Synthesis and Docking Study of N-(Cinnamoyl)-N'-(substituted)acryloyl Hydrazide Derivatives Containing Pyridinium Moieties as a Novel Class of Filamentous Temperature-Sensitive Protein Z Inhibitors against the Intractable Xanthomonas oryzae pv. oryzae Infections in Rice

Identification of novel 4-substituted 7H-pyrrolo[2,3-d]pyrimidine derivatives as new FtsZ inhibitors: Bioactivity evaluation and computational simulation

Bacterial infections and the consequent outburst of bactericide-resistance issues are fatal menace to both global health and agricultural produce. Hence, it is crucial to explore candidate bactericides with new mechanisms of action. The filamenting temperature-sensitive mutant Z (FtsZ) protein has been recognized as a new promising and effective target for new bactericide discovery. Hence, using a scaffold-hopping strategy, we designed new 7H-pyrrolo[2,3-d]pyrimidine derivatives, evaluated their antibacterial activities, and investigated their structure-activity relationships. Among them, compound B6 exhibited the optimal in vitro bioactivity (EC50 = 4.65 µg/mL) against Xanthomonas oryzae pv. oryzae (Xoo), which was superior to the references (bismerthiazol [BT], EC50 = 48.67 µg/mL; thiodiazole copper [TC], EC50 = 98.57 µg/mL]. Furthermore, the potency of compound B6 in targeting FtsZ was validated by GTPase activity assay, FtsZ self-assembly observation, fluorescence titration, Fourier-transform infrared spectroscopy (FT-IR) assay, molecular dynamics simulations, and morphological observation. The GTPase activity assay showed that the final IC50 value of compound B6 against XooFtsZ was 235.0 μM. Interestingly, the GTPase activity results indicated that the B6-XooFtsZ complex has an excellent binding constant (KA = 103.24 M-1). Overall, the antibacterial behavior suggests that B6 can interact with XooFtsZ and inhibit its GTPase activity, leading to bacterial cell elongation and even death. In addition, compound B6 showed acceptable anti-Xoo activity in vivo and low toxicity, and also demonstrated a favorable pharmacokinetic profile predicted by ADMET analysis. Our findings provide new chemotypes for the development of FtsZ inhibitors as well as insights into their underlying mechanisms of action.

Dual actions of chloroinconazide on pepper blight in Capsicum annuum: disruption of Phytophthora capsici mycelium and activation of CaCNGC9-mediated SA signaling

BACKGROUND

Pepper blight, caused by Phytophthora capsici, is a devastating disease that seriously threatens pepper production worldwide. With the emergence of resistance in P. capsici against conventional fungicides, there is an urgent need to explore novel alternatives for pepper blight management. This study aims to assess the inhibitory effect of chloroinconazide (CHI), a compound synthesized from tryptophan, against pepper blight, and to explore its potential mechanisms of action.

RESULTS

The results demonstrated that CHI effectively targeted P. capsici, disrupting its growth and mycelial structure, which resulted in the release of dissolved intracellular substances. Additionally, CHI significantly inhibited the sporangium formation, zoospores release, and zoospores germination, thereby reducing the re-infection of P. capsici. In contrast, the commercial pesticide methylaxyl only inhibited mycelial growth and had limited effect on re-infection, while azoxystrobin inhibited re-infection but had a weak inhibitory effect on mycelial growth. Furthermore, CHI activated the salicylic acid (SA) signaling pathway-mediated immune response to inhibit P. capsici infection in pepper, with this activation being contingent upon cyclic nucleotide-gated ion channel CaCNGC9.

CONCLUSION

CHI exhibited potent dual inhibitory effects on P. capsici by disrupting mycelial structure and activating the CaCNGC9-mediated SA signaling pathway. These dual mechanisms of action suggested that CHI could serve as a promising alternative chemical fungicide for the effective management of pepper blight, offering a new approach to control this devastating disease. Our findings highlighted the potential of CHI as a sustainable and efficient solution to combat the increasing resistance of P. capsici to conventional fungicides, ensuring better crop protection and yield. © 2024 Society of Chemical Industry.

