Enzyme Activity Research Articles

Discovery and validation of a novel inhibitor of HYPE-mediated AMPylation.

Adenosyl monophosphate (AMP)ylation (the covalent transfer of an AMP from Adenosine Triphosphate (ATP) onto a target protein) is catalyzed by the human enzyme Huntingtin Yeast Interacting Partner E (HYPE)/FicD to regulate its substrate, the heat shock chaperone binding immunoglobulin protein (BiP). HYPE-mediated AMPylation of BiP is critical for maintaining proteostasis in the endoplasmic reticulum and mounting a unfolded protein response in times of proteostatic imbalance. Thus, manipulating HYPE's enzymatic activity is a key therapeutic strategy towardthe treatment of various protein misfolding diseases, including neuropathy and early-onset diabetes associated with two recently identified clinical mutations of HYPE. Herein, we present an optimized, fluorescence polarization-based, high-throughput screening (HTS) assay to discover activators and inhibitors of HYPE-mediated AMPylation. After challenging our HTS assay with over 30,000 compounds, we discovered a novel AMPylase inhibitor, I2.10. We also determined a low micromolar IC50 for I2.10 and employed biorthogonal counter-screens to validate its efficacy against HYPE's AMPylation of BiP. Further, we report low cytotoxicity of I2.10 on human cell lines. We thus established an optimized, high-quality HTS assay amenable to tracking HYPE's enzymatic activity at scale, and provided the first novel small-molecule inhibitor capable of perturbing HYPE-directed AMPylation of BiP in vitro. Our HTS assay and I2.10 compound serve as a platform for further development of HYPE-specific small-molecule therapeutics.

Evaluation of Flavonoid-rich Fraction of Portulaca Grandiflora Aerial Part Extract in Atherogenic Diet-induced Atherosclerosis.

Portulaca grandiflora is a tiny, upright herb that contains a variety of chemical components, including alkaloids, glycosides, mucilage, proteins, tannins, flavonoids, saponins, polysaccharides, and triterpenoids possessing properties that may help with atherosclerosis. The reported pharmacological properties of Portulaca grandiflora are antioxidant, antidiabetic, antiasthmatic, antibacterial, antiulcer and anti-inflammatory properties. The yield of methanol extract is higher than that of ethanol and acetone, and its phytoconstituents, like flavonoids and polyphenols, and has potent antioxidant properties. In order to determine the effectiveness ofPortulaca grandiflora methanol extract fraction against high-fat diet (HFD)-induced hyperlipidemia, hemodynamic change, antioxidant levels, and vascular dysfunction in rats, a study was carried out on a flavonoid-rich methanol extract fraction of the aerial part of Portulaca grandiflora Hook. This method involves a study of 30 days involving male Wistar rats (240-250 g) (n=5) that were fed with an Ath diet. Study groups were divided into (i) The Control Group, (ii) the Diseases Control Group, (iii) Disease + Standard drug (Atorvastatin 20mg/kg, orally, (iv) Disease + Test Extract dose 1 (Portulaca grandiflora 200mg/kg orally), and (v) Disease + Test Extract dose 2 (Portulaca grandiflora 400mg/kg orally). Both the test drug Portulaca grandiflora and the standard drug Atorvastatin were given orally for 30 days. At the end of the study, blood samples were taken to measure the serum lipid profile, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and levels of oxidative tissue stress. Hemodynamic parameters and aortic staining were performed. Portulaca grandiflora treatment improved the lipid profile and considerably reduced oxidative stress levels. Aortic staining examination revealed a marked reduction in atherosclerotic lesions. These results revealed that Portulaca grandiflora is an effective treatment approach in preventing atherosclerotic lesion progression, which is attributed to its protection against oxidative stress and various enzymatic activities in the Atherogenic model.

