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Soilborne Ralstonia solanacearum species complex (RSSC) pathogens disrupt microbial communities as they invade roots and fatally wilt plants. RSSC pathogens secrete antimicrobial toxins using a type VI secretion system (T6SS). To investigate how evolution and ecology have shaped the T6SS of these bacterial pathogens, we analyzed the T6SS gene content and architecture across the RSSC and their evolutionary relatives. Our analysis reveals that two ecologically similar Burkholderiaceae taxa, xylem-pathogenic RSSC and Paracidovorax, have convergently evolved to wield large arsenals of T6SS toxins. To understand the mechanisms underlying genomic enrichment of T6SS toxins, we compiled an atlas of 1,066 auxiliary T6SS toxin clusters (aux clusters) across 99 high-quality RSSC genomes. We classified 25 types of aux clusters with toxins that predominantly target lipids, nucleic acids, or unknown cellular substrates. The aux clusters were located in diverse genetic neighborhoods and had complex phylogenetic distributions, suggesting frequent horizontal gene flow. Phages and other mobile genetic elements account for most of the aux cluster acquisition on the chromosome but very little on the megaplasmid. Nevertheless, RSSC genomes were more enriched in aux clusters on the megaplasmid. Although the single, ancestral T6SS was broadly conserved in the RSSC, the T6SS has been convergently lost in atypical, non-soilborne lineages. Overall, our data suggest dynamic interplay between the lifestyle of RSSC lineages and the evolution of T6SSes with robust arsenals of toxins. This pangenomic atlas poises the RSSC as an emerging, tractable model to understand the role of the T6SS in shaping pathogen populations.IMPORTANCEWe explored the eco-evolutionary dynamics that shape the inter-microbial warfare mechanisms of a globally significant plant pathogen, the Ralstonia solanacearum species complex. We discovered that most Ralstonia wilt pathogens have evolved extensive and diverse repertoires of type VI secretion system-associated antimicrobial toxins. These expansive toxin arsenals potentially enhance the ability of Ralstonia pathogens to invade plant microbiomes, enabling them to rapidly colonize and kill their host plants. We devised a classification system to categorize the Ralstonia toxins. Interestingly, many of the toxin gene clusters are encoded on mobile genetic elements, including prophages, which may be mutualistic symbionts that enhance the inter-microbial competitiveness of Ralstonia wilt pathogens. Moreover, our findings suggest that the convergent loss of this multi-gene trait contributes to genome reduction in two vector-transmitted lineages of Ralstonia pathogens. Our findings demonstrate that the interplay between microbial ecology and pathogen lifestyle shapes the evolution of a genetically complex antimicrobial weapon.

Summary Legumes establish nitrogen‐fixing symbioses with rhizobia. On the contrary, they can be attacked concomitantly by pathogens, raising the question of potential trade‐offs between mutualism and immunity. In order to study such trade‐offs, we used a tripartite system involving the model legume Lotus japonicus, its rhizobial symbiont Mesorhizobium loti and the soilborne pathogen Ralstonia solanacearum. We investigated the impact of mutualism on plant defense and the reciprocal influence of plant defense on mutualism. We found that Lotus age‐related resistance against Ralstonia was improved by the interaction with rhizobia especially when nodulation is triggered. Conversely, age‐related resistance did not compromise nodule organogenesis or functioning under pathogen attack. Proteomic characterization indicates that this resistance is associated with distinct proteome modifications in roots and nodules. This resistance questions the concept of interference between efficient defense reactions and mutualistic interactions and is of great interest for agricultural purposes as it not only restricts pathogen colonization, but would also preserve nitrogen fixation and yield. [ABSTRACT FROM AUTHOR]

Background: Bacterial wilt (BW), caused by Ralstonia solanacearum (Ral), results in substantial yield losses in pepper crops. Developing resistant pepper varieties through breeding is the most effective strategy for managing BW. To achieve this, a thorough understanding of the genetic information connected with resistance traits is essential. Despite identifying three major QTLs for bacterial wilt resistance in pepper, Bw1 on chromosome 8, qRRs-10.1 on chromosome 10, and pBWR-1 on chromosome 1, the genetic information of related BW pepper varieties has not been sufficiently studied. Here, we resequenced two pepper inbred lines, C. annuum 'MC4' (resistant) and C. annuum 'Subicho' (susceptible), and analyzed genomic variations through SNPs and Indels to identify candidate genes for BW resistance. Results: An average of 139.5 Gb was generated among the two cultivars, with coverage ranging from 44.94X to 46.13X. A total of 8,815,889 SNPs was obtained between 'MC4' and 'Subicho'. Among them, 31,190 (0.35%) were non-synonymous SNPs (nsSNPs) corresponding to 10,926 genes, and these genes were assigned to 142 Gene Ontology (GO) terms across the two cultivars. We focused on three known BW QTL regions by identifying genes with sequence variants through gene set enrichment analysis and securing those belonging to high significant GO terms. Additionally, we found 310 NLR genes with nsSNP variants between 'MC4' (R) and 'Subicho' (S) within these regions. Also, we performed an Indel analysis on these genes. By integrating all this data, we identified eight candidate BW resistance genes, including two NLR genes with nsSNPs variations in qRRs-10.1 on chromosome 10. Conclusion: We identified genomic variations in the form of SNPs and Indels by re-sequencing two pepper cultivars with contrasting traits for bacterial wilt. Specifically, the four genes associated with pBWR-1 and Bw1 that exhibit both nsSNP and Indel variations simultaneously in 'Subicho', along with the two NLR genes linked to qRRs-10.1, which are known for their direct involvement in immune responses, are identified as most likely BW resistance genes. These variants in leading candidate genes associated with BW resistance can be used as important markers for breeding pepper varieties. [ABSTRACT FROM AUTHOR]

Bacterial wilt disease, caused by Ralstonia solanacearum poses a severe threat to ginger plants. The present study aimed to determine the effect of Bacillus strains to combat R. solanacearum-induced bacterial wilt in ginger by inducing defense enzymes viz., peroxidase(POX), Polyphenol oxidase (PPO), Phenylalanine ammonia-lyase (PAL) and total phenol content, while also promoting growth and yield. The Bacillus strains were isolated from soil samples collected from the Western Ghats, one of India's biological diversity hot spots through random sampling. Two strains exhibiting better antagonistic activity were identified as Bacillus spp through 16S rRNA sequencing. Pot studies were conducted to evaluate the biocontrol efficacy and plant growth promoting ability of these bacterial strains against R. solanacearum. Results showed that ginger plants treated with NIIST NB120 significantly increased shoot length 70.80 cm, leaf length 30.03 cm, leaf breadth 3.42 cm, number of leaves 22, and yield 355.81% compared to plants treated with R. solanacearum, which had lower values. Furthermore, plants treated with NIIST NB120 had the lowest bacterial wilt incidence at 25%, in contrast to 66% in plants treated with pathogen. Application of Bacillus strains also enhanced the activities of defense-related enzymes, including, PAL 0.030 units/ g tissue, PPO 0.0016 units/ g tissue, POD 68.28 units/ g tissue, and total phenolic content 219.5 units/ g tissue, with the lowest enzyme activity observed in pathogen treated plants. These findings suggest that the Bacillus strains NIIST B16 B. siamensis and NIIST NB120 B. amyloliquefaciens could be effective biocontrol agents of ginger bacterial wilt disease. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by strains of the Ralstonia solanacearum species complex is a severe disease affecting plants. The type III secretion system delivers type III effectors (T3Es) from the pathogen to the host plant and is one of the main virulence determinants of R. solanacearum strains. However, the functions of most T3Es, including the R. solanacearum effectors RipAX1 and RipAX2, are not completely understood. In this study, we determined that RipAX1 and RipAX2 share a potential but highly conserved M91 metalloenzyme structural domain. Heterologous overexpression of RipAX1 or RipAX2 neither caused nor inhibited the hypersensitive response (HR) of plant tissues, and their expression in Saccharomyces cerevisiae did not inhibit yeast growth. RipAX1 and RipAX2 localized to the cytoplasm of Nicotiana benthamiana leaf epidermal cells and Arabidopsis thaliana protoplasts. The two effectors interacted with specific members of the plant mitogen-activated protein kinase (MAPK) family. However, RipAX1 and RipAX2 did not directly cleave MAPKs, despite their predicted metalloenzyme activity, although RipAX1 inhibited the phosphorylation of plant MAPKs. These results elucidate a novel aspect of the molecular mechanism underlying the repression of host immunity by T3Es from R. solanacearum species complex strains. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum and R. pseudosolanacearum are well-known bacterial plant pathogens that cause significant losses to both ornamental and agricultural plants. It has been suggested that they are not the primary cause of bacterial wilt in Eucalyptus species, but rather are opportunistic, taking advantage of trees predisposed to infection by abiotic and biotic factors. To test this hypothesis, the bacterial community within the vascular tissue of asymptomatic Eucalyptus grandis x E. urophylla trees, and those displaying varying stages of infection in China and Indonesia were compared using 16S rRNA profiling. Asymptomatic trees growing in areas where bacterial infections had never previously been reported to occur were included as controls. Ralstonia species were found within the vascular tissue of both asymptomatic and symptomatic trees, in high abundance. In the control samples, bacterial diversity within the vascular tissue was high with a low abundance of Ralstonia species. The presence of Ralstonia species in asymptomatic and control samples supports the hypothesis that these species are latent and/or opportunistic pathogens in E. grandis x E. urophylla trees. [ABSTRACT FROM AUTHOR]

