Search Results (148)

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

Syringin is a phenylpropanoid glycoside isolated from the bark of Syringa vulgaris. Phillygenin is a lignan obtained mainly from the fruits and flowers of Forsythia intermedia. Both compounds have shown potent anti-inflammatory and antioxidant properties. We investigated the potential role of syringin and phillygenin in preventing lipid deposition in macrophages. Syringin and phillygenin significantly (p < 0.001) reduced lipid deposition in macrophages in a dose-dependent manner. For syringin, the greatest reduction in CD36 receptor expression was found to be over 80% (50 μg/mL) compared to the cholesterol-stimulated control (p < 0.001). Phillygenin inhibited CD36 receptor expression by approximately 25% (50 μg/mL), compared to the stimulated control (p < 0.05). For syringin, the CD36 receptor regulation pathway was PPAR-γ dependent. Phillygenin showed a statistically significant (p < 0.001) increase in the expression of the ABCA1 transporter: 2.5-fold (10 μg/mL), 3-fold (20 μg/mL) and 4-fold (50 μg/mL) compared to the cholesterol-stimulated control. Syringin did not significantly increase ABCA1 expression. For phillygenin, the activation pathway of the ABCA1 transporter was HO-1dependent. Our study showed that syringin inhibits the cholesterol-induced differentiation of macrophages into foam cells. Moreover, phillygenin increased cholesterol efflux from macrophages. Therefore, syringin and phillygenin may be valuable agents in the prevention of early and late atherosclerosis. 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

Common in Fungal Extracellular Membrane (CFEM) effectors, a unique class of fungal-specific proteins, play critical roles in host-pathogen interactions. While CFEM proteins have been extensively characterized in phytopathogens, their presence and functions in Fusarium verticillioides remained unexplored. Here, we systematically identified 19 CFEM-containing proteins in F. verticillioides, among which FvCFEM12 exhibited secretory activity and plant infection-induced expression. Functional characterization revealed that FvCFEM12 suppressed Bax- and INF1-triggered cell death in Nicotiana benthamiana leaves. Furthermore, heterologous expression of FvCFEM12 in maize leaves using P. syringae strain D36E can compromise immune responses against bacterial pathogens. Deletion of FvCFEM12 impaired fungal virulence, altered hyphal morphology, and reduced cell wall stress tolerance. Interestingly, FvCFEM12 physically interacted with the maize wall-associated receptor kinase ZmWAK17ET, and targeted silencing of ZmWAK17 in maize enhanced susceptibility to F. verticillioides. Our findings revealed that FvCFEM12 is a dual-function effector that suppresses plant immunity and maintains fungal cell wall integrity, thereby orchestrating fungal pathogenicity at the host–pathogen interface. 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

Forest trees significantly affect human life. The spread of pathogens, including bacterial ones, poses a serious threat to their health. Despite this, however, the species composition and distribution of pathogenic bacteria, as well as the etiology of common diseases affecting forest trees, remain virtually unstudied. In this study, we, for the first time, describe different species of Pseudomonas and Pantoea as new etiological agents associated with the symptoms of leaf spotting and wood darkening on Acer tataricum L., Fraxinus pennsylvanica L., Ulmus minor Mill. Ulmus laevis Pallas. and Populus tremula L. For the identification of bacteria species, we used an integrated approach based on the characterization of their morphology, biochemistry, physiology and genetics. Phylogenetic analysis was performed using multilocus typing for five genes for Pseudomonas and six genes for Pantoea. Leaf spotting on A. tataricum, F. pennsylvanica, U. minor and U. laevis was shown to be caused by Pseudomonas cerasi, Pseudomonas congelans, Pseudomonas graminis, Pseudomonas syringae and Pantoea agglomerans both in monoinfection and coinfection. Wood darkening in U. minor U. laevis and P. tremula was found to be associated with the presence of Pantoea sp. and P. agglomerans. The coinfection of forest trees with bacteria of the genera Pseudomonas and Pantoea indicates a complex mechanism of interaction between the two populations, which will be the subject of future studies. Full article

