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SUMMARY Hyaloperonospora arabidopsidis (Hpa) is an oomycete pathogen that causes downy mildew disease on Arabidopsis. This obligate biotroph manipulates the homeostasis of its host plant by secreting numerous effector proteins, among which are the RxLR effectors. Identifying the host targets of effectors and understanding how their manipulation facilitates colonization of plants are key to improve plant resistance to pathogens. Here we characterize the interaction between the RxLR effector HaRxL106 and BIM1, an Arabidopsis transcription factor (TF) involved in Brassinosteroid (BR) signaling. We report that HaRxL106 interacts with BIM1 in vitro and in planta. BIM1 is required by the effector to increase the host plant susceptibility to (hemi)biotrophic pathogens, and thus can be regarded as a susceptibility factor. Mechanistically, HaRxL106 requires BIM1 to induce the transcriptional activation of BR‐responsive genes and cause alterations in plant growth patterns that phenocopy the shade avoidance syndrome. Our results support previous observations of antagonistic interactions between activation of BR signaling and suppression of plant immune responses and reveal that BIM1, a new player in this crosstalk, is manipulated by the pathogenic effector HaRxL106. [ABSTRACT FROM AUTHOR]

Fungal communities inhabiting plant tissues are complex systems of inter-species interactions, consisting of both the "abundant biosphere" and "rare biosphere". However, the composition, assembly, and stability of these subcommunities, as well as their contributions to productivity remain unclear. In this study, the taxonomic and functional composition, co-occurrence, and ecological assembly of abundant and rare fungal subcommunities in different tissues of three Panax species were investigated. Abundant subcommunities were dominated by potential plant pathogens belonging to Microbotryomycetes, while saprotrophic fungi like Agaricomycetes and Mortierellomycetes were more prevalent in rare subcommunities. The rare taxa played a central role in upholding the stability of the fungal networks as driven by Dothideomycetes and Sordariomycetes. Homogeneous selection played a larger role in the assembly of abundant fungal subcommunities compared to the rare counterparts, which was more dominated by stochastically ecological drift in all plant species. Rare biospheres played a larger role in the accumulation of saponin compared to their abundant counterparts, especially in the leaf endosphere, which was mainly affected by environmental factors (Mg, pH, OC, and etc.). Furthermore, we found that rare species belonging to unidentified saprotrophs were associated with saponin formation. This study provides hypotheses for future experiments to understand mechanisms accounting for the variations in the composition and function of rare fungal subcommunities across different Panax species. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are critical components of innate immunity in diverse organisms, including plants, vertebrates, and insects. This study identified and characterized a novel Lepidoptera‐specific AMP, named lepidoptin, from the invasive pest Spodoptera frugiperda (Lepidoptera: Noctuidae). Lepidoptin is a 116‐amino acid protein containing a signal peptide and a novel β‐sandwich domain that is distinct from previously reported AMPs. Temporal and spatial expression analyses revealed a significant upregulation of the lepidoptin gene in vivo and in cultured SF9 cells in response to pathogens. Molecular docking analysis identified a specific binding cavity. Enzyme‐linked immunosorbent assay and binding assays confirmed that lepidoptin can bind to pathogen‐associated molecular patterns, bacteria, and fungi. Recombinant lepidoptin exhibited potent antibacterial activity by inducing bacterial agglutination, inhibiting bacterial growth, increasing bacterial membrane permeability, and preventing biofilm formation. Lepidoptin also showed antifungal activity against the entomopathogenic fungus Beauveria bassiana by inhibiting spore germination, increasing fungal cell permeability, and increasing reactive oxygen species. Injection of recombinant lepidoptin into S. frugiperda larvae increased survival after B. bassiana infection, whereas knockdown of lepidoptin by RNA interference decreased larval survival. In addition, lepidoptin showed antimicrobial activity against the plant pathogen Fusarium graminearum by inhibiting spore germination and alleviating disease symptoms in wheat seedlings and cherry tomatoes. This study demonstrates the remarkable dual functionality of lepidoptin in enhancing S. frugiperda immunity and controlling plant pathogens, making it a promising candidate for biocontrol strategies in both pest management and plant disease prevention. [ABSTRACT FROM AUTHOR]

Sugar transporters play a crucial role in plant responses to environmental factors. During plant–pathogen interactions, it is well established that sugar transporters and cell wall invertases are essential for regulating sugar availability at the plant–pathogen interface, impacting both plant resistance and pathogen proliferation. Despite these insights, their role in grapevine defence against pathogens remains underexplored. We examined the expression of sugar transporter and invertase genes in grape leaves infected with the necrotrophic fungus Botrytis cinerea. Our results highlighted significant coordinated upregulation of VvHT5, VvcwINV and defence genes, suggesting a role in enhancing sink strength in infected leaves and implementing host defences. Heterologous expression of GFP‐fused proteins confirmed VvHT5 as a plasma membrane‐localized hexose symporter and phylogenetic analysis indicated its close relation with STP13‐like proteins, which are known to be implicated in host resistance across several plant–pathogen interactions. VvHT5 was heterologously expressed in Arabidopsis thaliana, resulting in high constitutive expression of the VvHT5 protein and increased glucose uptake activity. Phenotypic analysis revealed that VvHT5 enhanced basal resistance to B. cinerea and rescued the wild‐type phenotype in STP13‐deficient plants, indicating that VvHT5 is the grapevine orthologue of AtSTP13. Our findings suggest that VvHT5 may facilitate the reabsorption of extracellular monosaccharides, released from VvcwINV activity or damaged tissues during infection. This activity allows host cells to compete with necrotrophic pathogens for extracellular hexoses, thereby restricting sugar availability to the fungus. It would also support host metabolic demands for defence or serve as a signalling mechanism to orchestrate intracellular processes. [ABSTRACT FROM AUTHOR]

AbstractFungal plant pathogens produce spores for survival and dispersion. Developing an understanding of the mechanisms involved in spore dormancy and germination will aid in mitigating the impact of diseases they cause. The thick-walled diploid teliospores of Ustilago maydis were used as a model for studying fungal spore dormancy and germination. These spores develop only in infected maize tissue and can remain dormant for long periods of time. Teliospores germinate under favourable conditions, resume meiosis, and produce basidiospores to initiate new rounds of infection. Previous research identified changing gene transcripts during teliospore germination, but analysis was hampered by asynchronous germination. The more comprehensive RNA-seq analysis of U. maydis teliospore germination presented here aimed to identify gene altered transcript levels detectable above the background of fluctuating changes resulting from asynchronous germination. The analyses identified 18 different patterns of gene transcript level changes. It also indicated that gene expression is controlled at the transcriptional and post-transcriptional levels. Gene ontology term enrichment analyses of these patterns revealed genes that are involved in cell morphogenesis, metabolism, and RNA metabolism. [ABSTRACT FROM AUTHOR]