Drought priming improves tolerance of Alhagi sparsifolia to subsequent drought: A coordinated interplay of phytohormones, osmolytes, and antioxidant potential

Perennial trees are often stressed by drought more than once during their life cycle. Our study exposed three-month-old Alhagisparsifolia, with (drought-primed) or without (nonprimed) prior drought stress to subsequent drought for two months, aiming to reveal whether pre-exposure to drought could enhance seedling resistance to subsequent drought and investigated possible underlying mechanisms. Root biomass, leaf relative water content, chlorophyll a, and carotenoids were significantly higher in drought-primed than nonprimed seedlings. They also had reduced concentrations of malondialdehyde, hydrogen peroxide (H2O2), and superoxide anions (O2•−), indicating relief from oxidative stress. This relief was associated with a coordinated upregulation of enzymes scavenging O2•− and H2O2, particularly superoxide dismutase (SOD) and catalase (CAT), and the maintenance of the ascorbate-glutathione (AsA-GSH) redox pool and enzymatic activities (ascorbate peroxidase, mono- and dehydroascorbate reductase, and glutathione reductase), leading to the better regulation of reactive oxygen species. The failure of nonprimed seedlings to upregulate the SOD, CAT, and AsA-GSH cycles nevertheless made the seedlings susceptible to oxidative stress. The increased levels of strigolactones, jasmonic acid, and abscisic acid in drought-primed seedlings reveal their roles in subsequent stress. They also displayed higher gibberellic acid and indole acetic acid. A principal component analysis showed that the seedlings responded differently to drought if they had previously suffered a drought, mainly due to a higher capacity for pigment protection, oxidative scavenging, osmolytes, and anti-stress hormones. Our study provides insights into the benefits of stress memory induced in seedlings by early drought priming as a strategy for overcoming subsequent stress.

Significantly improving the thermal stability of alginate lyase AlyC3 from Psychromonas sp. C-3 by computational redesign

Alginate lyase is a key enzyme in the bioproduction of alginate oligosaccharides. The alginate lyase AlyC3, derived from Psychromonas sp. C-3, can hydrolyze homopolymerized mannuronic acid into oligosaccharides (primarily composed of mannuronate trimer), which possess physiological properties such as bacteriostatic and antioxidant activities and show a better application prospect. However, the poor thermal stability hinders its potential application in industrial production. In this study, AlyC3 mutants A35P, L95F, N138Y and M162I were obtained through the protein repair one-stop shop (PROSS) design combined with protein data bank in Europe (proteins, interfaces, structures and assemblies) (PDBePISA) analysis of the dimer interface. The results demonstrated that the thermodynamic and kinetic stability of these single-point mutants were significantly improved compared to the wild-type (WT), with the melting temperature increased by 4.33, 9.35, 9.74 and 11.24 °C, respectively, while the half-life (t1/2) was 1.66, 1.02, 1.02 and 1.53 times higher than that of WT, respectively. Based on this, the beneficial mutations were further combined to obtain a combinatorial mutant, A35P-L95F–N138Y-M162I, which exhibited the superior thermal stability. Notably, the combinatorial mutant's melting and optimal temperature increased by 17.05 and 10 °C, respectively; moreover, the mutant enzyme's t1/2 and enzyme activity were 8.21 times and 123.93% higher than those of the WT, respectively. Structural analyses indicated that increased hydrophobic interactions and polar bonding between the mutated and nearby residues, with improved rigidity in the flexible loop, might account for the significantly improved thermal stability of the reengineered AlyC3, which makes it a robust candidate for alginate oligosaccharide production.

Unveiling myricetin's pharmacological potency: A comprehensive exploration of the molecular pathways with special focus on PI3K/AKT and Nrf2 signaling.

