Defect Engineering of Ultrasmall TiO2 Nanoparticles Enables Highly Efficient Photocatalysts for Solar H2 Production from Woody Biomass.

The conversion of woody biomass to H2 through photocatalysis provides a sustainable strategy to generate renewable hydrogen fuel but was limited by the slow decomposition rate of woody biomass. Here, we fabricate ultrasmall TiO2 nanoparticles with tunable concentration of oxygen vacancy defects (VO-TiO2) as highly efficient photocatalysts for photocatalytic conversion of woody biomass to H2. Owing to the positive role of oxygen vacancy in reducing energy barrier for the generation of •OH which was the critical species to oxidize woody biomass, the obtained VO-TiO2 achieves rapid photocatalytic conversion of α-cellulose and poplar wood chip to H2 in the presence of Pt nanoclusters as the cocatalyst. As expected, the highest H2 generation rate in α-cellulose and poplar wood chip system respectively achieve 1146 and 59 µmol h-1 g-1, and an apparent quantum yield of 4.89% at 380 nm was obtained in α-cellulose aqueous solution.

Mild hypothermia reduces lipopolysaccharide-induced microglial activation via down-regulation of Tent5c.

Microglial activation is a critical factor in the pathogenesis and progression of neuroinflammatory diseases. Mild hypothermia, known for its neuroprotective properties, has been shown to alleviate microglial activation. In this study, we explore the differentially expressed (DE) mRNAs and long non-coding RNAs (lncRNAs) in BV-2 microglial cells under different conditions: normal temperature (CN), mild hypothermia (YT), normal temperature with lipopolysaccharide (LPS), and mild hypothermia with LPS (LPS + YT). Venn analysis revealed 119 DE mRNAs that were down-regulated in the LPS + YT vs LPS comparison but up-regulated in the CN vs LPS comparison, primarily enriched in Gene Ontology terms related to immune and inflammatory responses. Furthermore, through Venn analysis of YT vs CN and LPS + YT vs LPS comparisons, we identified 178 DE mRNAs and 432 DE lncRNAs. Among these transcripts, we validated the expression of Tent5c at the protein and mRNA levels. Additionally, siRNA-knockdown of Tent5c attenuated the expression of pro-inflammatory genes (TNF-α, IL-1ß, Agrn, and Fpr2), cellular morphological changes, NLRP3 and p-P65 protein levels, immunofluorescence staining of p-P65 and number of cells with ASC-speck induced by LPS. Furthermore, Tent5c overexpression further potentiated the aforementioned indicators in the context of mild hypothermia with LPS treatment. Collectively, our findings highlight the significant role of Tent5c down-regulation in mediating the anti-inflammatory effects of mild hypothermia.

Photocatalytic Nitrogen Fixation Coupled with the Generation of Value-Added Chemicals from N2 and Cellulose over MoO3 Nanosheets.

Photocatalytic nitrogen fixation from N2 provides an alternative strategy for ammonia (NH3) production, but it was limited by the consumption of a sacrificial electron donor for the currently reported half-reaction system. Here, we use naturally abundant and renewable cellulose as the sacrificial reagent for photocatalytic nitrogen fixation over oxygen-vacancy-modified MoO3 nanosheets as the photocatalyst. In this smartly designed photocatalytic system, the photooxidation of cellulose not only generates value-added chemicals but also provides electrons for the N2 reduction reaction and results in the production of NH3 with a maximum rate of 68 µmol·h-1·g-1. Also, the oxygen vacancies provide efficient active sites for both cellulose oxygenolysis and nitrogen fixation reactions. This work represents useful inspiration for realizing nitrogen fixation coupled with the generation of value-added chemicals from N2 and cellulose through a photocatalysis strategy.

Accelerated Charge Transfer through Interface Chemical Bonds in MoS2/TiO2 for Photocatalytic Conversion of Lignocellulosic Biomass to H2.