Application of natural-products repurposing strategy to discover novel FtsZ inhibitors: Bactericidal evaluation and the structure-activity relationship of sanguinarine and its analogs

The novel bactericidal target-filamentous temperature-sensitive protein Z (FtsZ)-has drawn the attention of pharmacologists to address the emerging issues with drug/pesticide resistance caused by pathogenic bacteria. To enrich the structural diversity of FtsZ inhibitors, the antibacterial activity and structure-activity relationship (SAR) of natural sanguinarine and its analogs were investigated by using natural-products repurposing strategy. Notably, sanguinarine and chelerythrine exerted potent anti-Xanthomonas oryzae pv. oryzae (Xoo) activity, with EC50 values of 0.96 and 0.93 mg L-1, respectively, among these molecules. Furthermore, these two compounds could inhibit the GTPase activity of XooFtsZ, with IC50 values of 241.49 μM and 283.14 μM, respectively. An array of bioassays including transmission electron microscopy (TEM), fluorescence titration, and Fourier transform infrared spectroscopy (FT-IR) co-verified that sanguinarine and chelerythrine were potential XooFtsZ inhibitors that could interfere with the assembly of FtsZ filaments by inhibiting the GTPase hydrolytic ability of XooFtsZ protein. Additionally, the pot experiment suggested that chelerythrine and sanguinarine demonstrated excellent curative activity with values of 59.52% and 54.76%, respectively. Excitedly, these two natural compounds also showed outstanding druggability, validated by acceptable drug-like properties and low toxicity on rice. Overall, the results suggested that chelerythrine was a new and potential XooFtsZ inhibitor to develop new bactericide and provided important guiding values for rational drug design of FtsZ inhibitors. Notably, our findings provide a novel strategy to discover novel, promising and green bacterial compounds for the management of plant bacterial diseases.

Design and synthesis of bis(indolyl)-hydrazide-hydrazone derivatives and their antifungal activities against plant pathogen fungi

A series of bis(indolyl)-hydrazide-hydrazone derivatives were synthesised, and their structures were characterised using 1H-NMR and HRMS. The antifungal activity of the prepared compounds was evaluated against Pyricularia oryzae Cav., Colletotrichum -gloeosporioides Penz., Botrytis cinerea Pers.: Fr. and Rhizoctonia solani Kühn using the mycelial growth rate method. The preliminary bioassays revealed that most of the synthesised compounds exhibited antifungal activity against the four tested fungi and displayed a remarkable inhibitory effect on the mycelium growth of R. solani. In particular, compounds 3b, 3c, and 3k demonstrated significant antifungal activity against R. solani, with EC50 values of 26.42, 20.74, and 22.41 μM, respectively, outperforming the positive control shenqinmycin (47.18 μM) and carvacrol (49.13 μM).

Design and Enantioselective Synthesis of Chiral Pyranone Fused Indole Derivatives with Antibacterial Activities against Xanthomonas oryzae pv oryzae for Protection of Rice

A new class of chiral pyranone fused indole derivatives were prepared by means of N-heterocyclic carbene (NHC) organocatalysis and demonstrated notable antibacterial activity against Xanthomonas oryzae pv oryzae (Xoo). Bioassays showed that compounds (3S,4R)-5b, (3S,4R)-5d, and (3S,4R)-5l exhibited promising in vitro efficacy against Xoo, with EC50 values of 9.05, 9.71, and 5.84 mg/L, respectively, which were superior to that of the positive controls with commercial antibacterial agents, bismerthiazol (BT, EC50 = 27.8 mg/L) and thiodiazole copper (TC, EC50 = 70.1 mg/L). Furthermore, single enantiomer (3S,4R)-5l was identified as an optimal structure displaying 55.3% and 52.0% curative and protective activities against Xoo in vivo tests at a concentration of 200 mg/L, which slightly surpassed the positive control with TC (curative and protective activities of 47.2% and 48.8%, respectively). Mechanistic studies through molecular docking analysis revealed preliminary insights into the distinct anti-Xoo activity of the two single enantiomers (3S,4R)-5l and (3R,4S)-5l, wherein the (3S,4R)-configured stereoisomer could form a more stable interaction with XooDHPS (dihydropteroate synthase). These findings underscore the significant anti-Xoo potential of these chiral pyranone fused indole derivatives, and shall inspire further exploration as promising lead structures for a novel class of bactericides to combat bacterial infections and other plant diseases.

Short pathways to highly active antimicrobial: structurally diverse polyamines derivatives from Amino-Aldehyde condensation strategy

BACKGROUND

Chemical fungicides are the mainstay of plant disease control in agricultural production, but there are a very limited number of drugs that can effectively control plant diseases. Two series of secondary amine derivatives were synthesized using the diamine skeleton combined with saturated aromatic and aliphatic aldehydes, and their antibacterial and antifungal activities against plant pathogens were determined. In addition, the antimicrobial mechanism of the highly active compound A26 was preliminarily examined against Xanthomonas oryzae (Xoo).

