Design, synthesis and evaluation of quinazoline derivatives as Gαq/11 proteins inhibitors against uveal melanoma.

Uveal melanoma (UM) represents the predominant ocular malignancy among adults, exhibiting high malignancy and proclivity for liver metastasis. GNAQ and GNA11 encoding Gαq and Gα11 proteins are key genes to drive UM, making the selective inhibition of Gαq/11 proteins to be a potential therapeutic approach for combating UM. In this study, forty-six quinazoline derivatives were designed, synthesized, and assessed for their ability to inhibit Gαq/11 proteins and UM cells. Compound F33 emerged as the most favorable candidate, and displayed moderate inhibitory activity against Gαq/11 proteins (IC50 = 9.4 µM) and two UM cell lines MP41 (IC50 = 6.7 µM) and 92.1 (IC50 = 3.7 µM). Being a small molecule inhibitor of Gαq/11 proteins, F33 could effectively suppress the activation of downstream signaling pathways in a dose-dependent manner, and significantly inhibits UM in vitro.F33 represents a promising lead compound for developing therapeutics for UM by targeting Gαq/11 proteins.

Antimicrobial mechanisms of g-C3 N4 @ZnO against oomycetes Phytophthora capsici: from its metabolism, membrane structures and growth.

BACKGROUND: Phytophthora capsici, a refractory and model oomycete plant pathogen, especially threatens multiple vegetable crops. A limited number of chemical pesticides play a vital role in controlling oomycete plant diseases. However, this approach often leads to excessive use of chemical agent, exacerbates environmental issues and more and more drug-resistant strains of oomycete. Therefore, it is imperative to devise innovative solutions that can effectively address the infection of oomycete while maintaining high levels of environmental sustainability and low toxicity. RESULTS: In this study, g-C3 N4 @ZnO heterostructure was synthesized and characterized. The g-C3 N4 @ZnO showed higher toxicity on Phytophthora capsici than graphitic carbon nitride (g-C3 N4 ) nanosheets and zinc oxide (ZnO) nanoparticles in vitro and in vivo. Except the hyphal growth of Phytophthora capsici, their germination rate of spores, sporangium formation and number of spores were all suppressed by g-C3 N4 @ZnO heterostructure. Furthermore, we found that this g-C3 N4 @ZnO heterostructure has higher photocatalytic activity under visible light, which potentially enhanced the reactive oxygen species (ROS) mediated stress on Phytophthora capsici. Ultrastructural morphology, global changes of gene expression and weighted gene co-expression network analysis all supported that the anti-oomycete activity of g-C3 N4 @ZnO was manifested in the destruction of membrane system and inhibition of multiple metabolisms of Phytophthora capsici under visible irradiation, which also could be attributed to the ROS and zinc ion (Zn2+ ) mediated stress. CONCLUSION: This works offers a novel oomycete disease management strategy by using g-C3 N4 @ZnO, which were attributed to the ROS stress, destruction of membrane system and inhibition of multiple metabolisms. © 2023 Society of Chemical Industry.

Discovery of novel indazole derivatives as SOS1 agonists that activate KRAS signaling.

KRAS serves as a vital regulator for cellular signaling and drives tumor pathogenesis after mutation. Despite extensive research efforts spanning several decades, targeting KRAS is still challenging due to the multiple KRAS mutations and the emergence of drug resistance. Interfering the interactions between KRAS and SOS1 is one of the promising approaches for modulating KRAS functions. Herein, we discovered small-molecule SOS1 agonists with novel indazole scaffold. Through structure-based optimization, compound 11 was identified with high SOS1 activation potency (p-ERK EC50 = 1.53 µM). In HeLa cells, compound 11 enhances cellular RAS-GTP levels and exhibits biphasic modulation of ERK1/2 phosphorylation through an on-target mechanism and presents the therapeutic potential to modulate RAS signaling by activating SOS1.