Pathogenic fungi employ numerous strategies to colonize plants, infect them, reduce crop yield and quality, and cause significant losses in agricultural production. The increasing use of chemical pesticides has led to various ecological and environmental issues, including the emergence of resistant weeds, soil compaction, and water pollution, all negatively impacting agricultural sustainability. Additionally, the extensive development of synthetic fungicides has adverse effects on animal and human health, prompting the exploration of alternative approaches and green strategies for phytopathogen control. Microorganisms living in sponges represent a promising source of novel bioactive secondary metabolites, potentially useful in developing new nematicidal and antimicrobial agents. This study focuses on extracting bioactive compounds from endosymbiotic bacteria associated with the marine sponge Hyrtios erect sp. (collected from NIOF Station, Hurghada, Red Sea, Egypt) using various organic solvents. Bacillus sp. was isolated and identified through 16 S rRNA gene sequencing. The biocidal activity of Bacillus gotheilii MSB1 extracts was screened against plant pathogenic bacteria, fungi, and nematodes. The n-butanol extract showed significant potential as a biological fungicide against Alternaria alternata and Fusarium oxysporum. Both n-hexane and ethyl acetate extracts exhibited negative impacts against the plant pathogenic bacteria Erwinia carotovora and Ralstonia solanacearum, whereas the n-butanol extract had a positive effect. Regarding nematicidal activity, ethyl acetate and n-butanol extracts demonstrated in-vitro activity against the root-knot nematode Meloidogyne incognita, which causes serious vegetable crop diseases, but the n-hexane extract showed no positive effects. The findings suggest that bioactive compounds from endosymbiotic bacteria associated with marine sponges, particularly B. gotheilii MSB1, hold significant potential as alternative biological control agents against plant pathogens. The n-butanol extract, in particular, displayed promising biocidal activities against various plant pathogenic fungi, bacteria, and nematodes. These results support further exploration and development of such bioactive compounds as sustainable, environmentally friendly alternatives to synthetic pesticides and fungicides in agricultural practices. [ABSTRACT FROM AUTHOR]

Local adaptation has been a central theme of eco-evolutionary research for decades. It is generally assumed that plant pathogens are locally adapted due to their standing interactions with biotic and abiotic factors in the ecosystem. Effectors, secreted small proteins encoded by pathogens, play critical roles in host–pathogen interactions, by activating host genotype-specific resistance, suppressing plant immunity, and playing other functions. In this study, we investigated the potential involvement of RXLR effector genes in ecological adaptation by examining the simple sequence repeat (SSR), virulence, and effector profiles in Phytophthora infestans isolates collected from two geographic regions differing in ecological environments. Genotypic analyses with SSR markers and virulence assays showed that the pathogen from the two regions shared genetic background but differed in virulence spectrums. High-throughput sequencing and expression analysis of 24 selected P. infestans isolates further showed variations in the RXLR effector repertoire, ranging from 536 to 548 for each isolate and the expression of effector genes was highly associated with the accumulation of homologous sRNA. Regional specific alleles were detected at 94 RXLR effector genes, and a specific accumulation of homologous 25–26 nt sRNAs was found at 67 RXLR effector genes. Two of the regional specific RXLR effector genes were confirmed to be virulence factors. Taken together, these results suggest that genomic and epigenetic variations in RXLR effector genes contribute significantly to the ecological adaptation of P. infestans populations and that regional specific effector genes will help to understand the adaptive landscape of pathogens and efficient use of host resistance genes. [ABSTRACT FROM AUTHOR]

Climate change is reshaping the interactions between plants and pathogens, exerting profound effects on global agricultural systems. Elevated tropospheric ozone levels due to climate change hinder plant photosynthesis and increase vulnerability to biotic invasion. The prevailing atmospheric conditions, including temperature and humidity, profoundly influence fungal pathogenesis, as each stage of a pathogen's life cycle is intricately linked to temperature variations. Likewise, climate change alters bacterial behaviour, fostering increased production of extracellular polysaccharides by plant‐pathogenic bacteria in warmer temperatures. Heat‐adapted bacteria, such as Burkholderia glumea and Ralstonia solanacearum, are emerging as significant global threats as temperature rise. Viruses, too, respond dynamically to climate shifts, with certain species favouring warmer climates for replication, resulting in expanded geographical ranges and modified transmission patterns. Nematodes, formidable constraints in crop production, exhibit temperature‐dependent life cycles and would have potentially accelerated proliferation and distribution as global warming progresses. Molecular‐level changes in pathogenesis, induced by temperature fluctuations, influence various pathogens, thereby impacting their virulence and interactions with host plants. Modelling studies predict changes in disease risks and distributions under future climate scenarios, highlighting the necessity of integrating climate data into crop disease models for accurate forecasts. Mechanistic and observational models illustrate pathogen behaviours amidst changing environmental conditions, providing crucial insights into future disease dynamics. In addition, controlled experiments study disease responses under simulated climate scenarios, underscoring the urgency for comprehensive research to devise effective resistance strategies against severe plant diseases. [ABSTRACT FROM AUTHOR]

Plant pathogens secrete nuclear effectors into the host nuclei to modulate the host immune system. Although several nuclear effectors of fungal pathogens have been recently reported, the molecular mechanism of NLS-associated transport vehicles of nuclear effectors and the roles of NLS in transcriptional reprogramming of host immunity genes remain enigmatic. We previously reported the MoHTR1, a nuclear effector of the rice blast fungus, Magnaporthe oryzae. MoHTR1 is translocated to rice nuclei but not in fungal nuclei. Here, we identify the core NLS (RxKK) responsible for MoHTR1's nuclear localization. MoHTR1 is translocated in the host nucleus through interaction with rice importin α. MoHTR1 NLS empowers it to translocate the cytoplasmic effectors of M. oryzae into rice nuclei. Furthermore, other nuclear effector candidates of the blast pathogen and rice proteins which have RxKK also exhibit nuclear localization, highlighting the crucial role of RxKK in this process. We also unveil the importance of SUMOylation in the stability of MoHTR1 and translocation of MoHTR1 to host nuclei. Moreover, MoHTR1 NLS is essential for the pathogenicity of M. oryzae by reprogramming immunity-associated genes in the host. Our findings provide insights into the significance of plant-specific NLS on fungal nuclear effectors and its role in plant-pathogen interactions. Nuclear effectors of plant pathogens modulate the host immunity. Here, Lim et al. unveiled the core sequence and mechanism for nuclear localization of the rice blast fungal effector, MoHTR1, revealing its role in regulating the host immune system. [ABSTRACT FROM AUTHOR]

Common ragweed (Ambrosia artemisiifolia) is one of the leading causes of allergenic rhinitis, as well as a major weed of many crops. Biological control with plant pathogens, such as fungi and bacteria, represents an attractive alternative to the application of synthetic herbicides to control this noxious weed. In this study, we isolated a Xanthomonas strain (designated as 10‐10) from a diseased common ragweed plant collected in southern Quebec, Canada. We characterized the bioherbicidal potential of this strain against common ragweed, and determined whether it can infect other plant species. Its genome was sequenced using PacBio's SMRT technology, enabling us to gain insight into the phylogenetic placement of this strain within the genus Xanthomonas, and to study the repertoire of virulence‐associated genes and clusters. Xanthomonas sp. 10‐10 belongs to a clearly defined subclade within clade C (group 2), which includes X. vesicatoria, X. dyei and X. pisi. While this strain is closely related to X. pisi, it represents a new species within the genus Xanthomonas. Surprisingly, this strain lacks a type III secretion system, which is the main virulence determinant in pathogenic Xanthomonas spp., but harbours an arsenal of cell wall‐degrading enzymes. The addition of the organosilicone surfactant Silwet L‐77 drastically increased the disease symptoms caused by Xanthomonas sp. 10‐10 on common ragweed plants grown under controlled conditions, but the plants remained alive. This strain also caused disease symptoms on tomato, pepper and lettuce. More research is needed to develop Xanthomonas‐based bioherbicide specifically targeting common ragweed. [ABSTRACT FROM AUTHOR]