Endophytic bacteria are an important source for developing antimicrobial substances. With the aim to find eco-friendly antimicrobial agents from natural sources, Streptomyces sp. R6 was isolated from Azadirachta indica. After that, a new spirotetronate natural product, lobophorin S (compound 2), together with lobophorin H8 (compound 1) and a known macrolide compound divergolide C (compound 3) were isolated from the cultural solution of strain R6. These compounds mark the first isolation of marine-derived microbial natural products known as lobophorins (LOBs) from endophytic bacteria. The structures of these three compounds were identified by extensive NMR and HRMS analyses. The antimicrobial activities of these three compounds against eight fungal and four bacterial phytopathogens were separately evaluated. Compound 1 demonstrated better antibacterial activity against Erwinia carotovora, Pseudomonas syringae pv. tomato, and P. syringae pv. lachrymans with MIC values of 3.91, 7.81, and 15.63 μg/mL, respectively. Additionally, compounds 1–3 all showed antifungal activity against Botrytis cinerea, with the MIC values of 1.95, 7.81, and 15.63 μg/mL, respectively. Notably, the in vivo antifungal effect of 1 against B. cinerea was up to 78.51 ± 3.80% at 1.95 µg/mL, significantly surpassing polyoxin B (70.70 ± 3.81%). These results highlight the potential of lobophorins as promising lead compounds for the development of new, sustainable agents to control plant diseases. Full article

Globally, forests are constantly threatened by a plethora of disturbances of natural and anthropogenic origin, such as climate change, forest fires, urbanization, and pollution. Besides the most common stressors, during the last few years, Portuguese forests have been impacted by severe decline phenomena caused by invasive pathogens, many of which belong to the genus Phytophthora. The genus Phytophthora includes a large number of species that are invading forest ecosystems worldwide, chiefly as a consequence of global trade and human activities. This paper reports the results of a survey of Phytophthora diversity in natural and semi-natural forest ecosystems in Portugal along an elevation gradient. Isolations performed from 138 symptomatic plant tissues and rhizosphere samples collected from 26 plant species yielded a total of 19 Phytophthora species belonging to 6 phylogenetic clades, including P. cinnamomi (36 isolates), P. multivora (20), P. plurivora (9), P. cactorum (8), P. lacustris (8), P. pseudocryptogea (8), P. amnicola (6), P. hedraiandra (6), P. pseudosyringae (5), P. thermophila (5), P. bilorbang (4), P. inundata (4), P. asparagi (3), P. citricola (3), P. gonapodyides (3), P. rosacearum (3), P. chlamydospora (2), P. pachypleura (2), and P. syringae (1). Overall, the data obtained highlight the widespread occurrence of P. cinnamomi in natural ecosystems from sea level to mountain habitats. The results of the pathogenicity tests carried out on 2-year-old chestnut plants confirmed the key role of P. cinnamomi in the recrudescence of chestnut ink disease and the additional risk posed by P. pachypleura, P. plurivora, and P. multivora to Portuguese chestnut forests. Finally, three species, P. citricola, P. hedraiandra, and P. pachypleura, are reported for the first time in the natural ecosystems of Portugal. Full article

Pseudomonas syringae pv. syringae is the main causal agent of bacterial canker in sweet cherry in Chile, causing significant economic losses. Cultivars exhibit diverse susceptibility in the field and the molecular mechanisms underlying the differential responses remain unclear. RNA-seq analysis was performed to characterize the transcriptomic response in cultivars Santina and Bing (less and more susceptible to P. syringae pv. syringae, respectively) after 1 and 7 days post-inoculation (dpi) with the bacterium. Symptoms of bacterial canker became evident from the fifth day. At 1 dpi, cultivar Santina showed a faster response to infection and a larger number of differentially expressed genes (DEGs) than cultivar Bing. At 7 dpi, cultivar Bing almost doubled its DEGs, while cultivar Santina tended to the normal DEG levels. P. syringae pv. syringae infection downregulated the expressions of key genes of the photosynthesis process at 1 dpi in the less susceptible cultivar. The results suggest that the difference in susceptibility to P. syringae pv. syringae is linked to the timeliness of pathogen recognition, limiting the bacteria’s dispersion through modeling its cell wall, and regulation of genes encoding photosynthesis pathway. Through this study, it has been possible to progress the knowledge of relevant factors related to the susceptibility of the two studied cherry cultivars to P. syringae pv. syringae. Full article

The objective of this systematic review (SR) was to select studies on the activity of glycerol as a molecule that induces disease resistance in plants. We sought to evaluate articles deposited in five electronic databases using a search string and predefined inclusion and exclusion criteria. The most studied crops are Arabidopsis thaliana, Glycine max, and Coffea spp. The most commonly cited biotic agents include Pseudomonas syringae, Blumeria graminis, and Colletotrichum higginsianum. Numerous doses of glycerol were studied, and concentrations ranged from 0.004 to 9.21%, with a 3% concentration of glycerol being considered most effective for most plant species, where greater resistance was observed with increased glycerol-3-phosphate (G3P) and decreased oleic acid levels. The main means of application of the product were spraying and immersion. The SR also revealed the evaluation of resistance-inducing genes, such as PR proteins (PR-1, PR2, PR-5, etc.), HPS70, HSP90, SCAM4, and Tapr1, among others. The information collected in this SR helps to understand the state of the art on the use of glycerol as a molecule inducing resistance against biotic stressors to understand the mechanisms involved in most host–pathogen relationships. This information will be useful in plant breeding programs and for growers/producers. Full article