Soil acidification represents a severe threat to tobacco cultivation regions in South China, exacerbating bacterial wilt caused by Ralstonia solanacearum. The comprehension of the underlying mechanisms that facilitate the restoration of rhizosphere microbial communities in “healthy soils” is imperative for ecologically managing tobacco bacterial wilt. This study focuses on acidified tobacco soils that have been subjected to continuous cultivation for 20 years. The experimental treatments included lime (L), biochar (B), and a combination of lime and biochar (L+B), in addition to a control group (CK). Utilizing rhizosphere biology and niche theory, we assessed disease suppression effects, changes in soil properties, and the co-evolution of the rhizosphere bacterial community. Each treatment significantly reduced tobacco bacterial wilt by 16.67% to 20.14% compared to the control group (CK) (p < 0.05) and increased yield by 7.86% to 27.46% (p < 0.05). The biochar treatment (B) proved to be the most effective, followed by the lime-biochar combination (L+B). The key factors controlling wilt were identified through random forest regression analysis as an increase in soil pH and exchangeable bases, along with a decrease in exchangeable acidity. However, lime treatment alone led to an increase in soil bulk density and a decrease in available nutrients, whereas both biochar and lime-biochar treatments significantly improved these parameters (p < 0.05). No significant correlation was found between the abundance of Ralstonia and wilt incidence. Nonetheless, all treatments significantly expanded the ecological niche breadth and average variation degree (AVD), enhanced positive interactions and cohesion within the community, and intensified negative interactions involving Ralstonia. This study suggests that optimizing community niches and enhancing pathogen antagonism are key mechanisms for mitigating tobacco wilt in acidified soils. It recommends using lime-biochar mixtures as soil amendments due to their potential ecological and economic benefits. This study offers valuable insights for disease control strategies and presents a novel perspective for research on Solanaceous crops. [ABSTRACT FROM AUTHOR]

Background: Fertilization practices control bacterial wilt-causing Ralstonia solanacearum by shaping the soil microbiome. This microbiome is the start of food webs, in which nematodes act as major microbiome predators. However, the multitrophic links between nematodes and the performance of R. solanacearum and plant health, and how these links are affected by fertilization practices, remain unknown. Results: Here, we performed a field experiment under no-, chemical-, and bio-organic-fertilization regimes to investigate the potential role of nematodes in suppressing tomato bacterial wilt. We found that bio-organic fertilizers changed nematode community composition and increased abundances of bacterivorous nematodes (e.g., Protorhabditis spp.). We also observed that pathogen-antagonistic bacteria, such as Bacillus spp., positively correlated with abundances of bacterivorous nematodes. In subsequent laboratory and greenhouse experiments, we demonstrated that bacterivorous nematodes preferentially preyed on non-pathogen-antagonistic bacteria over Bacillus. These changes increased the performance of pathogen-antagonistic bacteria that subsequently suppressed R. solanacearum. Conclusions: Overall, bacterivorous nematodes can reduce the abundance of plant pathogens, which might provide a novel protection strategy to promote plant health. 6HVRaGfzCN9g8_uHWKg5j1 Video Abstract [ABSTRACT FROM AUTHOR]

Background: Tomato (Solanum lycopersicum L.) production is severely threatened by bacterial wilt, caused by the phytopathogenic bacterium Ralstonia solanacearum. Recently, nano-enabled strategies have shown tremendous potential in crop disease management. Objectives: This study investigates the efficacy of biogenic nanoformulations (BNFs), comprising biogenic silica nanoparticles (SiNPs) and melatonin (MT), in controlling bacterial wilt in tomato. Methods: SiNPs were synthesized using Zizania latifolia leaves extract. Further, MT containing BNFs were synthesized through the one-pot approach. Nanomaterials were characterized using standard characterization techniques. Greenhouse disease assays were conducted to assess the impact of SiNPs and BNFs on tomato plant immunity and resistance to bacterial wilt. Results: The SiNPs and BNFs exhibited a spherical morphology, with particle sizes ranging from 13.02 nm to 22.33 nm for the SiNPs and 17.63 nm to 21.79 nm for the BNFs, indicating a relatively uniform size distribution and consistent shape across both materials. Greenhouse experiments revealed that soil application of BNFs outperformed SiNPs, significantly enhancing plant immunity and reducing bacterial wilt incidence by 78.29% in tomato plants by maintaining oxidative stress homeostasis via increasing the activities of antioxidant enzymes such as superoxide dismutase (31.81%), peroxidase (32.9%), catalase (32.65%), and ascorbate peroxidase (47.37%) compared to untreated infected plants. Additionally, BNFs induced disease resistance by enhancing the production of salicylic acid and activating defense-related genes (e.g., SlPAL1, SlICS1, SlNPR1, SlEDS, SlPD4, and SlSARD1) involved in phytohormones signaling in infected tomato plants. High-throughput 16 S rRNA sequencing revealed that BNFs promoted growth of beneficial rhizosphere bacteria (Gemmatimonadaceae, Ramlibacter, Microscillaceae, Anaerolineaceae, Chloroplast and Phormidium) in both healthy and diseased plants, while suppressing R. solanacearum abundance in infected plants. Conclusion: Overall, these findings suggest that BNFs offer a more promising and sustainable approach for managing bacterial wilt disease in tomato plants. [ABSTRACT FROM AUTHOR]

Plant probiotics are live microbial cells or cultures that support plant growth and control plant pathogens through different mechanisms. They have various effects on plants, including plant growth promotion through the production of indole acetic acid (IAA), biological control activity (BCA), and production of cellulase enzymes, thus inducing systemic resistance and increasing the availability of mineral elements. The present work aimed to study the potential of Achromobacter marplatensis and Bacillus velezensis as plant probiotics for the field cultivation of potatoes. In vitro studies have demonstrated the ability of selected probiotics to produce IAA and cellulase, as well as antimicrobial activity against two plant pathogens that infect Solanum tuberosum as Fusarium oxysporum and Ralstonia solanacearum under different conditions at a broad range of different temperatures and pH values. In vivo study of the effects of the probiotics A. marplatensis and B. velezensis on S. tuberosum plants grown in sandy clay loamy soil was detected after cultivation for 90 days. Probiotic isolates A. marplatensis and B. velezensis were able to tolerate ultraviolet radiation (UV) exposure for up to two hours, the dose response curve exhibited that the D10 values of A. marplatensis and B. velezensis were 28 and 16 respectively. In the case of loading both probiotics with broth, the shoot dry weight was increased significantly from 28 in the control to 50 g, shoot length increased from 24 to 45.7 cm, branches numbers increased from 40 to 70 branch, leaves number increased from 99 to 130 leaf, root dry weight increased from 9.3 to 12.9 g, root length increased from 24 to 35.7 cm, tuber weight increased from 15 to 37.0 g and tubers number increased from 9 to 24.4 tuber, the rot percentage was reduced to 0%. The addition of both probiotic isolates, either broth or wheat grains load separately has enhanced all the growth parameters; however, better results and increased production were in favor of adding probiotics with broth more than wheat. On the other hand, both probiotics showed a remarkable protective effect against potato pathogens separately and reduced the negative impact of the infection using them together. [ABSTRACT FROM AUTHOR]

Curcuma longa L. is a medicinal plant that contains bioactive constituents with various pharmacological properties. However, turmeric is vulnerable to the bacterial wilt disease caused by Ralstonia solanacearum, substantially lowering yields and resulting in death. Thus, this study aims to induce mutations of turmeric cv. 'Trang 2' by applying electron beams (8 MeV) and selecting the resulting populations resistant to bacterial wilt disease. Sixty-day-old plantlets cultured in vitro were exposed to 0, 50, 100 and 150 Gy electron beams with a 240 Gy/min dose rate. The experiment was performed at the Thailand Institute of Nuclear Technology. To explore the potential of electron beam sensitivity in the survival and growth rate, unirradiated plantlets were used to normalize the radiation treatments. Plantlet survival was used to calculate the lethal dose (LD), and the number of new shoots was used to estimate the growth reduction (GR) dose through regression analysis. The survival and growth rates of the plantlets decreased as the radiation dose increased. At doses of 100 and 150 Gy, the turmeric plantlets could not produce new shoots. The median lethal dose (LD50) was 58.6 Gy. A 50 % growth reduction dose (GR50) was observed at 45.3 Gy. Symptom severity ranged from 11.7 to 91.7 %, demonstrating significantly lower levels in the EBRTP-2 and EBRTP-4 M1V5 electron-beam-irradiated populations. Furthermore, the disease incidence was 33.3 % in the EBRTP-6 population. Finally, turmeric populations resistant to bacterial wilt (EBRTP-2, EBRTP-4 and EBRTP-6) were isolated after electron-beam-induced mutation at 50 Gy. [ABSTRACT FROM AUTHOR]

