Peroxidase Enzyme Research Articles

Microbacterium azadirachtae CNUC13 Enhances Salt Tolerance in Maize by Modulating Osmotic and Oxidative Stress.

Soil salinization is one of the leading threats to global ecosystems, food security, and crop production. Plant growth-promoting rhizobacteria (PGPRs) are potential bioinoculants that offer an alternative eco-friendly agricultural approach to enhance crop productivity from salt-deteriorating lands. The current work presents bacterial strain CNUC13 from maize rhizosphere soil that exerted several PGPR traits and abiotic stress tolerance. The strain tolerated up to 1000 mM NaCl and 30% polyethylene glycol (PEG) 6000 and showed plant growth-promoting (PGP) traits, including the production of indole-3-acetic acid (IAA) and siderophore as well as phosphate solubilization. Phylogenetic analysis revealed that strain CNUC13 was Microbacterium azadirachtae. Maize plants exposed to high salinity exhibited osmotic and oxidative stresses, inhibition of seed germination, plant growth, and reduction in photosynthetic pigments. However, maize seedlings inoculated with strain CNUC13 resulted in significantly improved germination rates and seedling growth under the salt-stressed condition. Specifically, compared with the untreated control group, CNUC13-treated seedlings exhibited increased biomass, including fresh weight and root system proliferation. CNUC13 treatment also enhanced photosynthetic pigments (chlorophyll and carotenoids), reduced the accumulation of osmotic (proline) and oxidative (hydrogen peroxide and malondialdehyde) stress indicators, and positively influenced the activities of antioxidant enzymes (catalase, superoxide dismutase, and peroxidase). As a result, CNUC13 treatment alleviated oxidative stress and promoted salt tolerance in maize. Overall, this study demonstrates that M. azadirachtae CNUC13 significantly enhances the growth of salt-stressed maize seedlings by improving photosynthetic efficiency, osmotic regulators, oxidative stress resilience, and antioxidant enzyme activity. These findings emphasize the potential of utilizing M. azadirachtae CNUC13 as a bioinoculant to enhance salt stress tolerance in maize, providing an environmentally friendly approach to mitigate the negative effects of salinity and promote sustainable agriculture.

Physiological and oxidative stress response of carrot (Daucus carota L.) to jumping plant-louse Bactericera trigonica Hodkinson (Hemiptera: Psylloidea) infestation

BackgroundCarrot is an important vegetable crop grown worldwide. The major economic problem in carrot cultivation is yellow disease caused by Bactericera trigonica, which induces biotic stress and has the greatest impact on crop productivity. Comprehensive studies on the mechanism of carrot defense response to biotic stress caused by B. trigonica infestation have yet to be conducted.MethodsThe changes in photosynthetic pigments, proline, TPC, H2O2 and MDA content, DPPH radical scavenging ability, and antioxidant enzyme activity of SOD, CAT, and POX in carrot leaves in response to insect sex (female and male), rapid response (during the first six hours), and long-term response to B. trigonica infestation were evaluated.ResultsThe results of our study strongly suggest that B. trigonica infestation causes significant changes in primary and secondary metabolism and oxidative status of carrot leaves. Photosynthetic pigment content, TPC, and DPPH and CAT activities were significantly reduced in carrot leaves in response to insect infestation. On the other hand, proline, H2O2 content, and the activity of the antioxidant enzymes superoxide dismutase and peroxidase were increased in carrot leaves after B. trigonica infestation. The results indicate that B. trigonica attenuates and delays the oxidative stress responses of carrot, allowing long-term feeding without visible changes in the plant. Carrot responded to long-term B. trigonica infestation with an increase in SOD and POX activity, suggesting that these enzymes may play a key role in plant defense mechanisms.ConclusionsThis is the first comprehensive study strongly suggesting that B. trigonica infestation causes significant changes in primary and secondary metabolism and an attenuated ROS defense response in carrot leaves that enables long-term insect feeding. The information provides new insights into the mechanisms of carrot protection against B. trigonica infestation.