Solar photocatalytic H2 production from lignocellulosic biomass has attracted great interest, but it suffers from low photocatalytic efficiency owing to the absence of highly efficient photocatalysts. Herein, we designed and constructed ultrathin MoS2-modified porous TiO2 microspheres (MT) with abundant interface Ti-S bonds as photocatalysts for photocatalytic H2 generation from lignocellulosic biomass. Owing to the accelerated charge transfer related to Ti-S bonds, as well as the abundant active sites for both H2 and ●OH generation, respectively, related to the high exposed edge of MoS2 and the large specific surface area of TiO2, MT photocatalysts demonstrate good performance in the photocatalytic conversion of α-cellulose and lignocellulosic biomass to H2. The highest H2 generation rate of 849 µmol·g-1·h-1 and apparent quantum yield of 4.45% at 380 nm was achieved in α-cellulose aqueous solution for the optimized MT photocatalyst. More importantly, lignocellulosic biomass of corncob, rice hull, bamboo, polar wood chip, and wheat straw were successfully converted to H2 over MT photocatalysts with H2 generation rate of 10, 19, 36, 29, and 8 µmol·g-1·h-1, respectively. This work provides a guiding design approach to develop highly active photocatalysts via interface engineering for solar H2 production from lignocellulosic biomass.

[Research Progress in the Correlation Between Dopamine and Clinical Characterization of Narcolepsy].

Dopamine,a neurotransmitter ubiquitous in the body fluids,blood,and urine of mammals and humans,is responsible for regulating their functions and metabolism.The dopamine system is involved in the neurobiological mechanisms of narcolepsy in animals and humans.However,researchers have drawn different or even opposite conclusions when measuring the dopamine level in the cerebrospinal fluid of narcolepsy patients.Studies have confirmed that the occurrence of narcolepsy is related to the irreversible loss of orexins.The autoimmune reaction caused by the interactions of environmental factors with genetic factors destroys the hypothalamic orexin neurons and reduces orexin secretion,thereby lowering the level of arousal.We introduce the research progress and current status of dopamine and clinical characterization of narcolepsy by reviewing more than 40 articles published from 1982 to 2023,aiming to provide a reference for studying the relationship between the dopamine level and clinical characterization of narcolepsy and searching for the biomarkers of type 2 narcolepsy.

[Separation/Conversion Disorders in Functional Coma With Pseudocataplexy: Report of One Case and Literature Review].

Separation/conversion disorders in functional coma with pseudocataplexy are rare.On December 9,2021,a young female patient with separation/conversion disorders was treated in the Department of Neurology in the First Affiliated Hospital of Shandong First Medical University.The main symptoms were episodic consciousness disorders,sudden fainting,and urinary incontinence.Complete laboratory tests and cranial magnetic resonance imaging showed no obvious abnormalities.Standard multi-channel sleep monitoring and multiple sleep latency tests were performed.The patient was unable to wake up during nap and underwent stimulation tests.There was no response to orbital pressure,loud calls,or tapping,while the α rhythm in all electroencephalogram leads and the increased muscular tone in the mandibular electromyography indicated a period of wakefulness.The results of 24-hour sleep monitoring suggested that the patient had sufficient sleep at night and thus was easy to wake up in the morning.The results of daytime unrestricted sleep and wake-up test showed that the patient took one nap in the morning and one nap in the afternoon.When the lead indicated the transition from N3 to N2 sleep,a wake-up test was performed on the patient.At this time,the patient reacted to the surrounding environment and answered questions correctly.Because the level of orexin in the cerebrospinal fluid was over 110 pg/mL,episodic sleep disorder was excluded and the case was diagnosed as functional coma accompanied by pseudocataplexy.The patient did not present obvious symptom remission after taking oral medication,and thus medication withdrawl was recommended.Meanwhile,the patient was introduced to adjust the daily routine and mood.The follow-up was conducted six months later,and the patient reported that she did not experience similar symptoms after adjusting lifestyle.Up to now,no similar symptoms have appeared in multiple follow-up visits for three years.Functional coma with pseudocataplexy is prone to misdiagnosis and needs to be distinguished from true coma and episodic sleep disorders.