Myricetin can be found in the traditional Chinese medicinal plant, Myrica rubra. Myricetin is a flavonoid that is present in many vegetables, fruits, and plants and is considered to have strong antioxidant properties as well as a wide range of therapeutic applications. Growing interest has been piqued by its classification as a polyphenolic molecule because of its potential therapeutic benefits in both the prevention and management of numerous medical conditions. To clarify myricetin's traditional medical uses, modern research has investigated various pharmacological effects such as antioxidant, anticancer, anti-inflammation, antiviral, antidiabetic, immunomodulation, and antineurodegenerative effects. Myricetin shows promise as a nutritional flavonol that could be beneficial in the prevention and mitigation of prevalent health conditions like diabetes, cognitive decline, and various types of cancer in humans. The findings included in this study indicate that myricetin has a great deal of promise for application in the formulation of medicinal products and nutritional supplements since it affects several enzyme activities and alters inflammatory markers. However, comprehensive preclinical studies and research studies are necessary to lay the groundwork for assessing myricetin's possible effectiveness in treating these long-term ailments. This review summarizes both in vivo and in vitro studies investigating myricetin's possible interactions through the nuclear factor-E2-related factor 2 (Nrf2) as well as PI3K (phosphatidylinositol 3-kinase)/AKT(protein kinase B) signaling pathways in an attempt to clarify the compound's possible clinical applicability across a range of disorders.

Integrated multiple-omics reveals the regulatory mechanism underlying the effects of homologous Bacillus tequilensis (GCB-3) on growth performance of grass carp (Ctenopharyngodon idellus)

The purpose of this study was to investigate the regulatory mechanism of Bacillus tequilensis (GCB-3) in improving the growth performance of grass carp by microbiome and targeted metabolomics analysis. Fish were fed with different amounts of GCB-3 including B0 (0 CFU/g), B6 (1×106 CFU/g), B7 (1×107 CFU/g), B8 (1×108 CFU/g), and B9 (1×109 CFU/g) for 8 weeks. The results indicate that with the increase of dietary GCB-3 concentration, grass carp showed a significant linear trend in growth performance, and appetite factors showed a significant linear and quadratic trend, the growth performance and appetite-promoting factors in the B8 group reach their maximum value in the B8 group. Microbiome analysis found that Proteobacteria and Actinobacteria were the most abundant phylum in the gut microbiota of grass carp. The functional potential predicted that GCB-3 affected the synthesis and degradation of carbohydrates, amino acids, fatty acids and lipids. It found that GCB-3 also affected the tricarboxylic acid (TCA) cycle VII (acetate-producers) pathway. The results of targeted metabolomics showed a significant linear and quadratic increase in intestinal acetate with GCB-3 concentration and a maximum in the B8 group. The results of the correlation analysis showed a significant positive correlation between Actinobacteria abundance and acetic acid content, and also between TCA cycle VII (acetate-producers) pathway abundance and Actinobacteria abundance and acetic acid content. In B8 group, grass carp showed a faster regulation speed of blood glucose levels after glucose injection, and the GLP-1 content remained stable. The activities of glycolytic enzymes, lipolytic enzymes, protein metabolism enzymes, and their related mRNA expression levels in grass carp showed a linear or quadratic increasing trend. However, the expression levels of gluconeogenic enzymes and fatty acid synthesis enzyme related mRNA showed an opposite trend. In summary, the addition of 1×108 CFU/g GCB-3 in grass carp feed can improve the abundance of dominant bacterial phyla in the intestine, especially Actinobacteria, increase the concentration of intestinal acetate, provide substrate for the TCA cycle VII (acetate-producers) pathway, thereby regulating the nutrient metabolism of grass carp and ultimately promoting growth.