Effects of sperm concentration on the quality of cryopreserved sperm in Yangtze sturgeon (Acipenser dabryanus)

The Yangtze sturgeon (Acipenser dabryanus) is extinct in the wild; however, artificial propagation in captivity under fully controlled conditions has been successful. Sperm cryopreservation is an effective method for germplasm conservation and aquaculture. Sperm concentration affects the quality of cryopreserved spermatozoa. Thus, in this study, we optimized the concentration (0.25 × 109, 0.5 × 109, 1.0 × 109, and 2.0 × 109 spermatozoa [spz]/mL) for Yangtze sturgeon sperm cryopreservation in a 0.5 mL plastic straw. The greatest value for the kinetic parameters was achieved when sperm were cryopreserved at 0.5 × 109 spz/mL. In comparison to other concentrations, there was a notable increase in both acrosomal and plasma membrane integrity when sperm was cryopreserved at a concentration of 0.5 × 109 spz/mL. No significant difference of superoxide dismutase and glutathione peroxidase enzyme activity was present in post-thaw sperm, except in sperm cryopreserved at a concentration of 2.0 × 109 spz/mL. Catalase activity was significantly higher in post-thaw sperm at a concentration of 0.5 × 109 spz/mL than at other concentrations. Excluding sperm cryopreserved at 2.0 × 109 spz/mL, the fertilization rate of cryopreserved sperm was not significantly different among the different concentrations. This concentration optimization improves cryopreserved sperm quality and standardizes sperm cryopreservation procedures for the Yangtze sturgeon. These findings are especially beneficial for the establishment of a sperm cryobank.

Controlled Atmosphere Storage and Sorbitol Dipping Minimize Chilling Injuries in ‘Palmer’ Mangoes

Our previous studies have shown that ‘Palmer’ mangoes immersed in solutions containing 2.5% sorbitol and stored under a controlled atmosphere (CA) at 8 °C for 30 days had fewer symptoms of a chilling injury. However, there is no information regarding the effectiveness of sorbitol treatment in other atmospheres and/or in combination with lower temperatures. Thus, the objective of this study was to assess the impact of dipping ‘Palmer’ mangoes in 0.1% and 2.5% (w/v) sorbitol solutions and storing the fruit under a CA without atmosphere modification (21 kPa O2 + 0.03 kPa CO2) at 8 °C/95% relative humidity (RH) or with 5 kPa O2 + 5 kPa CO2 at 4 °C/95% RH for 28 days. The fruits were evaluated periodically for chilling injuries, quality, and oxidative metabolism. A chilling injury (CI) was correlated with increased fresh weight loss (FWL) and changes in the color of the epicarp (Lpeel, h°peel, and Cpeel) and mesocarp (L*pulp). Lipid peroxidation (LPpulp and LPpeel) and the hydrogen peroxide content (H2O2peel and H2O2pulp) were associated with the development of a CI, particularly after being transferred to ambient. The treatment with 2.5% sorbitol was more effective in minimizing the chilling injury symptoms and did not compromise the fruit quality, especially when it was stored at 4 °C in association with a CA containing 5 kPa O2 + 5 kPa CO2. This treatment reduced lipid peroxidation and increased the activities of the superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymes in the epicarp and mesocarp, providing greater cold tolerance. The use of 2.5% sorbitol has been identified as the most efficacious approach for mitigating the adverse impacts of chilling injuries, preserving the fruit quality, and enhancing oxidative metabolism, even at lower temperatures. Thus, this treatment represents a viable alternative for managing chilling injuries in mangoes.

Physiological, anatomical and transcriptome analyses reveal ‘Huaizhi’ as widely compatible rootstock in Litchi chinensis Sonn. grafting