RESULTS

Compound A26 exhibited the highest antibacterial potency among all the target compounds, with MIC values of 3.12, 3.12 and 12.5 μg mL-1 against Xoo, Xanthomonas axonopodis pv. Citri and Pseudomonas sollamacearum, respectively. In addition, compound A26 had powerful curative and protective effects against Xoo at 200 μg mL-1 , and was better than the control agent Xinjunan. Preliminary mechanistic studies showed that compound A26 reduced the bacterial pathogenicity by targeting cell membranes and inhibiting the secretion of extracellular polysaccharides. Meanwhile, the toxicity of compound A26 to Human Embryonic Kidney 293 cells and Human Liver-7702 was similar to that of Xinjunan, and it had moderate toxicity according to the World Health Organization classification standard of oral exogenous toxicity, with an LD50 of 245.47 mg kg-1 .

CONCLUSION

Secondary amines have efficient and broad-spectrum antibacterial activity against plant pathogenic bacteria and are expected to be a new class of candidate compounds for antibacterial drugs. © 2023 Society of Chemical Industry.

Derivative of cinnamic acid inhibits T3SS of Xanthomonas oryzae pv. oryzae through the HrpG-HrpX regulatory cascade

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) has a significant impact on rice yield and quality worldwide. Traditionally, bactericide application has been commonly used to control this devastating disease. However, the overuse of fungicides has led to a number of problems such as the development of resistance and environmental pollution. Therefore, the development of new methods and approaches for disease control are still urgent. In this paper, a series of cinnamic acid derivatives were designed and synthesized, and three novel T3SS inhibitors A10, A12 and A20 were discovered. Novel T3SS inhibitors A10, A12 and A20 significantly inhibited the hpa1 promoter activity without affecting Xoo growth. Further studies revealed that the title compounds A10, A12 and A20 significantly impaired hypersensitivity in non-host plant tobacco leaves, while applications on rice significantly reduced symptoms of bacterial leaf blight. RT-PCR showed that compound A20 inhibited the expression of T3SS-related genes. In summary, this work exemplifies the potential of the title compound as an inhibitor of T3SS and its efficacy in the control of bacterial leaf blight.

Alternative Splicing, An Overlooked Defense Frontier of Plants with Respect to Bacterial Infection

Disease represents a major problem in sustainable agricultural development. Plants interact closely with various microorganisms during their development and in response to the prevailing environment. In particular, pathogenic microorganisms can cause plant diseases, affecting the fertility, yield, and longevity of plants. During the long coevolution of plants and their pathogens, plants have evolved both molecular pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) signaling networks in order to regulate host cells in response to pathogen infestation. Additionally, in the postgenomic era, alternative splicing (AS) has become uncovered as one of the major drivers of proteome diversity, and abnormal RNA splicing is closely associated with bacterial infections. Currently, the complexity of host-bacteria interactions is a much studied area of research that has shown steady progress over the past decade. Although the development of high-throughput sequencing technologies and their application in transcriptomes have revolutionized our understanding of AS, many mechanisms related to host-bacteria interactions remain still unclear. To this end, this review summarizes the changes observed in AS during host-bacteria interactions and outlines potential therapeutics for bacterial diseases based on existing studies. In doing so, we hope to provide guidelines for plant disease management in agriculture.

Repurposing Salicylamides to Combat Phytopathogenic Bacteria and Induce Plant Defense Responses

Based on the research strategy of "drug repurposing", a series of derivatives and marketed drugs that containing salicylic acid skeleton were tested for their antibacterial activities against phytopathogens. Salicylic acid can not only regulate some important growth metabolism of plants, but also induce plant disease resistance. The bioassay results showed that the salicylamides exhibited excellent antibacterial activity. Especially, oxyclozanide showed the best antibacterial effect against Xanthomonas oryzae, Xanthomonas axonopodis pv. citri and Pectobacterium atroseptica with MICs of 0.78, 3.12 and 12.5 μg.mL-1, respectively. In vivo experiments with rice bacterial leaf blight had further demonstrated that oxyclozanide exhibited stronger antibacterial activity than the commercial bactericide, thiodiazole copper. Oxyclozanide could induce plant defense responses through the determination of salicylic acid content and the activities of defense-related enzymes including CAT, POD, and SOD in rice. The preliminarily antibacterial mechanism study indicated that oxyclozanide exhibited the antibacterial activity by disrupting cell integrity and reducing bacterial pathogenicity. Additionally, oxyclozanide could induce plant defense responses through the determination of salicylic acid content.