Introduction: Understanding the microbial diversity and potential functional dynamics within the rhizocompartments of Dendrobium huoshanense is crucial for unraveling the plant–microbe interactions that influence its medicinal properties. Methods: This study is the first to characterize the microbiome associated with the rhizocompartments of D. huoshanense , including its cultivation medium, rhizosphere, rhizoplane, and root endosphere, using high-throughput sequencing and subsequent bioinformatic analysis. Results: Bacterial phylogenetic diversity was significantly higher in the endosphere than in the rhizosphere, while fungal α-diversity significantly decreased from the cultivation medium to the endosphere. Both bacterial and fungal niche widths decreased from the cultivation medium to the endosphere. β-Diversity analysis revealed distinct spatial patterns in both bacterial and fungal communities across the rhizocompartments, with the most pronounced differences between the cultivation medium and the endosphere. Taxonomically, Proteobacteria and Ascomycota were predominant in the endosphere for bacterial and fungal communities, respectively. Functional predictions showed significant enrichment of pathways related to xenobiotics biodegradation, lipid metabolism, and nitrogen fixation in the endosphere, while functions associated with plant pathogens and saprotrophs were significantly reduced. Discussion: The results indicate a shift from generalist to specialist microbes from the cultivation medium to the endosphere, suggesting that D. huoshanense exerts strong selective pressure for endophytic fungi. Interestingly, a high proportion of fungi with unknown functions were found in the endosphere, highlighting an area for further research regarding the medicinal efficacy of D. huoshanense. Overall, this study provides foundational data for understanding the adaptive evolution of these microbial communities in response to specific microhabitats. [ABSTRACT FROM AUTHOR]

Epigenetics has emerged as a potent field of study for understanding the factors influencing the effectiveness of human disease treatments and for identifying alternations induced by pathogens in host plants. However, there has been a paucity of research on the epigenetic control of the proliferation and pathogenicity of fungal plant pathogens. Fungal plant pathogens such as Magnaporthe oryzae , a significant threat to global rice production, provide an important model for exploring how epigenetic mechanisms govern fungal proliferation and virulence. In M. oryzae , epigenetic alterations, such as DNA methylation, histone modification, and non-coding RNAs, regulate gene expression patterns that influence the pathogen's ability to infect its host. These modifications can enhance fungal adaptability, allowing the pathogen to survive in diverse environments and evade host immune responses. Our primary objective is to provide a comprehensive review of the existing epigenetic research on M. oryzae and shed light on how these changes influence the pathogen's lifecycle, its ability to invade host tissues, and the overall severity of the disease. We begin by examining the epigenetic alterations occurring in M. oryzae and their contributions to the virulence and proliferation of the fungus. To advance our understanding of epigenetic mechanisms in M. oryzae and similar plant diseases, we emphasize the need to address unanswered questions and explore future research directions. This information is crucial for developing new antifungal treatments that target epigenetic pathways, which could lead to improved disease management. [ABSTRACT FROM AUTHOR]

Societal Impact Statement Summary Wine production has a significant impact on the global economy. Despite this, the microbial composition of the terroir has not been studied sufficiently, particularly in the southern hemisphere. Here, we investigated how bulk soil fungal communities are affected by several abiotic and biotic factors across 1,000 km of Chilean vineyards. We found that geographical distance was the main driver of vineyard soil fungal communities. Irrespective of variety, older vineyards host a higher relative abundance of arbuscular mycorrhizal fungi (AMF) and a lower relative abundance of plant pathogenic fungi. This result could lead to significant recommendations on when to apply AMF‐based inoculants. The microbial dimension of the terroir has been increasingly recognized as an essential factor determining vineyard productivity and quality. Despite this, few studies have analyzed the factors affecting soil fungal communities of vineyards in the southern hemisphere. Across a 1,000 km gradient encompassing 34 Chilean vineyards, we investigated the effects of grapevine variety, geographical distance, maturity, and soil chemical properties on the diversity and composition of soil fungi. We implemented standard soil chemical analyses and ITS‐based DNA metabarcoding of bulk soil. We found that the total soil fungal composition was significantly affected by geographical distance but not by grapevine variety and maturity. Soil chemical dissimilarity also significantly affected soil fungal composition. When analyzing specific fungal guilds, we found a contrasting successional pattern: arbuscular mycorrhizal fungal relative abundance was significantly higher at medium and old‐maturity vineyards compared with young vineyards, on which plant pathogenic fungi had a markedly lower abundance. Our results present several caveats: the molecular marker was not the most commonly used for arbuscular mycorrhizal fungi, bulk soil was sampled (instead of roots), and all abundances were relative. Still, this study constitutes one of the most extensive studies on soil fungi – both for vineyards and Chile – and might have practical implications, as knowing the drivers of fungal and mycorrhizal biodiversity can inform agricultural management decisions. [ABSTRACT FROM AUTHOR]

SUMMARY Monomeric flavan‐3‐ols and their oligomeric forms, proanthocyanidins (PAs), are closely related to the bitterness of tea beverages. Monomeric flavan‐3‐ols are characteristic flavor compounds in tea. Increasing the content of PAs and anthocyanins enhances the resistance of tea plants to pathogen invasion but decreases the quality of tea beverages. MATE family transporters play a critical role in transferring monomeric flavan‐3‐ols and anthocyanins into vacuoles for storage or subsequent condensation into PAs. Their activities modulate the ratio of monomeric flavan‐3‐ols to PAs and increase anthocyanin content in tea plants. In this study, it was observed that the gene expression and protein phosphorylation level of the MATE transporter CsTT12, a vacuole‐localized flavonoid transporter, were notably upregulated following exogenous sucrose treatment, promoting PA synthesis in tea plants. Further analysis revealed that overexpression of CsTT12 and CsTT12S17D significantly increased the content of anthocyanins and PAs in plants, whereas CsTT12S17A did not. In CsTT12 knockdown plants, PA's accumulation decreased significantly, while monomeric catechin content increased. Moreover, phosphorylation modification enhanced the vacuolar membrane localization of CsTT12, whereas dephosphorylation weakened its vacuolar membrane localization. This study uncovers the crucial role of phosphorylation in flavonoid biosynthesis and provides insights into balancing quality improvements and resistance enhancement. [ABSTRACT FROM AUTHOR]

Plant pathogenic fungi provoke devastating agricultural losses and are difficult to control. How these organisms acquire micronutrients during growth in the host environment remains poorly understood. Here we show that efficient regulation of copper acquisition mechanisms is crucial for plant colonization and virulence in the soilborne ascomycete Fusarium oxysporum, the causal agent of vascular wilt disease in more than 150 different crops. Using a combination of RNA-seq and ChIP-seq, we establish a direct role of the transcriptional regulator Mac1 in activation of copper deficiency response genes, many of which are induced during plant infection. Loss of Mac1 impaired growth of F. oxysporum under low copper conditions and abolishes pathogenicity on tomato plants and on the invertebrate animal host Galleria mellonella. Importantly, overexpression of two Mac1 target genes encoding a copper reductase and a copper transporter was sufficient to restore virulence in the mac1 mutant background. Our results establish a previously unrecognized role of copper reduction and uptake in fungal infection of plants and reveal new ways to protect crops from phytopathogens. Author summary: Fusarium oxysporum is the causal agent of vascular wilt disease and an opportunistic pathogen of humans. How fungal pathogens obtain micronutrients, such as metal ions, during growth inside the host remains unclear. The role of copper acquisition during fungal infection has been investigated in human pathogenic fungi but so far never in a plant pathogen. Here, we show that efficient regulation of copper uptake mechanisms, including copper reduction in the extracellular space and its internalization into the cytoplasm, is critical for effective plant colonization and virulence in F. oxysporum. Genes encoding metalloreductases and high-affinity copper transporters, whose activation is directly mediated by the copper-responsive transcription factor Mac1 and is required for growth under copper-limiting conditions, are transcriptionally induced during colonization of plant roots. Inactivation of Mac1 reduces growth of F. oxysporum during copper limitation and abolishes pathogenicity on tomato plants. Importantly, we provide evidence that the loss-of-virulence phenotype of the mac1 null mutant is strictly linked with its inability to acquire copper. Since copper is found primarily in its oxidized form in the xylem vessels of tomato plants, our work suggests that targeting copper acquisition mechanisms may represent a promising strategy for controlling diseases caused by phytopathogenic fungi. [ABSTRACT FROM AUTHOR]