Coating seeds with biopolymers extracted from waste-activated sludge

Seeds can be coated with biopolymers extracted from waste-activated sludge, and the seeds of lettuce and spinach can be coated. When coated with the biopolymers, these seeds exhibited largely improved resistance to high temperature and humidity. The seeds coated or not coated with the biopolymers were aged, and the germination potential, germination ratio, and antioxidant enzyme activity of the coated seeds exhibited markedly greater differences than did those of the uncoated seeds. Moreover, the CAT, POD, and APX activities in the coated lettuce and spinach seeds increased by 56%, 2%, and 17%, respectively (lettuce), as did the activity of 8%, 3%, and 31%, respectively (spinach). In the pot trials, the contents of soluble protein and soluble sugar and the activities of antioxidant enzymes were also enhanced—42% and 56% (lettuce) as well as 34% and 23% (spinach). Thus, biopolymers can contribute to protecting against the aging of some rare seeds.

Eco-endocrinological dynamics: Unraveling dexamethasone's influence on the interrenal axis in juvenile carp Cyprinus carpio

This study delves into the eco-endocrinological dynamics concerning the impact of dexamethasone (DXE) on the interrenal axis in juvenile carp, Cyprinus carpio. Through a comprehensive analysis, we investigated the effects of DXE exposure on oxidative stress, biochemical biomarkers, gene expression, and bioaccumulation within the interrenal axis. Results revealed a concentration-dependent escalation of cellular oxidation biomarkers, including 1) hydroperoxides content (HPC), 2) lipid peroxidation level (LPX), and 3) protein carbonyl content (PCC), indicative of heightened oxidative stress. Concurrently, the activity of critical antioxidant enzymes, superoxide dismutase (SOD), and catalase (CAT), significantly increased, underscoring the organism's response to oxidative insult. Notable alterations were observed in biochemical biomarkers, particularly Gamma-glutamyl-transpeptidase (GGT) and alkaline phosphatase (ALP) activity, with GGT displaying a significant decrease with increasing DXE concentrations. Gene expression analysis revealed a significant upregulation of stress and inflammation response genes, as well as those associated with sensitivity to superoxide ion presence and calcium signaling, in response to DXE exposure. Furthermore, DXE demonstrated a concentration-dependent presence in interrenal tissue, with consistent bioconcentration factors observed across all concentrations tested. These findings shed light on the physiological and molecular responses of juvenile carp to DXE exposure, emphasizing the potential ecological implications of DXE contamination in aquatic environments. Understanding these dynamics is crucial for assessing the environmental impact of glucocorticoid pollutants and developing effective management strategies to mitigate their adverse effects on aquatic ecosystems.

Physiological and transcriptomic analyses provide new insights into the regulatory mechanisms of accelerated senescence of litchi fruit in response to strigolactones

Strigolactones (SLs), a class of plant hormones that are derived from carotenoid metabolism, play pivotal roles in regulating various physiological processes in plants. However, the action mode of SLs in regulating postharvest physiology of fruits is not well understood. This study aimed to explore the effect of exogenous GR24 (a synthetic analogue of SLs) on litchi senescence and its possible mechanisms based on physiological and transcriptomic analyses. The results demonstrated that GR24 treatment at 0.5 μM accelerated the development of pericarp browning and discoloration in litchi fruit during storage at ambient conditions, which was related to exacerbated oxidative stress and aggravated membrane deterioration, as indicated by increased reactive oxygen species production, membrane permeability and malondialdehyde content. Compared to those in the control fruit, lower activities of antioxidant enzyme (superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase and glutathione peroxidase) and contents of antioxidants (ascorbic acid and reduced glutathione), but higher prooxidant enzyme (peroxidase) activity were observed in GR24-treated fruit. Transcriptomic analysis revealed that GR-24 treatment downregulated the expression of genes associated with antioxidant system, pentose phosphate pathway, oxidative phosphorylation and energy metabolism, which was aligned with the physiological results. These findings provide insights into the role of SLs in regulating senescence of harvested litchi fruit.

Short-Lived Active Prorenin: Precursor of So-Called Native Prorenin.

