The Blimp-1 transcription factor acts in non-neuronal cells to regulate terminal differentiation of the Drosophila eye.

The formation of a functional organ such as the eye requires specification of the correct cell types and their terminal differentiation into cells with the appropriate morphologies and functions. Here, we show that the zinc-finger transcription factor Blimp-1 acts in secondary and tertiary pigment cells in the Drosophila retina to promote the formation of a bi-convex corneal lens with normal refractive power, and in cone cells to enable complete extension of the photoreceptor rhabdomeres. Blimp-1 expression depends on the hormone ecdysone, and loss of ecdysone signaling causes similar differentiation defects. Timely termination of Blimp-1 expression is also important, as its overexpression in the eye has deleterious effects. Our transcriptomic analysis revealed that Blimp-1 regulates the expression of many structural and secreted proteins in the retina. Blimp-1 may function in part by repressing another transcription factor; Slow border cells is highly upregulated in the absence of Blimp-1, and its overexpression reproduces many of the effects of removing Blimp-1. This work provides insight into the transcriptional networks and cellular interactions that produce the structures necessary for visual function.

First Report of Clonostachys rosea Causing Bulb Rot on Fritillaria taipaiensis in China.

Taibai Beimu (Fritillaria taipaiensis) is a species of Fritillaria commonly used in traditional Chinese medicine for its antitussive, expectorant, and antihypertensive properties. In April of 2021 and 2022, an incidence 10-30% of yellowing or purpling, wilting, and dying symptoms was observed on Taibai Beimu in Wanyuan, Sichuan province. Infected roots and bulbs displayed spots ranging from brown to black, along with necrotic rot. In severe cases, the entire bulbs rotted. Fifteen symptomatic bulbs were cut into 0.5 × 0.5 cm pieces, surface sterilized in 75% ethanol for 30 s and 1% sodium hypochlorite for 3 min under aseptic conditions, rinsed with sterile water 3 times, and air-dried. The segments were placed on potato dextrose agar (PDA) and incubated at 25℃ for 7 days in the dark. Six Clonostachys-like monospore isolates were obtained. Colonies on PDA reached 32 to 43 mm in diameter in 7 days at 25℃ in the dark, felty to tomentose to granulose aerial mycelia with a white or light yellow appearance, and reverse colors matching. On cornmeal-dextrose agar, primary conidiophores had a Verticillium-like structure with 1 to 3 levels. Stipes were 36.1 to 236.3µm long. Phialides formed in whorls of 2 to 5, 15.3 to 45.7µm long, 1.1 to 3.4µm wide at the base, and 1.03 to 2.41µm wide near opening (n=95). Each producing a small hyaline drop of conidia. Conidia were 3.7 to 11.3µm × 2.1 to 4.1µm (n=110). Secondary conidiophores displayed Penicillium-like structures, and stipes were 23.1 to 142.3µm long. Phialides formed in compressed whorls of 4 to 8 per metula, 7.0 to 16.0µm in length, 1.3 to 3.1µm in width at the base, 1.8 to 3.6µm at the widest point, and 0.8 to 1.8µm near opening (n=50). Conidia were 3.0 to 6.4µm ×1.6 to 3.4µm (n=65). The morphology was consistent with the previous description of Clonostachys rosea (Hans-Josef et al. 1999). The ATP citrate lyase (ACL1), ß-tubulin (TUB2), translation elongation factor 1-α (tef1α), and the nuclear ribosomal internal transcribed spacer (ITS) of three strains were amplified and sequenced using primers acl1-230up/acl1-1220low (Gräfenhan et al. 2011), T1/CYLTUB1R (Crous et al. 2004; O'Donnell and Cigelnik 1997), EF1-728F/EF2 (Carbone and Kohn 1999; O'Donnell et al. 1998), and ITS1/ITS4 (White et al. 1990), respectively. Blastn homology search showed a > 97% similarity to the ex-type strains of C. rosea (CBS710.86). All sequences have been deposited in GenBank (PP394342 to PP394350, and PP396901 to PP396903). A phylogenetic tree was constructed using Bayesian analysis based on the alignment of the combined ACL1, TUB2, tef1α, and ITS sequences through IQ-TREE. The tree displayed clustering with known strains of C. rosea. Pathogenicity was confirmed by inoculating five healthy five-year-old Taibai beimu plants with a spore suspension (1.0 × 106 spores mL-1) of the strain WYEB1101, while sterilized water was used as a control. The inoculation process involved pouring the spore suspension over the wounded bulbs and covering with them sterile soil. Subsequently, all plants were cultivated in sterile soil indoors under natural conditions suitable for Taibai beimu. The pathogenicity assays were repeated twice. After 20 days of cultivation, the infected plants displayed symptoms similar to those observed in the field, while all control plants remained asymptomatic. Sequencing confirmed the re-isolation of C. rosea from the inoculated plants, satisfying Koch's hypothesis. Clonostachys rosea has been previously reported to cause root rot of Chinese medicine herb, such as Astragalus membranaceus and Gastrodia elata (Lee et al. 2020; Qi et al. 2022). To our knowledge, this is the first report of C. rosea infecting Taibai Beimu in China, highlighting a potential risk to this crop.