Composite g-C3 N4 @ZnO NP electrostatic self-assembly: enhanced ROS as a key factor for high-efficiency control of tobacco wildfire disease.

BACKGROUND: The utilization of non-metallic inorganic nanomaterials for antimicrobial photocatalytic technology has emerged as a promising approach to combat drug-resistant bacteria. Recently, g-C3 N4 nanosheets have attracted significant attention due to their exceptional stability, degradability, low cost, and remarkable antibacterial properties. In this study, a facile electrostatic self-assembly approach was utilized to functionalize ZnO nanoparticles with g-C3 N4 nanosheets, resulting in the formation of g-C3 N4 @ZnO nanoparticle composites. RESULTS: The Z-shaped heterojunction architecture of these composites facilitates efficient separation of photogenerated electron-hole pairs and enhances visible light catalytic performance. Moreover, the formation of the g-C3 N4 @ZnO heterostructure showed a higher photocatalytic capacity and the generation of reactive oxygen species (ROS) than g-C3 N4 nanosheets. The photocatalytic antibacterial mechanisms of g-C3 N4 @ZnO at the transcriptomic level primarily involve disrupting bacterial membrane synthesis and inhibiting motility and energy metabolism. Therefore, the antibacterial mechanism of g-C3 N4 @ZnO can be attributed to a combination of physical membrane damage, chemical damage (ROS enhancement) and inhibition of chemotaxis, biofilm formation and flagellar motility. CONCLUSION: These findings collectively provide novel high potential and insights into the practical application of photocatalysts in plant disease management. © 2023 Society of Chemical Industry.

Antimicrobial mechanisms of ZnO nanoparticles to phytopathogen Pseudomonas syringae: Damage of cell envelope, suppression of metabolism, biofilm and motility, and stimulation of stomatal immunity on host plant.

Nanoparticles have recently been employed as a new strategy to act as bactericides in agricultural applications. However, the effects and mechanisms of foliar deposition of nanoparticles on bacterial pathogens, plant physiology and particularly plant immunity have not been sufficiently understood. Here, we investigated the effects and mechanisms of ZnO NPs in controlling of tobacco wildfire caused by Pseudomonas syringae pv. tabaci, through the comprehensive analysis of biological changes of both bacteria and plants. The global gene expression changes of Pseudomonas syringae pv. tabaci supported that the functions of "protein secretion", "membrane part", "signal transducer activity", "locomotion", "chemotaxis" and "taxis" in bacteria, as well as the metabolic pathways of "bacterial chemotaxis", "two-component system", "biofilm formation", "ABC transporters" and "valine, leucine and isoleucine degradation" were significantly down-regulated by ZnO NPs. Correspondingly, we reconfirmed that the cell envelope structure, biofilm and motility of Pseudomonas syringae pv. tabaci were directly disrupted or suppressed by ZnO NPs. Different from completely killing Pseudomonas syringae pv. tabaci, ZnO NPs (0.5 mg/mL) potentially improved plant growth and immunity through enzymatic activity and global molecular response analysis. Furthermore, the changes of gene expression in ABA signaling pathway, ABA concentration and stomatal aperture all supported that ZnO NPs can specifically stimulate stomatal immunity, which is important to defend bacterial infection. Taken together, we proposed that both the inhibition or damage of motility, biofilm, metabolisms, virulence and cell envelope on P. syringae pv. tabaci, and the activation of the stomatal immunity formed two-layered antibacterial mechanisms of ZnO NPs on phytopathogenic bacteria.

Additive effect of the Streptomyces albus XJC2-1 and dimethomorph control pepper blight (Capsicum annuum L.).