The enzymatic activity of the aspartic protease, renin, is critical for its function in blood pressure regulation and sodium homeostasis. Incubation of so-called native prorenin at low pH leads to its activation. After binding to transition-state mimicking renin inhibitors at neutral pH, prorenin attains the active conformation, as indicated by immunosorbent assay using monoclonal antibodies specific for epitopes of the prosegment or the renin body. A comparison of immunosorbent assay with enzyme-kinetic assay revealed the intermediary steps of prorenin auto-activation/inactivation. The kinetically identified intermediary steps of activation/inactivation correspond with the published crystal structures of free renin, free prorenin, and renin in complex with inhibitors. Both renin and activated prorenin exist in 2 forms, α and β. The α form is active, and the α/β quantity ratio is 2.5. The kidney produces renin and prorenin, while the ovarium, placenta, and eye produce inactive prorenin. The production of renin by these organs has never been demonstrated. We propose that the so-called native prorenin in extracellular fluid, including the circulation, is derived, at least partly, from short-lived active prorenin. Its potential paracrine function is discussed.

Comprehensive physiology and proteomics analysis revealed the molecular toxicological mechanism of Se stress on indica and japonica rice

Selenium pollution can lead to a decrease in crop yield and quality. However, the toxicological mechanisms of high Se concentrations on crops remain unclear. This study aimed to elucidate the physiological and proteomic molecular responses to Se stress in Oryza sativa. The results showed that under selenium stress, enzymatic activities of catalase, peroxidase, and superoxide dismutase in indica rice decreased by 61%, 28%, and 68%, respectively. The contents of non-enzymatic antioxidant substances ascorbic acid, glutathione, cysteine, proline, anthocyanidin, and flavonoids were decreased by 13%, 39%, 46%, 32%, 20%, and 5%, respectively, which significantly inhibited the antioxidant stress process of plants. At the same time, the results of proteomics analysis showed that rice seedlings, under Se stress, are involved in photosynthesis, photosynthesis-antenna proteins, carbon fixation, porphyrin metabolism, glyoxylate, and dicarboxylate. The differentially expressed proteins in metabolism and glutathione metabolism pathways showed a downward trend. It significantly inhibited the anti-oxidative stress, photosynthesis, and energy cycling process in plant cells, destroyed the homeostasis balance of rice plants, and inhibited the growth and development of rice. This finding reveals the molecular toxicological mechanism of Se stress on rice seedlings and provides a possible way to improve Se-resistant rice seedlings.

Elucidating the mechanism of amylolytic enzyme activity inhibition by rice glutelin amyloid fibril aggregates

Elucidating the mechanism of amylolytic enzyme activity inhibition by rice glutelin amyloid fibril aggregates

Antagonistic effects of a COX1/2 inhibitor drug in human HepG2 cells exposed to an environmental carcinogen

Understanding interactions between legacy and emerging environmental contaminants has important implications for risk assessment, especially when involving mutagens and carcinogens whose critical effects are chronic and therefore difficult to predict. The current work aimed to investigate potential interactions between benzo[a]pyrene (B[a]P), a carcinogenic polycyclic aromatic hydrocarbon and legacy pollutant, and diclofenac (DFC), a non-steroidal anti-inflammatory drugs and pollutant of emerging concern and how DFC affects B[a]P toxicity. Exposure to binary mixtures of these chemicals resulted in substantially reduced cytotoxicity in human HepG2 cells compared to single-chemical exposures. Significant antagonistic effects were observed in response to high concentrations of B[a]P in combination with DFC at IC50 and ⅕ IC50. While additive effects were found on levels of intracellular reactive oxygen species, antagonistic mixture effects were observed for genotoxicity. B[a]P induced DNA strand breaks, γH2AX activation, and micronuclei formation at ½ IC50 concentrations or lower while DFC only induced low levels of DNA strand breaks. Their mixture caused significantly lower levels of genotoxicity by all three endpoints compared to those expected based on concentration additivity. In addition, antagonistic mixture effects on CYP1 enzyme activity suggested that the observed reduced genotoxicity of B[a]P was due to its reduced metabolic activation as a result of enzymatic inhibition by DFC. Overall, the findings further support the increasing concern that co-exposure to environmental toxicants and their non-additive interactions can be a confounding factor that should not be neglected in environmental and human health risk assessment.