Summary Ralstonia pseudosolanacearum, a plant pathogen responsible for bacterial wilt in numerous plant species, exhibits paradoxical growth in the host by achieving high bacterial densities in xylem sap, an environment traditionally considered nutrient‐poor. This study combined in vitro experiments and mathematical modeling to elucidate the population dynamics of R. pseudosolanacearum within plants. To simulate the xylem environment, a tomato xylem‐mimicking medium was developed. Then, a mathematical model was constructed using in vitro data and employed to simulate the dynamics of bacterial density and xylem sap composition during plant infection. The model accurately reproduced in planta experimental observations, including high bacterial densities and the depletion of glutamine and asparagine. Additionally, the model estimated the minimal number of bacteria required to initiate infection, the timing of infection post‐inoculation, the bacterial mortality rate within the plant and the rate at which bacterial putrescine is assimilated by the plant. The findings demonstrate that xylem sap can sustain high bacterial densities, provides an explanatory framework for the presence of acetate, putrescine and 3‐hydroxybutyrate in the sap of infected xylem and give clues as to the role of putrescine in the virulence of R. pseudosolanacearum. [ABSTRACT FROM AUTHOR]

Introduction: Pantoea ananatis has emerged as a significant plant pathogen affecting various crops worldwide, causing substantial economic losses. Bacteriophages and their endolysins offer promising alternatives for controlling bacterial infections, addressing the growing concerns of antibiotic resistance. Methods: This study isolated and characterized the Pantoea phage PA1 and investigated the role of PA1-LRP in directly damaging bacteria and assisting endolysin PA1-Lys in cell lysis, comparing its effect to exogenous transmembrane domains following the identification and analysis of the PA1-Lys and the PA1-LRP based on whole genome analysis of phage PA1. Additionally, this study also explored how hydrophobic region of PA1-LRP (HPP) contributes to bacterial killing when combined with PA1-Lys and examined the stability and lytic spectrum of PA1-Lys under various conditions. Results and discussion: Phage PA1 belonging to the Chaseviridae family exhibited a broad host range against P. ananatis strains, with a latent period of 40 minutes and a burst size of 17.17 phages per infected cell. PA1-Lys remained stable at pH 6-10 and temperatures of 20-50°C and showed lytic activity against various Gram-negative bacteria, while PA1-Lys alone could not directly lyse bacteria, its lytic activity was enhanced in the presence of EDTA. Surprisingly, PA1-LRP inhibited bacterial growth when expressed alone. After 24 h of incubation, the OD600 value of pET28a-LRP decreased by 0.164 compared to pET28a. Furthermore, the lytic effect of co-expressed PA1-LRP and PA1-Lys was significantly stronger than each separately. After 24 h of incubation, compared to pET28a-LRP, the OD600 value of pET28a-Lys-LRP decreased by 0.444, while the OD420 value increased by 3.121. Live/dead cell staining, and flow cytometry experiments showed that the fusion expression of PA1-LRP and PA1-Lys resulted in 41.29% cell death, with bacterial morphology changing from rod-shaped to filamentous. Notably, PA1-LRP provided stronger support for endolysin-mediated cell lysis than exogenous transmembrane domains. Additionally, our results demonstrated that the HPP fused with PA1-Lys, led to 40.60% cell death, with bacteria changing from rod-shaped to spherical and exhibiting vacuolation. Taken together, this study provides insights into the lysis mechanisms of Pantoea phages and identifies a novel lysis-related protein, PA1-LRP, which could have potential applications in phage therapy and bacterial disease control. [ABSTRACT FROM AUTHOR]

Honeybee larvae and pupae form the cornerstone of colony survival, development, and reproduction. Azoxystrobin is an effective strobilurin fungicide that is applied during the flowering stage for controlling plant pathogens. The contaminated nectar and pollen resulting from its application are collected by forager bees and impact the health of honeybee larvae and pupae. The current study evaluated the survival, development, and physiological effects of azoxystrobin exposure on the larvae and pupae of Apis mellifera worker bees. The field-recommended concentrations of azoxystrobin were found to suppress the survival indices and lifespan in the larval as well as pupal stages; moreover, the rates of the survival and pupation of larvae as well as the body weights of the pupae and newly-emerged adult bees were significantly reduced upon long-term exposure to azoxystrobin. In addition, azoxystrobin ingestion induced changes in the expression of genes critical for the development, immunity, and nutrient metabolism of larvae and pupae, although the expression profile of these genes differed between the larval and pupal stages. Results indicated the chronic toxicity of azoxystrobin on the growth and development of honeybee larvae and pupae, which would affect their sensitivity to pathogens and other external stresses during the development stage and the study will provide vital information regarding the pollination safety and rational use of pesticides. [ABSTRACT FROM AUTHOR]

The editorial discusses the significant role of microorganisms and their metabolites in agriculture, food production, and environmental sustainability. Microbes like plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi enhance soil fertility and crop resilience, while microbial metabolites offer eco-friendly biocontrol solutions. Research highlights the potential of engineered microbial communities for sustainable agriculture, food safety, and environmental restoration, emphasizing the need for further exploration in optimizing microbial interactions and biodegradation pathways. The studies presented in the editorial showcase advancements in leveraging microorganisms for various applications, underscoring the importance of microbial solutions in achieving global food security and environmental health. [Extracted from the article]

Fungi of the genus Ceratocystis are aggressive tree pathogens that cause serious diseases in several crops around the world. Ceratocystis wilt disease caused by C. cacaofunesta has been shown to be responsible for severe reductions in cacao production. In this study, headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) was used in combination with chemometric analysis for monitoring volatile organic compounds (VOCs) released from C. cacaofunesta. Low-molecular-weight esters, alcohols, ketones, and sulphur compounds were identified in the liquid broth. Monitoring the volatile profile over five days of fungal growth revealed that the concentrations of alcohol and esters were inversely proportional. Acetate esters were responsible for the intense fruity aroma of the C. cacaofunesta culture produced within the first hours after fungal inoculation, which decreased over time, and are likely associated with the attraction of insect vectors to maintain the life cycle of the pathogen. PCA revealed that 3-methylbutyl acetate was the metabolite with the highest factor loading for the separation of the VOC samples after 4 h of fungal growth, whereas ethanol and 3-methylbutan-1-ol had the highest factor loadings after 96 and 120 h. 3-Methylbutan-1-ol is a phytotoxic compound that is likely associated with host cell death since C. cacaofunesta is a necrotrophic fungus. Fungal VOCs play important roles in natural habitats, regulating developmental processes and intra- and interkingdom interactions. This is the first report on the volatiles released by C. cacaofunesta. [ABSTRACT FROM AUTHOR]