Engineering Phenothiazine-Based Functional Mimics of Host Defense Peptides as New Agrochemical Candidates: Design, Synthesis, and Antibacterial Evaluation

In the protracted "arms race" between host and plant pathogenic bacteria, host organisms have evolved powerful weapons known as host defense peptides (HDPs). However, natural HDPs are not suitable for large-scale applications; therefore, researchers have chosen to develop bespoke small-molecule functional mimics. Phenothiazine derivatives were developed as functional HDPs mimics, owing to their broad biological activity and high lipophilicity. The phenothiazine analogues designed in this study exhibited excellent in vitro bioactivity against the three Gram-negative bacteria Xanthomonas oryzae pv oryzae, Xanthomonas axonopodis pv citri, and Pseudomonas syringae pv actinidiae, with optimal EC50 values of 0.80, 0.31, and 1.91 μg/mL, respectively. Preliminary evidence suggests that compound C2 may act on bacterial cell membranes and interact with bacterial Deoxyribonucleic acid in the groove binding mode. In vivo trials showed that compound C2 was highly effective against rice leaf blight (51.97-56.69%), with activity superior to those of bismerthiazol (40.7-43.4%) and thiodiazole copper (30.2-37.1%). Our study provides strong evidence to support the development of phenothiazine derivatives into pesticide candidates.

Design, synthesis, antibacterial activity, and mechanism of novel resveratrol derivatives containing an 1,3,4-oxadiazole moiety

Rice bacterial diseases seriously threaten the development of rice industry in the world, and chemical control is still one of the effective means to control it. To find novel antibacterial agents, 42 resveratrol derivatives were designed and synthesized based on natural product resveratrol as lead structure, and their antibacterial activities were evaluated. Most compounds have excellent antibacterial activities. Among them, the EC₅₀ values of compound B1 against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) were 4.76 and 8.85 mg/L, respectively. The curative activities of compound B1 against bacterial leaf blight and bacterial leaf streak were 45.57 and 38.40%, and the protective activities were 49.41 and 35.93%, respectively. In addition, compound B1 could change bacterial cell surface morphology by inhibiting biofilm formation and exopolysaccharide production, and increasing membrane permeability, thereby affecting the normal growth of bacteria. Furthermore, transcriptome analysis showed that differential expressed genes were mainly enriched in plant-pathogen interaction pathway and MAPK signaling pathway-plant after compound B1 treated susceptible rice. We will further optimize the structure of compound B1 in future work to find more efficient antibacterial agents.

Exploiting Natural Maltol for Synthesis of Novel Hydroxypyridone Derivatives as Promising Anti-Virulence Agents in Bactericides Discovery

Anti-infection strategies based on suppression of bacterial virulence factors represent a crucial direction for the development of new antibacterial agents to address the resistance triggered by traditional drugs'/pesticides' bactericidal activity. To identify and obtain more effective and diverse molecules targeting virulence, we prepared a series of 3-hydroxy-2-methyl-1-pyridin-4-(1H)-one derivatives and evaluated their antibacterial behaviors. Compound B₆ exhibited the highest bioactivity, with half-maximal effective concentration (EC₅₀) values ranging fro9m 10.03 to 30.16 μg mL^-1 against three plant pathogenic bacteria. The antibacterial mechanism showed that it could considerably reduce various virulence factors (such as extracellular enzymes, biofilm, and T3SS effectors) and inhibit the expression of virulence factor-related genes. In addition, the control efficiency of compound B₆ against rice bacterial leaf blight at 200 μg mL^-1 was 46.15-49.15%, and their control efficiency was improved by approximately 12% after the addition of pesticide additives. Thus, a new class of bactericidal candidates targeting bacterial virulence factors was developed for controlling plant bacterial diseases.

Natural Products-Based Botanical Bactericides Discovery: Novel Abietic Acid Derivatives as Anti-Virulence Agents for Plant Disease Management

The discovery of natural product-based pesticides is critical for agriculture. In this work, a series of novel tricyclic diterpenoid derivatives decorated with an amino alcohol moiety were elaborately prepared from natural abietic acid, and their antibacterial behavior was explored. Bioassay results indicated that compound C₂ exhibited the most promising bioactivity (EC₅₀ = 0.555 μg mL^-1) against Xanthomonas oryzae pv. oryzae (Xoo), about 73 times higher than the effect of commercial thiodiazole copper (TC). Results of in vivo bioassays showed that compound C₂ displayed significantly higher control of rice bacterial leaf blight (curative activity: 63.8%; protective activity: 58.4%) than TC (curative activity: 43.6%; protective activity: 40.8%), and their bioactivity could be improved maximally 16% by supplementing the auxiliaries. Antibacterial behavior suggested that compound C₂ could suppress various virulence factors. Overall, these findings suggested that new botanical bactericide candidates could control intractable plant bacterial diseases by suppressing virulence factors.