Litchi chinensis Sonn. cv. ‘Huaizhi’ (HZ) is an ancient cultivar of litchi. It has been used as widely compatible rootstock for litchi grafting for a long time. However, the mechanism of HZ as widely compatible rootstock is still unclear. In the present study, physiology, morphological anatomy, as well as transcriptomics were conducted to reveal the reasons for HZ with wide compatibility in litchi grafting. Field observation were conducted on the grafting combinations of HZ/HZ (homografting as the control), FZX/HZ and MGL/HZ (the scion with good grafting compatibility in production), SYH/HZ, HHDHL/HZ and WHL/HZ (the scion with weak grafting compatibility in production), embodying that HZ as rootstock did show a wide compatibility. The physiological and biochemical indicators of scion new shoot leaves and scion mother tree indicated that nutrients contents (dry matter weight, total soluble sugar, and starch), mineral nutrition (N and P) levels, and antioxidant enzyme (superoxide dismutase and peroxidase) activities, might be related to the wide compatibility of HZ as rootstock. Microscopic observation of the paraffin sections of healing sites at different stages showed that the necrotic layer of three representative litchi grafting combinations of HZ/HZ, WHL/HZ and MGL/HZ basically disappeared from 14 d to 21 d after grafting, and the callus differentiated into a large number of protoxylem cells, indicating a compatible healing dynamics. Subsequently, a total of 14,384 differentially expressed genes (DEGs) were identified by RNA-seq, of which 2,831 DEGs exhibited the same expression trend within three grafting combinations, enriching into phenylpropanoid biosynthesis, plant hormone biosynthesis and signal transduction, sucrose and starch metabolism, MAPK signaling pathway, peroxisome and other metabolic pathways. These results provide a theoretical basis for the adjustment of cultivar structure in litchi production.

Effects of humic acid water-soluble fertilizer on growth and physiological characteristics of Bupleurum chinense seedlings

The effects of humic acid water-soluble fertilizer on the growth and physiological characteristics of Bupleurum chinense seedlings(Zhongchai No.1) were studied by using a single factor experiment design. When the seedling age was 60 days, the humic acid water-soluble fertilizer was diluted 1 200 times(T1), 1 500 times(T2), 1 800 times(T3), and 2 100 times(T4) for seedling treatment, respectively, and water was used as the control(CK). The effects of different treatments on growth indexes, biomass accumulation, root activity, antioxidant enzyme activity, membrane lipid peroxidation, and photosynthetic characteristics of B. chinense seedlings were analyzed after 30 days. The results showed that compared with CK, stem height, leaf number, root diameter, and root length of the B. chinense seedlings under T3 treatment were significantly increased by 36.82%, 37.03%, 42.78%, and 22.38%, respectively. Root fresh weight, leaf fresh weight, root dry weight, and leaf dry weight under T3 treatment were significantly increased by 90.36%, 98.68%, 123.84%, and 104.38%, respectively. In addition, humic acid water-soluble fertilizer also enhanced TTC reducing activity of the root of B. chinense seedlings, inhibited malonaldehyde(MDA) content, increased superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) enzyme activities, improved chlorophyll content, and enhanced P_n, G_s, T_r, and other photosynthetic parameters. In conclusion, the application of humic acid water-soluble fertilizer diluted 1 800 times can significantly promote the growth of B. chinense seedlings, enhance root vitality, improve seedling stress resistance, and enhance photosynthesis. The results of this study can provide a theoretical basis for fertilization of B. chinense seedlings.

Electron-beam generated X-ray irradiation could retard the senescence of postharvest Hericium erinaceus via regulating reactive oxygen metabolism

Fresh Hericium erinaceus, a type of white mushroom, is prone to browning and microbial invasion after harvest due to high rate of metabolism. This study aimed to clarify how electron-beam generated X-ray (EBGX) irradiation (0, 1.0, 1.5, and 2.0 kGy) affects the senescence of postharvest fresh H. erinaceus during storage at 15 °C for 9 d. The effects of EBGX irradiation on biological properties of H. erinaceus were evaluated. Results indicated that EBGX irradiation reduced the incidence of browning in H. erinaceus, increased firmness, inhibited the respiration rate, lowered malondialdehyde (MDA) content and electrolyte leakage relative to untreated samples. Moreover, the natural microflora presents on H. erinaceus were prominently inhibited (P < 0.05) in 1.0 kGy compare to control group after storage, such as total bacterial count (35.6%), molds and yeasts (31.4%), and Pseudomonas (33.2%). Meanwhile, exposure to 1.0 kGy of irradiation treatment exhibited a minimum hydrogen peroxide content (51.2 nmol kg−1) and superoxide anion production rate (1.88 μmol kg−1 min−1) at 9 d, enhanced the activities of antioxidative enzymes (superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase), as well as declined oxidative stress by regulating the expression of related genes (HeSOD1, HeSOD2, HeCAT1, HeCAT2, HePOX1, and HePOX2).TUNEL analysis also observed that H. erinaceus treated with 1.0 kGy remarkably retained a lower nuclear DNA fragmentation. This finding suggests that the dose of 1.0 kGy EBGX irradiation could postpone the senescence process of fresh H. erinaceus and has the potential to be a promising physical preservation technology for fresh H. erinaceus.