Bacterial wilt (BW) is caused by Ralstonia solanacearum species complex (RSSC) and can lead to severe losses in a wide range of crops, including many traditional African vegetables (TAV). Given the critical role of TAV in African food security, investigations of BW incidence, distribution, and effective breeding strategies are needed to support public and private TAV breeding programs. In this review, we address key questions related to the diversity of BW pathogens, susceptible TAV hosts, distribution, incidence, breeding strategies, sources of resistance, and gaps in the development of resistant TAV varieties in Africa. We also discuss the potential of multiomics integration to enhance our understanding of the host plant defense system against BW in Solanaceae crops. We curated BW strain databases obtained from several online platforms, representing a total of 948 BW strains. Using a refined database, we highlighted the diversity of RSSC and TAV crops affected by RSSC in different regions of Africa. Out of 29 species documented to be affected by BW in Africa, ten are TAV, including widely consumed TAV such as Amaranths and nightshades. In addition, phylotypes I and III are reported to affect TAV, and the incidence can reach up to 72.4% in farmers' fields. An overview of the first reports revealed that the disease has become a serious threat to TAV in the past decade. Finally, this review proposes a schematic map of possible avenues for successful breeding of BW-resistant TAV using Gboma eggplant as a case study. [ABSTRACT FROM AUTHOR]

Summary: Ethylene response factors (ERFs) have been associated with biotic stress in Arabidopsis, while their function in non‐model plants is still poorly understood. Here we investigated the role of potato ERF StPti5 in plant immunity.We show that StPti5 acts as a susceptibility factor. It negatively regulates potato immunity against potato virus Y and Ralstonia solanacearum, pathogens with completely different modes of action, and thereby has a different role than its orthologue in tomato. Remarkably, StPti5 is destabilised in healthy plants via the autophagy pathway and accumulates exclusively in the nucleus upon infection. We demonstrate that StEIN3 and StEIL1 directly bind the StPti5 promoter and activate its expression, while synergistic activity of the ethylene and salicylic acid pathways is required for regulated StPti expression.To gain further insight into the mode of StPti5 action in attenuating potato defence responses, we investigated transcriptional changes in salicylic acid deficient potato lines with silenced StPti5 expression. We show that StPti5 regulates the expression of other ERFs and downregulates the ubiquitin‐proteasome pathway as well as several proteases involved in directed proteolysis.This study adds a novel element to the complex puzzle of immune regulation, by deciphering a two‐level regulation of ERF transcription factor activity in response to pathogens. [ABSTRACT FROM AUTHOR]

Background: LysR-type transcriptional regulators (LTTRs) are one of the largest families of regulators in prokaryotic organism, which help the bacterium adapt to diverse conditions by controlling a wide array of regulons, encompassing genes responsible for nitrogen and carbon fixation, oxidative stress response, bacterial virulence, and the breakdown of diverse compounds. Ralstonia solanacearum strain GMI1000 possesses 80 LTTR genes, yet the precise roles and functional contributions of only three of these LTTRs have been conclusively established among the total. In this work, our group reveal a novel LTTR member LysR7 (RS_RS02375) that exerts multiple regulatory roles in motility, carbon metabolism and virulence. Results: In this investigation, an in-frame deletion mutant ΔlysR7 and a complemented strain CΔlysR7 were prepared. The mutant ΔlysR7 had increased swimming motility on semi-soft medium and showed a reduced replication rate in nutrient-rich medium and in planta. Moreover, ΔlysR7 was unable to grow on nutrient-limited medium, supplemented with galactose as a single carbon resource. RT-qPCR analysis and GUS activity detection indicated that the expression of lysR7 was induced in the presence of galactose. The mutant ΔlysR7 caused weaker wilt disease on either Solanum lycopersicum or Capsicum annuum plants compared to both wild type GMI1000 and CΔlysR7. Transcriptome analysis revealed that 12 upregulated and 8 downregulated differentially expressed genes (DEGs) in ΔlysR7 were restored in CΔlysR7 relative to wild type. In particular, the expression of hrpG, a key gene responsible for type III secretion system, was downregulated. KEGG analysis revealed that, except for lysR7 gene, the 19 DEGs were most enriched in microbial metabolism in diverse environments and metabolic pathways. Conclusions: The data indicate that LysR7 regulates multiple processes in association with motility, galactose metabolism and virulence in R. solanacearum. The study offers valuable evidence to understand comprehensive regulatory mechanisms mediated by LTTR family members in R. solanacearum. [ABSTRACT FROM AUTHOR]

Background: Soil nutrient status and soil-borne diseases are pivotal factors impacting modern intensive agricultural production. The interplay among plants, soil microbiome, and nutrient regimes in agroecosystems is essential for developing effective disease management. However, the influence of nutrient availability on soil-borne disease suppression and associated plant-microbe interactions remains to be fully explored. T his study aims to elucidate the mechanistic understanding of nutrient impacts on disease suppression, using phosphorous as a target nutrient. Results: A 6-year field trial involving monocropping of tomatoes with varied fertilizer manipulations demonstrated that phosphorus availability is a key factor driving the control of bacterial wilt disease caused by Ralstonia solanacearum. Subsequent greenhouse experiments were then conducted to delve into the underlying mechanisms of this phenomenon by varying phosphorus availability for tomatoes challenged with the pathogen. Results showed that the alleviation of phosphorus stress promoted the disease-suppressive capacity of the rhizosphere microbiome, but not that of the bulk soil microbiome. This appears to be an extension of the plant trade-off between investment in disease defense mechanisms versus phosphorus acquisition. Adequate phosphorus levels were associated with elevated secretion of root metabolites such as L-tryptophan, methoxyindoleacetic acid, O-phosphorylethanolamine, or mangiferin, increasing the relative density of microbial biocontrol populations such as Chryseobacterium in the rhizosphere. On the other hand, phosphorus deficiency triggered an alternate defense strategy, via root metabolites like blumenol A or quercetin to form symbiosis with arbuscular mycorrhizal fungi, which facilitated phosphorus acquisition as well. Conclusion: Overall, our study shows how phosphorus availability can influence the disease suppression capability of the soil microbiome through plant-microbial interactions. These findings highlight the importance of optimizing nutrient regimes to enhance disease suppression, facilitating targeted crop management and boosting agricultural productivity. 5_PfxzZNKyxgT3zPqUmUdg Video Abstract [ABSTRACT FROM AUTHOR]

The effectiveness of agroecological management strategies (AEMS) in controlling bacterial wilt caused by Ralstonia solanacearum species complex (RSSC) remains a critical question. A quantitative review was conducted based on publications reporting agroecological bacterial wilt management practices under on‐station or on‐farm field conditions in electronic libraries, without geographical restrictions, on tomato, pepper, eggplant and potato. After applying inclusion and exclusion criteria, 48 papers were retained, resulting in 644 and 146 observations of bacterial wilt incidence (BWI) and yield, respectively. The effectiveness of AEMS for each crop was evaluated based on BWI and crop yield. The effect size was calculated as the natural logarithm of the response ratio, and confidence intervals were determined by bootstrapping. Varietal control, biological control (used of biological control agents) and combinations of many AEMS were the most reported practices, both under on‐station and on‐farm conditions. The use of plant extracts (Thymus spp., Crotalaria spp.), grafting, solarization, soil amendments (manure, compost) and crop rotations (with maize, beans) were also reported. All AEMS significantly reduced bacterial wilt incidence and increased yields compared to the untreated plots. Grafting, combinations of control methods, varietal control and biological control were the most effective agroecological practices in reducing BWI and increasing yield in tomato and eggplant. Varietal control was the most effective compared to biological control on pepper. The effectiveness of AEMS also varied with crop susceptibility and origin, climatic zone and soil acidity. This study highlights the potential of AEMS in reducing BWI and increasing crop yield in infested soils. [ABSTRACT FROM AUTHOR]

Background: Protein–protein interactions are the primary means through which proteins carry out their functions. These interactions thus have crucial roles in life activities. The wide availability of fully sequenced animal and plant genomes has facilitated establishment of relatively complete global protein interaction networks for some model species. The genomes of cultivated and wild peanut (Arachis hypogaea L.) have also been sequenced, but the functions of most of the encoded proteins remain unclear. Results: We here used homologous mapping of validated protein interaction data from model species to generate complete peanut protein interaction networks for A. hypogaea cv. 'Tifrunner' (282,619 pairs), A. hypogaea cv. 'Shitouqi' (256,441 pairs), A. monticola (440,470 pairs), A. duranensis (136,363 pairs), and A. ipaensis (172,813 pairs). A detailed analysis was conducted for a putative disease-resistance subnetwork in the Tifrunner network to identify candidate genes and validate functional interactions. The network suggested that DX2UEH and its interacting partners may participate in peanut resistance to bacterial wilt; this was preliminarily validated with overexpression experiments in peanut. Conclusion: Our results provide valuable new information for future analyses of gene and protein functions and regulatory networks in peanut. [ABSTRACT FROM AUTHOR]