Discovery of Simple Diacylhydrazine-Functionalized Cinnamic Acid Derivatives as Potential Microtubule Stabilizers

To develop novel microtubule-binding agents for cancer therapy, an array of N-cinnamoyl-N'-(substituted)acryloyl hydrazide derivatives were facilely synthesized through a two-step process. Initially, the antiproliferative activity of these title compounds was explored against A549, 98 PC-3 and HepG2 cancer cell lines. Notably, compound I₂₃ exhibited the best antiproliferative activity against three cancer lines with IC₅₀ values ranging from 3.36 to 5.99 μM and concurrently afforded a lower cytotoxicity towards the NRK-52E cells. Anticancer mechanism investigations suggested that the highly bioactive compound I₂₃ could potentially promote the protofilament assembly of tubulin, thus eventually leading to the stagnation of the G2/M phase cell cycle of HepG2 cells. Moreover, compound I₂₃ also disrupted cancer cell migration and significantly induced HepG2 cells apoptosis in a dosage-dependent manner. Additionally, the in silico analysis indicated that compound I₂₃ exhibited an acceptable pharmacokinetic profile. Overall, these easily prepared N-cinnamoyl-N'-(substituted)acryloyl hydrazide derivatives could serve as potential microtubule-interacting agents, probably as novel microtubule-stabilizers.

Discovery of Epipodophyllotoxin-Derived B2 as Promising XooFtsZ Inhibitor for Controlling Bacterial Cell Division: Structure-Based Virtual Screening, Synthesis, and SAR Study

The emergence of phytopathogenic bacteria resistant to antibacterial agents has rendered previously manageable plant diseases intractable, highlighting the need for safe and environmentally responsible agrochemicals. Inhibition of bacterial cell division by targeting bacterial cell division protein FtsZ has been proposed as a promising strategy for developing novel antibacterial agents. We previously identified 4'-demethylepipodophyllotoxin (DMEP), a naturally occurring substance isolated from the barberry species Dysosma versipellis, as a novel chemical scaffold for the development of inhibitors of FtsZ from the rice blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). Therefore, constructing structure-activity relationship (SAR) studies of DMEP is indispensable for new agrochemical discovery. In this study, we performed a structure-activity relationship (SAR) study of DMEP derivatives as potential XooFtsZ inhibitors through introducing the structure-based virtual screening (SBVS) approach and various biochemical methods. Notably, prepared compound B₂, a 4'-acyloxy DMEP analog, had a 50% inhibitory concentration of 159.4 µM for inhibition of recombinant XooFtsZ GTPase, which was lower than that of the parent DMEP (278.0 µM). Compound B₂ potently inhibited Xoo growth in vitro (minimum inhibitory concentration 153 mg L^-1) and had 54.9% and 48.4% curative and protective control efficiencies against rice blight in vivo. Moreover, compound B₂ also showed low toxicity for non-target organisms, including rice plant and mammalian cell. Given these interesting results, we provide a novel strategy to discover and optimize promising bactericidal compounds for the management of plant bacterial diseases.

Discovery of novel rost-4-ene derivatives as potential plant activators for preventing phytopathogenic bacterial infection: Design, synthesis and biological studies

BACKGROUND

Gradually aggravated disease caused by phytopathogenic bacteria severely restricts food security and crop yield, and few pesticides can relieve this severe situation. Thus, development and excavation of new agrochemicals with high bioactivity and novel action mechanism may be a feasible strategy to control intractable bacterial diseases. As a privileged molecular framework, steroid molecules exhibit diversiform bioactivities. Herein, a series of novel androst-4-ene derivatives were designed, synthesised and investigated for their antibacterial behaviour to excavate novel agrochemicals on the base of steroid molecules.

RESULTS

Bioassay results indicated that target compounds displayed high bioactivities toward three destructive phytopathogenic bacteria, including Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac) and Pseudomonas syringae pv. actinidiae (Psa). Compound III₁₉ displayed excellent in vitro antibacterial profiling (EC₅₀  = 2.37 mg L^-1 towards Xoo, EC₅₀  = 2.10 mg L^-1 towards Xac, EC₅₀  = 9.50 mg L^-1 towards Psa). Furthermore, compound III₁₉ showed outstanding in vivo protective activities, with values of 81.81% and 58.75% towards kiwifruit bacterial canker and rice bacterial leaf blight, respectively. Analysis of the antibacterial mechanism disclosed that compound III₁₉ enhanced host defence enzyme activities superoxide dismutase (SOD), peroxidase (POD), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and catalase (CAT) and increased the salicylate synthase content to induce host resistance. In addition, compound III₁₉ increased the membrane permeability, destroyed the cell membrane and killed the bacteria.

CONCLUSION

Given these profiles of target compounds, we highlight a new strategy for controlling intractable plant bacterial diseases by inducing plant resistance and targeting the bacterial cell membrane. © 2022 Society of Chemical Industry.