BACKGROUND: Pepper blight, caused by Phytophthora capsici, is a destructive soilborne disease, which poses a serious threat to pepper, Capsicum annuum L., production. Chemical fungicides, which mainly are used to control pepper blight, have a negative effect on the environment, rendering biological control as a promising alternative to maintain the balance between ecology and pest management. The purpose of this study was to screen the biocontrol bacteria, reduce the dosage of fungicides and increase the stability of biocontrol bacteria, and to find the mixing ratio of biocontrol bacteria and fungicides giving the best control effect. RESULTS: We isolated actinomycetes strains from the soil surrounding the roots of healthy pepper plants amongst field-grown plants infected with P. capsici. Of these, Streptomyces albus XJC2-1 showed a strong inhibition effect on the growth of P. capsici, with an inhibition rate of ≤85%. XJC2-1 effectively inhibited the formation of sporangium and release of zoospores of P. capsici as well as directly destroyed its hyphae, to achieve the inhibitory effect. Transcriptomic profiling of pepper leaves, postirrigation of plants with the XJC2-1 fermentation broth, revealed upregulation of genes related to the photosynthesis pathway in pepper. Furthermore, XJC2-1 treatment improved the net photosynthetic rate and intercellular CO2 concentration, thereby improving the pepper plant's resistance to pathogens. The combination of XJC2-1 with the fungicide dimethomorph (8 µg mL-1 ) displayed strong synergism in inhibition of P. capsici infection, with a control efficiency as high as 75.16%, thus providing a basis for its application in the field. CONCLUSION: Our study demonstrated that S. albus XJC2-1 inhibited Phytophthora pathogens from infecting pepper plants and enhanced plant host resistance. The combination of XJC2-1 and dimethomorph displayed a more stable and stronger control effect on pepper blight, showing potential for the future application of XJC2-1 in the field of biological control. © 2023 Society of Chemical Industry.

Fabrication of an alginate-based ZhiNengCong gel showed an enhanced antiviral and plant growth promoting functions.

Tobacco mosaic disease is a worldwide viral disease that can cause huge economic losses. Plant immune inducers have become the main force in the prevention and treatment of viral disease own to their high efficiency and rapid effect. However, since tobacco mosaic disease can occur at any point in the plant growth cycle, a single application period cannot guarantee the completely management. In this study, an extract from Paecilomyces variotii named ZhiNengCong (ZNC), which can fight against tobacco mosaic disease with 65% control effect, and improve the promotion of tobacco stem girth, was selected from five commercial antiviral medicines, and a sustained release sodium alginate (Alg)-based ZNC (ZNC@Alg) was prepared by physical absorption. ZNC@Alg, who contains only 5 mg/mL ZNC, can release ZNC for 7 consecutive days, and displayed an enhanced effect in inducing the PAL-mediated salicylic acid signaling pathway activation to participate in the inhibition of green fluorescent protein (GFP)-tagged tobacco mosaic virus (TMV-GFP) infection, even after 7 days of the application. Notably, field experiments showed that the control effect of ZNC@Alg was up to 88%, which was significantly better than that of ZNC with the same concentration (10 µg per plant). In addition, ZNC@Alg exhibited a stronger growth-promoting effect than ZNC, which significantly increased the wet weight of tobacco. Taken together, we screened out a plant immune inducer ZNC that can effectively inhibit tobacco virus disease, and created ZNC@Alg with higher control effect and growth promotion effect, laying a foundation for effective field management of tobacco mosaic disease.

Fabrication of polydopamine reduced CuO nanoparticle-alginate composite nanogels for management of Pseudomonas synringae pv. tabaci in tobacco.