The destructive bacterial wilt disease caused by Ralstonia solanacearum leads to substantial losses in tomato production worldwide. RNA‐seq is a powerful technology to decipher various biological processes of host–pathogen interactions by analysing differentially expressed genes (DEGs). In the current study, we used RNA‐seq to analyse the transcriptome changes during the interaction of R. solanacearum and susceptible tomato leaves at the time point of 24 h. Gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used to annotate functions of DEGs in tomato plants. DEGs related to plant and pathogen interaction pathways, photosynthesis pathways and hormone signalling pathways were further analysed. Our results revealed that R. solanacearum inoculation activated plant defence response pathways to induce a number of core defence genes against bacterial invasion, inhibited expression of genes related to photosynthesis processes and activated the salicylic acid (SA) signalling pathway to induce defence responses. We quantified SA and jasmonic acid (JA) contents after bacterial inoculation. SA treatment alleviated plant disease symptoms and induced immune‐related reactive oxygen species (ROS) bursts in tomato leaves. The extent of disease symptoms was much greater in SlNPR1‐silenced plants than wild‐type plants. Together, our results will provide a better understanding of the mechanisms of plant induced defences against bacterial invasion and provide a theoretical basis for breeding resistance of tomato against R. solanacearum in future. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Ralstonia solanacearum is one of the most important diseases in solanaceous plants, including peppers. It generally tends to be more serious under warm−temperature and moist (WM) conditions than at moist room−temperature (RM) conditions. Although immunity mechanisms at room temperature have been intensively studied, the mechanisms underlying WM conditions remain poorly understood. Herein, the pepper cysteine protease CaZingipain2 was expressed and functionally characterized in pepper immunity against R. solanacearum at WM conditions and at room temperature. The results showed that CaZingipain2 localized to the nucleus and was upregulated at the transcript level in pepper plants upon R. solanacearum infection under WM conditions (RSWM). Virus−induced gene silencing of CaZingipain2 significantly increased the susceptibility of pepper plants to RSWM, and was coupled with the downregulation of CaPRP1 and CaMgst3, which are specifically related to pepper immunity against RSWM, according to our previous studies, while its overexpression significantly reduced the susceptibility of N. benethamiana plants to RSWM compared to that of wild−type plants. In addition, our data showed that CaZingipain2 also acts positively in pepper immunity against R. solanacearum infection at room temperature by upregulating the SA− and JA−responsive PR genes, including CaNPR1 and CaDEF1. All these results indicate that CaZingipain2 improves pepper immunity against R. solanacearum under WM conditions and at room temperature by regulating different PR genes. [ABSTRACT FROM AUTHOR]

Summary Soil nitrogen (N) significantly influences the interaction between plants and pathogens, yet its impact on host defenses and pathogen strategies via alterations in plant metabolism remains unclear. Through metabolic and genetic studies, this research demonstrates that high‐N‐input exacerbates tomato bacterial wilt by altering γ‐aminobutyric acid (GABA) metabolism of host plants. Under high‐N conditions, the nitrate sensor NIN‐like protein 7 (SlNLP7) promotes the glutamate decarboxylase 2/4 (SlGAD2/4) transcription and GABA synthesis by directly binding to the promoters of SlGAD2/4. The tomato plants with enhanced GABA levels showed stronger immune responses but remained susceptible to Ralstonia solanacearum. This led to the discovery that GABA produced by the host actually heightens the pathogen's virulence. We identified the R. solanacearum LysR‐type transcriptional regulator OxyR protein, which senses host‐derived GABA and, upon interaction, triggers a response involving protein dimerization that enhances the pathogen's oxidative stress tolerance by activating the expression of catalase (katE/katGa). These findings reveal GABA's dual role in activating host immunity and enhancing pathogen tolerance to oxidative stress, highlighting the complex relationship between tomato plants and R. solanacearum, influenced by soil N status. [ABSTRACT FROM AUTHOR]

Rhizome rot poses a significant threat to ginger cultivation, caused by a complex interaction of pathogens such as Pythium aphanidermatum, Fusarium oxysporum, Ralstonia solanacearum, Sclerotium rolfsii and Meloidogyne incognita. The pathogens were individually inoculated at 75, 105 and 135 days after planting (DAP), as well as in various combinations, to evaluate disease severity and symptom development. Results revealed that R. solanacearum exhibited the highest disease severity and fastest symptom development across all stages of inoculation, followed by P. aphanidermatum, F. oxysporum, S. rolfsii and M. incognita. The combined inoculation of pathogens significantly increased disease incidence and rhizome rot compared to individual inoculations, indicating synergistic interactions among the pathogens. Sequential inoculation experiments demonstrated that pre‐infection by M. incognita exacerbated disease severity, highlighting the role of nematodes in predisposing plants to secondary infections. [ABSTRACT FROM AUTHOR]

The effectiveness of SiO 2 nanoparticles for their potential to control bacterial wilt (BW) disease in tomato plants was studied. Different concentrations of nanoparticles were first evaluated for their in-vitro antibacterial potential against Ralstonia solanacearum , the causal agent of BW disease. The disease suppressive effect of NP was investigated through in-planta experiments in tomato plants. Nanoparticles exhibited maximum toxicity to R. solanacearum at the concentration of 25 µg/ml and showed a 14.2 ± 0.5 mm growth inhibition zone in a lab test. Tomato plants were grown in pathogen-inoculated soil that was amended with NP suspension. The efficacy of NP application was evaluated for their effect on disease suppression, soil pathogen population, and plant growth and defense response. Results showed that NP at 150 ppm significantly reduced the pathogen population in the soil, as indicated by population count through molecular and dilution count analysis. The NP treatment suppresses the disease index and improves plant growth. The activities of plant antioxidant enzymes were increased, and the expression of resistance genes PR1, PR5, PAL , and PDF - 1.2 were enhanced after NP application. Plants grown in NP-treated soil showed improved photosynthesis and reduced oxidative stress as compared to untreated plants under pathogen stress, and the total phenolic and flavonoid content was enhanced significantly. Moreover, DPPH and FRAP content and AsA/DHA and GSH/GSSG ratios were enhanced, followed by NP application, implying that the non-enzymatic antioxidant capacity of the plants was improved. This study reveals the molecular and physiological action mechanism of managing BW in tomato plants. It suggests that SiO 2 nanoparticles could be included in the integrated management of BW disease as one of the effective components. [Display omitted] • SiO 2 nanoparticles exhibited antibacterial activity against ralstonia solanacearum. • Soil treatment with SiO 2 NP suppress pathogen population in soil. • Application of SiO 2 NP enhanced plant growth and resistance. [ABSTRACT FROM AUTHOR]

Abstract Background LysR-type transcriptional regulators (LTTRs) are one of the largest families of regulators in prokaryotic organism, which help the bacterium adapt to diverse conditions by controlling a wide array of regulons, encompassing genes responsible for nitrogen and carbon fixation, oxidative stress response, bacterial virulence, and the breakdown of diverse compounds. Ralstonia solanacearum strain GMI1000 possesses 80 LTTR genes, yet the precise roles and functional contributions of only three of these LTTRs have been conclusively established among the total. In this work, our group reveal a novel LTTR member LysR7 (RS_RS02375) that exerts multiple regulatory roles in motility, carbon metabolism and virulence. Results In this investigation, an in-frame deletion mutant ΔlysR7 and a complemented strain CΔlysR7 were prepared. The mutant ΔlysR7 had increased swimming motility on semi-soft medium and showed a reduced replication rate in nutrient-rich medium and in planta. Moreover, ΔlysR7 was unable to grow on nutrient-limited medium, supplemented with galactose as a single carbon resource. RT-qPCR analysis and GUS activity detection indicated that the expression of lysR7 was induced in the presence of galactose. The mutant ΔlysR7 caused weaker wilt disease on either Solanum lycopersicum or Capsicum annuum plants compared to both wild type GMI1000 and CΔlysR7. Transcriptome analysis revealed that 12 upregulated and 8 downregulated differentially expressed genes (DEGs) in ΔlysR7 were restored in CΔlysR7 relative to wild type. In particular, the expression of hrpG, a key gene responsible for type III secretion system, was downregulated. KEGG analysis revealed that, except for lysR7 gene, the 19 DEGs were most enriched in microbial metabolism in diverse environments and metabolic pathways. Conclusions The data indicate that LysR7 regulates multiple processes in association with motility, galactose metabolism and virulence in R. solanacearum. The study offers valuable evidence to understand comprehensive regulatory mechanisms mediated by LTTR family members in R. solanacearum. Graphical Abstract

Abstract Background Protein–protein interactions are the primary means through which proteins carry out their functions. These interactions thus have crucial roles in life activities. The wide availability of fully sequenced animal and plant genomes has facilitated establishment of relatively complete global protein interaction networks for some model species. The genomes of cultivated and wild peanut (Arachis hypogaea L.) have also been sequenced, but the functions of most of the encoded proteins remain unclear. Results We here used homologous mapping of validated protein interaction data from model species to generate complete peanut protein interaction networks for A. hypogaea cv. ‘Tifrunner’ (282,619 pairs), A. hypogaea cv. ‘Shitouqi’ (256,441 pairs), A. monticola (440,470 pairs), A. duranensis (136,363 pairs), and A. ipaensis (172,813 pairs). A detailed analysis was conducted for a putative disease-resistance subnetwork in the Tifrunner network to identify candidate genes and validate functional interactions. The network suggested that DX2UEH and its interacting partners may participate in peanut resistance to bacterial wilt; this was preliminarily validated with overexpression experiments in peanut. Conclusion Our results provide valuable new information for future analyses of gene and protein functions and regulatory networks in peanut.