1,3,4-Oxadiazole Derivatives as Plant Activators for Controlling Plant Viral Diseases: Preparation and Assessment of the Effect of Auxiliaries

Plant viral diseases cause the loss of millions of dollars to agriculture around the world annually. Therefore, the development of highly efficient, ultra-low-dosage agrochemicals is desirable for protecting the health of crops and ensuring food security. Herein, a series of 1,3,4-oxadiazole derivatives bearing an isopropanol amine moiety was prepared, and the inhibitory activity against tobacco mosaic virus (TMV) was assessed. Notably, compound A₁₄ exhibited excellent anti-TMV protective activity with an EC₅₀ value of 137.7 mg L^-1, which was superior to that of ribavirin (590.0 mg L^-1) and ningnanmycin (248.2 mg L^-1). Moreover, the anti-TMV activity of some compounds could be further enhanced (by up to 5-30%) through supplementation with 0.1% auxiliaries. Biochemical assays suggested that compound A₁₄ could suppress the biosynthesis of TMV and induce the plant's defense response. Given these merits, designed compounds had outstanding bioactivities and unusual action mechanisms and were promising candidates for controlling plant viral diseases.

Fabrication of Isopropanolamine-Decorated Coumarin Derivatives as Novel Quorum Sensing Inhibitors to Suppress Plant Bacterial Disease

Emerging pesticide-resistant phytopathogenic bacteria have become a stumbling block in the development and use of pesticides. Quorum sensing (QS) blockers, which interfere with bacterial virulence gene expression, are a compelling way to manage plant bacterial disease without resistance. Herein, a series of isopropanolamine-decorated coumarin derivatives were designed and synthesized, and their potency in interfering with QS was investigated. Notably, compound A₅ exhibited a better bioactivity with median effective concentration (EC₅₀) values of 6.75 mg L^-1 against Xanthomonas oryzae pv. oryzae (Xoo) than bismerthiazol (EC₅₀ = 21.9 mg L^-1). Further biochemical studies revealed that compound A₅ disturbed biofilm formation and suppressed bacterial virulence factors and so forth. Moreover, compound A₅ decreased the expression of QS-related genes. Interestingly, compound A₅ had the acceptable control effect (53.2%) toward Xoo in vivo. Overall, this study identifies a novel lead compound for the development of bactericide candidates to control plant bacterial diseases by interfering with QS.

Exploring an Innovative Strategy for Suppressing Bacterial Plant Disease: Excavated Novel Isopropanolamine-Tailored Pterostilbene Derivatives as Potential Antibiofilm Agents

Bacterial biofilms are the root cause of persistent and chronic phytopathogenic bacterial infections. Therefore, developing novel agrochemicals that target the biofilm of phytopathogenic bacteria has been regarded as an innovative tactic to suppress their invasive infection or decrease bacterial drug resistance. In this study, a series of natural pterostilbene (PTE) derivatives were designed, and their antibacterial potency and antibiofilm ability were assessed. Notably, compound C₁ displayed excellent antibacterial potency in vitro, affording an EC₅₀ value of 0.88 μg mL^-1 against Xoo (Xanthomonas oryzae pv. oryzae). C₁ could significantly reduce biofilm formation and extracellular polysaccharides (EPS). Furthermore, C₁ also possessed remarkable inhibitory activity against bacterial extracellular enzymes, pathogenicity, and other virulence factors. Subsequently, pathogenicity experiments were further conducted to verify the above primary outcomes. More importantly, C₁ with pesticide additives displayed excellent control efficiency. Given these promising profiles, these pterostilbene derivatives can serve as novel antibiofilm agents to suppress plant pathogenic bacteria.

Synthesis and Biological Evaluation of 1,2,4-Triazole Thioethers as Both Potential Virulence Factor Inhibitors against Plant Bacterial Diseases and Agricultural Antiviral Agents against Tobacco Mosaic Virus Infections