• Fungal metabolites and nanoparticles suppress disease severity. • Fungal metabolites and nanoparticles reduced oxidative stress in tomato plants. • These treatments positively regulate microbial communities in the soil. • Microbial communities showed more abundance by the application of fungal metabolites and nanoparticles. Numerous techniques have been adopted to promote crop growth and improve the effectiveness of biological control. One of these strategies includes the utilization of antimicrobial metabolites from biocontrol agents combined with other strategies. Nanotechnology is a novel and emerging trend in controlling plant diseases. The present study aimed to improve the understanding through an assessment of the mechanism of how the co-application of nanoparticles (SiNPS) and fungal metabolites prevent tomato bacterial wilt infection and explore how the applied treatments regulate the soil microbial community structures present in the rhizosphere of tomato plants. It was demonstrated under in-vitro conditions that the silicon nanoparticles and metabolites of fungi restricted the growth of Ralstonia solanacearum , the causal agent of bacterial wilt. The combined application of nanoparticles and fungal metabolites during planta investigation significantly reduced the disease severity and improved plant growth. These treatments caused significant changes in rhizosphere microbial communities and enhanced the abundance of plant-beneficial microbes. The results of the current study hence advocate the application of fungal metabolites and SiNPS as an effective and environment-friendly strategy for controlling the wilt disease of bacteria in tomato plants and various other host crops. [ABSTRACT FROM AUTHOR]

RNA silencing is both a gene regulatory system and a defense mechanism in plants. Most plant pathogens produce RNA silencing suppressors as part of their infection strategy. The extracellular and intracellular presence of pathogen-derived molecules disrupts the normal functioning of the host RNA silencing. miRNAs regulate multiple genes involved in the RNA silencing machinery, defense, and transcription factor genes. Pathogen-activated silencing suppression results in activation of genes that are under miRNA regulation. miRNAs work as intracellular sensors of pathogen threats that, upon dysfunction, enable a new layer of defense. Within the continuous tug-of-war between plants and microbes, RNA silencing stands out as a key battleground. Pathogens, in their quest to colonize host plants, have evolved a diverse arsenal of silencing suppressors as a common strategy to undermine the host's RNA silencing-based defenses. When RNA silencing malfunctions in the host, genes that are usually targeted and silenced by microRNAs (miRNAs) become active and can contribute to the reprogramming of host cells, providing an additional defense mechanism. A growing body of evidence suggests that miRNAs may act as intracellular sensors to enable a rapid response to pathogen threats. Herein we review how plant miRNA targets play a crucial role in immune responses against different pathogens. [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]

In this study, the antimicrobial activity of silver nanoparticles (AgNPs L21, AgNPs L22) produced using aqueous extracts of the Laser trilobum harvested in 2021 and 2022 was optimized. The experimental design and optimization of antimicrobial activity were performed using the response surface method (RSM). Using RSM, independent variables, such as silver concentration, extraction time, and synthesis temperature, were optimized as a result of the inhibition zone diameter against Staphylococcus aureus, Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes. Based on the optimization results, the extraction time, silver concentration, and temperature for AgNP L21 and L22 synthesis were determined to be 60 min, 5 mM, and 25 °C, respectively. When the XRD and TEM results of the nanoparticles synthesized under optimal conditions were evaluated, it was determined that the AgNPs were spherical in shape and had an average size of 30 ± 12 nm. Our study revealed that the year of harvest is unimportant for nanoparticles synthesized from L. trilobum, using a cheap and simple method that does not require toxic substances. Owing to the antimicrobial activity of nanoparticles produced under optimal conditions, it is possible to biocontrol and prevent contamination by these bacteria in food science and industry. [ABSTRACT FROM AUTHOR]

Summary: Hosts and pathogens typically engage in a coevolutionary arms race. This also applies to phytopathogenic powdery mildew fungi, which can rapidly overcome plant resistance and perform host jumps.Using experimental evolution, we show that the powdery mildew pathogen Blumeria hordei is capable of breaking the agriculturally important broad‐spectrum resistance conditioned by barley loss‐of‐function mlo mutants.Partial mlo virulence of evolved B. hordei isolates is correlated with a distinctive pattern of adaptive mutations, including small‐sized (c. 8–40 kb) deletions, of which one is linked to the de novo insertion of a transposable element. Occurrence of the mutations is associated with a transcriptional induction of effector protein‐encoding genes that is absent in mlo‐avirulent isolates on mlo mutant plants. The detected mutational spectrum comprises the same loci in at least two independently isolated mlo‐virulent isolates, indicating convergent multigenic evolution. The mutational events emerged in part early (within the first five asexual generations) during experimental evolution, likely generating a founder population in which incipient mlo virulence was later stabilized by additional events.This work highlights the rapid dynamic genome evolution of an obligate biotrophic plant pathogen with a transposon‐enriched genome. [ABSTRACT FROM AUTHOR]

Plant resistance (R) genes play a crucial role in the detection of effector proteins secreted by pathogens, either directly or indirectly, as well as in the subsequent activation of downstream defence mechanisms. However, little is known about how R genes regulate the defence responses of conifers, particularly Pinus massoniana, against the destructive pine wood nematode (PWN; Bursaphelenchus xylophilus). Here, we isolated and characterised PmHs1pro‐1, a nematode‐resistance gene of P. massoniana, using bioinformatics, molecular biology, histochemistry and transgenesis. Tissue‐specific expressional pattern and localisation of PmHs1pro‐1 suggested that it was a crucial positive regulator in response to PWN attack in resistant P. massoniana. Meanwhile, overexpression of PmHs1pro‐1 was found to activate reactive oxygen species (ROS) metabolism‐related enzymes and the expressional level of their key genes, including superoxide dismutase, peroxidase and catalase. In addition, we showed that PmHs1pro‐1 directly recognised the effector protein BxSCD1of PWN, and induced the ROS burst responding to PWN invasion in resistant P. massoniana. Our findings illustrated the molecular framework of R genes directly recognising the effector protein of pathology in pine, which offered a novel insight into the plant–pathogen arms race. Summary statement: We first identified and functionally characterised that PmHs1pro‐1 could directly recognise the effector protein BxSCD1, which consequently initiated the ROS burst to defend against pine wood nematode to prevent the withered appearance in the resistant Pinus massoniana. Our findings demonstrated the molecular framework of R genes directly recognising the effector protein of pathology in pines and offered a novel insight into the plant‐arm race of pathogens and plants. [ABSTRACT FROM AUTHOR]

Plant pathogens cause devastating diseases, leading to serious losses to agriculture. Mechanistic understanding of pathogenesis of plant pathogens lays the foundation for the development of fungicides for disease control. Mitophagy, a specific form of autophagy, is important for fungal virulence. The role of cardiolipin, mitochondrial signature phospholipid, in mitophagy and pathogenesis is largely unknown in plant pathogenic fungi. The functions of enzymes involved in cardiolipin biosynthesis and relevant inhibitors were assessed using a set of assays, including genetic deletion, plant infection, lipidomics, chemical‐protein interaction, chemical inhibition, and field trials. Our results showed that the cardiolipin biosynthesis‐related gene MoGEP4 of the rice blast fungus Magnaporthe oryzae regulates growth, conidiation, cardiolipin biosynthesis, and virulence. Mechanistically, MoGep4 regulated mitophagy and Mps1‐MAPK phosphorylation, which are required for virulence. Chemical alexidine dihydrochloride (AXD) inhibited the enzyme activity of MoGep4, cardiolipin biosynthesis and mitophagy. Importantly, AXD efficiently inhibited the growth of 10 plant pathogens and controlled rice blast and Fusarium head blight in the field. Our study demonstrated that MoGep4 regulates mitophagy, Mps1 phosphorylation and pathogenesis in M. oryzae. In addition, we found that the MoGep4 inhibitor, AXD, displays broad‐spectrum antifungal activity and is a promising candidate for fungicide development. Summary Statement: This study demonstrated that MoGep4 regulates mitophagy, Mps1 activation and pathogenesis in Magnaporthe oryzae. Additionally, we found that the MoGep4 inhibitor, alexidine dihydrochloride, displays broad‐spectrum antifungal activity and is effective in disease control in the field. [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]

