Search Results (373)

Genomic islands (GIs) including integrative and conjugative elements (ICEs), prophages, and integrative plasmids are central drivers of horizontal gene transfer in bacterial plant pathogens. These elements often carry cargo genes encoding virulence factors, antibiotic and metal resistance determinants, and metabolic functions that enhance environmental adaptability. In plant-pathogenic species such as Pseudomonas syringae, GIs contribute to host specificity, immune evasion, and the emergence of novel pathogenic variants. ICEclc and its homologs represent integrative and mobilizable elements whose tightly regulated excision and transfer are driven by a specialized transcriptional cascade, while ICEs in P. syringae highlight the ecological impact of cargo genes on pathogen virulence and fitness. Pathogenicity islands further modulate virulence gene expression in response to in planta stimuli. Beyond P. syringae, GIs in genera such as Erwinia, Pectobacterium, and Ralstonia underpin critical traits like toxin biosynthesis, secretion system acquisition, and topoisomerase-mediated stability. Leveraging high-throughput genomics and structural biology will be essential to dissect GI regulation and develop targeted interventions to curb disease spread. This review synthesizes the current understanding of GIs in plant-pathogenic gammaproteobacteria and outlines future research priorities for translating mechanistic insights into sustainable disease control strategies. Full article

A previously undescribed cis-clerodane diterpenoid, diangelate solidagoic acid J (1), along with two known cis-clerodane diterpenoids, solidagoic acid C (2) and solidagoic acid D (3), as well as two known unsaturated monoacylglycerols, 1-linoleoyl glycerol (4) and 1-α-linolenoyl glycerol (5), were isolated and characterized from the n-hexane leaf extract of Solidago gigantea (giant goldenrod). Compounds 2–5 were identified first in this species, and compounds 4 and 5 are reported here for the first time in the Solidago genus. The bioassay-guided isolation procedure included thin-layer chromatography (TLC) coupled with a Bacillus subtilis antibacterial assay, preparative flash column chromatography, and TLC–mass spectrometry (MS). Their structures were elucidated via extensive spectroscopic and spectrometric techniques such as one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy and high-resolution tandem mass spectrometry (HRMS/MS). The antimicrobial activities of the isolated compounds were evaluated by a microdilution assay. All compounds exhibited weak to moderate antibacterial activity against the Gram-positive plant pathogen Clavibacter michiganensis, with MIC values ranging from 17 to 133 µg/mL, with compound 5 being the most potent. Only compound 1 was active against Curtobacterium flaccumfaciens pv. flaccumfaciens, while compound 3 demonstrated a weak antibacterial effect against B. subtilis and Rhodococcus fascians. Additionally, the growth of B. subtilis and R. fascians was moderately inhibited by compounds 1 and 5, respectively. None of the tested compounds showed antibacterial activity against Gram-negative Pseudomonas syringae pv. tomato and Xanthomonas arboricola pv. pruni. No bactericidal activity was observed against the tested microorganisms. Compounds 2 and 3 displayed weak antifungal activity against the crop pathogens Bipolaris sorokiniana and Fusarium graminearum. Our results demonstrate the efficacy of bioassay-guided strategies in facilitating the discovery of novel bioactive compounds. Full article

The immune response triggered when plant cell surface receptors recognize pathogen-associated molecular patterns (PAMPs) is known as PAMP-triggered immunity (PTI). Several studies have demonstrated that extracellular plant ferredoxin-like protein (PFLP) can enhance PTI signaling, thereby conferring resistance to bacterial diseases in various plants. The C-terminal casein kinase II (CK2) phosphorylation region of PFLP is essential for strengthening PTI. However, whether phosphorylation at this site directly enhances PTI signaling and consequently increases plant disease resistance remains unclear. To investigate this, site-directed mutagenesis was used to generate PFLPT90A, a non-phosphorylatable mutant, and PFLPT90D, a phospho-mimetic mutant, for functional analysis. Based on the experimental results, none of the recombinant proteins were able to enhance the hypersensitive response induced by the HrpN protein or increase resistance to the soft rot pathogen Pectobacterium carotovorum subsp. carotovorum ECC17. These findings suggest that phosphorylation at the T90 residue might be essential for PFLP-mediated enhancement of plant immune responses, implying that this post-translational modification is likely required for its disease resistance function in planta. To further explore the relationship between PFLP phosphorylation and endogenous CK2, the Arabidopsis insertion mutant cka2 and the complemented line CKA2R were analyzed under treatment with flg22_Pst from Pseudomonas syringae pv. tomato. The effects of PFLP on the hypersensitive response, rapid oxidative burst, callose deposition, and susceptibility to soft rot confirmed that CK2 is required for these immune responses. Furthermore, expression analysis of PTI-related genes FRK1 and WRKY22/29 in the mitogen-activated protein kinase (MAPK) signaling pathway demonstrated that CK2 is necessary for PFLP to enhance flg22_Pst-induced immune signaling. Taken together, these findings suggest that PFLP enhances A. thaliana resistance to bacterial soft rot primarily by promoting the MAPK signaling pathway triggered by PAMP recognition, with CK2-mediated phosphorylation being essential for its function. Full article