First Report of Root Rot Caused by Ilyonectria robusta in the Medicinal Herb Aconitum carmichaelii in China.

Aconitum carmichaelii Debeaux is used as a traditional Chinese medicine with antiarrhythmic, antiinflammatory and other pharmacological functions. It is widely cultivated in China. According to our survey, about 60% of A. carmichaelii in Qingchuan, Sichuan, suffered from root rot, reducing yields by 30% in the past five years. Symptomatic plants exhibited stunted growth, dark brown roots, reduced root biomass, and fewer root hairs. The disease caused root rot and plant death in 50% of the infected plants. In October 2019, ten symptomatic 6-month-old plants were collected from fields in Qingchuan. Diseased pieces of the roots were surface sterilized with sodium hypochlorite solution (2%), rinsed three times in sterile water, plated on potato dextrose agar (PDA), and incubated at 25°C in the dark. Six single-spore isolates of a Cylindrocarpon-like anamorp were obtained. The colonies on PDA were 35 to 37 mm diam after seven days with regular margins. The plates were covered with felty aerial mycelium, white to buff, and the reverse side chestnut near center with a ochre to yellowish leading edge. On spezieller nährstoffarmer agar (SNA), macroconidia were 1 to 3 septate, straight or slightly curved, cylindrical, with rounded ends, and varied in size: 1-septate 15.1 to 33.5 × 3.7 to 7.3 µm (n=250), 2-septate 16.5 to 48.5 × 3.7 to 7.6 µm (n=85), and 3-septate 22.0 to 50.6 × 4.9 to 7.4 µm (n=115). Microconidia were ellipsoid to ovoid, and 0 to 1 septate; aseptate spores were 4.5 to 16.8 × 1.6 to 4.9 µm (n=200), and 1-septate spores were 7.4 to 20.0 × 2.4 to 5.1 µm (n=200). The chlamydospores were brown, thick-walled, globose to subglobose, 7.9 to 15.9 µm (n=50). The morphology of these isolates was consistent with the previous description of Ilyonectria robusta (Cabral et al. 2012). Isolate QW1901 was characterized by sequencing the ITS, TUB, H3, and tef1α loci using previously reported primer pairs: ITS1/ITS4 (White et al. 1990), T1/Bt-2b (O'Donnell and Cigelnik 1997), CYLH3F/CYLH3R (Crous et al. 2004), and EF1/EF2 (O'Donnell et al. 1998). A Blastn search of the sequences of ITS, TUB, H3, and tef1α showed that QW1901 shared 99.26, 97.89, 97.79, and 99.17 % identities, respectively, with the ex-type strain of I. robusta (CBS308.35). The ITS, TUB, H3, and tef1α sequences were deposited in GenBank under accession nos. MW534715, and MW880180 to MW880182, respectively. A phylogenetic tree was constructed from a neighbor-joining analysis on the alignment of the combined ITS, TUB, H3, and tef1α sequence. QW1901 was clustered with the ex-type strain of I. robusta. To confirm the pathogenicity of I. robusta, bare roots of healthy 6-month-old A. carmichaelii were inoculated with mycelial plugs of 7-day-old QW1901 colonies selected randomly (Lu et al. 2015). Five needle-wound lateral roots and five intact roots were inoculated as replicates with pathogen-free agar plugs as a control. Then, all plants were grown in sterile soil in a growth chamber at 20±1°C and watered regularly. Pathogenicity assays were repeated twice. After 20 days of cultivation, infected plants exhibited symptoms similar to those observed in the field. All control plants remained asymptomatic. Sequencing confirmed the re-isolation of I. robusta from the inoculated plants, satisfying Koch's hypothesis. Ilyonectria robusta has been reported to cause root rot of plants such as Codonopsis tangshen and Panax ginseng ( Lu et al. 2015; Zheng et al. 2021), and has also been reported to be isolated from Aconitum kongboense in China (Wang et al. 2015). However, this is the first report of the pathogen causing root rot of A. carmichaelii. Management measures, such as growing disease-free seedlings in sterile soil, should be used to minimize the risk of this pathogen.