Variables of phytopathological interest correlated to the impact of plant diseases, such as incidence and severity, may display a spatial pattern resulting from an underlying, yet unknown gradient. Along the main direction of the gradient the variable assessed at the site level either increases, or decreases. Spatial gradients may also arise because of the movement of a front of invasion, an imaginary moving contour separating areas already infested by a plant pathogen from those still pathogen-free. Adequate geostatistical tools may shed light on gradients directional properties, as well as on the direction the front of invasion is coming from or moving to. Tools currently available for that may be impractical due to the advanced computational and programming skills required for their application. Hence, the goals of this study were: (I) to develop, test and validate a new user-friendly geostatistical tool named DirGrad (Direction of Gradient) aimed at analyzing spatial gradients resulting from the impact of plant diseases; (II) to build an algorithm able to run DirGrad on R, one the most widespread open source software for statistics; and (III) to apply DirGrad for the ex post modelling of the invasion front dynamics. The designed algorithm was successfully validated both in silico and in the field by using data from real case studies such as those of the invasive fungal pathogens Heterobasidion irregulare and Ophiostoma novo-ulmi in a forest stand of Central Italy and across the Swedish island of Gotland, respectively. The algorithm is released as a user-friendly open-source script. [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]

Hydroponic greenhouses and vertical farms provide an alternative crop production strategy in regions that experience low temperatures, suboptimal sunlight, or inadequate soil quality. However, hydroponic systems are soilless and, therefore, have vastly different bacterial microbiota than plants grown in soil. This review highlights some of the most prevalent plant growth-promoting bacteria (PGPB) and destructive phytopathogenic bacteria that dominate hydroponic systems. A complete understanding of which bacteria increase hydroponic crop yields and ways to mitigate crop loss from disease are critical to advancing microbiome research. The section focussing on plant growth-promoting bacteria highlights putative biological pathways for growth promotion and evidence of increased crop productivity in hydroponic systems by these organisms. Seven genera are examined in detail, including Pseudomonas, Bacillus, Azospirillum, Azotobacter, Rhizobium, Paenibacillus, and Paraburkholderia. In contrast, the review of hydroponic phytopathogens explores the mechanisms of disease, studies of disease incidence in greenhouse crops, and disease control strategies. Economically relevant diseases caused by Xanthomonas, Erwinia, Agrobacterium, Ralstonia, Clavibacter, Pectobacterium, and Pseudomonas are discussed. The conditions that make Pseudomonas both a friend and a foe, depending on the species, environment, and gene expression, provide insights into the complexity of plant–bacterial interactions. By amalgamating information on both beneficial and pathogenic bacteria in hydroponics, researchers and greenhouse growers can be better informed on how bacteria impact modern crop production systems. [ABSTRACT FROM AUTHOR]

Sugarcane white leaf (SCWL) disease, caused by Candidatus Phytoplasma sacchari, poses a significant threat to sugarcane cultivation. An obligate parasite, phytoplasma is difficult to culture in laboratory conditions, making the isolation of its DNA from the massive amount of plant host DNA extremely challenging. Yet, the appropriate amount and quality of plant microbiome-derived DNA are key for high-quality DNA sequencing data. Here, a simple, cost-effective, alternative method for DNA isolation was applied using a guanidine-HCl-hydroxylated silica (GuHCl-Silica)-based method and microbiome DNA enrichment based on size-selective low-molecular-weight (LMW) DNA by PEG/NaCl precipitation. qPCR analysis revealed a significant enrichment of phytoplasma DNA in the LMW fraction. Additionally, the NEBNext Microbiome DNA enrichment kit was utilized to further enrich microbial DNA, demonstrating a remarkable increase in the relative abundance of phytoplasma DNA to host DNA. Shotgun sequencing of the isolated DNA gave high-quality data on the metagenome assembly genome (MAG) of Ca. Phytoplasma sacchari SCWL with completeness at 95.85 and 215× coverage. The results indicate that this combined approach of PEG/NaCl size selection and microbiome enrichment is effective for obtaining high-quality genomic data from phytoplasma, surpassing previous methods in efficiency and resource utilization. This low-cost method not only enhances the recovery of microbiome DNA from plant hosts but also provides a robust framework for studying plant pathogens in complex plant models. [ABSTRACT FROM AUTHOR]

The use of Trichoderma filamentous fungi in the wide concept of biocontrol is still a highly relevant topic. The multifaceted nature of their impact on phytopathogenic microorganisms results from the species diversity and complexity of their antagonistic action. The presented research aimed to determine optimal cultivation conditions of two T. citrinoviride strains for the biosynthesis of major enzymes especially those involved in the biocontrol process. Culture conditions were optimized using a three-factor Box-Behnken design to maximize the yield of chitinase and lichenase. The following independent variables were included in the model: incubation temperature, initial pH, and supplementation with fungal biomass. As a result of statistical optimization, unprecedented activities of extracellular lytic enzyme were achieved. For the B1 and B3 strains, the optimal pH was 3.5 or 7.5, respectively, in the determination of chitinase biosynthesis. It was similar for the biosynthesis of β-1.3 and β-1.4 glucanases, but at higher cultivation temperature. The exception was the B3 strain, for which the optimal pH in glucanase biosynthesis was 5.5. The most stimulating culture temperature in the process of chitinase biosynthesis and β-1.3 and β-1.4 glucanases was above 25 °C. In that, the levels of enzyme biosynthesis and corresponding composition culture environment were confirmed to be strain-dependent. [ABSTRACT FROM AUTHOR]

Fungicides are used to control phytopathogens but all these fungicides have deleterious effects. Allelopathic interactions can be harnessed as a natural way to control the pathogens but there are no reports that show the allelopathic interactions of donor plant, recipient crop, as well as the target plant pathogen and the material used for inoculum production. So, in the present study, the suitability of Carthamus oxyacantha M. Bieb. was assessed against Macrophomina phaseolina, the cause of charcoal rot in maize. Among the various treatments in pot experiment, a negative control, 3 concentrations of inoculum (1.2×105, 2.4×105, and 3.6×105 colony forming units (CFU) mL-1, 3 concentrations (0.5, 1.0, and 1.5% w/w) of C. oxyacantha along with an autoclaved M. phaseolina (Mp) and C. oxyacantha alone were included to investigate their allelopathic effects on maize, not investigated earlier. Maximum suppression of the disease was observed by 1.5% (w/w) concentration of C. oxyacantha. Soil amendment with C. oxyacantha significantly suppressed the disease incidence (DI) and disease severity index (DSI) in charcoal rot of maize up to 40 and 55%, respectively over the strongest level of inoculum (Mp3). C. oxyacantha not only reduced area under disease incidence progress curve (AUDIPC) and area under disease severity progress curve (AUDSPC), but also improved the morphological, biochemical and physiological parameters of maize. The maximum increase of 48, 65, and 75% in values of shoot length (SL), shoot dry mass (SDM), and root dry mass (RDM), respectively was observed by application of the highest concentration of C. oxyacantha in the treatment Mp1+Co3, over infested control (Mp1). Photosynthetic pigments, such as chlorophyll a, chlorophyll b and carotenoids were increased to 58, 64, and 46%, respectively over Mp1, by the application of C. oxyacantha. Carbon assimilation rate (A), stomatal conductance (gs), rate of transpiration (E), and internal carbon dioxide concentration (Ci) were significantly increased to 58, 48, 48, and 20%, respectively over infested control (Mp3), by application of C. oxyacantha concentration 1.5 (w/w). Moreover, defense enzymes like superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were boosted up to 27, 28, and 28% over Mp3, respectively. Positive allelopathy of C. oxyacantha towards maize and negative allelopathy towards M. phaseolina makes C. oxyacantha a suitable candidate for charcoal rot disease control in maize. [ABSTRACT FROM AUTHOR]