RNase D Is Involved in 5S rRNA Degradation and Exopolysaccharide Production in Xanthomonas campestris pv. campestris.

Ribonucleases (RNases) play critical roles in RNA metabolism and are collectively essential for cell viability. However, most knowledge about bacterial RNases comes from the studies on Escherichia coli; very little is known about the RNases in plant pathogens. The crucifer black rot pathogen Xanthomonas campestris pv. campestris (Xcc) encodes 15 RNases, but none of them has been functionally characterized. Here, we report the physiological function of the exoribonuclease RNase D in Xcc and provide evidence demonstrating that the Xcc RNase D is involved in 5S rRNA degradation and exopolysaccharide (EPS) production. Our work shows that the growth and virulence of Xcc were not affected by deletion of RNase D but were severely attenuated by RNase D overexpression. However, deletion of RNase D in Xcc resulted in a significant reduction in EPS production. In addition, either deletion or overexpression of RNase D in Xcc did not influence the tRNAs tested, inconsistent with the finding in E. coli that the primary function of RNase D is to participate in tRNA maturation and its overexpression degrades tRNAs. More importantly, deletion, overexpression, and in vitro enzymatic analyses revealed that the Xcc RNase D degrades 5S rRNA but not 16S and 23S rRNAs that share an operon with 5S rRNA. Our results suggest that Xcc employs RNase D to realize specific modulation of the cellular 5S rRNA content after transcription and maturation whenever necessary. The finding expands our knowledge about the function of RNase D in bacteria.

Anastomotic leak risk factors following colon cancer resection: a systematic review and meta-analysis.

BACKGROUND: Despite improved surgical techniques, anastomotic leakage is still a serious complication that can occur after colon cancer resection, resulting in increased morbidity and mortality. The aim of this study was to evaluate the risk factors for anastomotic leakage after colon cancer surgery, provide a theoretical basis for reducing its occurrence, and guide the practice of clinicians. METHODS: A systematic review of PubMed, Ovid, Web of Science and Cochrane Central Register of Controlled Trials databases was conducted by using a combination of subject terms and free words for online searches. The databases were searched from their inception to 31 March 2022, and all cross-sectional, cohort or case‒control studies examining the risk factors for the development of anastomotic fistula after surgery for colon cancer were identified. RESULT: A total of 2133 articles were searched for this study, and 16 publications were ultimately included, all of which were cohort studies. A total of 115,462 subjects were included, and a total of 3959 cases of anastomotic leakage occurred postoperatively, with an incidence of 3.4%. The odds ratio (OR) and 95% confidence interval (CI) were used for evaluation. Male sex (OR = 1.37, 95% CI: 1.29-1.46, P < 0.00001), BMI (OR = 1.04, 95% CI: 1.00-1.08, P = 0.03), diabetes (OR = 2.80, 95% CI: 1.81-4.33, P < 0.00001), combined lung disease (OR = 1.28, 95% CI: 1.15-1.42, P < 0.00001), anaesthesia ASA score (OR = 1.35, 95% CI: 1.24-1.46, P < 0.00001), ASA class ≥ III (OR = 1.34, 95% CI: 1.22-1.47, P < 0.00001), emergency surgery (OR = 1.31, 95% CI: 1.11-1.55, P = 0.001), open surgery (OR = 1.94, 95% CI: 1.69-2.24, P < 0.00001) and type of surgical resection (OR = 1.34, 95% CI: 1.12-1.61, P = 0.002) are risk factors for anastomotic leakage after colon cancer surgery. There is still a lack of strong evidence on whether age (OR = 1.00, 95% CI: 0.99-1.01, P = 0.36) and cardiovascular disease (OR = 1.18, 95% CI: 0.94-1.47, P = 0.16) are factors influencing the occurrence of anastomotic leakage after colon cancer surgery. CONCLUSIONS: Male sex, BMI, obesity, coexisting pulmonary disease, anaesthesia ASA score, emergency surgery, open surgery and type of resection were risk factors for anastomotic leakage after colon cancer surgery. The effect of age and cardiovascular disease on postoperative anastomotic leakage in patients with colon cancer needs further study.