Reactive oxygen species (ROS) play a crucial role in regulating numerous functions in organisms. Among the key regulators of ROS production are NADPH oxidases, primarily referred to as respiratory burst oxidase homologues (RBOHs). However, our understanding of whether and how pathogens directly target RBOHs has been limited. In this study, we revealed that the effector protein RipBJ, originating from the phytopathogenic bacterium Ralstonia solanacearum, was present in low‐ to medium‐virulence strains but absent in high‐virulence strains. Functional genetic assays demonstrated that the expression of ripBJ led to a reduction in bacterial infection. In the plant, RipBJ expression triggered plant cell death and the accumulation of H2O2, while also enhancing host defence against R. solanacearum by modulating multiple defence signalling pathways. Through protein interaction and functional studies, we demonstrated that RipBJ was associated with the plant's plasma membrane and interacted with the tomato RBOH known as SlWfi1, which contributed positively to RipBJ's effects on plants. Importantly, SlWfi1 expression was induced during the early stages following R. solanacearum infection and played a key role in defence against this bacterium. This research uncovers the plant RBOH as an interacting target of a pathogen's effector, providing valuable insights into the mechanisms of plant defence. Summary Statement: This study demonstrates that a tomato plasma membrane‐bound NADPH oxidase is a direct interactor of a bacterial effector protein to mediate plant defence, providing important new information on the interplay between this devastating pathogen and its host plant. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Ralstonia solanacearum, is one of the most notorious plant diseases of potato and causes severe yield losses globally. R. solanacearum produces fluidal white coloured colonies with a light pink centre on casamino acid-peptone-glucose medium. Bacterial wilt pathogen is soil as well as tuber borne, so early detection of bacterial wilt pathogen is necessary to take up timely management practices. Traditional methods used for detection of R. solanacearum are labour-intensive, expensive, time-consuming and can be carried out only in well-equipped laboratories. Hence, the present study was aimed to develop a loop-mediated isothermal amplification (LAMP) assay for R. solanacearum, as an alternative approach for quick and efficient detection of the bacterial wilt. LAMP reaction mix was optimized by adjusting the concentrations of MgSO4, dNTPs, betaine, and time, temperature etc. The optimum temperature and time for the detection of R. solanacearum were 65 °C and 50 min, respectively. The positive samples showed colour change from violet and were reconfirmed in 2% agarose gel electrophoresis which produced ladder like bands. The LAMP assay developed was highly specific to detect R. solanacearum from other bacteria and sensitive with a lowest detection limit of 10 pg/µl of template DNA. The developed LAMP assay was validated with R. solanacearum isolates, infected stems, tubers and soil, and also, it was capable of detecting latent infection of R. solanacearum in seed tubers. Hence, the LAMP assay protocol provides a rapid, specific and sensitive tool for the latent detection of R. solanacearum in seed potato tubers. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum usually infects the vascular bundle system through the roots of host plants, causing bacterial wilt and leading to irreversible wilting and death of plants. Bacterial wilt is a devastating soil-borne bacterial disease. At present, it has been one of the main diseases restricting the production of Solanaceae crops in China. Type Ⅲ secretion system (T3SS) plays an important role in the pathogenesis of R. solanacearum, using T3SS to inject large amounts of Type Ⅲ effectors (T3Es) into host cells to interfere with the immune response of the host. Scholars at home and abroad are committed to exploring how R. solanacearum interferes with host cells and regulates host immune function by identifying target proteins in the host. Therefore, the identification of host proteins that can be targeted by T3Es is helpful to understand the biological function of R. solanacearum T3Es, the pathogenic process of R. solanacearum, and to explore the R. solanacearum resistance-related proteins and their mechanism of action in hosts. Although most of the functions of T3Es are still unknown, so far, it has been reported that R. solanacearum T3Es can regulate host resistance to bacterial wilt by interfering with plant innate immunity, inducing plant hypersensitivity response and affecting plant metabolism and hormone signal transduction through a variety of molecular mechanisms. In this review, we summarize the current research progress on the characteristics and functional identification methods of T3Es of R. solanacearum, and its research progress in participating in the regulation of pathogenicity and plant immunity mechanism of R. solanacearum, which can provide an in-depth understanding of the pathogenic mechanism of R. solanacearum and the response mechanism of the host immune system. The mechanism of interaction between R. solanacearum T3Es and the host are prospected, which will provide an effective reference for the analysis of the host resistance mechanism induced by R. solanacearum and the prevention and control of bacterial wilt.

Temperature elevation drastically affects plant defense responses to Ralstonia solanacearum and inhibits the major source of resistance in Arabidopsis thaliana, which is mediated by the receptor pair RRS1-R/RPS4. In this study, we refined a previous genome-wide association (GWA) mapping analysis by using a local score approach and detected the primary cell wall CESA3 gene as a major gene involved in plant response to R. solanacearum at both 27°C and an elevated temperature, 30°C. We functionally validated CESA3 as a susceptibility gene involved in resistance to R. solanacearum at both 27 and 30°C through a reverse genetic approach. We provide evidence that the cesa3mre1 mutant enhances resistance to bacterial disease and that resistance is associated with an alteration of root cell morphology conserved at elevated temperatures. However, even by forcing the entry of the bacterium to bypass the primary cell wall barrier, the cesa3mre1 mutant still showed enhanced resistance to R. solanacearum with delayed onset of bacterial wilt symptoms. We demonstrated that the cesa3mre1 mutant had constitutive expression of the defense-related gene VSP1, which is upregulated at elevated temperatures, and that during infection, its expression level is maintained higher than in the wild-type Col-0. In conclusion, this study reveals that alteration of the primary cell wall by mutating the cellulose synthase subunit CESA3 contributes to enhanced resistance to R. solanacearum, remaining effective under heat stress. We expect that these results will help to identify robust genetic sources of resistance to R. solanacearum in the context of global warming. [Figure: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Abstract Background Several WRKY transcription factors (TFs), including CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40 are known to govern the resistance of pepper (Capsicum annuum L.) plants to Ralstonia solanacearum infestation (RSI) and other abiotic stresses. However, the molecular mechanisms underlying these processes remain elusive. Methods This study functionally described CaWRKY3 for its role in pepper immunity against RSI. The roles of phytohormones in mediating the expression levels of CaWRKY3 were investigated by subjecting pepper plants to 1 mM salicylic acid (SA), 100 µM methyl jasmonate (MeJA), and 100 µM ethylene (ETH) at 4-leaf stage. A virus-induced gene silencing (VIGS) approach based on the Tobacco Rattle Virus (TRV) was used to silence CaWRKY3 in pepper, and transiently over-expressed to infer its role against RSI. Results Phytohormones and RSI increased CaWRKY3 transcription. The transcriptions of defense-associated marker genes, including CaNPR1, CaPR1, CaDEF1, and CaHIR1 were decreased in VIGS experiment, which made pepper less resistant to RSI. Significant hypersensitive (HR)-like cell death, H2O2 buildup, and transcriptional up-regulation of immunological marker genes were noticed in pepper when CaWRKY3 was transiently overexpressed. Transcriptional activity of CaWRKY3 was increased with overexpression of CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40, and vice versa. In contrast, Pseudomonas syringae pv tomato DC3000 (Pst DC3000) was easily repelled by the innate immune system of transgenic Arabidopsis thaliana that overexpressed CaWRKY3. The transcriptions of defense-related marker genes like AtPR1, AtPR2, and AtNPR1 were increased in CaWRKY3-overexpressing transgenic A. thaliana plants. Conclusion It is concluded that CaWRKY3 favorably regulates phytohormone-mediated synergistic signaling, which controls cell death in plant and immunity of pepper plant against bacterial infections.

The mitogen-activated protein kinase kinase kinase kinase (M4K) family is evolutionarily conserved across plants and animals. In Arabidopsis, the protein kinase SIK1, an M4K member, is known to positively modulate reactive oxygen species (ROS) production during pattern-triggered immunity (PTI) by stabilizing BIK1, a key receptor-like cytoplasmic kinase (RLCK). While homologs of SIK1 exhibit conserved protein domain architectures across a range of land plants, their functional conservation remains incompletely understood. This study investigates the functional conservation and divergence of SIK1 homologs, focusing particularly on NbM4K3 in Nicotiana benthamiana. Silencing NbM4K3 resulted in an impairment of the flg22-induced ROS burst and expression of PTI marker genes. Additionally, silencing NbM4K3 led to diminished protein accumulation of RLCKs, while overexpression of the RLCKs prominently enhanced the flg22-induced ROS burst in NbM4K3-silenced plants. Furthermore, NbM4K3-silenced plants exhibited a compromised hypersensitive response (HR), reduced ROS accumulation, and diminished expression of effector-triggered immunity (ETI) marker genes when challenged with the avirulent strains Ralstonia solanacearum GMI1000 and Pseudomonas syringae DC3000, suggesting that NbM4K3 is a positive regulator of ETI. The attenuated HR phenotype observed in NbM4K3-silenced plants upon expression of RipP1 or RipE1, two avirulent type III effectors of GMI1000, further supports the affirmative role of NbM4K3 in ETI. In summary, our data indicate that the M4K NbM4K3 positively regulates both PTI and ETI in N. benthamiana, potentially by stabilizing RLCKs. These findings not only strengthen the role of M4K family in plant immunity but also suggest its potential in improving disease resistance in plants. [ABSTRACT FROM AUTHOR]