Static and dynamic disorder in Aß40 fibrils.

Deposition of Aß aggregates in the form of amyloid fibrils is a pathological hallmark of Alzheimer's disease. Understanding the structure and dynamics of Aß fibrils is important for delineating the mechanism of Aß aggregation and developing effective therapeutic strategies. Here we used site-directed spin labeling and EPR spectroscopy to study the Aß40 fibril structure and dynamics. We obtained the EPR spectra of 40 spin-labeled Aß40 fibril samples, with spin labeling coverage of the entire Aß40 sequence. Analysis of the spin exchange interaction and spin label mobility using spectral simulations suggest that the strength of spin exchange interaction is primarily determined by static disorder in the Aß40 fibrils. EPR data suggest that the entire Aß40 sequence except residue D1 is highly ordered and the two hydrophobic regions at residues 17-20 and 31-36 show the lowest static disorder. Dynamic disorder is relatively constant across all reside positions, with residues 22 and 23 having the highest dynamic disorder. Comparison of the EPR data for Aß40 and Aß42 fibrils shows overall more ordered packing interactions in Aß40 fibrils. Another noteworthy difference is the C-terminal residue, which has high static disorder in Aß42 fibrils, but is ordered in Aß40 fibrils. The higher static disorder in Aß42 fibrils may lead to increased fragmentation, monomer dissociation, and structural defects, which may contribute to increased aggregation through secondary nucleation.

[Research progress on production districts of Sichuan Dao-di herbs].

Dao-di herbs are the Chinese herbs which have high quality and best clinic effects. Sichuan is one of the proviences most rich in Chinese herb resources,which has 7 290 species of Chinese herbs, such as Curcumae Longae Rhizoma, Chuanxiong Rhizoma, Aconiti Lateralis Radix Praeparata, Ophiopogonis Radix, Coptidis Rhizoma, Gentianae Radix, Rhei Radix et Rhizoma, Curcumae Rhizoma, Gardeniae Fructus, ect. After textual research on materia medica of the 7 290 Chinese herbs, we find there are 86 Dao-di herbs in Sichuan, such as Chuanxiong Rhizoma from Dujiangyan, Aconiti Lateralis Radix Praeparata from Jiangyou, Fritillariae Radix, Notoptergii Rhizoma et Radix, Angelicae Dahuricae Radix from Suining, Ophiopogonis Radix from Santai, Salviae Miltiorrhizae Radix et Rhizoma from Zhongjiang, Magnoliae Officinalis Cortex from Pingwu. In China more attention is paid to the production of Dao-di herbs. In 2018, the State Administration of Traditional Chinese Medicine launched the "Construction Plan of national production base of genuine medicinal materials". Developing genuine medicinal materials in genuine production areas is one of the effective ways to ensure the quality of medicinal materials. Based on the study of geographical environment and ecological factors(altitude, climate, soil) in Sichuan province. The Dao-di herbs of Sichuan province are divided into 4 districts, including, Sichuan basin medicinal materials production area, mountain and the basin edge medicinal materials production area, Panxi medicinal materials production area, Plateau Mountain Canyon medicinal materials production area. The suitable regions and best suitable regions of the 86 Dao-di herbs in Sichuan are determined by remote sensing and GIS spatial analysis of the suitable environmental indicators of these Dao-di herbs. Our study is beneficial to the rational distribution of the production and to improvement of the quality of traditional Chinese medicine in Sichuan province.