BACKGROUND: The wildfire disease on tobacco can seriously hinder plants. Meanwhile, its pathogen, Pseudomonas syringae, can also infect over 200 plants and threat agriculture production. However, the disease usually occurs after summer rains which washes away most copper (Cu)-based bactericides, allowing the disease to invade. Therefore, we fabricate a new nanogel with high disease control and anti-erosion ability and study the effects of the reductant on the performance of the copper oxide nanoparticle (CuONP) composite nanogel. RESULTS: Polydopamine (PDA) is a polycation for both in situ reduction of CuONP in alginate nanogels and for adjusting the copper ion (Cu2+ ) releasing rate in this work. The composite nanogel fabricated by PDA (PDA-CuONP@ALGNP@CTAC) had a higher Cu2+ releasing rate, damaging the pathogen membrane more efficiently, allowing for better disease control and plant growth promotion when compared to sodium borohydride (SBH)-fabricated nanogel (SBH-CuONP@ALGNP@CTAC) or the commercial bactericide, thiodiazole copper. The PDA-CuONP@ALGNP@CTAC had a high anti-erosion ability and could remain adhered to the leaf surface even after five rain event simulations. CONCLUSION: The addition of polycations (like PDA) into CuONP composite nanogel could increase the Cu2+ releasing rate, resulting in improved disease management when compared to SBH-CuONP@ALGNP@CTAC or thiodiazole copper. The PDA containing gel had an improved anti-erosion ability and water resistance. This new composite nanogel has a high potential for wildfire disease control, improving agricultural production. © 2022 Society of Chemical Industry.

Identification of novel Pyrrolo[2,3-d]Pyrimidine-based KRAS G12C inhibitors with anticancer effects.

Oncogene KRAS plays predominant roles in human cancers by regulating cell proliferation, differentiation, and migration. Recent progress revealed that directly target KRAS G12C with allosteric inhibitors that covalently bind to the switch Ⅱ pocket is feasible. Herein, series of pyrrolo[2,3-d]pyrimidine derivatives were designed and synthesized through systematic structural optimization, leading to the discovery of compound 2-((S)-1-acryloyl-4-(2-(((2R,7aS)-2-fluorohexahydro-1H-pyrrolizin-7a(5H)-yl)methoxy)-7-methyl-6-(8-methylnaphthalen-1-yl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperazin-2-yl)acetonitrile (50) with high KRAS/SOS1 inhibitory potency (IC50 = 0.21 µM) and strong anti-proliferation activities on cancer cells harboring KRAS p.G12C. Compound 50 also exhibited satisfactory selectivity, moderate pharmacokinetic characters, and good anticancer effects in vivo. Meaningfully, the identification of these compounds highlights the necessity of an appropriate conformational constraint for acquiring the applicable binding pose in the cryptic pocket of KRAS, and the results support efforts toward design of KRAS inhibitors with novel skeleton and binding mechanism could be beneficial for targeting the acquired drug resistance.

Polymorphic Microsatellite Development, Genetic Diversity, Population Differentiation and Sexual State of Phytophthora capsici on Commercial Peppers in Three Provinces of Southwest China.

Pepper blight, caused by the oomycete pathogen Phytophthora capsici (P. capsici), is one of the most destructive soilborne diseases worldwide. Between 2019 and 2020, 235 single spore isolates of P. capsici were collected from 36 commercial pepper planting areas in Sichuan, Chongqing, and Guizhou provinces in China. A novel full set of 323 high-quality polymorphic microsatellites was obtained by resequencing 10 isolates. In total, 163 isolates with two alleles per microsatellite locus were used for population analysis and resulted in 156 genotypes on 10 microsatellite loci. The genetic diversity, population differentiation, principal component, genetic structure, and genetic relationships analyses showed an extensive variety of the P. capsici in Sichuan and Guizhou with clonal lineages, two shared genotypes, and no geographic differentiation. The population from Chongqing was differentiated from that of Sichuan and Guizhou and had the highest genetic diversity. There was no significant distinction between the populations of the two sampling years, but there was a small differentiation between the populations from bell peppers and hot peppers. The isolates from Southwest China were largely distant from the two reference isolates from the USA. The analysis of molecular variance showed that the major variance of the populations was within populations. The linkage equilibrium test, mating type composition, and oospore detection indicated that only P. capsici from the Jiulongpo district of Chongqing had appeared in sexual recombination. Overall, this study revealed that the high and complex genetic diversity population of P. capsici in Sichuan, Chongqing, and Guizhou with uneven geographic variation and limited sexual reproductive behavior in Chongqing, potentially driven by differences in the geographical environment, reproductive patterns, different cultivars, and artificial long-distance transfers. IMPORTANCE Phytophthora capsici, a notorious soilborne and rapidly evolving pathogen with a wide range of hosts, is a huge threat to pepper production worldwide. However, the detailed genetic structure and dynamics of P. capsici in most Chinese provinces are still unclear, even though China is the world's largest producer and consumer of peppers. Here, a novel full set of high-quality polymorphic microsatellites, obtained by genome resequencing data of 10 isolates from Southwest China, was provided for future population analyses. In this study, we further investigated and established the genetic structure, sexual recombination, geographic subdivisions, interannual stability, differentiation in different types of host peppers, and member relationships of P. capsici from three provinces in Southwest China. These results reveal the genetic structure and dynamics of P. capsici in three provinces of Southwest China and help us to execute more effective management strategies in the future.