As the world moves toward a green economy and sustainable agriculture, bacterial viruses or bacteriophages (phages) become attractive biocontrol agents for controlling crop diseases. Effective utilization of phages in farms requires integrated knowledge of crops, pathogens, phages, and surroundings. Phages must encounter environmental fluctuations, including temperature, and must remain infectious for successful bacteria lysis. This work studied a soilborne RSJ2 phage discovered in Thailand, which can eliminate Ralstonia solanacearum, causing bacterial wilt disease in chili. We investigated how phage infectivity and nanomechanics responded to thermal changes. The plaque-based assay showed that the infectivity of the RSJ2 phage was stable within 24–40 °C, an average temperature fluctuation in tropical regions. The structural examination also showed that the phage remained intact. The nanomechanical property of the phage was inspected by the atomic force microscopy-based nanoindentation. The result revealed that the phage stiffness within 24–40 °C was statistically similar (0.05–0.06 N/m). Upon heating at 40 °C for 1, 5, and 10 h and resting at 25 °C, the stiffness of the phage particles increased to 0.09–0.11 N/m (54–83% increase). The stiffness results suggest structural adaptation of the protein subunits as a response to thermal alteration. The study exhibits that the phage structure is highly dynamic and can nanomechanically respond to varying temperatures. The phage stiffness may reveal insight into phage adaptation to environmental factors. Equipped with the knowledge of phage infectivity, structure, and nanomechanics, we can design practical guidelines for effective phage usage in farming and propelling green and safe agriculture. [ABSTRACT FROM AUTHOR]

Bacterial wilt (BW) is a devastating plant disease caused by the soil-borne bacterium Ralstonia solanacearum species complex (Rssc). Numerous efforts have been exerted to control BW, but effective, economical, and environmentally friendly approaches are still not available. Bacteriophages are a promising resource for the control of bacterial diseases, including BW. So, in this study, a crop BW pathogen of lytic bacteriophage was isolated and named PQ43W. Biological characterization revealed PQ43W had a short latent period of 15 min, 74 PFU/cell of brust sizes, and good stability at a wide range temperatures and pH but a weak resistance against UV radiation. Sequencing revealed phage PQ43W contained a circular double-stranded DNA genome of 47,156 bp with 65 predicted open reading frames (ORFs) and genome annotation showed good environmental security for the PQ43W that no tRNA, antibiotic resistance, or virulence genes contained. Taxonomic classification showed PQ43W belongs to a novel genus of subfamily Kantovirinae under Caudoviricetes. Subsequently, a dose of PQ43W for phage therapy in controlling crop BW was determined: 108 PFU*20 mL per plant with non-invasive irrigation root application twice by pot experiment. Finally, a field experiment of PQ43W showed a significantly better control effect in crop BW than the conventional bactericide Zhongshengmycin. Therefore, bacteriophage PQ43W is an effective bio-control resource for controlling BW diseases, especially for crop cultivation. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum usually infects the vascular bundle system through the roots of host plants, causing bacterial wilt and leading to irreversible wilting and death of plants. Bacterial wilt is a devastating soil-borne bacterial disease. At present, it has been one of the main diseases restricting the production of Solanaceae crops in China. Type Ⅲ secretion system (T3SS) plays an important role in the pathogenesis of R. solanacearum, using T3SS to inject large amounts of Type Ⅲ effectors (T3Es) into host cells to interfere with the immune response of the host. Scholars at home and abroad are committed to exploring how R. solanacearum interferes with host cells and regulates host immune function by identifying target proteins in the host. Therefore, the identification of host proteins that can be targeted by T3Es is helpful to understand the biological function of R. solanacearum T3Es, the pathogenic process of R. solanacearum, and to explore the R. solanacearum resistancerelated proteins and their mechanism of action in hosts. Although most of the functions of T3Es are still unknown, so far, it has been reported that R. solanacearum T3Es can regulate host resistance to bacterial wilt by interfering with plant innate immunity, inducing plant hypersensitivity response and affecting plant metabolism and hormone signal transduction through a variety of molecular mechanisms. In this review, we summarize the current research progress on the characteristics and functional identification methods of T3Es of R. solanacearum, and its research progress in participating in the regulation of pathogenicity and plant immunity mechanism of R. solanacearum, which can provide an in-depth understanding of the pathogenic mechanism of R. solanacearum and the response mechanism of the host immune system. The mechanism of interaction between R. solanacearum T3Es and the host are prospected, which will provide an effective reference for the analysis of the host resistance mechanism induced by R. solanacearum and the prevention and control of bacterial wilt. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum species complex (RSSC) includes soilborne bacterial plant pathogens with worldwide distribution and wide host ranges. Virulence factors are regulated via four hierarchically organized cell–cell contact independent quorum‐sensing (QS) signalling systems: the Phc, which uses as signals (R)‐methyl 3‐hydroxypalmitate [(R)‐3‐OH PAME] or (R)‐methyl 3‐hydroxymyristate [(R)‐3‐OH MAME], the N‐acyl homoserine lactone (AHL)‐dependent RasI/R and SolI/R systems, and the recently identified anthranilic acid‐dependent system. The unique Phc QS system has been extensively studied; however, the role of the two AHL QS systems has only recently been addressed. In this microreview, we present and discuss current data of the SolI/R and RasI/R QS systems in the RSSC. We also present the distribution and frequency of these AHL QS systems in the RSSC, discuss possible ecological roles and evolutive implications. The complex QS hierarchical networks emphasizes the crucial role of cell–cell signalling in the virulence of the RSSC. [ABSTRACT FROM AUTHOR]

This study was conducted to identify resistant pepper accessions against the destructive disease bacterial wilt (BW) caused by Ralstonia solanacearum. A total of 338 pepper (Capsicum species) germplasms collected from different countries and deposited in the National Agrobiodiversity Genebank, Rural Development Administration (RDA), Republic of Korea, were evaluated. The evaluated accessions comprise samples from five distinct species: Capsicum annuum (213), Capsicum baccatum (47), Capsicum chinense (45), Capsicum frutescens (31), and Capsicum chacoense (2). Disease severity scores were recorded over four consecutive weeks and showed an increase in severity from initial inoculation to the end of the evaluation period. A strong correlation was observed between week 1 and 2, as well as between week 3 and 4. Ten resistant pepper accessions were identified. All selected accessions consistently exhibited low disease scores ranging from 0 to 1 throughout the observation period. These accessions belong to C. chinense (2), C. annuum (6), C. chacoense (1), and C. frutescens (1). Accessions such as IT236738 (C. chinense) and IT283498 (C. chinense) were demonstrated to have high resistance, showing no symptoms over all four weeks. Other accessions belonging to C. annuum (IT247232 and IT236340) and C. chacoense (IT158713) maintained a disease score of 0 (no symptoms) for the first three consecutive weeks; however, they developed symptoms with a score of 1 in the fourth week. Other important characteristics of the resistant materials were evaluated, including carotenoids and fruit characteristics. These accessions have important traits beyond resistance to the destructive pepper disease. They will serve as promising resources for breeding resistant pepper varieties against BW to enhance productivity. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) seed production using the aeroponic system has been widely implemented in Indonesia. However, aeroponic systems in tropical areas such as Indonesia faced obstacles in the form of high wilt attacks caused by the bacteria Ralstonia solanacearum. This research aimed to control R. solanacearum wilt disease in an aeroponic system using various microbes. The research was carried out from September 2022 to January 2023. This research consisted of four stages, namely exploration and isolation of microorganisms, identification of microbial antagonism, testing of in vitro potential microbial antagonism and testing of selected microbial antagonism in the aeroponic system. The nutrients used in the aeroponic system contained R. solanacearum with a concentration of 104 CFU mL-1, while the concentration of the microbial solution used was 108 CFU mL-1. Pseudomonas fluorescence was consistently the best microbe both in vitro and in aeroponics, whereas Bacillus subtilis could only overcome wilt in vitro and could not overcome wilt in aeroponic system. Pseudomonas fluorescence required 5 min soaking time and could increase wilt with increasing soaking time. The consortium between B. subtilis and P. fluorescence with 10 min soaking time could overcome wilt by 85% and increase the number of tubers and tuber weight by 79% and 85%, respectively, so this prospective microbial consortium could be applied to aeroponic systems environmentally friendly in tropical areas with high R. solanacearum opportunities. [ABSTRACT FROM AUTHOR]

As important transcription factors, WRKYs play a vital role in the defense response of plants against the invasion of multiple pathogens. Though some WRKY members have been reported to participate in pepper immunity in response to Ralstonia solanacearum infection, the functions of the majority of WRKY members are still unknown. Herein, CaWRKY22b was cloned from the pepper genome and its function against R. solanacearum was analyzed. The transcript abundance of CaWRKY22b was significantly increased in response to the infection of R. solanacearum and the application of exogenous methyl jasmonate (MeJA). Subcellular localization assay in the leaves of Nicotiana benthamiana showed that CaWRKY22b protein was targeted to the nuclei. Agrobacterium-mediated transient expression in pepper leaves indicated that CaWRKY22b overexpression triggered intensive hypersensitive response-like cell death, H2O2 accumulation, and the up-regulation of defense- and JA-responsive genes, including CaHIR1, CaPO2, CaBPR1, and CaDEF1. Virus-induced gene silencing assay revealed that knock-down of CaWRKY22b attenuated pepper's resistance against R. solanacearum and the up-regulation of the tested defense- and jasmonic acid (JA)-responsive genes. We further assessed the role of CaWRKY22b in modulating the expression of JA-responsive CaDEF1, and the result demonstrated that CaWRKY22b trans-activated CaDEF1 expression by directly binding to its upstream promoter. Collectively, our results suggest that CaWRKY22b positively regulated pepper immunity against R. solanacearum in a manner associated with JA signaling, probably by modulating the expression of JA-responsive CaDEF1. [ABSTRACT FROM AUTHOR]