Correction to: Phloretin reduces cell injury and inflammation mediated by Staphylococcus aureus via targeting sortase B and the molecular mechanism.

The images of cells under microscope in Figure 2 and Figure S2 were misused from Wang G et al. Front Cell Infect Microbiol. 2018 Nov 30;8:418. These images were generated in the same set of assays.

Titer Variation of Citrus Tristeza Virus in Aphids at Different Acquisition Access Periods and Its Association with Transmission Efficiency.

Tristeza, caused by citrus tristeza virus (CTV; Closterovirus, Closteroviridae), is of significant economic importance. Tristeza epidemics have caused severe declines in productivity, and even death, of millions of citrus trees on sour orange rootstock in many regions all over the world. In the field, CTV is most efficiently vectored by the brown citrus aphid (Toxoptera citricida (Kirkaldy)) in a semipersistent manner. The transmission efficiency of the vector is influenced by its acquisition access period (AAP) for CTV. A real-time RT-PCR assay using SYBR Green fluorescent dye was used to estimate the CTV titers in groups of 15 aphids under AAPs after 0.5 to 48 h for three CTV isolates (CT11A, CT16-2, and CTLJ). Similar trends for CTV titer in viruliferous aphids were displayed for the three isolates. The maximum CTV titer was at AAP 6 h for isolates CT11A and CT16-2, and at 4 h for isolate CTLJ. During the AAPs from 0.5 to 6 h, the mean CTV titer of CT16-2 increased from 7.8 × 104 to 1.71 × 107 copies per 15 aphids, and was correlated with an increase in transmission rate from 20 to 90.9%. This suggests that the transmission efficiency is positively correlated with viral titer in the insect from 0.5 h until 6 h AAPs. While a downward trend in CTV titer was observed after a 6-h AAP, the transmission rate remained higher than 90% up to 48 h. These results indicate that factors other than the virus titer in the vector contribute to successful transmission under long acquisition conditions. This is the first detailed quantitative analysis of CTV in its main vector species following different AAPs and its association with transmission efficiency, and should enhance our understanding of T. citricida-CTV interactions.

Phloretin reduces cell injury and inflammation mediated by Staphylococcus aureus via targeting sortase B and the molecular mechanism.

Sortase B (SrtB) is a vital virulence factor that plays a critical role in Staphylococcus aureus (S. aureus) infections, indicating that it could be a latent target for S. aureus infections. In this study, phloretin, a natural compound that primarily exists in the pericarp and velamen of apples and pears, shows little anti-S. aureus activity, but significantly inhibited SrtB activity in vitro. The results of lactate dehydrogenase release and live/dead cell assays suggested that phloretin reduced human alveolar epithelial cell damage caused by S. aureus. Additionally, an adhesion assay confirmed that phloretin lowered the colony count of S. aureus in human alveolar cells. Phloretin treatment significantly attenuated the inflammatory response in macrophage cells (J774) co-cultured with S. aureus as determined by an enzyme-linked immune-sorbent assay. Furthermore, the results of molecular dynamics simulation, site-directed mutagenesis, and fluorescence spectroscopy quenching indicated that phloretin was directly located in the active pocket of SrtB and blocked substrate binding, leading to the loss of SrtB activity. These results indicate that phloretin is a possible candidate for treatment of S. aureus infections.

Acetylcholinesterase Biosensor Based On Mesoporous Hollow Carbon Spheres/Core-Shell Magnetic Nanoparticles-Modified Electrode for the Detection of Organophosphorus Pesticides.