Toxicity Effects and Mechanisms of MgO Nanoparticles on the Oomycete Pathogen Phytophthora infestans and Its Host Solanum tuberosum.

Engineered nanoparticles have recently been used for innovation in agricultural disease management. However, both the toxicity effects and mechanisms of nanoparticles in target pathogens and their host plants are still largely unknown. Here, we found that magnesium oxide nanoparticles (MgO NPs) could protect potatoes against Phytophthora infestans (P. infestans) at a low dosage (50 µg/mL). Through scanning electron microscopy observation, antioxidant enzymes activity measurement, and gene transcriptome analysis, we found that the cell surfaces of P. infestans were destroyed, endogenous superoxide dismutase continuously remained in a higher active state, oxidoreductase activity-related gene ontology (GO) terms were enriched with upregulation, and transporter-activity related GO terms and six essential metabolism-related pathways were enriched with downregulation in P. infestans after 30 min MgO NPs treatment, whereas only 89 genes were changed without enriched GO and pathways terms, and no change in antioxidant activities and phenylalnine ammonialyase in potato appeared at 6 h post-MgO NPs treatment. Only the "plant hormone signal transduction pathway" was enriched with upregulation under differential expression analysis in potatoes. In conclusion, cell surface distortion, continuous oxidative stress, and inhibitions of membrane transport activity and metabolic pathways were toxic mechanisms of Mg ONPs in P. infestans, and the "plant hormone signal transduction pathway" was potentially regulated by Mg-ONPs without obviously harmful effects on potato after Mg ONPs exposure.

Tobacco mosaic virus hijacks its coat protein-interacting protein IP-L to inhibit NbCML30, a calmodulin-like protein, to enhance its infection.

Calcium is an important plant immune signal that is essential for activating host resistance, but how RNA viruses manipulate calcium signals to promote their infections remains largely unknown. Here, we demonstrated that tobacco mosaic virus (TMV) coat protein (CP)-interacting protein L (IP-L) associates with calmodulin-like protein 30 (NbCML30) in the cytoplasm and nucleus, and can suppress its expression at the nucleic acid and protein levels. NbCML30, which lacks the EF-hand conserved domain and cannot bind to Ca2+ , was located in the cytoplasm and nucleus and was downregulated by TMV infection. NbCML30 silencing promoted TMV infection, while its overexpression inhibited TMV infection by activating Ca2+ -dependent oxidative stress in plants. NbCML30-mediated resistance to TMV mainly depends on IP-L regulation as the facilitation of TMV infection by silencing NbCML30 was canceled by co-silencing NbCML30 and IP-L. Overall, these findings indicate that in the absence of any reported silencing suppressor activity, TMV CP manipulates IP-L to inhibit NbCML30, influencing its Ca2+ -dependent role in the oxidative stress response. These results lay a theoretical foundation that will enable us to engineer tobacco (Nicotiana spp.) with improved TMV resistance in the future.

Synthesis and evaluation of imidazo[1,2-a]pyrazine derivatives as small molecule Gαq/11 inhibitors against uveal melanoma.