Biofilms are major virulence factors formed by pathogenic bacteria to invade their host and maintain their colony. While biofilms usually develop on diverse solid surfaces, floating biofilms, also called pellicles, are formed at the air–liquid interface. To address the problem of biofilm formation by bacterial pathogens, honey has been extensively studied. However, information on the effect of honey on biofilm formation by plant pathogens is scarce. This study aimed to determine the effects of manuka honey on biofilm and pellicle formation by Pectobacterium brasiliense and analyze the expression of genes encoding proteins needed to form biofilm by using semiquantitative PCR and RT‐qPCR. Treatment with 5% (w/v) of manuka honey significantly decreased biofilm and pellicle formation by P. brasiliense. RT‐qPCR results showed that the expression of bcsA, fis, hrpL, and expI decreased 7.07‐fold, 5.71‐fold, 13.11‐fold, and 6.26‐fold, respectively, after exposure to 5% (w/v) manuka honey. Our findings reveal that manuka honey may effectively inhibit biofilm and pellicle formation. [ABSTRACT FROM AUTHOR]

Pathogenic microorganisms often target seedlings shortly after germination. If plants exhibit resistance or resilience to pathogens, those exposed to pathogen challenge may grow further and form new unchallenged leaves. The purpose of this study was to examine disease resistance in the newly formed leaves of plants subjected to pathogen challenge. We used Arabidopsis thaliana and the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa) as the model pathosystem. We found that Arabidopsis seedlings primarily challenged with the avirulent isolate Hpa exhibited enhanced disease resistance against the virulent isolate Hpa in newly formed rosette leaves (NFRLs). Our observations indicated that the transcript levels of the transcription factor gene WRKY70, which is essential for full resistance to the virulent isolate HpaNoco2, were elevated and maintained at high levels in the NFRLs. In contrast, the transcript levels of the salicylic acid marker gene PR1 and systemic acquired resistance‐related genes did not exhibit sustained elevation. The maintenance of increased transcript levels of WRKY70 operated independently of non‐expressor of pathogenesis‐related gene 1. These findings suggest that prolonged upregulation of WRKY70 represents a defensive state synchronized with plant development to ensure survival against subsequent infections. [ABSTRACT FROM AUTHOR]

ABSTRACT Heterotrophic microbes rely on host‐derived carbon sources for their growth and survival. Depriving pathogens of plant carbon is therefore a promising strategy for protecting plants from disease and reducing yield losses. Importantly, this carbon starvation‐mediated resistance is expected to be more broad‐spectrum and durable than race‐specific R‐gene‐mediated resistance. Although sugars are well characterized as major carbon sources for bacteria, emerging evidence suggests that plant‐derived lipids are likely to be an essential carbon source for some fungal microbes, particularly biotrophs. Here, we comprehensively discuss the dual roles of carbon sources (mainly sugars and lipids) and their transport processes in immune signalling and microbial nutrition. We summarize recent findings revealing the crucial roles of lipids as susceptibility factors at all stages of pathogen infection. In particular, we discuss the potential pathways by which lipids and other plant carbon sources are delivered to biotrophs, including protein‐mediated transport, vesicle trafficking and autophagy. Finally, we highlight knowledge gaps and offer suggestions for clarifying the mechanisms that underlie nutrient uptake by biotrophs, providing guidance for future research on the application of carbon starvation–mediated resistance. [ABSTRACT FROM AUTHOR]

Plant pathogens adapt at speeds that challenge contemporary disease management strategies like the deployment of disease resistance genes. The strong evolutionary pressure to adapt, shapes pathogens' genomes, and comparative genomics has been instrumental in characterizing this process. With the aim to capture genomic variation at high resolution and study the processes contributing to adaptation, we here leverage an innovative, multi-genome method to construct and annotate the first pangenome graph of an oomycete plant pathogen. We expand on this approach by analysing the graph and creating synteny based single-copy orthogroups for all genes. We generated telomere-to-telomere genome assemblies of six genetically diverse isolates of the oomycete pathogen Peronospora effusa, the economically most important disease in cultivated spinach worldwide. The pangenome graph demonstrates that P. effusa genomes are highly conserved, both in chromosomal structure and gene content, and revealed the continued activity of transposable elements which are directly responsible for 80% of the observed variation between the isolates. While most genes are generally conserved, virulence related genes are highly variable between the isolates. Most of the variation is found in large gene clusters resulting from extensive copy-number expansion. Pangenome graph-based discovery can thus be effectively used to capture genomic variation at exceptional resolution, thereby providing a framework to study the biology and evolution of plant pathogens. Author summary: Plant pathogens are known to evolve rapidly and overcome disease resistance of newly introduced crop varieties. This swift adaptation is visible in the genomes of these pathogens, which can be highly variable. Such genomic variation cannot be captured with contemporary comparative genomic methods that rely on a single reference genome or focus solely on protein coding genes. To overcome these limitations and compare multiple genomes in a robust and scalable method, we constructed the first pangenome graph for an oomycete filamentous plant pathogen with six telomere-to-telomere genome assemblies of Peronospora effusa. This high-resolution pangenomic framework enabled detailed comparisons of the genomes at any level, from the nucleotide to the chromosome, and for any subset of protein-coding genes or transposable elements, to discover novel biology and potential mechanisms for the rapid evolution of this devastating pathogen. [ABSTRACT FROM AUTHOR]

Xylella fastidiosa is a xylem‐limited bacterial plant pathogen transmitted by insect vectors. It infects a wide range of plant species and causes devastating diseases. Botanical gardens are global repositories of plant diversity exposed to local biotic and abiotic stresses. We used molecular diagnostic tools for the detection of X. fastidiosa in a collection of New Zealand indigenous plants grown in a X. fastidiosa‐infected Californian area to determine if any species were infected with this bacterial pathogen and to help inform biosecurity responses. To this end, 130 New Zealand indigenous plant species comprising 72 genera, growing in the University of California Botanical Garden at Berkeley, California, were screened for X. fastidiosa. Multiple PCR‐based methods were used to detect the pathogen at the subspecies and sequence‐type levels directly from plant material; nine plant species tested positive by at least two PCR‐based methods. All nine infections were identified as X. fastidiosa subsp. multiplex sequence types 6 or 7 by the amplification of seven housekeeping genes. Three strains were cultured in vitro and their whole genome sequences were obtained; these strains belonged to three distinct clades within subspecies multiplex, indicating that the infections were not transmitted among these New Zealand indigenous plant species. The information gathered in this study will help to assess the risk of X. fastidiosa to New Zealand indigenous flora and the potential spillover to crops of agricultural importance. The work also shows the applied value of botanical garden collections as sentinels for international plant pathogen biosecurity risk assessment. [ABSTRACT FROM AUTHOR]