Chaperonin 60 proteins plays an important role in plant growth and development as well as the response to abiotic stress. As part of the protein homeostasis system, molecular chaperones have attracted increasing attention in recent years due to their involvement in the folding and assembly of key proteins in photosynthesis. However, little is known about the function of maize chaperonin 60 protein. In the study, a gene encoding the chaperonin 60 proteins was cloned from the maize inbred line B73, and named ZmCpn60-3. The gene was 1, 818 bp in length and encoded a protein consisting of 605 amino acids. Phylogenetic analysis showed that ZmCpn60-3 had high similarity with OsCPN60-1, belonging to the β subunits of the chloroplast chaperonin 60 protein family, and it was predicted to be localized in chloroplasts. The ZmCpn60-3 was highly expressed in the stems and tassels of maize, and could be induced by exogenous plant hormones, mycotoxins, and pathogens; Overexpression of ZmCpn60-3 in Arabidopsis improved the resistance to Pst DC3000 by inducing the hypersensitive response and the expression of SA signaling-related genes, and the H₂O₂ and the SA contents of ZmCpn60-3-overexpressing Arabidopsis infected with Pst DC3000 accumulated significantly when compared to the wild-type controls. Experimental data demonstrate that flg22 treatment significantly upregulated transcriptional levels of the PR1 defense gene in ZmCpn60-3-transfected maize protoplasts. Notably, the enhanced resistance phenotype against Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) in ZmCpn60-3-overexpressing transgenic lines was specifically abolished by pretreatment with ABT, a salicylic acid (SA) biosynthetic inhibitor. Our integrated findings reveal that this chaperonin protein orchestrates plant immune responses through a dual mechanism: triggering a reactive oxygen species (ROS) burst while simultaneously activating SA-mediated signaling cascades, thereby synergistically enhancing host disease resistance. Additionally, yeast two-hybrid assay preliminary data indicated that ZmCpn60-3 might bind to ZmbHLH118 and ZmBURP7, indicating ZmCpn60-3 might be involved in plant abiotic responses. The results provided a reference for comprehensively understanding the resistance mechanism of ZmCpn60-3 in plant responses to abiotic or biotic stress. Full article

Hyperspectral imaging (HSI) integrates spectroscopy and imaging, providing detailed spectral–spatial information, and the selection of task-relevant wavelengths can streamline data acquisition and processing for field deployment. Anomaly detection aims to identify observations that deviate from normal patterns, typically in a one-class classification framework. In this study, we extend this framework to a binary classification by employing a U-Net based deterministic autoencoder augmented with attention blocks to analyze HSI data of sesame plants inoculated with Pseudomonas syringae pv. sesami. Single-band grayscale images across the full spectral range were used to train the model on healthy samples, while the presence of disease was classified by assessing the reconstruction error, which we refer to as the anomaly score. The average classification accuracy in the visible region spectrum (430–689 nm) exceeded 0.8, with peaks at 641 nm and 689 nm. In comparison, the near-infrared region (>700 nm) attained an accuracy of approximately 0.6. Several visible bands demonstrated potential for early disease detection. Some lesion samples showed a gradual increase in anomaly scores over time, and notably, Band 23 (689 nm) exhibited exceeded anomaly scores even at early stages before visible symptoms appeared. This supports the potential of this wavelength for the early-stage detection of bacterial leaf spots in sesame. Full article