Effects of hypothermia–hypoxia pulping, high hydrostatic pressure processing, and repeat freeze–thaw cycles on the quality of raw kiwifruit puree

AbstractThis study evaluated the effects of the whole process of non‐thermal processing (hypothermia–hypoxia pulping and high hydrostatic pressure (HHP) pasteurization), different freezing methods, and repeat freeze–thaw cycles on physicochemical and nutritional quality of kiwifruit puree. Results showed that hypothermia–hypoxia treatment can retain the vitamin C, total phenol content, and antioxidant capacity of the puree better. Different pasteurization treatments can effectively kill microorganisms and improve the total phenol content and antioxidant capacity of the raw puree. Compared with thermal treatment, HHP can better retain the color, viscosity, and aroma components of the raw puree. The freezing methods have little impact on the quality of the raw puree, but peroxidase enzyme activity after quick freezing was significantly higher than that of slow freezing. Different freeze–thaw treatments had adverse effects on the quality of kiwifruit, and the damage of 25°C thawing conditions was more serious than that of 4°C thawing conditions. This research would provide new ideas for the production and storage of high‐quality kiwifruit puree and potential technical support for kiwifruit puree commercial production.Practical ApplicationsThe results of this study showed that non‐thermal processing can maintain the quality of kiwifruit puree better than traditional thermal processing, which provides a new idea for the production of high‐quality kiwifruit puree. In addition, this study suggests that temperature fluctuations should be minimized during storage to better maintain kiwifruit quality. This will provide potential technical support for the commercialization of kiwifruit puree.

Safety evaluation of an extension of use of the food enzyme peroxidase from the genetically modified Aspergillus niger strain MOX.

The food enzyme peroxidase (phenolic donor: hydrogen-peroxide oxidoreductase, EC 1.11.1.7) is produced with the genetically modified Aspergillus niger strain MOX by DSM Food Specialties B.V. A safety evaluation of this food enzyme was made previously, in which EFSA concluded that this food enzyme did not give rise to safety concerns when used in one food manufacturing process. Subsequently, the applicant requested to extend its use to include an additional process. In this assessment, EFSA updated the safety evaluation of this food enzyme when used in a total of two food manufacturing processes: processing of dairy products for the production of modified milk proteins and the production of plant-based analogues of milk and milk products. The dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.091 mg TOS/kg body weight (bw) per day in European populations. Using the no observed adverse effect level previously reported (2162 mg TOS/kg bw per day), the Panel derived a margin of exposure (MoE) of at least 23,758. Based on the data provided for the previous evaluation and the revised MoE, the Panel concluded that this food enzyme does not give rise to safety concerns under the revised intended conditions of use.

The Physiological Response of Apricot Flowers to Low-Temperature Stress.

The growth and development of apricot flower organs are severely impacted by spring frosts. To better understand this process, apricot flowers were exposed to temperatures ranging from 0 °C to -8 °C, including a control at 18 °C, in artificial incubators to mimic diverse low-temperature environments. We aimed to examine their physiological reactions to cold stress, with an emphasis on changes in phenotype, membrane stability, osmotic substance levels, and antioxidant enzyme performance. Results reveal that cold stress induces significant browning and cellular damage, with a sharp increase in browning rate and membrane permeability below -5 °C. Soluble sugars and proteins initially rise as osmoprotectants, but their content decreases at lower temperatures. Proline content consistently increases, suggesting a protective role. Antioxidant enzyme activities, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), exhibit a complex pattern, with initial increases followed by declines at more severe cold conditions. Correlation and principal component analyses highlight the interplay between these responses, indicating a multifaceted adaptation strategy. The findings contribute to the understanding of apricot cold tolerance and inform breeding efforts for improved crop resilience.