The present study investigated the synthesis of mesoporous hollow carbon spheres (MHCS) and magnetic mesoporous hollow carbon spheres with core-shell structures (Fe3O4@MHCS). Two acetylcholinesterase sensors (acetylcholinesterase/mesoporous hollow carbon spheres/glassy carbon electrode (AChE/MHCS/GCE) and acetylcholinesterase/core-shell magnetic mesoporous hollow carbon spheres/glassy carbon electrode (AChE/Fe3O4@MHCS/GCE) based on mesoporous carbon materials were prepared. Under the optimum conditions, using Malathion as the model compound, the developed biosensors showed a wide detection range, low detection limit, good reproducibility, and high stability. The AChE/MHCS/GCE electrochemical sensor response exhibited two good linear ranges at the incubation time of 10 min at the Malathion concentration ranges of 0.01 to 100 ppb and 100 to 600 ppb, with a detection limit of 0.0148 ppb (S/N = 3). The AChE/Fe3O4@MHCS/GCE electrochemical sensor that was operated with an incubation time of 12 min at the malathion concentration ranges between 0.01⁻50 ppb and 50⁻600 ppb had a detection limit of 0.0182 ppb (S/N = 3). Moreover, the AChE/MHCS/GCE and AChE/Fe3O4@MHCS/GCE biosensors were effective for the detection of real samples, and were demonstrated to be suitable for the field-testing of organophosphorus pesticide (OP) residues.

Novel Inhibitor Discovery of Staphylococcus aureus Sortase B and the Mechanism Confirmation via Molecular Modeling.

SortaseB (SrtB) plays a critical role in Staphylococcus aureus (S. aureus) infections. According to the reports in the literature, SrtB can anchor the IsdC to the cell wall to capture iron from the host to achieve a successful invasion. On the other hand, SrtB could also affect the adhesion of S. aureus to host cells based on previous studies. Here, we report about a novel SrtB inhibitor, coptisine, a natural compound that does not exhibit antibacterial activity but can inhibit the SrtB activity in vitro. A cytotoxicity test indicated that coptisine protects human lung epithelial cells from S. aureus. In addition, coptisine can reduce the adhesion of S. aureus to human lung epithelial cells based on the result of plate colony counting assay. Molecular dynamics simulation revealed that coptisine can bind to the active pocket of SrtB, leading to its activity loss. Through the calculation of binding free energy between ligand and protein, site-directed mutagenesis and fluorescence spectroscopy quenching methods, it was confirmed that residues of Arg115, Asn116, and Ile182 played a vital role in the interaction of SrtB with coptisine. These data provide the theoretical basis for the therapy option to the infections caused by S. aureus.

Molecular Mechanism of the Flavonoid Natural Product Dryocrassin ABBA against Staphylococcus aureus Sortase A.

The intractability of bacterial resistance presents a dilemma for therapies against Staphylococcus aureus (S. aureus) infection. Effective anti-virulence strategies are urgently needed, reflecting the proliferation of resistant strains. Inhibitors of sortase A (SrtA), enzymes that anchor virulence-related surface proteins, are regarded as promising candidates for countermeasures against bacterial infections. In the present study, the inhibitory effect of dryocrassin ABBA (ABBA) against SrtA and its molecular basis has been examined. Fluorescence resonance energy transfer (FRET) assays were used to determine the inhibitory activity of ABBA against SrtA. To identify the mechanism underlying this activity, molecular dynamics simulations and mutagenesis assays were applied, and the results revealed that the direct engagement of SrtA via ABBA through binding to V166 and V168 significantly attenuated the catalytic activity of SrtA. Taken together, these findings indicated that ABBA is a potential novel antimicrobial agent for S. aureus infection via targeting SrtA.

A hydrogen-bonded curdlan-chitosan/polyvinyl alcohol edible dual functional hydrogel bandage against MRSA promotes wound healing.