Uveal melanoma (UM) is an aggressive malignancy with high mortality in adults and lacks effective systemic therapies. Activating gene mutations related to the Gαq/11 signaling pathway are prevalent in UM, and Gαq/11 inhibitors have shown anti-UM activity in vitro and in vivo. In this study, we designed and synthesized a series of imidazo[1,2-a]pyrazine derivatives as Gαq/11 inhibitors, and discovered GQ352 with the selective antiproliferative activity against UM cells. Importantly, GQ352 directly binds to the Gαq and inhibits the dissociation of Gαßγ heterotrimers with the IC50 value of 8.9 µM. GQ352 inhibits UM tumorigenesis by suppressing Gαq/11 downstream ERK phosphorylation and YAP dephosphorylation, as shown in Western blot analysis. In addition, GQ352 displayed reasonable physiochemical properties and human liver microsome stability, indicating the potential application in UM treatment.

Fabrication of copper nanoparticle composite nanogel for high-efficiency management of Pseudomonas syringae pv. tabaci on tobacco.

BACKGROUND: Copper nanoparticles (CuNPs) can release copper ions (Cu2+ ) to control bacterial diseases on crops. However, the high concentration of the CuNPs applied in disease controlling can highly limit their application. In this work, by in situ reducing CuNPs in alginate nanogels and coated with cetyl trimethyl ammonium chloride (CTAC), a CuNP composite nanogel was fabricated as a new nanopesticide with low copper content. RESULTS: Data showed that the CTAC coating would affect the antibacterial activity and leaf surface adhesion of the nanogel, while CuNP content could also influence the membrane damage ability of the gel. The nanogel could depress the growth of bacteria by rupturing its membrane and show a minimum inhibitory concentration (MIC) as low as 500 µg mL-1 , which only contain 58 µg mL-1 CuNP, and achieve a 64% of therapeutic efficiency (with 1000 µg mL-1 nanogel) in in vivo experiments, higher than that of commercial bactericide thiodiazole copper. Furthermore, the application of the nanogel can also perform a growth-promoting effect on the plant, which may be due to the supplement of copper element provided by CuNP. CONCLUSION: The CuNP composite nanogel fabricated in this work performed high leaf disease controllability and safety compared to the commercial bactericide thiodiazole copper. We hope this nanogel can provide a potential high-efficiency nano-bactericide that can be used in the leaf bacterial disease control.

Nicotiana benthamiana asparagine synthetase associates with IP-L and confers resistance against tobacco mosaic virus via the asparagine-induced salicylic acid signalling pathway.

Asparagine synthetase is a key enzyme that catalyses the conversion of amide groups from glutamine or ammonium to aspartate, which leads to the generation of asparagine. However, the role of asparagine synthetase in plant immunity remains largely unknown. Here, we identified a Nicotiana benthamiana asparagine synthetase B (NbAS-B) that associates with tomato mosaic virus coat protein-interacting protein L (IP-L) using the yeast two-hybrid assay and examined its role in tobacco mosaic virus (TMV) resistance. The association of IP-L with NbAS-B was further confirmed by in vivo co-immunoprecipitation, luciferase complementation imaging, and bimolecular fluorescence complementation assays. IP-L and NbAS-B interact in the nucleus and cytosol and IP-L apparently stabilizes NbAS-B, thus enhancing its accumulation. The expressions of IP-L and NbAS-B are continuously induced on TMV-green fluorescent protein (GFP) infection. Co-silencing of IP-L and NbAS-B facilitates TMV-GFP infection. Overexpression of NbAS-B in tobacco reduces TMV-GFP infection by significantly improving the synthesis of asparagine. Furthermore, the external application of asparagine significantly inhibits the infection of TMV-GFP by activating the salicylic acid signalling pathway. These findings hold the potential for the future application of asparagine in the control of TMV.

Targeting mutated GTPase KRAS in tumor therapies.