Phytopathogens pose a serious threat to agriculture, causing a decrease in yield and product quality. This necessitates the development of methods for early detection of phytopathogens, which will reduce losses and improve product quality by using lower quantities of agrochemicals. In this study, the efficiency of spectral imaging in the early detection and differentiation of diseases caused by pathogens of different types (Potato virus X (PVX) and the bacterium Pseudomonas syringae) was analyzed. An evaluation of the visual symptoms of diseases demonstrated the presence of pronounced symptoms in the case of bacterial infection and an almost complete absence of visual symptoms in the case of viral infection. P. syringae caused severe inhibition of photosynthetic activity in the infected leaf, while PVX did not have a pronounced effect on photosynthetic activity. Reflectance spectra of infected and healthy plants were detected in the range from 400 to 1000 nm using a hyperspectral camera, and the dynamics of infection-induced changes during disease progression were analyzed. P. syringae caused a strong increase in reflectance in the blue and red spectral ranges, as well as a decrease in the near-infrared range. PVX-induced changes in the reflectance spectrum had smaller amplitudes compared to P. syringae, and were localized mainly in the red edge (RE) range. The entire set of normalized reflectance indices (NRI) for the analyzed spectral range was calculated. The most sensitive NRIs to bacterial (NRI_510/545, NRI_510/850) and viral (NRI_600/850, NRI_700/850) infections were identified. The use of these indices makes it possible to detect the disease at an early stage. The study of the identified NRIs demonstrated the possibility of using the multispectral imaging method in early pathogen detection, which has high performance and a low cost of analysis. Full article

Pests and diseases have caused significant problems since the domestication of crops, resulting in economic loss and hunger. To overcome these problems, synthetic pesticides were developed to control pests; however, there are significant detrimental side effects of synthetic pesticides on the environment and human health. There is an urgent need to develop safer and more sustainable pesticides. Industrial hemp is a reservoir of compounds that could potentially replace some synthetic bactericides, fungicides, and insecticides. We determined the efficacy of industrial hemp extracts against Pseudomonas syringae pv. tabaci (PSTA), Pseudomonas syringae pv. tomato (PSTO), and Erwinia carotovora (EC). The study revealed a minimum inhibitory concentration (MIC) of 2.05 mg/mL and a non-inhibitory concentration (NIC) of 1.2 mg/mL for PSTA, an MIC of 5.7 mg/mL and NIC of 0.66 mg/mL for PSTO, and an MIC of 12.04 mg/mL and NIC of 5.4 mg/mL for EC. Time-kill assays indicated the regrowth of E. carotovora at 4 × MIC after 15 h and P. syringae pv. tomato at 2 × MIC after 20 h; however, P. syringae pv. tabaci had no regrowth. The susceptibility of test bacteria to hemp extract can be ordered from the most susceptible to the least susceptible, as follows: P. syringae pv. tabaci > P. syringae pv. tomato > E. carotovora. Overall, the data indicate hemp extract is a potential source of sustainable and safe biopesticides against these major plant pathogens. Full article

Plant pathogenic Pseudomonas species cause a variety of diseases in plants. Each Pseudomonas species employs different virulence factors and strategies for successful infection. Moreover, even the same bacterial pathogens can differentially utilize virulence factors against various host plants. However, there has been relatively less emphasis on comparing the infection strategies of a single bacterial pathogen on different hosts and different bacterial pathogens on a single host. Here, we investigated plant–pathogen interactions using two Pseudomonas species, Pseudomonas cannabina pv. alisalensis (Pcal) KB211 and Pseudomonas syringae pv. tomato (Pst) DC3000, and their host plants, cabbage and tomato. Our findings reveal distinct behaviors and virulence patterns across different host plants. Pcal multiplies to greater levels in cabbage compared to tomato, suggesting that Pcal is more adaptive in cabbage than tomato. Conversely, Pst showed robust multiplication in tomato even at lesser inoculum levels, indicating its aggressiveness in the apoplastic space. Gene expression analyses indicate that these pathogens utilize distinct virulence-related gene expression profiles depending on the host plant. These insights highlight the importance of revealing the spatiotemporal regulation mechanisms of virulence factors. Full article