The most prevalent complication arising from skin injuries is bacterial infection, where pathogenic bacteria proliferate significantly at the wound site, leading to subsequent complications like septic shock and sepsis. Although antibiotics presently effectively manage wound infections caused by common bacteria, the escalating prevalence of antibiotic-resistant strains necessitates urgent novel approaches for addressing such infections. Here, we present CS9P1-RA, a dual functional hydrogel dressing, based on polyvinyl alcohol (PVA) matrix crosslinked through hydrogen bonding. CS9P1-RA combines chitosan (CS), a food-derived antibacterial agent, with the natural compound rosmarinic acid (RA) to specifically target skin injuries caused by MRSA. Computational and molecular biology assays illustrate RA's ability to selectively inhibit the activity of Staphylococcus aureus (S. aureus) serine/threonine phosphatase (Stp1), reducing the S. aureus pathogenicity. CS9P1-RA showcases exceptional antibacterial efficacy (MIC = 1 mg/mL) and demonstrates potency in reducing virulence (IC50 = 7.424 µM on Stp1). Notably, it effectively curbs bacterial growth and accelerates wound healing in the mice model, thereby fulfilling the practical requirements for clinical applications. Moreover, the mechanical properties of CS9P1-RA ensure user comfort during treatment. This work introduces a fresh design paradigm for dressing materials, offering a promising solution for treating skin injuries inflicted by antibiotic-resistant bacterial infections.

A natural inhibitor of diapophytoene desaturase attenuates methicillin-resistant Staphylococcus aureus (MRSA) pathogenicity and overcomes drug-resistance.

BACKGROUND AND PURPOSE: At present, the inhibition of staphyloxanthin biosynthesis has emerged as a prominent strategy in combating methicillin-resistant Staphylococcus aureus (MRSA) infection. Nonetheless, there remains a limited understanding regarding the bio-structural characteristics of staphyloxanthin biosynthetic enzymes, as well as the molecular mechanisms underlying the interaction between inhibitors and proteins. Furthermore, the functional scope of these inhibitors is relatively narrow. EXPERIMENTAL APPROACH: In this study, we address these limitations by harnessing the power of deep learning techniques to construct the 3D structure of diapophytoene desaturase (CrtN). We perform efficient virtual screening and unveil alnustone as a potent inhibitor of CrtN. Further investigations employing molecular modelling, site-directed mutagenesis and biolayer interferometry (BLI) confirmed that alnustone binds to the catalytic active site of CrtN. Transcriptomic analysis reveals that alnustone significantly down-regulates genes associated with staphyloxanthin, histidine and peptidoglycan biosynthesis. KEY RESULTS: Under the effects of alnustone, MRSA strains exhibit enhanced sensitivity to various antibiotics and the host immune system, accompanied by increased cell membrane permeability. In a mouse model of systemic MRSA infection, the combination of alnustone and antibiotics exhibited a significant therapeutic effect, leading to reduced bacterial colony counts and attenuated pathological damage. CONCLUSION AND IMPLICATIONS: Alnustone, as a natural inhibitor targeting CrtN, exhibits outstanding antibacterial properties that are single-targeted yet multifunctional. This finding provides a novel strategy and theoretical basis for the development of drugs targeting staphyloxanthin producing bacteria.

Transcriptomic and Metabolomic Analyses Reveal the Response Mechanism of Ophiopogon japonicus to Waterlogging Stress.

Ophiopogon japonicus, a plant that thrives in river alluvial dams, often faces waterlogging stress due to sustained rainfall and flood seasons, which significantly impacts its growth and development. Currently, the mechanisms of waterlogging tolerance in Ophiopogon japonicus are still unclear. This study analyzed the transcriptome and metabolome data for Ophiopogon japonicus in the Sichuan region (referred to as CMD) under varying degrees of waterlogging stress: mild, moderate, and severe. The results indicate that the group exposed to flooding stress exhibited a higher number of differentially expressed genes (DEGs) compared to the control group. Notably, most DEGs were downregulated and primarily enriched in phenylpropanoid biosynthesis, starch and sucrose metabolism, and plant hormone signal transduction pathways. A total of 5151 differentially accumulated metabolites (DAMs) were identified, with significantly upregulated DAMs annotated to two clusters, namely flavonoids such as apiin, pelargonin, and others. Furthermore, our study revealed significant upregulation in the expression of C2H2 (C2H2 zinc finger proteins) and AP2/ERF-ERF (the subfamily ERF proteins of APETALA2/ethylene-responsive element binding factors) transcription factors in CMD under flooding stress, suggesting their critical roles in enabling CMD to adapt to these conditions. In conclusion, this research provides insights into the intricate molecular mechanisms underlying CMD's response to flooding stress and reports valuable genetic data for the development of transgenic plants with improved waterlogging tolerance.