Effect of oil contaminants on antioxidant responses and antioxidant properties of Pleurotus florida (P. Kumm)

ABSTRACT This research investigated the antioxidant responses of Pleurotus florida at different concentrations of gas oil [0% (control), 2.5%, 5%, and 10% (v:v)] for 30 days. The activities of superoxide dismutase and catalase enzymes decreased in responses to the gas oil presence by an average of 83% and 49%, respectively. In contrast, the activities of the ascorbate peroxidase and glutathione peroxidase enzymes displayed an upward trend in the groups cultured in oil-contaminated media. The gas oil contaminant increased total phenol and flavonoid accumulation, reflecting the variation in secondary metabolism. According to the 1,2-diphenyl-2-picrylhydrazyl radical scavenging, the 2.5% gas oil treatment resulted in the highest antioxidant activity (48 μg mL−1). The highest scavenging activity of nitric oxide radicals (IC50 = 272 μg mL−1) was observed in the treatment with the highest gas oil concentration (10%). Also, this treatment showed an excellent ability to chelate Fe+2 ions (IC50 = 205 μg mL−1). The IC50 values of methanolic extract for nitric oxide scavenging activity and metal chelating ability were significantly reduced by increasing gas oil concentration in the treatments. With increasing the gas oil concentration, malondialdehyde content as a criterion measure of lipid peroxidation level showed significant reduction. These results show that P. florida is resistant to and a compatible mushroom with oil pollutants. Also, the activity of glutathione peroxidase and the ascorbate-glutathione cycle detoxify nitric oxide radicals and products of reactive oxygen species–induced lipid peroxidation in the gas oil treatments.

Nano Silver and melatonin effectively delay the senescence of cut carnation flowers under simulated vibrational stress

ABSTRACT Carnation (Dianthus caryophyllus L.) holds great significance as a cut flower, and its vase life plays a crucial role in determining its quality and market appeal. However, the extended transportation distances from the production location to consumer markets can have an unfavourable impact on the vase life and overall quality of cut flowers. The first experiment demonstrated that exposing cut carnation flowers to simulated vibrational stress (SVS) led to a decline in vase life and overall quality. Notably, the application of Nano Silver (NS; 25 and 50 μM) and melatonin (MT; 100 and 200 μM) into the holding solution proved effective in counteracting these negative effects, and extended the vase life by promoting cut flower water relations. In the second experiment, the optimal concentrations of NS and MT into the holding solution (25 and 100 μM, respectively) effectively reduced chlorophyll degradation, electrolyte leakage, and lipid peroxidation by enhancing the activity of catalase and peroxidase enzymes. As a result, it appears that the application of NS and MT in the holding solution has successfully prolonged vase life by both improving water balance and boosting antioxidant activity, while mitigating the negative effects of SVS.

Temporal Changes in Biochemical Responses to Salt Stress in Three Salicornia Species.

Halophytes adapt to salinity using different biochemical response mechanisms. Temporal measurements of biochemical parameters over a period of exposure to salinity may clarify the patterns and kinetics of stress responses in halophytes. This study aimed to evaluate short-term temporal changes in shoot biomass and several biochemical variables, including the contents of photosynthetic pigments, ions (Na+, K+, Ca2+, and Mg2+), osmolytes (proline and glycine betaine), oxidative stress markers (H2O2 and malondialdehyde), and antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) activities of three halophytic Salicornia species (S. persica, S. europaea, and S. bigelovii) in response to non-saline, moderate (300 mM NaCl), and high (500 mM NaCl) salinity treatments at three sampling times. Salicornia plants showed maximum shoot biomass under moderate salinity conditions. The results indicated that high Na+ accumulation in the shoots, coupled with the relative retention of K+ and Ca2+ under salt stress conditions, contributed significantly to ionic and osmotic balance and salinity tolerance in the tested Salicornia species. Glycine betaine accumulation, both constitutive and salt-induced, also seems to play a crucial role in osmotic adjustment in Salicornia plants subjected to salinity treatments. Salicornia species possess an efficient antioxidant enzyme system that largely relies on the ascorbate peroxidase and peroxidase activities to partly counteract salt-induced oxidative stress. The results also revealed that S. persica exhibited higher salinity tolerance than S. europaea and S. bigelovii, as shown by better plant growth under moderate and high salinity. This higher tolerance was associated with higher peroxidase activities and increased glycine betaine and proline accumulation in S. persica. Taking all the data together, this study allowed the identification of the biochemical mechanisms contributing significantly to salinity tolerance of Salicornia through the maintenance of ion and osmotic homeostasis and protection against oxidative stress.