Targeting the virulence factors of phytopathogenic bacteria is an innovative strategy for alleviating or eliminating the pathogenicity and rapid outbreak of plant microbial diseases. Therefore, several types of 1,2,4-triazole thioethers bearing an amide linkage were prepared and screened to develop virulence factor inhibitors. Besides, the 1,2,4-triazole scaffold was exchanged by a versatile 1,3,4-oxadiazole core to expand molecular diversity. Bioassay results revealed that a 1,2,4-triazole thioether A₁₀ bearing a privileged N-(3-nitrophenyl)acetamide fragment was extremely bioactive against Xanthomonas oryzae pv. oryzae (Xoo) with an EC₅₀ value of 5.01 μg/mL. Label-free quantitative proteomics found that compound A₁₀ could significantly downregulate the expression of Xoo's type III secretion system (T3SS) and transcription activator-like effector (TALE) correlative proteins. Meanwhile, qRT-PCR detection revealed that the corresponding gene transcription levels of these virulence factor-associated proteins were substantially inhibited after being triggered by compound A₁₀. As a result, the hypersensitive response and pathogenicity were strongly depressed, indicating that a novel virulence factor inhibitor (A₁₀) was probably discovered. In vivo anti-Xoo trials displayed that compound A₁₀ yielded practicable control efficiency (54.2-59.6%), which was superior to thiadiazole-copper and bismerthiazol (38.1-44.9%). Additionally, compound A₁₀ showed an appreciable antiviral activity toward tobacco mosaic virus (TMV) with the curative and protective activities of 54.6 and 76.4%, respectively, which were comparable to ningnanmycin (55.2 and 60.9%). This effect was further validated and visualized by the inoculation test using GFP-labeled TMV, thereby leading to the reduced biosynthesis of green-fluorescent TMV on Nicotiana benthamiana. Given the outstanding features of compound A₁₀, it should be deeply developed as a versatile agricultural chemical.

Novel Cinnamic Acid Derivatives Containing the 1,3,4-Oxadiazole Moiety: Design, Synthesis, Antibacterial Activities, and Mechanisms

There is a lack of effective antibacterial agents against rice bacterial leaf streak and leaf blight. Cinnamic acid derivatives containing the 1,3,4-oxadiazole moiety were synthesized, and their antibacterial activities against Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo) were evaluated. Based on the three-dimensional quantitative structure-activity relationship (3D-QSAR) model, compound 31 with better antibacterial activity against Xoc was designed and synthesized, and the 50% effective concentration (EC₅₀) value was 0.2 mg/L. The curative and protective activities of compound 31 against rice bacterial leaf streak at 100 mg/L were 39.5 and 35.4%, respectively, which were higher than those of thiodiazole copper (28.4 and 20.7%, respectively). The antibacterial activity of compound 31 against rice bacterial leaf streak is closely associated with the activity of related defensive enzymes and the increase in glutathione metabolism.

Discovery of facile amides-functionalized rhodanine-3-acetic acid derivatives as potential anticancer agents by disrupting microtubule dynamics

Microtubule dynamics are crucial for multiple cell functions, and cancer cells are particularly sensitive to microtubule-modulating agents. Here, we describe the design and synthesis of a series of (Z)-2-(5-benzylidene-4-oxo-2-thioxothiazolidin-3-yl)-N-phenylacetamide derivatives and evaluation of their microtubule-modulating and anticancer activities in vitro. Proliferation assays identified I₂₀ as the most potent of the antiproliferative compounds, with 50% inhibitory concentrations ranging from 7.0 to 20.3 µM with A549, PC-3, and HepG2 human cancer cell lines. Compound I₂₀ also disrupted cancer A549 cell migration in a concentration-dependent manner. Immunofluorescence microscopy, transmission electron microscopy, and tubulin polymerisation assays suggested that compound I₂₀ promoted protofilament assembly. In support of this possibility, computational docking studies revealed a strong interaction between compound I₂₀ and tubulin Arg β369, which is also the binding site for the anticancer drug Taxol. Our results suggest that (Z)-2-(5-benzylidene-4-oxo-2-thioxothiazolidin-3-yl)-N-phenylacetamide derivatives could have utility for the development of microtubule-stabilising therapeutic agents.

Design, Synthesis, Antibacterial Activity, and Mechanisms of Novel 1,3,4-Thiadiazole Derivatives Containing an Amide Moiety

To discover novel antibacterial agents, a series of novel 1,3,4-thiadiazole derivatives containing an amide moiety were designed and synthesized, and their antibacterial activities were tested. Compound 30 was designed and synthesized according to the CoMFA model. Compound 30 exhibited higher antibacterial activities against Xanthomonas oryzae pv. oryzicola and Xanthomonas oryzae pv. oryzae, with EC₅₀ values of 2.1 and 1.8 mg/L, respectively, which were superior to those of thiodiazole copper (99.6 and 92.5 mg/L). The protective and curative activities of compound 30 against rice bacterial leaf blight were 51.3 and 46.1%, respectively, which were better than those of thiodiazole copper (37.8 and 38.5%). The protective and curative activities of compound 30 against rice bacterial leaf streak were 45.9 and 40.5%, respectively, which were better than those of thiodiazole copper (36.2 and 31.1%). In addition, the protective activity of compound 30 against rice bacterial leaf streak was related to increased activities of related defense enzymes and upregulated the differentially expressed proteins of the glycolysis/gluconeogenesis pathway.