Preparation of a novel glucose oxidase-N-succinyl chitosan nanospheres and its antifungal mechanism of action against Colletotrichum gloeosporioides.

In this work, a new glucose oxidase-N-succinyl chitosan (GOD-NSCS) nanospheres was prepared through the immobilization of glucose oxidase (GOD) on N-succinyl chitosan (NSCS) nanospheres. Compared to the free GOD, GOD-NSCS nanospheres demonstrated the excellent anti-Colletotrichum gloeosporioides activity with the EC50 values of 211.2 and 10.7 µg/mL against mycelial growth and spores germination. The computational biology analysis demonstrated that the substrate presented the similar binding free energy with GOD-NSCS nanospheres (-27.64 kcal/mol) compared with the free GOD (-24.04 kcal/mol), indicating that GOD-NSCS nanospheres had the same oxidation efficiency and produced more H2O2. Moreover, the enzyme activity stability of GOD-NSCS nanospheres could be prolonged to 10 d. The cell membrane was destructed by the treatment of H2O2 produced by GOD, leading to the cell death. In vivo test, GOD-NSCS nanospheres treatment significantly prolonged the preservation period of mangoes 2-fold. Collectively, these results suggested that GOD-NSCS nanospheres suppresses anthracnose in postharvest mangoes by inhibiting the growth of C. gloeosporioides and might become a potential natural preservative for fruits and vegetables.

Molecular mechanism of green tea polyphenol epicatechin gallate attenuating Staphylococcus aureus pathogenicity by targeting Ser/Thr phosphatase Stp1.

In this study, through virtual screening and in vitro bioactivity assays, we discovered that (-)-epicatechin gallate (ECG), a polyphenol compound extracted from green tea, demonstrated marked anti-Ser/Thr phosphatase (Stp1) activity towards Staphylococcus aureus (S. aureus) with an IC50 value of 8.35 µM. By targeting S. aureus Stp1, ECG prevented the up-regulation of virulence gene and the formation of antibody membrane and protected the mice from S. aureus infection. Through MD simulation, the allosteric inhibitory mechanism of ECG on Stp1 was determined. The Stp1-ECG complex model underwent a significant change in conformation; its flap subdomain changed from opening to closing, whereas Stp1 activity was lost when bound to ECG. In addition, the MD simulation results of Stp1 and several tea polyphenol compounds showed that gallate groups and fewer adjacent phenolic hydroxyl groups contributed to the binding of Stp1 and inhibitors. As an inhibitor targeting S. aureus Stp1, ECG reduced the pathogenicity of S. aureus without inhibiting S. aureus, which largely reduced the possibility of drug resistance. Our findings demonstrated a novel molecular mechanism of green tea as the usual drink against S. aureus infection and elucidated the future design of allosteric inhibitors targeting Stp1.

Dibenzylideneacetone Overcomes Botrytis cinerea Infection in Cherry Tomatoes by Inhibiting Chitinase Activity.

Chitinase, a crucial component of the fungal cell wall and septa, plays an important role in fungal germination by hydrolyzing chitin to provide carbon and energy for fungal growth and reproduction. In this study, we initially screened dibenzylideneacetone (DBA), a small molecule with inhibitory activity against Botrytis cinerea Chitinase, exhibiting an IC50 of 13.10 µg/mL. By constructing a three-dimensional (3D) model of the B. cinerea Chitinase and utilizing computational biology approaches, we found DBA bound to the active site pocket and formed strong π-π interactions and hydrophobic interactions with Chitinase, indicative of its competitive inhibitory mode. Site-directed mutagenesis also revealed that TRP-382, TRP-135, and ALA-215 were key amino acid residues involved in DBA binding. Subsequent antifungal assays showed that DBA had an MIC of 32 µg/mL against B. cinerea and EC50 values of 16.29 and 14.64 µg/mL in inhibiting mycelial growth and spore germination, respectively. Importantly, in vivo experiments demonstrated that DBA treatment significantly extended the shelf life of cherry tomatoes by 2-fold. Therefore, DBA represents a promising antifungal agent for fruit preservation applications.