Evaluation of different probiotics on growth, body composition, antioxidant capacity, and histoarchitecture of Mugil capito

We investigated the dietary effects of the single application of Saccharomyces cerevisiae, Lactobacillus bulgaricus, and their combination on growth, proximate composition of whole fish body, antioxidant defense, and histoarchitecture of hapa-reared Mugil capito. Healthy fish (Fish weighed = 10.30 ± 0.10 g at first) were randomly allocated into 4 equal groups, each with three replicates. These groups were designed as follows: (1) a group fed a basal diet without probiotics (control), (2) a group fed a diet containing S. cerevisiae (4 g/kg diet), (3) a group fed a diet containing L. bulgaricus (2 g/kg diet), and (4) the last group fed a diet containing a combination of both, all for a duration of 60 days. Probiotic-treated groups showed significantly better growth and nutrition utilization than the control group. Significant differences were observed in the crude fat and crude protein contents among the groups, with the combination group exhibiting the highest levels. However, there were no significant variations in ash content across all groups. The highest hepatic antioxidant capacity (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) enzyme activities) was observed in the combination group. Thiobarbituric acid reactive substance (TBARS) concentrations were decreased significantly in all probiotic groups, suggesting improved oxidative stress resilience in these groups. The histomorphological analysis of the hepatopancreatic tissues revealed well-arranged parenchyma, increased glycogen storage, and melanomacrophage centers in probiotic-treated groups, particularly the combined probiotics group. Furthermore, the probiotic supplementation improved the histoarchitecture of the intestinal villi compared to the control group. To put it briefly, combined dietary administration of these probiotics improved growth, body composition, antioxidant defenses, and hepatic and intestinal health in hapa-reared M. capito, highlighting their promising role in promoting welfare and productivity.

Exploration of the immune response of grass carp (Ctenopharyngodon idellus) erythrocytes during bacterial infection

In teleost blood, red blood cells (RBCs) are the most common type of cell, and they differ from mammalian RBCs in having a nucleus and other organelles. As nucleated cells, teleost RBCs contribute to the immune response against pathogens, but their antibacterial mechanism remains unclear. Here, we utilized RNA-Seq to analyze gene expression patterns of grass carp (Ctenopharyngodon idellus) RBCs (GcRBCs) stimulated by Aeromonas hydrophila, Escherichia coli, and Staphylococcus aureus. Our transcriptomic data showed that bacterial stimulation generated many differentially expressed genes (DEGs). Furthermore, several inflammatory pathways responded to bacterial activation, and the TLR, IL-17, and tumor necrosis factor (TNF) signaling pathways were significantly activated based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Furthermore, the findings of qRT-PCR showed markedly elevated expression of various cytokines, including IL-1β, IL4, IL6, IL8, IL12, and TNFα, in GcRBCs after incubation with bacteria. Reactive oxygen species (ROS) production in GcRBCs was markedly increased after the cells were stimulated with the three bacteria, and the expression of superoxide dismutase, glutathione peroxidase, and antioxidant enzymes, including catalase, was altered. Flow cytometry analysis showed that the apoptosis rate of GcRBCs was enhanced after stimulation with the three bacteria for different times. In summary, our findings reveal that bacterial stimulation activates the immune response of GcRBCs by regulating ROS release, cytokine expression, and the antioxidant system, leading to apoptosis of GcRBCs.