Structural basis for zinc-induced activation of a zinc uptake transcriptional regulator.

The zinc uptake regulator (Zur) is a member of the Fur (ferric uptake regulator) family transcriptional regulators that plays important roles in zinc homeostasis and virulence of bacteria. Upon zinc perception, Zur binds to the promoters of zinc responsive genes and controls their transcription. However, the mechanism underlying zinc-mediated Zur activation remains unclear. Here we report a 2.2-Å crystal structure of apo Zur from the phytopathogen Xanthomonas campestris pv. campestris (XcZur), which reveals the molecular mechanism that XcZur exists in a closed inactive state before regulatory zinc binding. Subsequently, we present a 1.9-Å crystal structure of holo XcZur, which, by contrast, adopts an open state that has enough capacity to bind DNA. Structural comparison and hydrogen deuterium exchange mass spectrometry (HDX-MS) analyses uncover that binding of a zinc atom in the regulatory site, formed by the hinge region, the dimerization domain and the DNA binding domain, drives a closed-to-open conformational change that is essential for XcZur activation. Moreover, key residues responsible for DNA recognition are identified by site-directed mutagenesis. This work provides important insights into zinc-induced XcZur activation and valuable discussions on the mechanism of DNA recognition.

The Therapeutic Potential of CDK4/6 Inhibitors, Novel Cancer Drugs, in Kidney Diseases.

Inflammation is a crucial pathological feature in cancers and kidney diseases, playing a significant role in disease progression. Cyclin-dependent kinases CDK4 and CDK6 not only contribute to cell cycle progression but also participate in cell metabolism, immunogenicity and anti-tumor immune responses. Recently, CDK4/6 inhibitors have gained approval for investigational treatment of breast cancer and various other tumors. Kidney diseases and cancers commonly exhibit characteristic pathological features, such as the involvement of inflammatory cells and persistent chronic inflammation. Remarkably, CDK4/6 inhibitors have demonstrated impressive efficacy in treating non-cancerous conditions, including certain kidney diseases. Current studies have identified the renoprotective effect of CDK4/6 inhibitors, presenting a novel idea and potential direction for treating kidney diseases in the future. In this review, we briefly reviewed the cell cycle in mammals and the role of CDK4/6 in regulating it. We then provided an introduction to CDK4/6 inhibitors and their use in cancer treatment. Additionally, we emphasized the importance of these inhibitors in the treatment of kidney diseases. Collectively, growing evidence demonstrates that targeting CDK4 and CDK6 through CDK4/6 inhibitors might have therapeutic benefits in various cancers and kidney diseases and should be further explored in the future.

Cellular Protein Aggregates: Formation, Biological Effects, and Ways of Elimination.

The accumulation of protein aggregates is the hallmark of many neurodegenerative diseases. The dysregulation of protein homeostasis (or proteostasis) caused by acute proteotoxic stresses or chronic expression of mutant proteins can lead to protein aggregation. Protein aggregates can interfere with a variety of cellular biological processes and consume factors essential for maintaining proteostasis, leading to a further imbalance of proteostasis and further accumulation of protein aggregates, creating a vicious cycle that ultimately leads to aging and the progression of age-related neurodegenerative diseases. Over the long course of evolution, eukaryotic cells have evolved a variety of mechanisms to rescue or eliminate aggregated proteins. Here, we will briefly review the composition and causes of protein aggregation in mammalian cells, systematically summarize the role of protein aggregates in the organisms, and further highlight some of the clearance mechanisms of protein aggregates. Finally, we will discuss potential therapeutic strategies that target protein aggregates in the treatment of aging and age-related neurodegenerative diseases.

Effect of Lacking ZKSCAN3 on Autophagy, Lysosomal Biogenesis and Senescence.