Novel FtsZ inhibitor with potent activity against Staphylococcus aureus

OBJECTIVES

FtsZ is an essential bacterial protein and an unexplored target for the development of antibacterial drugs. The development of a novel inhibitor targeting FtsZ offers a potential opportunity to combat drug resistance. DS01750413, a new derivative of PC190723, is a novel FtsZ inhibitor with improved in vitro and in vivo activity. The objective of this study was to investigate the efficacy of DS01750413 against Staphylococcus spp., including MRSA, in in vitro and in vivo models.

METHODS

In vitro activities of DS01750413 and standard-of-care antibiotics were evaluated against clinical isolates of Gram-positive pathogens. The in vivo efficacy was evaluated in a murine systemic infection model caused by MRSA.

RESULTS

DS01750413 showed potent in vitro activity against MRSA clinical isolates with MIC ranges of 0.5-1 mg/L and also demonstrated concentration-dependent bactericidal killing. In the murine bacteraemia infection model of MRSA, treatment with DS01750413 resulted in prolonged survival of animals compared with placebo-treated animals and exhibited a significant reduction in the bacterial load in liver, spleen, lungs and kidneys.

CONCLUSIONS

DS01750413 showed encouraging in vitro and in vivo activity against MRSA. As a novel chemical class, DS01750413 has the potential to become clinically viable antibiotics to address the drug resistance problem by its unique novel targeting mechanism of action.

Dysregulation of ClpP by Small-Molecule Activators Used Against Xanthomonas oryzae pv. oryzae Infections

Rice bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is considered a destructive plant bacterial disease. The looming crisis of antibiotic resistance necessitates the discovery of antibiotics with new modes of action. Activated caseinolytic protease P (ClpP) can degrade bacterial FtsZ proteins that are essential for cell division; thus, we hypothesized that small-molecule-induced dysregulation of XooClpP may result in degradation of XooFtsZ to treat leaf blight diseases. In this work, we have determined the crystal structures of XooClpP, and its mutant bound with ADEP4, which revealed the action modes of XooClpP assemblies and XooFtsZ degradation by dysregulated XooClpP in the presence of small-molecule activators, such as ONC212 and ADEP4. Additionally, an antibacterial assessment demonstrated that ONC212 displays excellent activity against Xoo and prevents rice bacterial leaf blight in vivo. Thus, these unique antibacterial effects of small-molecule activators of XooClpP represent a potential strategy for the development of agricultural antibiotics by targeting bacterial ClpP.

Synthesis, Antibacterial Activity, and Mechanisms of Novel 6-Sulfonyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole Derivatives

A series of novel 6-sulfonyl-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole derivatives were designed and synthesized. CoMFA models were established to analyze the quantitative structure-activity relationships on the basis of the EC₅₀ values of the compounds. The models were used to design and synthesize compounds 32 and 33 with higher activities. The EC₅₀ values of compound 33 against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) were 0.59 and 1.63 mg/L, respectively, which were higher than those of thiodiazole copper (90.43 and 97.93 mg/L) and bismerthiazol (68.37 and 75.59 mg/L). Moreover, protective activities of compound 33 against bacterial leaf streak (BLS) and bacterial leaf blight (BLB) were 49.65% and 49.42%, respectively, which were superior to those of thiodiazole copper (44.28% and 41.51%) and bismerthiazol (38.89% and 40.09%). Protective activity of compound 33 against BLS was closely related to the improvement of defense-related enzyme activities, chlorophyll content, and photosynthesis activation. This is consistent with the upregulated expression of defense responses and photosynthesis-related proteins.

Transcriptome Analysis on the Mechanism of Ethylicin Inhibiting Pseudomonas syringae pv. actinidiae on Kiwifruit

Bacterial canker disease caused by Pseudomonas syringae pv. actinidiae (Psa) is a devastating disease of kiwifruit, which is severely limiting the development of the kiwifruit industry. Ethylicin is a broad-spectrum plant biomimetic fungicide. However, its application in the control of kiwifruit bacterial canker is rarely reported, and the mechanism of ethylicin on Psa remains unknown. In this study, we investigated the effect of ethylicin on Psa in vitro and in vivo and found that ethylicin can inhibit the growth of Psa and prevent the cankering in the plant stem. Mechanism investigation indicated that ethylicin acted by limiting the movement of Psa, destroying the cell membrane of Psa, and inhibiting the formation of Psa biofilm. In addition, it was also found through transcriptomics research that ethylicin can up-regulate the expression of genes related to protein export and biofilm formation-Pseudomonas aeruginosa and down-regulate the expression of genes related to flagellar assembly in Psa. This study concluded that ethylicin can effectively inhibit Psa growth, and it could help to gain a better understanding of the mechanisms of ethylicin inhibiting Psa and provide practical data for the application of ethylicin as a highly potent agent for controlling the bacterial canker disease of kiwifruit.