The Impact of Combining Robinia pseudoacacia Leaves and Corn Straw on Soil Carbon Content and Corn Yield in Loess Plateau

In the agroforestry system, the organic matter in the farmland and natural ecosystem enters the farmland soil in a mixed form to improve soil fertility and carbon pool quality. However, it is unclear how soil microbial carbon-degrading enzyme activity responds to carbon dynamics in this process. Therefore, we took farmland in the Loess Plateau as the research object, combining the application of corn straw and Robinia pseudoacacia leaves in a mass ratio of 4:0, 3:1, 2:2, 1:3, and 0:4 for returning to the field. We measured corn grain yield, carbon emission, organic carbon pool component content, and carbon-degrading enzyme activity of the farmland. The results showed that combining corn straw and Robinia pseudoacacia leaves had a significant impact on soil organic carbon components (readily oxidizable organic carbon and recalcitrant organic carbon), carbon-degrading enzymes (polyphenol oxidase, peroxidase, and cellobiohydrolase), and cumulative carbon emissions. The trend of different indicators in different treatments during the corn growth period was similar. We found that soil carbon emissions were closely related to ROC and soil oxidase activity, while soil carbon content was closely related to soil hydrolase activity. Compared to not returning straw to the field, the corn straw and Robinia pseudoacacia leaves returned to the field in a mass ratio of 1:3(Y1C3) can increase corn grain yield by 32.04%. The Y1C3 treatment has the highest soil carbon content and the lowest crop carbon emission efficiency. Soil water content plays a crucial role in the process of carbon pool transformation driven by soil carbon-degrading enzymes. In conclusion, soil carbon dynamics are closely related to the activity of soil carbon-degrading enzymes. Combining the application of corn straw and Robinia pseudoacacia leaves may be a more suitable farming measure for fragile habitats in the Loess Plateau than other solutions.

Enhanced peroxidase-like activity of Cu–Cu2O composite film through PtPd immobilization for colorimetric glucose detection

In this study, Cu–Cu2O/PtPd nanocomposites were synthesized and characterized for their peroxidase-like enzyme activity. X-ray diffraction and energy dispersive X-ray spectroscopy analyses confirmed the successful synthesis of the nanocomposites, which exhibited a flower-like morphology and a more uniform dispersion than Cu–Cu2O. The catalytic activity of Cu–Cu2O/PtPd was evaluated using the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB), finding that Cu–Cu2O/PtPd outperformed Cu–Cu2O. The optimal temperature and pH for the catalytic activity of Cu–Cu2O/PtPd were determined to be 40 °C and pH 4.0, respectively. A kinetic analysis revealed that Cu–Cu2O/PtPd followed Michaelis–Menten kinetics and exhibited a higher affinity toward TMB than the horseradish peroxidase enzyme. The catalytic mechanism of Cu–Cu2O/PtPd involved the generation of hydroxyl radicals, which facilitated the oxidation of TMB. Furthermore, the Cu–Cu2O/PtPd nanocomposite was successfully applied for the colorimetric detection of glucose, demonstrating a linear range of 8–90 μM, a detection limit of 2.389 μM, and high selectivity for glucose over other sugars.

The impact of chitooligosaccharides with a certain degree of polymerization on diabetic nephropathic mice and high glucose-damaged HK-2 cells.

Diabetic nephropathy (DN) is a primary diabetic complication ascribed to the pathological changes in renal microvessels. This study investigated the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch ECH associating protein (Keap1)/antioxidant response element (ARE) signaling pathway impact of chitooligosaccharides (COS) with a certain degree of polymerization (DP) on DN mouse models and high glucose-damaged human kidney 2 (HK-2) cells. The findings indicated that COS effectively reduced the renal function indexes (uric acid [UA], urinary albumin excretion rate [UAER], urine albumin-to-creatinine ratio [UACR], blood urea nitrogen [BUN], and creatinine [Cre]) of DN mice. It increased (p < .05) the superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) antioxidant enzyme activity in the serum and kidneys, and decreased (p < .05) the malondialdehyde (MDA) content. The mechanistic investigation showed that COS significantly increased (p < .05) Nrf2 and downstream target gene (GCLM, GCLC, HO-1, and NQO-1) expression, and substantially decreased (p < .05) Keap1 expression. The protein level was consistent with the messenger RNA (mRNA) level in invitro and invivo models. The docking data indicated that COS and Keap1 protein binding included six hydrogen bond formation processes (Gly364, Arg415, Arg483, His436, Ser431, and Arg380). The COS intervention mechanism may be related to the Nrf2/Keap1/ARE antioxidant pathway. Therefore, it provides a scientific basis for COS application in developing special medical food for DN patients.