Invasive bacteria have caused tremendous losses to global ecosystems and agricultural production, yet effective control measures remain elusive. Plant specialized metabolites are being investigated as an important source of antimicrobial active substances. And Ailanthus altissima is an abundant tree widespread throughout Northeast China. In this study, we identified 21 compounds from A. altissima leaves, including steroids, terpenes, phenolics, and coumarins. Two new steroidal compounds, ailanstigol A (1) and ailanstigol B (2), and one new coumarin (2′R,3′R)-7-(2′,3′,6′-trihydroxy-3′-methylhexyloxy)-6,8-dimethoxycoumarin (3) were isolated. Antibacterial screening revealed that compounds 1 and 2 exhibited inhibitory activity against two invasive bacteria, Xanthomonas oryzae pv. oryzae PXO 71A and PXO 86A and Pseudomonas syringae pv. maculicola ES4326. Further mechanistic screening unveiled that the steroidal compounds 1 and 2 may inhibit bacterial growth and reproduction by reducing cell viability, disrupting the cell membrane and increasing protein leakage, and inhibiting biofilm formation. In summary, our results enriched the known chemical diversity of A. altissima and provided a foundation for investigating the mechanisms by which steroidal compounds inhibit invasive bacterial growth. Full article

The increasing demand for sustainable agricultural practises has sparked interest in microbes that promote plant immunity. Among these, Pseudomonas species have shown the potential to enhance induced systemic resistance (ISR) in crops. While type III secretion systems (T3SSs) in pathogenic bacteria have been widely studied for their role in local immunosuppression, their function in beneficial Pseudomonas species and on a systemic level remains largely unexplored. We show for the first time that the T3SS of a plant-beneficial Pseudomonas strain induces ISR by root colonisation. T3SS-positive Pseudomonas isolates were applied to the roots of sugar beet (Beta vulgaris L.) and systemic effects on plant immunity were assessed in leaves exposed to the pathogen P. syringae pv. aptata P21. Our results show that P. marginalis ORh26 reduced lesion size and pathogen proliferation in sugar beet leaves. ORh26 activated peroxidase and phenylalanine ammonia-lyase and upregulated NPR1 and MYC2 defence genes. Remarkably, a T3SS-deficient mutant of ORh26 failed to induce these effects. Genomic analysis identified T3SS structural genes and effector proteins, including a pectate lyase and an effector of the HopJ family, that may mediate these responses. This study reveals a previously uncharacterised role of T3SS in the induction of ISR and improves our understanding of plant–microbe interactions. Full article

Endophytes, as an integral part of plants, form unique relationships with their hosts that go beyond classical definitions of symbiosis and influence plant development, immunity, and stress responses. The pepper endophyte strain Pseudomonas putida A32 has several plant growth-promoting properties and increases the tolerance of pepper to drought, but its biocontrol potential is unknown. In this study, we investigated the protective role of P. putida A32 against infection with the pathogenic bacterium P. syringae pv. aptata P21 in two pepper genotypes in laboratory experiments. The percentage of lesion reduction in genotype 26 treated with P. putida A32 was 46.62%. The results showed a significant reduction in hydrogen peroxide and malondialdehyde levels by 29.45 and 20.22%, respectively, in infected genotype 26. The treated but uninfected controls showed a significant increase in superoxide dismutase activity in genotype 26 by 41.26% and ascorbate peroxidase activity in genotype 19 by 40.28% in the treated infected plants. The tolerant genotype 19 was much less dependent on the bacterial treatment under stress conditions than the susceptible genotype 26. Future research will investigate the role of P. putida A32 in the induced systemic resistance of different pepper genotypes to protect against pathogens. Full article

Due to their secondary metabolite content, plant extracts are an alternative method for controlling pathogenic organisms in agriculture and post-harvest operations. Botrytis cinerea and Pseudomonas syringae are among the causative agents of diseases and losses in agricultural production. The species Larrea tridentata is abundant in the arid and semi-arid zones of Mexico and has no defined use; however, it contains secondary metabolites with microbicidal potential that could aid in biological control and enhance its harvest status. Growth inhibition (halo) of B. cinerea and P. syringae was evaluated by applying alcoholic extract of L. tridentata leaves at doses of 50, 100, 250, 500, 750, 1000, and 2000 µg mL⁻¹ in vitro, using poisoned medium and potato dextrose agar for the fungus and the agar well method for the bacteria, in a completely randomized design with five replicates. The flavonoids quercetin, apigenin, narigenin, kaempferol, and galangin were identified as possible agents of microbicidal activity. The extract inhibited the growth of B. cinerea from 100 µg mL⁻¹ and completely inhibited it with 1000 and 2000 µg mL⁻¹. For P. syringae, inhibition was observed from 250 µg mL⁻¹, demonstrating that the higher the concentration, the greater the growth inhibitory effect. The secondary metabolite content of the L. tridentata extract is sufficient to have an impact on microorganisms with economic impact in agriculture. Full article