Kirsten rat sarcoma virus oncogene (KRAS) mutation accounts for approximately 85% of RAS-driven cancers, and participates in multiple signaling pathways and mediates cell proliferation, differentiation and metabolism. KRAS has been considered as an "undruggable" target due to the lack of effective direct inhibitors, although high frequency of KRAS mutations have been identified in multiple carcinomas in the past decades. Encouragingly, the KRASG12C inhibitor AMG510 (sotorasib), which has been approved for treating NSCLC and CRC recently, makes directly targeting KRAS the most promising strategy for cancer therapy. To better understand the current state of KRAS inhibitors, this review summarizes the biological functions of KRAS, the structure-activity relationship studies of the small-molecule inhibitors that directly target KRAS, and highlights the therapeutic agents with improved selectivity, bioavailability and physicochemical properties. Furthermore, the combined medication that can enhance efficacy and overcome drug resistance of KRAS covalent inhibitors is also reviewed.

Antimicrobial mechanisms of g-C3N4 nanosheets against the oomycetes Phytophthora capsici: Disrupting metabolism and membrane structures and inhibiting vegetative and reproductive growth.

To understand the potential of urea-synthesized g-C3N4 nanosheets (0.125-1 mg/mL) as antimicrobial agents against oomycetes, an investigation of the interaction mechanism between g-C3N4 nanosheets and Phytophthora capsici was conducted. Transcription analysis showed that after being exposed to g-C3N4 nanosheets for 1 h, P. capsici triggered a sharp upregulation of antioxidant activities and structural constituents and a downregulation of metabolic pathways, including ATP generation, autophagy disruption, membrane system disorders and other complex adaptive processes. All the life stages of P. capsici, including mycelial growth, sporangium formation, zoospore numbers and zoospore germination were remarkably inhibited and even injured. A mutual mechanism is proposed in this work: ROS stress upon exposure to visible irradiation and, combined with their sharp nanosheet structure, cause perturbations of the cell membrane and induce damage to the ultrastructure of mycelial growth, sporangium and zoospores. Given that the antimicrobial action of g-C3N4 nanosheets were derived from the damage throughout the duration of treatment and was not limited to a single target, these complex mechanisms could favor the avoidance of drug resistance and benefit other oomycetes management. More importantly, in addition to restraining P. capsici infection in host plants, g-C3N4 nanosheets promoted pepper plant growth. Hence, g-C3N4 nanosheets have potential as a new non-metal antimicrobial agent to control oomycotal disease in crops.

The photocatalytic antibacterial molecular mechanisms towards Pseudomonas syringae pv. tabaci by g-C3 N4 nanosheets: insights from the cytomembrane, biofilm and motility disruption.

BACKGROUND: Antibacterial photocatalytic therapy has been employed as a promising strategy to combat antibiotic-resistant bacteria in the water disinfection field, especially some non-metal inorganic nanomaterials. However, their antibacterial activities on plant phytopathogens are poorly understood. Here, the photocatalytic antibacterial mechanism of the urea-synthesized graphitic carbon nitride nanosheets (g-C3 N4 nanosheets) against Pseudomonas syringae pv. tabaci was systematically investigated in vitro and in vivo. RESULTS: The g-C3 N4 nanosheets exhibited remarkable concentration-dependent and irradiation-time-dependent antibacterial properties, and the 0.5 mg mL-1 concentration ameliorated tobacco wildfire disease in host plants. Specifically, under visible irradiation, g-C3 N4 nanosheets produced numerous reactive oxygen species (ROS), supplementing the plentiful extracellular and intracellular ROS in bacteria. After exposing light-induced g-C3 N4 nanosheets for 1 h, 500 genes were differentially expressed, according to transcriptome analyses. Notably, the expression of genes related 'antioxidant activity' and 'membrane transport' was sharply upregulated, and those related to 'bacterial chemotaxis', 'biofilm formation', 'energy metabolism' and 'cell motility' were downregulated. After exposure for over 2 h, the longer-time pressure on the target bacteria cause the decreased biofilm formation and flagellum motility, further injuring the cell membranes leading to cytoplasm leakage and damaged DNA, eventually resulting in the bacterial death. Concomitantly, the attachment of g-C3 N4 nanosheets was a synergistic physical antibacterial pathway. The infection capacity assessment also supported the earlier supposition. CONCLUSION: These results provide novel insights into the photocatalytic antibacterial mechanisms of g-C3 N4 nanosheets at the transcriptome level, which are expected to be useful for dissecting the response pathways in antibacterial activities and for improving g-C3 N4 -based photocatalysts practices in plant disease control. © 2021 Society of Chemical Industry.