Therapeutic potentials of Hibiscus trionum: Antioxidant, anti-lipid peroxidative, hypoglycemic, and hepatoprotective effects in type 1 diabetic rats

Recent advances in diabetes treatment have primarily focused on insulin and hypoglycemic agents; however, there is growing interest in exploring herbal and synthetic alternatives. Numerous studies have highlighted the preventive effectiveness of regular plant consumption in managing chronic conditions, particularly diabetes. Hibiscus, a medicinal plant recognized in various cultures, is known for its diverse health benefits. This study investigated the impact of Hibiscus trionum on glycemic control and assessed its influence on glucose and insulin levels in diabetes-induced rats. The concentrations of antioxidant enzymes, particularly superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), were scrutinized across multiple body tissues (plasma, heart, muscle, liver, and kidney). The malondialdehyde (MDA) concentration, an indicator of lipid peroxidation, was examined in both plasma and tissue samples. Serum total cholesterol (TC), triglyceride (TG), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels were evaluated. Diabetic Group (D) exhibited a significant decrease in body weight, increased fluid and food consumption, elevated blood glucose levels, and increased antioxidant enzyme activity. Moreover, the diabetic group also showed increased levels of MDA, TC, TG, AST, and ALT, along with reduced insulin levels, compared to the control group. A substantial improvement in all parameters impaired by diabetes was observed following the application of Hibiscus trionum (HTT) in the Diabetes+HTT group. The antioxidative stress-reducing, lipid peroxidation-improving, and hepatoprotective potential of Hibiscus trionum in mitigating diabetes-induced oxidative stress is noteworthy. These findings indicate that HTT supplementation has valuable beneficial effects in protecting against the harmful impacts of diabetes.

Unveiling the functional food properties of Pepromia pellucida: Phytochemical profiling, antioxidative potential, and their nanoemulsion fraction in wound healing efficacy

Peperomia pellucida, a tropical plant belonging to the Piperaceae family, has long been recognized for its potential medicinal properties, including anti-inflammatory, analgesic, and antimicrobial effects. This study investigates the efficacy of Peperomia pellucida nanoemulsion (PPNE) as a novel therapeutic approach for improving burn wound healing in Wistar rats. The nanoemulsion was formulated using the high-energy ultrasonication method, optimized for droplet size, polydispersity index, and stability. A 30% burn wound was induced on the dorsum of 60 Wistar rats, which were then divided into three groups: control (untreated), silver sulfadiazine (SSD) treated, and PPNE treated. Inflammatory cytokine levels (TNF-α, IL-6, and IL-1) were measured using enzyme-linked immunosorbent assay (ELISA). Results showed that PPNE treatment significantly accelerated wound closure rates compared to both control and SSD-treated groups, with complete wound closure achieved by day 10 in the PPNE-treated group. Histopathological examination revealed improved re-epithelialization, granulation tissue formation, and collagen deposition in the PPNE group compared to the control and SSD groups. Additionally, PPNE treatment significantly reduced inflammatory cytokine levels and enhanced antioxidant enzyme activities, suggesting a reduction in inflammation and oxidative stress in the treated wounds. In conclusion, this study demonstrates the potential of P. pellucida nanoemulsion as a promising and effective therapeutic approach for improving burn wound healing. The observed enhanced wound healing properties may be attributed to the combined anti-inflammatory, antioxidant, and antimicrobial effects of the PPNE, warranting further investigation and potential clinical application.