Jatropha dioica Sessé (JD) is a plant from arid and semiarid zones of Mexico related to local therapeutic uses and possible use in food and agriculture as a control agent of pest organisms that helps to reduce impacts on the environment, human health and resistance by phytopathogens. In vitro bactericidal activity was evaluated with the well diffusion method in doses of 1000, 2500, 5000, 7500, 10,000 and 20,000 µg mL⁻¹, and fungistatic activity was evaluated with the agar dilution method (500, 1000, 1500, 2000 and 4000 µg mL⁻¹) in Pseudomonas syringae, Botrytis cinerea and Fusarium oxysporum using hydroalcoholic extracts of J. dioica root in a completely randomized design with five replications. Total phenol and flavonoid contents were recorded by the Folin–Ciocalteu and aluminum chloride methods. Ethanol and methanol extracts showed fungistatic activity on B. cinerea, inhibiting from 42.27 ± 1.09 to 46.68 ± 0.98 mg mL⁻¹, with an IC₅₀ of 5.04 mg mL⁻¹, with no differences by solvent type. In F. oxysporum, inhibition ranged from 14.77 ± 1.08 to 29.19 ± 0.89 mg mL⁻¹, and the methanol extract was more efficient, generating a stress response to the ethanol extract. The bactericidal activity on P. syringae recorded inhibition zones of 17.66 ± 0.33 and 16.66 ± 0.33 mg mL⁻¹, with ethanol being more efficient. The phenol content ranged from 8.92 ± 0.25 to 12.10 ± 0.34 mg EAG g⁻¹ and flavonoid content ranged from 20.49 ± 0.33 to 28.21 ± 0.73 mg QE g⁻¹ of sample dry weight. The results highlight the biological activity of J. dioica as an alternative to biopesticides that minimize agrochemical applications and generate pathogen resistance. These advances contribute to the revaluation and conservation of the species. Full article

Enhanced disease susceptibility1 (EDS1) is a key node in the plant immune signaling network, regulating salicylic acid (SA) levels and other immune responses in Arabidopsis thaliana. We previously reported that modulation of SA by AGD2-like defense response protein 1 (ALD1) has been shown to influence the immune response in Lotus japonicus, but the role of LjEDS1 in this species remains unclear. Here, we identified and characterized the LjEDS1 gene in L. japonicus. The LjEDS1 protein contains a lipase-like domain and an EP domain similar to the Arabidopsis EDS1 protein. Subcellular localization studies revealed that the LjEDS1 protein is distributed in both the cytoplasm and nucleus. Heterologous expression of LjEDS1 in the Arabidopsis ateds1 mutant increased resistance to Pseudomonas syringae pv. Tomato (Pst) strain DC3000. In L. japonicus, roots of the ljeds1 mutants exhibited heightened susceptibility to Ralstonia solanacearum, with increased lesion areas and bacterial titers. Conversely, the overexpression of LjEDS1 reduced the lesion areas and bacterial titers in roots infected with R. solanacearum compared to those in the wild-type. Gene expression analysis showed that LjEDS1 regulates defense-related, basal immunity, and oxidative stress response genes in L. japonicus roots. These findings establish LjEDS1 as an important regulator of disease resistance in L. japonicus. Full article

Cross-kingdom infections, where pathogens from one kingdom infect organisms of another, were historically regarded as rare anomalies with minimal concern. However, emerging evidence reveals their increasing prevalence and potential to disrupt the delicate balance between plant, animal, and human health systems. Traditionally recognized as plant-specific, a subset of phytopathogens, including certain fungi, bacteria, viruses, and nematodes, have demonstrated the capacity to infect non-plant hosts, particularly immunocompromised individuals. These pathogens exploit conserved molecular mechanisms, such as immune evasion strategies, stress responses, and effector proteins, to breach host-specific barriers and establish infections. Specifically, fungal pathogens like Fusarium spp. and Colletotrichum spp. employ toxin-mediated cytotoxicity and cell-wall-degrading enzymes, while bacterial pathogens, such as Pseudomonas syringae, utilize type III secretion systems to manipulate host immune responses. Viral and nematode phytopathogens also exhibit molecular mimicry and host-derived RNA silencing suppressors to facilitate infections beyond plant hosts. This review features emerging cases of phytopathogen-driven animal and human infections and dissects the key molecular and ecological determinants that facilitate such cross-kingdom transmission. It also highlights critical drivers, including pathogen plasticity, horizontal gene transfer, and the convergence of environmental and anthropogenic stressors that breach traditional host boundaries. Furthermore, this review focuses on the underlying molecular mechanisms that enable host adaptation and the evolutionary pressures shaping these transitions. To address the complex threats posed by cross-kingdom phytopathogens, a comprehensive One Health approach that bridges plant, animal, and human health strategies is advocated. Integrating molecular surveillance, pathogen genomics, AI-powered predictive modeling, and global biosecurity initiatives is essential to detect, monitor, and mitigate cross-kingdom infections. This interdisciplinary approach not only enhances our preparedness for emerging zoonoses and phytopathogen spillovers but also strengthens ecological resilience and public health security in an era of increasing biological convergence. Full article