Lectins, a large group of proteins present in all kingdoms of life can bind reversibly to glycans. The roles of plant lectins are diverse and include resistance to biotic or abiotic stress, notably bacterial resistance. A gene family encoding amaranthin-like lectins termed MdAGGs in apple (Malus domestica) has been identified to be overexpressed upon treatment with the plant resistance inducer acibenzolar-S-methyl (ASM) which promotes enhanced resistance to the fire blight disease caused by Erwinia amylovora (Ea). In this study, we first screened the ability of purified MdAGG10 to agglutinate bacterial cells in vitro among a range of bacterial species. Several bacterial species, either Gram positive or negative, either plant- or human-pathogens were found to be agglutinated by MdAGG10 in acidic conditions. Apple and Arabidopsis lines constitutively overexpressing MdAGG10 were generated and evaluated for their resistance to, respectively, Ea and Ralstonia solanacearum, both plant pathogens that were found in our screening. Despite MdAGG10 protein accumulated in tissues of both apple and Arabidopsis lines, they remained susceptible to their respective pathogens. Interestingly, in vitro agglutination of Ea by MdAGG10 did not impair bacterial growth, suggesting that other plant molecules are involved in the resistance to fire blight triggered after an ASM treatment. [ABSTRACT FROM AUTHOR]

Purpose: Identify soil properties involved in the adsorption of the bacteriophages (phages) ΦITL-1 and ΦRSP, analyzing different soils and substrates used for greenhouse tomato crops. Methods: Soil samples were collected from greenhouses in Mexico Central, and soil properties were obtained using the NOM-021-RECNAT-2000. For phage adsorption, soil or substrate was mixed with a phage solution, using three different Water Retention Capacity (WRC) levels, incubated under shaking to room temperature, and finally, the plaque-forming units were counted for each phage by titration. Results: The phage elution counts showed that the amount of aqueous solution in the mixture is inversely related to the number of viral particles adsorbed on the soil. Furthermore, the soils with a sandy texture had lower adsorption of phages in comparison with the rest of the soils analyzed, which have clay, clay loam, and sandy loam textures. A correlation analysis showed that soil pH and texture are the properties that most influenced phage adsorption. Finally, a principal component analysis showed that Cation Exchange Capacity (CEC) has a direct relationship with phage adsorption. Conclusion: In the present study, we demonstrated that soil texture, pH, CEC, and WRC are determinant variables that affect the adsorption of R. solanacearum phages ΦITL-1 and ΦRSP. Furthermore, we propose that the responsible mechanism may be due to the richness of cations in the soil, which could imply an electrostatic interaction with some exposed phage proteins. These results highlight the influence of soil properties on biocontrol strategies based on phages, which try to reduce the impact of soil-borne bacterial phytopathogens. [ABSTRACT FROM AUTHOR]

Background: As a vital soil-borne pathogenic bacterium, Ralstonia solanacearum can cause wilt disease in multiple Solanaceae plants. Several phages, such as ϕPB2, could infect R. solanacearum acting as a potential biological control agent in soil. In addition, some nanoparticles, especially copper preparation, also showed high toxicity on R. solanacearum with low toxicity on plant. However, whether they can be administered in combination and how effective they are in inhibiting the plant disease caused by R. solanacearum is known very little. Results: In this work, the characterization of CuONPs using scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction ascertained the presence of CuONPs which were nanometer particle of 83 nm. Then it was found that combined application of CuONPs with phage (ϕPB2) was superior to that of ϕPB2 or CuONPs alone in controlling tobacco bacterial wilt, with the CuONPs (250 mg/mL) and phage (106 PFU/mL) ratio being the best, at 79.1%. The combination of CuONPs and ϕPB2 also showed no obvious toxicity on tobacco growth than control like single application of CuONPs or ϕPB2. Furthermore, the transcriptome changes of R. solanacearum analysis indicated that the combination application and single allocation of CuONPs could inhibit "biofilm formation", molecular function, biological processes, cellular components, metabolic process, and so on. In addition, the combination application showed higher inhibition of motility and biofilm, and better enhancement of cell membrane permeability, protein leakage, MDA concentration, and enzyme activity of their respiratory chain dehydrogenase than single application of CuONPs or phage (ϕPB2). Transcriptomes analysis also supported that the addition of ϕPB2 enhanced the toxicity of CuONPs by influencing the ABC transporters and quorum sensing, metabolic processes, and cellular biosynthetic processes of R. solanacearum. Conclusion: In total, our work not only proposed a novel way to increase the bactericidal effect of nanomaterials by adding phage, but also discovered the influence, synergistic effects, and mechanisms, which is useful to design novel way to combat phytopathogenic bacteria in the complicated environment. [ABSTRACT FROM AUTHOR]

Within a few years of the establishment of the convict settlement at Sydney Cove, the potato became one of the staple crops of the population due to its relatively high yield and the prior experience of the convicts and free settlers with growing the crop. In 1894, Henry Tryon described a new disease in southern Queensland that caused rapid wilting of plants, a ring of slightly translucent tissue just below the surface of affected tubers, oozing of a thick, white fluid from the 'eyes', and ultimately rotting of the tubers. It soon became known as 'Tryon's disease'. He found that a microbe (bacterium) was always associated with affected tubers and stems, provided a very brief description of the bacterial cells and named the microbe Bacillus vascularum solani. A few years later the American scientist Erwin Frink Smith wrote a paper on a new disease (brown rot) of solanaceous plants including the potato and tomato, in which he called the causal agent Pseudomonas solanacearum , now known as Ralstonia solanacearum. Smith dismissed Tryon's prior claim to the discovery of the disease with some of his comments being personal and scathing. Tryon had the last word, however, cloaking his response in restrained and somewhat convoluted tones. In 1894, the Queensland government entomologist, and later vegetable pathologist, Henry Tryon (1856–1943) discovered a new disease that caused potato tubers to become rotted and putrid. He consistently found bacterial cells in a thick mucilaginous gum in the vascular tissues of wilted stems and infected tubers, and gave it the name Bacillus vascularum solani. The American bacteriologist Erwin Frink Smith would not accept Tryon's discovery, instead naming the causal agent Pseudomonas solanacearum. That bacterium, now called Ralstonia solanacearum is a significant plant pathogen worldwide. Photograph by an unknown person. [ABSTRACT FROM AUTHOR]

Summary: To challenge the invasion of various pathogens, plants re‐direct their resources from plant growth to an innate immune defence system. However, the underlying mechanism that coordinates the induction of the host immune response and the suppression of plant growth remains unclear. Here we demonstrate that an auxin response factor, CaARF9, has dual roles in enhancing the immune resistance to Ralstonia solanacearum infection and in retarding plant growth by repressing the expression of its target genes as exemplified by Casmc4, CaLBD37, CaAPK1b and CaRROP1. The expression of these target genes not only stimulates plant growth but also negatively impacts pepper resistance to R. solanacearum. Under normal conditions, the expression of Casmc4, CaLBD37, CaAPK1b and CaRROP1 is active when promoter‐bound CaARF9 is complexed with CaIAA2. Under R. solanacearum infection, however, degradation of CaIAA2 is triggered by SA and JA‐mediated signalling defence by the ubiquitin‐proteasome system, which enables CaARF9 in the absence of CaIAA2 to repress the expression of Casmc4, CaLBD37, CaAPK1b and CaRROP1 and, in turn, impeding plant growth while facilitating plant defence to R. solanacearum infection. Our findings uncover an exquisite mechanism underlying the trade‐off between plant growth and immunity mediated by the transcriptional repressor CaARF9 and its deactivation when complexed with CaIAA2. [ABSTRACT FROM AUTHOR]

SUMMARY: Uncovering the function of phytopathogen effectors is crucial for understanding mechanisms of pathogen pathogenicity and for improving our ability to protect plants from diseases. An increasing number of effectors have been predicted in various plant pathogens. Functional characterization of these effectors has become a major focus in the study of plant–pathogen interactions. In this study, we designed a novel screening system that combines the TMV (tobacco mosaic virus)‐GFP vector and Agrobacterium‐mediated transient expression in the model plant Nicotiana benthamiana. This system enables the rapid identification of effectors that interfere with plant immunity. The biological function of these effectors can be easily evaluated by observing the GFP fluorescence signal using a UV lamp within just a few days. To evaluate the TMV‐GFP system, we initially tested it with well‐described virulence and avirulence type III effectors from the bacterial pathogen Ralstonia solanacearum. After proving the accuracy and efficiency of the TMV‐GFP system, we successfully screened a novel virulence effector, RipS1, using this approach. Furthermore, using the TMV‐GFP system, we reproduced consistent results with previously known cytoplasmic effectors from a diverse array of pathogens. Additionally, we demonstrated the effectiveness of the TMV‐GFP system in identifying apoplastic effectors. The easy operation, time‐saving nature, broad effectiveness, and low technical requirements of the TMV‐GFP system make it a promising approach for high‐throughput screening of effectors with immune interference activity from various pathogens. Significance Statement: The development of a robust high‐throughput functional screening assay for pathogen effectors will facilitate the study in plant‐pathogen interactions. We established a novel screening system using the TMV‐GFP vector, enabling the rapid identification of effectors that interfere with plant immunity by observing GFP fluorescence under a UV lamp within a few days. The TMV‐GFP system is a promising approach for high‐throughput screening of effectors from diverse pathogens. [ABSTRACT FROM AUTHOR]