Biodegradable pyroptosis inducer with multienzyme-mimic activity kicks up reactive oxygen species storm for sensitizing immunotherapy

Triggering pyroptosis is a major new weathervane for activating tumor immune response. However, biodegradable pyroptosis inducers for the safe and efficient treatment of tumors are still scarce. Herein, a novel tumor microenvironment (TME)-responsive activation nanoneedle for pyroptosis induction, copper-tannic acid (CuTA), was synthesized and combined with the sonosensitizer Chlorin e6 (Ce6) to form a pyroptosis amplifier (CuTA-Ce6) for dual activation and amplification of pyroptosis by exogenous ultrasound (US) and TME. It was demonstrated that Ce6-triggered sonodynamic therapy (SDT) further enhanced the cellular pyroptosis caused by CuTA, activating the body to develop a powerful anti-tumor immune response. Concretely, CuTA nanoneedles with quadruple mimetic enzyme activity could be activated to an “active” state in the TME, destroying the antioxidant defense system of the tumor cells through self-destructive degradation, breaking the “immunosilent” TME, and thus realizing the pyroptosis-mediated immunotherapy with fewer systemic side effects. Considering the outstanding oxygen-producing capacity of CuTA and the distinctive advantages of US, the sonosensitizer Ce6 was attached to CuTA via an amide reaction, which further amplified the pyroptosis and sensitized pyroptosis-induced immunotherapy with the two-pronged strategy of CuTA enzyme-catalyzed cascade and US-driven SDT pathway to generate a “reactive oxygen species (ROS) storm”. Conclusively, this work provided a representative paradigm for achieving safe, reliable and efficient pyroptosis, which was further enhanced by SDT for more robust immunotherapy.

Soil microbes deal with the nitrogen deposition enhanced phosphorus limitation by shifting community structure in an old-growth subtropical forest

Elevated atmospheric nitrogen (N) deposition potentially enhances the degree of phosphorus (P) limitation in tropical and subtropical forests. However, it remains elusive that how soil microorganisms deal with the N deposition-enhanced P limitation. We collected soils experienced 9 years of manipulative N input at various rates (0, 40, and 80 kg N ha−1 y−1) in an old-growth subtropical natural forest. We measured soil total and available carbon (C), N and P, microbial biomass C, N and P, enzyme activities involved in C, N and P acquisition, microbial community structure, as well as net N and P mineralization. Additionally, we calculated element use efficiency and evaluated microbial homeostasis index. Our findings revealed that N input increased microbial biomass C:P (MBC:P) and N:P (MBN:P) ratios. The homeostasis indexes of MBC:P and MBN:P were 0.68 and 0.75, respectively, indicating stoichiometric flexibility. Interestingly, MBC:P and MBN:P correlated significantly with the fungi:bacteria ratio (F:B), not with N and P use efficiencies, net N and P mineralization, and enzyme C:P (EEAC:P) and N:P (EEAN:P) ratios. Furthermore, EEAC:P and EEAN:P correlated positively with F:B but did not negatively correlate with the C:P and N:P ratios of available resources and microbial biomass. The effects of N deposition on MBC:P, MBN:P and EEAN:P became insignificant when including F:B as a covariate. These findings suggest that microbes flexibly adapted to the N deposition enhanced P limitation by changing microbial community structure, which not only alter microbial biomass C:N:P stoichiometry, but also the enzyme production strategy. In summary, our research advances our understanding of how soil microorganisms deal with the N deposition-enhanced soil P limitation in subtropical forests.

Various functions of detoxification enzymes against insecticides in Nilaparvata lugens selected by toxicity assays and RNAi methods

