10 (IL-10) in the intestine were significantly down-regulated with increasing carbonate alkalinity levels (p < 0.05), whereas the relative expressions of interleukin 6 (IL-6), interleukin 8 (IL-8) and tumor necrosis factor (TNF-α) in the intestine were significantly up-regulated (p < 0.05). The Proteobacteria abundance significantly increased with increasing carbonate alkalinity level (p < 0.05). The WGR significantly decreased as dietary protein levels increased (p < 0.05). The MDA contents in intestine and hepatopancreas also showed a significant rise with increasing dietary protein levels (p < 0.05). Increments in dietary protein levels significantly reduced the C3 and C4 contents of fish intestine (p < 0.05). Fish in the 370 g/kg diet protein level group showed a significantly lower relative expression of occludin and TNF-α (p < 0.05). There was an effect on the C3 content, the relative expression of occludin, the abundance of Firmicutes and Firmicutes: Bacteroidetes ratio between carbonate alkalinity and dietary proteins over time (p < 0.05).In summary, under the long-term carbonate alkalinity stress of 15 mmol/L, dietary protein level for Songpu mirror carp should be controlled below 310 g/kg, which could effectively weaken the oxidative damage produced by carbonate alkalinity stress and further strengthen the growth and intestinal immune response of fish.

Abscisic Acid Priming Creates Alkaline Tolerance in Alfalfa Seedlings (Medicago sativa L.)

Soil alkalization triggers ion toxicity and osmotic and alkaline (high pH) stresses in plants, damaging their growth and productivity. Therefore, we investigated whether priming with abscisic acid (ABA) increases the tolerance of alfalfa seedlings to alkaline stress, and then examined the underlying molecular mechanisms. Alfalfa seedlings were pretreated with ABA (10 μM) for 16 h and then subjected to alkaline stress using a 15 mM Na2CO3 solution (pH 10.87). Compared with the control, ABA pretreatment significantly alleviated leaf damage and improved the fresh weight, water content, and survival rate of alfalfa seedlings under alkaline conditions. Abscisic acid pretreatment reduced accumulation of reactive oxygen species (ROS), increased activities of the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD), maintained higher ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+, and increased accumulation of proline. In addition, ABA upregulated the expression of genes involved in proline biosynthesis (P5CS) and the sequestration of Na+ in vacuoles (NHX1 and AVP) under alkaline conditions. Abscisic acid priming increased tolerance to alkaline stress by maintaining homeostasis of ROS and metal ions and upregulating osmoprotection and the expression of stress tolerance-related genes.

Trichoderma asperellum alters fungal community composition in saline–alkaline soil maize rhizospheres

AbstractThe Songnen Plain is an important agricultural region in China with an abundance of saline–alkaline soil that significantly restricts maize growth. Trichoderma spp., free‐living fungi, are commonly used biofertilizers. The effects of Trichoderma asperellum on the fungal community in saline–alkaline soils remain unclear; hence, in this study, three T. asperellum conidium suspension concentrations were used: 0 g (control), 0.7 g (low dose), and 1.4 g (high dose) over three consecutive years, following which high‐throughput sequencing was conducted to analyze the effect of T. asperellum on fungal diversity in the rhizosphere soil. Changes in crop yield, soil salt ion content, and pH were also monitored. T. asperellum treatment effectively regulated the soil salt ion balance, lowered the pH, and improved the crop yield by 4.88–20.26%. Additionally, the T. asperellum treatment significantly increased the relative abundance of T. asperellum and Ceratobasidium sp and inhibited that of the pathogenic fungi Neonectria and Fusarium. Changes in the soil fungal community composition were closely associated with soil properties and yield. Our findings suggest that long‐term T. asperellum exposure can alleviate saline–alkaline stress for maize growth by decreasing soil pH and salt ion content and regulating the fungal microbial community, thereby increasing crop yield.