Electron coupling effect-triggered monatomic copper laccase-mimicking nanozyme for the degradation and detection of guaiacol produced by Alicyclobacillus acidoterrestris.

The generation of guaiacol by Alicyclobacillus acidoterrestris (A. acidoterrestris) in fruit juices negatively affects public health and causes severe environmental pollution. Therefore, the sensitive detection and efficient degradation of guaiacol in real samples are crucial. Here, we develop an electrochemical sensor utilizing a copper single-atom nanozyme (CuN4-G) to detect and degrade guaiacol at the picomolar level. Density functional theory (DFT) calculations verify that the bonding electron coupling effect in the CuN4-G facilitates rapid electron transfer, enhances electrical conductivity, and provides abundant active sites, thereby leading to exceptional catalytic performance. Moreover, CuN4-G demonstrates a Km value similar to that of natural laccase but a higher Vmax, highlighting its potential as a highly efficient biocatalyst. The CuN4-G-based electrochemical sensor achieves a detection from 5 to 50,000 pM for guaiacol, with a 1.2 pM (S/N = 3) detection limit. Additionally, CuN4-G-modified electrodes display high selectivity and excellent stability. CuN4-G nanozyme can keep its activity in conditions of pH (3-9), temperature (30-90 °C), ionic strength (0-400 mM), and organic solvent (0-50% (v/v)), overcoming the deficiencies of natural enzymes. Furthermore, our electrochemical sensor can not only accurately detect guaiacol, but also degrade it in actual fruit juice samples infected by A. acidoterrestris, demonstrating its potential applications in food and environmental monitoring.

Electrochemical sensor for detecting streptomycin in milk based on label-free aptamer chain and magnetic adsorption.

Exploiting a simple and sensitive sensor to efficiently detect streptomycin (STR) in milk is critical for resolving the harm caused to humans by STR residues. This study reports an electrochemical sensor using magnetic mesoporous carbon materials (MMCM) as a loaded material through magnetic adsorption immobilized on magnetic glassy carbon electrode (MGCE) and adsorbing unlabeled streptomycin aptamer (STP) as the identification element. The sensor can detect STR sensitively with a wide detection range (0.172-17.2 × 103 and 17.2 × 103 -17.2 × 105 nM) and a low detection limit of 0.015 nM. Experimental results revealed that the specific binding of STP with STR on the electrode changed the configuration of STP, thereby causing current change of differential pulse voltammetry curve. Compared with HPLC, this study provides a new method for rapid and sensitive detection of STR in milk (n = 5, 95 % confidence level, RSD＜5%).

Colorimetric sensor array based on Au2Pt nanozymes for antioxidant nutrition quality evaluation in food.

Total antioxidant capacity (TAC) has become an important index to evaluate the food quality. Effective antioxidant detection has been the research hotspot of scientists. In this work, a novel three-channel colorimetric sensor array founded on Au2Pt bimetallic nanozymes for the discrimination of antioxidants in food was constructed. Benefiting from the unique bimetallic doping structure, Au2Pt nanospheres exhibited the excellent peroxidase-like activity with Km of 0.044 mM and Vmax of 19.37 × 10-8 M s-1 toward TMB. The density functional theory (DFT) calculation revealed that Pt atom in the doping system was active sites and there was no energy barrier in catalytic reaction which made Au2Pt nanospheres had excellent catalytic activity. Accordingly, a multifunctional colorimetric sensor array was constructed based on Au2Pt bimetallic nanozymes for rapid and sensitive detection of five antioxidants. Based on the different reduction ability of antioxidants, oxidized TMB could be reduced in different degrees. In the presence of H2O2, the colorimetric sensor array could generate differential colorimetric signals (fingerprints) by using TMB as the chromogenic substrate, which could be accurately discriminated through linear discriminant analysis (LDA) with a detection limit of <0.2 µM. The sensor array was able to the evaluate TAC in three actual samples (milk, green tea and orange juice). Furthermore, we prepared a rapid detection strip to meet the needs of practical application, making a positive contribution to food quality evaluation.