Cytidine-to-Uridine RNA Editing Factor NbMORF8 Negatively Regulates Plant Immunity to Phytophthora Pathogens.

Mitochondria and chloroplasts play key roles in plant-pathogen interactions. Cytidine-to-uridine (C-to-U) RNA editing is a critical posttranscriptional modification in mitochondria and chloroplasts that is specific to flowering plants. Multiple organellar RNA-editing factors (MORFs) form a protein family that participates in C-to-U RNA editing, but little is known regarding their immune functions. Here, we report the identification of NbMORF8, a negative regulator of plant immunity to Phytophthora pathogens. Using virus-induced gene silencing and transient expression in Nicotiana benthamiana, we show that NbMORF8 functions through the regulation of reactive oxygen species production, salicylic acid signaling, and accumulation of multiple Arg-X-Leu-Arg effectors of Phytophthora pathogens. NbMORF8 is localized to mitochondria and chloroplasts, and its immune function requires mitochondrial targeting. The conserved MORF box domain is not required for its immune function. Furthermore, we show that the preferentially mitochondrion-localized NbMORF proteins negatively regulate plant resistance against Phytophthora, whereas the preferentially chloroplast-localized ones are positive immune regulators. Our study reveals that the C-to-U RNA-editing factor NbMORF8 negatively regulates plant immunity to the oomycete pathogen Phytophthora and that mitochondrion- and chloroplast-localized NbMORF family members exert opposing effects on immune regulation.

Genome-wide analysis of NDR1/HIN1-like genes in pepper (Capsicum annuum L.) and functional characterization of CaNHL4 under biotic and abiotic stresses.

Plant NDR1/HIN1-like (NHL) genes play an important role in triggering plant defenses in response to biotic stresses. In this study, we performed a genome-wide identification of the NHL genes in pepper (Capsicum annuum L.) and characterized the functional roles of these CaNHL genes in response to abiotic stresses and infection by different pathogens. Phylogenetic analysis revealed that CaNHLs can be classified into five distinct subgroups, with each group containing generic and specific motifs. Regulatory element analysis showed that the majority of the promoter regions of the identified CaNHLs contain jasmonic acid (JA)-responsive and salicylic acid (SA)-responsive elements, and transcriptomic analysis revealed that CaNHL genes are expressed in all the examined tissues of pepper. The CaNHL1, CaNHL4, CaNHL6, CaNHL10, CaNHL11, and CaNHL12 genes were significantly upregulated under abiotic stress as well as in response to different pathogens, such as TMV, Phytophthora capsici and Pseudomonas syringae. In addition, we found that CaNHL4 localizes to the plasma membrane. CaNHL4-silenced pepper plants display significantly increased susceptibility to TMV, Phytophthora capsici and Pseudomonas syringae, exhibiting reduced expression of JA-related and SA-related genes and reduced ROS production. However, transient overexpression of CaNHL4 in pepper increases the expression of JA-related and SA-related genes, enhances the accumulation of ROS, and inhibits the infection of these three pathogens. Collectively, for the first time, we identified the NHL genes in pepper and demonstrated that CaNHL4 is involved in the production of ROS and that it also regulates the expression of JA-related and SA-related genes in response to different pathogens, suggesting that members of the CaNHL family play an essential role in the disease resistance of pepper.