The brown planthopper (BPH), Nilaparvata lugens is a devastating agricultural pest of rice, and they have developed resistance to many pesticides. In this study, we assessed the response of BPH nymphs to nitenpyram, imidacloprid, and etofenprox using contact and dietary bioassays, and investigated the underlying functional diversities of BPH glutathione-S-transferase (GST), carboxylesterase (CarE) and cytochrome P450 monooxygenase (P450) against these insecticides. Both contact and ingestion toxicity of nitenpyram to BPH were significantly higher than either imidacloprid or etofenprox. Under the LC50 concentration of each insecticide, they triggered a distinct response for GST, CarE, and P450 activities, and each insecticide induced at least one detoxification enzyme activity. These insecticides almost inhibited the expression of all tested GST, CarE, and P450 genes in contact bioassays but induced the transcriptional levels of these genes in dietary bioassays. Silencing of NlGSTD2 expression had the greatest effect on BPH sensitivity to nitenpyram in both contact and dietary tests. The sensitivities of BPH to insecticide increased the most in the contact test was etofenprox after silencing of NlCE, while the dietary test was nitenpyram. Knockdown of NlCYP408A1 resulted in BPH sensitivities to insecticide increasing the most in the contact test was nitenpyram, while the dietary test was imidacloprid. Taken together, these findings reveal that NlGSTD2, NlCE, and NlCYP408A1 play an indispensable role in the detoxification of the contact and ingestion toxicities of different types of insecticides to BPH, which is of great significance for the development of new strategies for the sucking pest control.

Maintaining postharvest quality and enhancing shelf-life of bell pepper (Capsicum annuum L.) using brassinosteroids: A novel approach

Bell pepper is a major vegetable crop of global commercial interest, but the postharvest quality is constrained by faster deterioration and senescence. Brassinosteroids (BRs), are an emerging and novel biomolecule that delay ripening and senescence in various vegetables. Freshly harvested bell pepper fruit were immersed in an aqueous solution of BRs concentrations (0, 2, 5, 7 and 10 μM) for 20 min and subsequently stored for 20 d at 10 ± 1°C, 85–90% RH. The bell pepper treated with 10 μM BRs significantly reduced respiration rate (∼2.3 fold), delayed weight loss (∼2.2 fold), and retained higher firmness (∼2.5 fold), total phenolic (∼1.7 fold), flavonoid (∼1.7 fold), proline (∼2 fold) and ascorbic acid content (∼2 fold) over the control fruit at the end of cold storage. Also, it retained higher DPPH radical scavenging (∼1.8 fold) and antioxidant enzyme activity (∼1.5 fold) over the control at the end of cold storage. Moreover, BRs treated bell pepper exhibited reduced malondialdehyde accumulation and delayed capsaicin, and chlorophyll degradation. Remarkably, 10 μM BRs treatment prolonged the shelf-life of bell pepper up to 20 d (10 d extra over control) without compromising quality and sensory acceptability.

Mitigation of Surface Browning in Fresh-Cut Banana Blossom by Tamarind (Tamarindus indica L.) Pulp Extract: A Role in Regulating ROS Metabolism

T he surface browning of fresh-cut products not only diminishes their nutritional content but also lowers their market value. Fresh-cut banana blossom (FBB), an increasingly popular vegan food, is prone to browning on the cut surface, which poses a significant challenge for this fresh-cut produce. Chemicals and natural extracts are commonly used to address this issue in fresh-cut produce, offering alternatives to synthetic chemicals. Tamarind (Tamarindus indica L.) pulp extract (TPE), derived from the tamarind fruit, contains compounds such as polyphenols with antioxidant properties, making it an intriguing choice as an anti-browning agent. Therefore, this study investigated the effects of TPE on surface browning and reactive oxygen species (ROS) metabolism in FBB during storage at 30 ± 1 °C. FBB was immersed in 0 % (the control) and 2.5 % TPE for 5 min, then rinsed with distilled water, air-dried, and stored at 30 ± 1 °C for 60 h. The control group showed increasing surface browning and declining overall quality during storage. TPE immersion significantly enhanced antioxidant defense systems during storage compared to the control. The heightened activity of antioxidant enzymes and increased non-enzymatic antioxidant levels corresponded with decreased ROS levels, oxidative membrane damage, and surface browning. These findings suggest that TPE has the potential to effectively reduce browning in FBB and may serve as an effective anti-browning agent for other fresh-cut products.