Clustered regularly interspaced short palindromic repeats (CRISPR) has been widely characterized as a defense system against phages and other invading elements in bacteria and archaea. A low percentage of Ralstonia lanacearum species complex (RSSC) strains possess the CRISPR array and the CRISPR-associated proteins (Cas) that would confer immunity against various phages. To provide a wide-range screen of the CRISPR presence in the RSSC, weanalyzed 378 genomes of RSSC strains to find the CRISPR locus. We found that 20.1,14.3, and 54.5% of the R. solanacearum, pseudosolanacearum, and R. syzygii strains, respectively, possess the CRISPR locus. In addition, we performed further analysis to identify the respective phages that are restricted by the CRISPR arrays. We found 252 different phages infecting different strains of the RSSC, by means of the identification of similarities between the protospacers in phages and spacers in bacteria. We compiled this information in a database with web access called CRISPRals (https: #crisprals, yachaytech, edu. ec/). Additionally, we made available a number of tools to detect and identify CRI SPR array and Cas genes in genomic sequences that could be uploaded by users. Finally, a matching tool to relate bacteria spacer with phage protospacer sequences is available. CRISPRals is a valuable resource for the scientific community that contributes to the study of bacteria-phage interaction and a starti ng point that will help to design efficient phage therapy strategies. [ABSTRACT FROM AUTHOR]

Forty-two accessions of eggplant were screened against Ralstonia solanacearum in screen-house environments. This was followed by an assessment of the genetic diversity of the 42 eggplant successions originating from Bangladesh, China, Thailand and Malaysia, accomplished by exploring SSR markers for germplasm characterisation. Five selected resistant genotypes used as a rootstock were further assessed with UPMSE16 strain in a subsequent trial. The pathogenicity test based on area under the disease progress curve (AUDPC) and disease severity index (DSI) at four weeks after inoculation indicated that genotypes TB3, TB6, TB7, MB16 and BB9 had the greatest degree of resistance. Also, the results of the second trial for grafted and control plants based on DSI and AUDPC at 4 WAI showed that grafted plants had resistance to UPMSE16 strain with no symptoms at 4 WAI. The 42 accessions were grouped into nine major clusters based on SSR markers using Unweighted Pair Group Method with Arithmetic mean. Hence, the phenotyping screening reveals that five eggplant accessions were resistant to R. solanacearum and can be used as potential rootstock. As a result, the discovered SSR markers may be effective in marker-assisted selection for future use in developing new rootstock. [ABSTRACT FROM AUTHOR]

In the world, Ralstonia solanacearum, the second most harmful bacterial phytopathogen, poses a serious danger to potato crop by causing brown rot disease, which can result in losses of up to 100%. For that, this study aims to isolate and identify of pathogenic bacteria causing brown rot disease and biocontrol it using ZnONPs synthesized by fungal strain. Eighteen infected potato cv. Cara samples were collected from different six regions of El-Minya governorate, Egypt. Isolation, identification, and pathogenicity tests were done for the most common pathogenic bacteria. Also, 18 native agricultural soil samples from 6 regions of El-Minya governorate, Egypt. Additionally, isolation and identification of the most common fungal isolate can synthesize ZnONPs. Mycosynthesized ZnONPs were characterized by UV, TEM, SEM, EDX, XRD, FTIR, Zeta potential, and particle size. Cytotoxicity test for mycosynthesized ZnONPs was done to determine the safety level of obtained nanoparticles which its dominant spherical or hexagonal shapes and small in size at 42.2 ± 3.0 nm. Results showed that the pathogenic bacterial isolate was identified using morphological, biochemical, and molecular as Ralstonia solanacearum (OR533702). Also, 16 fungal isolates were isolated and the most common was selected and identified as Epicoccum nigrum (OR533699) using microscopic, macroscopic, and molecular identification. Additionally, the result showed the selected fungal strain E. nigrum has high efficacy with inhibition zone diameter (2.20 ± 0.20) mm at 100 μg/ mL (5mM) against R. solanacearum. This study concluded that mycosynthesized ZnONPs have a potent effect against R.solanacearum compared to Revanol 50% as a traditional product. [ABSTRACT FROM AUTHOR]

As an important member of mitogen-activated protein kinase (MAPK) cascades, MAPKs play an important role in plant defense response against biotic and abiotic stresses; however, the involvement of the majority of the MAPK family members against Ralstonia solanacearum and heat stress (HS) remains poorly understood. In the present study, CaMAPK1 was identified from the genome of pepper and its function against R. solanacearum and HS was analyzed. The transcript accumulations of CaMAPK1 and the activities of its native promoter were both significantly induced by R. solanacearum inoculation, HS, and the application of exogenous hormones, including SA, MeJA, and ABA. Transient expression of CaMAPK1 showed that CaMAPK1 can be targeted throughout the whole cells in Nicotiana benthamiana and triggered chlorosis and hypersensitive response-like cell death in pepper leaves, accompanied by the accumulation of H2O2, and the up-regulations of hormones- and H2O2-associated marker genes. The knock-down of CaMAPK1 enhanced the susceptibility to R. solanacearum partially by down-regulating the expression of hormones- and H2O2-related genes and impairing the thermotolerance of pepper probably by attenuating CaHSFA2 and CaHSP70-1 transcripts. Taken together, our results revealed that CaMAPK1 is regulated by SA, JA, and ABA signaling and coordinates responses to R. solanacearum infection and HS in pepper. [ABSTRACT FROM AUTHOR]

Bacterial wilt, caused by Ralstonia solanacearum, is one of the main challenges for sustainable tomato production in the Amazon region. This study evaluated the potential of bacteria isolated from sediments of the Solimões and Negro rivers for the biocontrol of this disease. From 36 bacteria selected through in vitro antibiosis, three promising isolates were identified: Priestia aryabhattai RN 11, Streptomyces sp. RN 24, and Kitasatospora sp. SOL 195, which inhibited the growth of the phytopathogen by 100%, 87.62%, and 100%, respectively. These isolates also demonstrated the ability to produce extracellular enzymes and plant growth-promoting compounds, such as indole-3-acetic acid (IAA), siderophore, and ammonia. In plant assays, during both dry and rainy seasons, P. aryabhattai RN 11 reduced disease incidence by 40% and 90%, respectively, while promoting the growth of infected plants. Streptomyces sp. RN 24 and Kitasatospora sp. SOL 195 exhibited high survival rates (85–90%) and pathogen suppression in the soil (>90%), demonstrating their potential as biocontrol agents. This study highlights the potential of Amazonian bacteria as biocontrol agents against bacterial wilt, contributing to the development of sustainable management strategies for this important disease. [ABSTRACT FROM AUTHOR]

BACKGROUND: Ralstonia solanacearum, a notorious and refractory bacterial plant pathogen, threatens multiple vegetable crops and causes significant economic loss in agriculture. Long‐term use of traditional medicines not only increases the problem of drug resistance, but also causes great environmental pollution. Therefore, there is an urgent need to develop new agents with high efficacy and low toxicity. RESULTS: In this study, we have synthesized and characterized graphitic carbon nitride incorporated copper oxide composite (g‐C3N4@CuO), which showed higher antimicrobial effect than graphitic carbon nitride nanosheets (g‐C3N4 nanosheets) and copper oxide nanoparticles (CuONPs). Ralstonia solanacearum exposed to g‐C3N4@CuO exhibited higher levels of oxygen toxicity, cell membrane damage, DNA damage, motility disruption and even cell death compared to g‐C3N4 nanosheets and CuONPs. In addition, g‐C3N4@CuO was more effective in the control of tobacco bacterial wilt than g‐C3N4 nanosheets and CuONPs. CONCLUSION: Thus, this study provides a new perspective on g‐C3N4@CuO control of bacterial diseases in crops, and the mechanism is related to the destruction of cell membrane damage and motility disruption. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Background: Several WRKY transcription factors (TFs), including CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40 are known to govern the resistance of pepper (Capsicum annuum L.) plants to Ralstonia solanacearum infestation (RSI) and other abiotic stresses. However, the molecular mechanisms underlying these processes remain elusive. Methods: This study functionally described CaWRKY3 for its role in pepper immunity against RSI. The roles of phytohormones in mediating the expression levels of CaWRKY3 were investigated by subjecting pepper plants to 1 mM salicylic acid (SA), 100 µM methyl jasmonate (MeJA), and 100 µM ethylene (ETH) at 4-leaf stage. A virus-induced gene silencing (VIGS) approach based on the Tobacco Rattle Virus (TRV) was used to silence CaWRKY3 in pepper, and transiently over-expressed to infer its role against RSI. Results: Phytohormones and RSI increased CaWRKY3 transcription. The transcriptions of defense-associated marker genes, including CaNPR1, CaPR1, CaDEF1, and CaHIR1 were decreased in VIGS experiment, which made pepper less resistant to RSI. Significant hypersensitive (HR)-like cell death, H2O2 buildup, and transcriptional up-regulation of immunological marker genes were noticed in pepper when CaWRKY3 was transiently overexpressed. Transcriptional activity of CaWRKY3 was increased with overexpression of CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40, and vice versa. In contrast, Pseudomonas syringae pv tomato DC3000 (Pst DC3000) was easily repelled by the innate immune system of transgenic Arabidopsis thaliana that overexpressed CaWRKY3. The transcriptions of defense-related marker genes like AtPR1, AtPR2, and AtNPR1 were increased in CaWRKY3-overexpressing transgenic A. thaliana plants. Conclusion: It is concluded that CaWRKY3 favorably regulates phytohormone-mediated synergistic signaling, which controls cell death in plant and immunity of pepper plant against bacterial infections. [ABSTRACT FROM AUTHOR]