The control of bacterial plant diseases is very challenging and often relies on the application of copper compounds, although the frequent emergence and spread of resistant bacterial strains compromise their efficacy. Additionally, copper-based compounds raise environmental and human health concerns, leading to their inclusion in the European Commission’s list of candidates for substitution. As a promising and sustainable alternative, we investigated the efficacy of biogenic zinc oxide nanoparticles (ZnO-NPs) in protecting tomato plants against Pseudomonas syringae pv. tomato (Pst), the causal agent of bacterial speck disease. ZnO-NPs exhibited significant in vitro antibacterial activity (EC₉₅ = 17.0 ± 1.1 ppm) against the pathogen. Furthermore, when applied to the foliage of tomato plants at 100 ppm before or following Pst inoculation, they induced significant reductions in symptom severity and bacterial growth in planta, which were comparable to those shown by plants treated with acibenzolar-S-methyl, a plant defense inducer. Gene expression assessed by qPCR revealed the involvement of the systemic acquired resistance (SAR) pathway in tomato plants treated with ZnO-NPs before inoculation, suggesting that the observed protection could be due to a priming effect. Finally, infected plants showed oxidative stress, with higher H₂O₂ and malondialdehyde (MDA) contents. ZnO-NPs reverted this effect, containing the content of the above molecules, and stimulated the production of metabolites involved in dealing with oxidative perturbations (carotenoids and phenols), while unaffecting flavonoids and anthocyanins. Full article

As sessile organisms, plants are exposed to a variety of environmental stresses caused by biotic and abiotic factors during their life cycle; as a result, plants have evolved complex defense mechanisms to cope with these stresses, among which the mitogen-activated protein kinase cascade signaling pathway is particularly critical. This study focused on MdMAPK6, a specific mitogen-activated protein kinase gene in Malus domestica, to illuminate its functions in stress responses. MdMAPK6 was successfully cloned from apple and shown to respond to various stressors, including drought, salt, and abscisic acid. Overexpressing MdMAPK6 in apple calli resulted in enhanced resistance to drought, salt, and Botryosphaeria dothidea. Ectopic expression of MdMAPK6 in Arabidopsis thaliana enhanced the resistance to drought, salt, and Pseudomonas syringae pathovar tomato DC3000. These results indicated that MdMAPK6 in apples is a traditional mitogen-activated protein kinase, which plays an important role in both biotic and abiotic stresses. Full article

The search for environmentally friendly solutions to effectively control crop pests while safeguarding human health has become a global priority. One promising strategy is to enhance plant defenses by pre-inducing their innate immune system. In this study, we developed rhamnolipid (RL)-stabilized nanoemulsions (NEs) encapsulating essential oils (EOs) as potential biopesticides and biostimulants for agroindustrial applications. These NEs were designed to improve the solubility and stability of EOs while effectively combining their insecticidal and/or repellent activities with the bioactive properties of RLs. In this regard, our interdisciplinary approach involved formulating and characterizing these NEs and evaluating their stability and wettability on plant leaf surfaces. We further evaluated their effects on bacterial growth in vitro and in the model plant Arabidopsis thaliana, along with their impact on beneficial soil microorganisms. We analyzed their ability to stimulate the plant’s immune system and their impact on the viability and reproduction of the aphid Myzus persicae. Additionally, we explored whether RLs stimulate plant defenses through alterations in the leaf cuticle. Our findings demonstrate that RL-stabilized EO-NEs are effective bioprotectants and biostimulants in the model plant, offering a sustainable alternative that could reduce reliance on chemical pesticides in agriculture. Full article