Transcription factors can affect autophagy activity by promoting or inhibiting the expression of autophagic and lysosomal genes. As a member of the zinc finger family DNA-binding proteins, ZKSCAN3 has been reported to function as a transcriptional repressor of autophagy, silencing of which can induce autophagy and promote lysosomal biogenesis in cancer cells. However, studies in Zkscan3 knockout mice showed that the deficiency of ZKSCAN3 did not induce autophagy or increase lysosomal biogenesis. In order to further explore the role of ZKSCAN3 in the transcriptional regulation of autophagic genes in human cancer and non-cancer cells, we generated ZKSCAN3 knockout HK-2 (non-cancer) and Hela (cancer) cells via the CRISPR/Cas9 system and analyzed the differences in gene expression between ZKSCAN3 deleted cells and non-deleted cells through fluorescence quantitative PCR, western blot and transcriptome sequencing, with special attention to the differences in expression of autophagic and lysosomal genes. We found that ZKSCAN3 may be a cancer-related gene involved in cancer progression, but not an essential transcriptional repressor of autophagic or lysosomal genes, as the lacking of ZKSCAN3 cannot significantly promote the expression of autophagic and lysosomal genes.

Synthesis and biological evaluation of 3ß-O-neoglycosides of caudatin and its analogues as potential anticancer agents.

In order to study the structure-activity relationship (SAR) of C21-steroidal glycosides toward human cancer cell lines and explore more potential anticancer agents, a series of 3ß-O-neoglycosides of caudatin and its analogues were synthesized. The results revealed that most of peracetylated 3ß-O-monoglycosides demonstrated moderate to significant antiproliferative activities against four human cancer cell lines (MCF-7, HCT-116, HeLa, and HepG2). Among them, 3ß-O-(2,3,4-tri-O-acetyl-ß-L-glucopyranosyl)-caudatin (2k) exhibited the highest antiproliferative activity aganist HepG2 cells with an IC50 value of 3.11 µM. Mechanical studies showed that compound 2k induced both apoptosis and cell cycle arrest at S phase in a dose dependent manner. Overall, these present findings suggested that glycosylation is a promising scaffold to improve anticancer activity for naturally occurring C21-steroidal aglycones, and compound 2k represents a potential anticancer agent deserved further investigation.

Extracellular HSPs: The Potential Target for Human Disease Therapy.

Heat shock proteins (HSPs) are highly conserved stress proteins known as molecular chaperones, which are considered to be cytoplasmic proteins with functions restricted to the intracellular compartment, such as the cytoplasm or cellular organelles. However, an increasing number of observations have shown that HSPs can also be released into the extracellular matrix and can play important roles in the modulation of inflammation and immune responses. Recent studies have demonstrated that extracellular HSPs (eHSPs) were involved in many human diseases, such as cancers, neurodegenerative diseases, and kidney diseases, which are all diseases that are closely linked to inflammation and immunity. In this review, we describe the types of eHSPs, discuss the mechanisms of eHSPs secretion, and then highlight their functions in the modulation of inflammation and immune responses. Finally, we take cancer as an example and discuss the possibility of targeting eHSPs for human disease therapy. A broader understanding of the function of eHSPs in development and progression of human disease is essential for developing new strategies to treat many human diseases that are critically related to inflammation and immunity.

The phytopathogen Xanthomonas campestris utilizes the divergently transcribed pobA/pobR locus for 4-hydroxybenzoic acid recognition and degradation to promote virulence.

Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot in crucifers. Our previous findings revealed that Xcc can degrade 4-hydroxybenzoic acid (4-HBA) via the ß-ketoadipate pathway. This present study expands on this knowledge in several ways. First, we show that infective Xcc cells induce in situ biosynthesis of 4-HBA in host plants, and Xcc can efficiently degrade 4-HBA via the pobA/pobR locus, which encodes a 4-hydroxybenzoate hydroxylase and an AraC-family transcription factor respectively. Next, the transcription of pobA is specifically induced by 4-HBA and is positively regulated by PobR, which is constitutively expressed in Xcc. 4-HBA directly binds to PobR dimers, resulting in activation of pobA expression. Point mutation and subsequent isothermal titration calorimetry and size exclusion chromatography analysis identified nine key conserved residues required for 4-HBA binding and/or dimerization of PobR. Furthermore, overlapping promoters harboring fully overlapping -35 elements were identified between the divergently transcribed pobA and pobR. The 4-HBA/PobR dimer complex specifically binds to a 25-bp site, which encompasses the -35 elements shared by the overlapping promoters. Finally, GUS histochemical staining and subsequent quantitative assay showed that both pobA and pobR genes are transcribed during Xcc infection of Chinese radish, and the strain ΔpobR exhibited compromised virulence in Chinese radish. These findings suggest that the ability of Xcc to survive the 4-HBA stress might be important for its successful colonization of host plants.

On a separation voltage polarity switching transient capillary isotachophoresis method for higher sample loading capacity and better separation performance.

Limited sample loading capacity is one of the major reasons that prevents the utility of capillary electrophoresis (CE) as a routine separation method as compared to liquid chromatography (LC). In our previous study, separation voltage polarity switching transient capillary isotachophoresis (PS-tCITP) was proposed. Both sample loading capacity and separation resolution could be improved using a single PS-tCITP instead of routine transient capillary isotachophoresis (tCITP). In this study, a detailed investigation on the optimization strategy of the PS-tCITP method was performed systematically. A possible mechanism of sample preconcentration in multiple PS-tCITP was first proposed to better understand the multiple PS-tCITP process. Several optimization experiments were then performed, including single PS-tCITP, paused PS-tCITP and multiple PS-tCITP, sequentially using a mixture of five peptides. By selecting an optimum polarity switching time, sample loading capacity of 100% capillary volume could be achieved in a single PS-tCITP. Introducing an additional pause between each polarity switching in a single PS-tCITP further improved the separation resolution. Experimental results showed a baseline separation of five selected peptide standards at 100% sample loading volume using a 100 min pause in a single PS-tCITP. To further improve separation efficiency while still maintaining 100% sample loading volume, a multiple PS-tCITP technique was developed through this study. Compared to the separation performance of the optimal single PS-tCITP at 100% sample loading volume with a 10 min pause, the separation window was improved by 54% and the peak capacity was improved by 48% in the optimal four PS-tCITP with the same sample loading volume and pause.

Extracellular Amylase Is Required for Full Virulence and Regulated by the Global Posttranscriptional Regulator RsmA in Xanthomonas campestris Pathovar campestris.

As with many phytopathogenic bacteria, the virulence of Xanthomonas campestris pv. campestris, the causal agent of black rot disease in cruciferous plants, relies on secretion of a suite of extracellular enzymes that includes cellulase (endoglucanase), pectinase, protease, and amylase. Although the role in virulence of a number of these enzymes has been assessed, the contribution of amylase to X. campestris pv. campestris virulence has yet to be established. In this work, we investigated both the role of extracellular amylase in X. campestris pv. campestris virulence and the control of its expression. Deletion of XC3487 (here renamed amyAXcc), a putative amylase-encoding gene from the genome of X. campestris pv. campestris strain 8004, resulted in a complete loss of extracellular amylase activity and significant reduction in virulence. The extracellular amylase activity and virulence of the amyAXcc mutant could be restored to the wild-type level by expressing amyAXcc in trans. These results demonstrated that amyAXcc is responsible for the extracellular amylase activity of X. campestris pv. campestris and indicated that extracellular amylase plays an important role in X. campestris pv. campestris virulence. We also found that the expression of amyAXcc is strongly induced by starch and requires activation by the global posttranscriptional regulator RsmA. RsmA binds specifically to the 5'-untranslated region of amyAXcc transcripts, suggesting that RsmA regulates amyAXcc directly at the posttranscriptional level. Unexpectedly, in addition to posttranscriptional regulation, the use of a transcriptional reporter demonstrated that RsmA also regulates amyAXcc expression at the transcriptional level, possibly by an indirect mechanism.