Abstract 90: In vitro functional evaluation of immuno-oncology drug candidates in customized bioassays

Abstract Increased understanding of the complex tumor microenvironment and its interactors has boosted therapeutic interest and highlighted the importance of the development of innovative in vitro bioassays to represent all the players of the cancer immune response and thereby potentially provide pivotal information on the functional dynamics of candidate therapeutics. Regulatory T cells play an important role by downregulating the anti-tumor response. Their regulation mechanisms constitute an important target for new therapeutics. To study these mechanisms in a human model, suppressive Treg bioassays, mimicking the suppressive action of these cells, were developed and optimized. We further highlight the study of neutrophil function in vitro using flow-cytometry or the Incucyte® live imaging system to monitor neutrophil functions such as antibody-dependent cell-mediated cytotoxicity (ADCC), Neutrophil Extracellular Traps (NETs) formation and the release of Reactive Oxygen Species (ROS). Additionally, multiplex cytokine and peroxidase enzyme analysis after activation and stimulation of neutrophils can be evaluated using ELISA or Luminex technology. Moreover, to refine/reduce non-human primate (NHP) usage, we aimed to develop cost-effective NHP in vitro assays with predictive value for in vivo studies. We isolated Cynomolgus Macaque monocytes and successfully differentiated/polarized them into M0- and M2-like macrophages with a cell surface phenotype comparable to that of their human counterparts. We further developed a Cynomolgus Macaque PBMC x human dendritic cell (DC) mixed lymphocyte reaction (MLR) assay for functional evaluation of test compounds, effectively generated Cynomolgus Macaque immature DCs and implemented Cynomolgus Macaque cytokine release assays.Using high quality primary human immune cells from our own biobank, in vitro bioassays have been developed with superior robustness and reproducibility to screen candidate Immuno-Oncology therapeutics. Citation Format: Martijn Vlaming, Emmanuelle Sidot, Jezabel Lefèvre, Ellen Boelen, Sofie Pattyn. In vitro functional evaluation of immuno-oncology drug candidates in customized bioassays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 90.

Exploring Options for Proximity-Dependent Biotinylation Experiments: Comparative Analysis of Labeling Enzymes and Affinity Purification Resins.

Proximity-dependent biotinylation (PDB) techniques provide information about the molecular neighborhood of a protein of interest, yielding insights into its function and localization. Here, we assessed how different labeling enzymes and streptavidin resins influence PDB results. We compared the high-confidence interactors of the DNA/RNA-binding protein transactive response DNA-binding protein 43 kDa (TDP-43) identified using either miniTurbo (biotin ligase) or APEX2 (peroxidase) enzymes. We also evaluated two commercial affinity resins for purification of biotinylated proteins: conventional streptavidin sepharose versus a new trypsin-resistant streptavidin conjugated to magnetic resin, which significantly reduces the level of contamination by streptavidin peptides following on-bead trypsin digestion. Downstream analyses involved liquid chromatography coupled to mass spectrometry in data-dependent acquisition mode, database searching, and statistical analysis of high-confidence interactors using SAINTexpress. The APEX2-TDP-43 experiment identified more interactors than miniTurbo-TDP-43, although miniTurbo provided greater overlap with previously documented TDP-43 interactors. Purifications on sepharose resin yielded more interactors than magnetic resin in small-scale experiments using a range of magnetic resin volumes. We suggest that resin-specific background protein binding profiles and different lysate-to-resin ratios cumulatively affect the distributions of prey protein abundance in experimental and control samples, which impact statistical confidence scores. Overall, we highlight key experimental variables to consider for the empirical optimization of PDB experiments.