Supercrystallographic Reconstruction of 3D Nanorod Assembly with Collectively Anisotropic Upconversion Fluorescence.

Constructing three-dimensional (3D) metamaterials from functional nanoparticles endows them with emerging collective properties tailored by the packing geometries. Herein, we report 3D supercrystals self-assembled from upconversion nanorods (NaYF4:Yb,Er NRs), which exhibit both translational ordering of NRs and orientational ordering between constituent NRs in the superlattice (SL). The construction of 3D reciprocal space mappings (RSMs) based on synchrotron-based X-ray scattering measurements was developed to uncover the complex structure of such an assembly. That is, the two main orthogonal sets of hexagonal close-packing (hcp)-like SLs share the [110]SL axis, and NRs within the SL possess orientational relationships of [120]NR//[100]SL, [210]NR//[010]SL, and [001]NR//[001]SL. Notably, these supercrystals containing well-aligned NRs exhibit collectively anisotropic upconversion fluorescence in two perpendicular directions. This study not only demonstrates novel crystalline superstructures and functionality of NR-based 3D assemblies but also offers a unique tool for deciphering a wide range of complex nanoparticle supercrystals.

[Research Progress on Insomnia and Microarousal].

Insomnia is a subjective experience of difficulty in falling asleep and/or maintaining sleep accompanied by the impairment of daytime social functioning due to insufficient sleep quality or quantity to meet normal physiological needs.It has chronic damage to all the human body systems and is the most common sleep disorder.The main mechanism for the occurrence and maintenance of insomnia is the hyperarousal hypothesis,and microarousal,as a cortical arousal,is also involved in the formation of the hyperarousal mechanism.The mechanism and clinical significance of microarousal were reviewed and summarized in this paper in order to guide the clinical work.

Chemical Targeting and Manipulation of Type III Secretion in the Phytopathogen Xanthomonas campestris for Control of Disease.

Xanthomonas campestris pv. campestris is the causative agent of black rot disease in crucifer plants. This Gram-negative bacterium utilizes the type III secretion system (T3SS), encoded by the hrp gene cluster, to aid in its resistance to host defenses and the ability to cause disease. The T3SS injects a set of proteins known as effectors into host cells that come into contact with the bacterium. The T3SS is essential for the virulence and hypersensitive response (HR) of X. campestris pv. campestris, making it a potential target for disease control strategies. Using a unique and straightforward high-throughput screening method, we examined a large collection of diverse small molecules for their potential to modulate the T3SS without affecting the growth of X. campestris pv. campestris. Screening of 13,129 different compounds identified 10 small molecules that had a significant inhibitory influence on T3SS. Moreover, reverse transcription-quantitative PCR (qRT-PCR) assays demonstrated that all 10 compounds repress the expression of the hrp genes. Interestingly, the effect of these small molecules on hrp genes may be through the HpaS and ColS sensor kinase proteins that are key to the regulation of the T3SS in planta Five of the compounds were also capable of inhibiting X. campestris pv. campestris virulence in a Chinese radish leaf-clipping assay. Furthermore, seven of the small molecules significantly weakened the HR in nonhost pepper plants challenged with X. campestris pv. campestris. Taken together, these small molecules may provide potential tool compounds for the further development of antivirulence agents that could be used in disease control of the plant pathogen X. campestris pv. campestris.IMPORTANCE The bacterium Xanthomonas campestris pv. campestris is known to cause black rot disease in many socioeconomically important vegetable crops worldwide. The management and control of black rot disease have been tackled with chemical and host resistance methods with variable success. This has motivated the development of alternative methods for preventing this disease. Here, we identify a set of novel small molecules capable of inhibiting X. campestris pv. campestris virulence, which may represent leading compounds for the further development of antivirulence agents that could be used in the control of black rot disease.