ABSTRACT Root‐knot nematodes (RKNs; Meloidogyne spp.) are a serious threat to crop production. The competition between plants and pathogens for assimilates influences the outcome of their interactions. However, the mechanisms by which plants and nematodes compete with each other for assimilates have not been elucidated. In this study, we demonstrated that miR396a plays a negative role in defense against RKNs and a positive role in sugar accumulation in tomato roots. The overexpression of SlGRF8 (Solanum lycopersicum growth‐regulating factor 8), the target of miR396a, decreased the sugar content of the roots and the susceptibility to RKNs, whereas the grf8‐cr mutation had the opposite effects. Furthermore, we confirmed that SlGRF8 regulated the sugar content in roots by directly activating the transcription of SlSTP10 (Solanum lycopersicum sugar transporter protein 10) in response to RKN stress. Moreover, SlSTP10 was expressed primarily in the tissues surrounding giant cells, and the SlSTP10 knockout increased both the sugar content in the roots and the plant's susceptibility to RKNs. Overall, this study provides important insight into the molecular mechanism through which the miR396a‐SlGRF8‐SlSTP10 module regulates sugar allocation in roots under RKN stress. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of Bacillus velezensis Bv-116 and its bio-organic fertilizer on the control of cucumber Fusarium wilt caused by Fusarium oxysporum f. sp. Cucumerinum (FOC), the promotion of growth of cucumber seedlings, and the soil microbial community. B. velezensis Bv-116 exhibited an inhibition rate of 84.93% against FOC, as well as broad-spectrum inhibitory activities against other soil-borne plant pathogenic fungi. Fermentation products of B. velezensis Bv-116 destroyed the cell structure of FOC and inhibited the growth of FOC mycelium. These products were identified as volatile antimicrobial gases, proteases and cellulases. In the greenhouse pot experiment, both B. velezensis Bv-116 and its bio-organic fertilizer exhibited significant promoting effects on cucumber growth, and a significant reduction in the incidence and disease severity index of cucumber wilt (p < 0.05). Analysis of the microbial community structure of cucumber rhizosphere soil revealed that inoculation of B. velezensis Bv-116 and its bio-organic fertilizer increased the abundance of genera with biocontrol capabilities against plant pathogens. In addition, inoculation of the bio-organic fertilizer reversed the excessive proliferation of Fusarium and Acidobacteria. Our results suggest the potential of inoculating B. velezensis Bv-116 and its bio-organic fertilizer as an environmentally friendly biocontrol strategy against cucumber wilt. [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]

Elsinoë species are phytopathogenic fungi that cause serious scab diseases on economically important plants. The disease symptoms arise from the effects of a group of phytotoxins known as elsinochromes, produced via a type-I polyketide synthase (PKS) biosynthetic pathway. The elsinochrome gene cluster was first annotated in Elsinoë fawcettii where the main type-I PKS gene was characterized as EfPKS1. A later study showed that this gene and the associated cluster had not been correctly annotated, and that EfPKS1 was actually the anchor gene of the melanin biosynthetic pathway. A new type-I PKS gene EfETB1 associated with elsinochrome production was also identified. The aim of this study was to identify all type-I PKS genes in the genomes of seven Elsinoë species with the goal of independently verifying the PKS containing clusters for both melanin and elsinochrome production. A total of six type-I PKS classes were identified, although there was variation between the species in the number and type of classes present. Genes similar to the E. fawcettii EfPKS1 and EfETB1 type-I PKS genes were associated with melanin and elsinochrome production respectively in all species. The complete melanin and elsinochrome PKS containing clusters were subsequently annotated in all the species with high levels of synteny across Elsinoë species. This study provides a genus-level overview of type-I PKS distribution in Elsinoë species, including an additional line of support for the annotation of the melanin and elsinochrome PKS containing clusters in these important plant pathogens. [ABSTRACT FROM AUTHOR]

Peptidoglycan (PG), a mesh-like structure which is the primary component of the bacterial cell wall, is crucial to maintain cell integrity and shape. While most bacteria rely on penicillin binding proteins (PBPs) for crosslinking, some species also employ LD-transpeptidases (LDTs). Unlike PBPs, the essentiality and biological functions of LDTs remain largely unclear. The Hyphomicrobiales order of the Alphaproteobacteria, known for their polar growth, have PG which is unusually rich in LD-crosslinks, suggesting that LDTs may play a more significant role in PG synthesis in these bacteria. Here, we investigated LDTs in the plant pathogen Agrobacterium tumefaciens and found that LD-transpeptidation, resulting from at least one of 14 putative LDTs present in this bacterium, is essential for its survival. Notably, a mutant lacking a distinctive group of 7 LDTs which are broadly conserved among the Hyphomicrobiales exhibited reduced LD-crosslinking and tethering of PG to outer membrane β-barrel proteins. Consequently, this mutant suffered severe fitness loss and cell shape rounding, underscoring the critical role played by these Hyphomicrobiales-specific LDTs in maintaining cell wall integrity and promoting elongation. Tn-sequencing screens further revealed non-redundant functions for A. tumefaciens LDTs. Specifically, Hyphomicrobiales-specific LDTs exhibited synthetic genetic interactions with division and cell cycle proteins, and a single LDT from another group. Additionally, our findings demonstrate that strains lacking all LDTs except one displayed distinctive phenotypic profiles and genetic interactions. Collectively, our work emphasizes the critical role of LD-crosslinking in A. tumefaciens cell wall integrity and growth and provides insights into the functional specialization of these crosslinking activities. Author summary: Peptidoglycan (PG) is essential for bacterial cell wall integrity. While most bacteria use penicillin binding proteins (PBPs) for crosslinking, some also employ LD-transpeptidases (LDTs); however, the essentiality and functions of LDTs remain poorly understood. Interestingly, Hyphomicrobiales bacteria have PG rich in LD-crosslinks, suggesting that LDTs play a vital role in maintaining cell wall integrity in these organisms. Our study of Agrobacterium tumefaciens revealed that LD-transpeptidation, mediated by at least one of 14 putative LDTs, is essential for maintaining both viability and morphogenesis. A mutant lacking 7 Hyphomicrobiales-specific LDTs suffered fitness and shape loss due to reduced LD-crosslinking and PG tethering to the outer membrane. Our results provide new insights into LD-transpeptidase specialized functions and conditional essentiality. The conservation of these enzymes across diverse polar-growing species suggests broader implications for understanding microbial cell wall growth and adaptation to environmental stresses. [ABSTRACT FROM AUTHOR]

Introduction: Fusarium wilt, a devastating soil-borne fungal disease in flax (Linum usitatissimum), is caused by Fusarium oxysporum f. sp. lini, a hemibiotrophic plant pathogen that penetrates plant roots. There are several reports of the molecular response of L. usitatissimum to F. oxysporum f. sp. lini; however, comparisons of the effects of mutualistic and pathogenic fungi on plants are more limited. Methods: In this study, we have integrated phenotyping and RNA-Seq approaches to examine the response of flax to F. oxysporum f.sp. lini and to a mutualistic arbuscular mycorrhizal fungus (AMF) Rhizoglomus irregulare. R. irregulare is a common soil fungus and also widely used as a commercial inoculant to improve plant growth. We measured flax growth parameters after plant inoculation with each or both fungi, in comparison with non-inoculated control. We performed transcriptome analysis of root tissues collected at 9 and 14 days post-inoculation. Results: We identified several differentially expressed genes (DEGs) in response to pathogenic and mutualistic fungi. These included genes related to ethylene and salicylic acid biosynthesis, carbohydrate binding, oxidoreductases, and sugar transmembrane transporters. Genes related to calcium signaling, nutrient transport, lipid metabolism, cell wall, and polysaccharide-modifying were upregulated by R. irregulare; however, the same genes were down-regulated by F. oxysporum f. sp. lini when treated independently. In the combined treatment, genes related to cell wall modifications, hormone regulation and nutrient uptake were up-regulated. These results suggest that inoculation with R. irregulare reduced gene expression related to F. oxysporum f. sp. lini infection, leading to a reduced response to the pathogen. In response to AMF, flax prioritized mutualism-related gene expression over defense, reversing the growth inhibition caused by F. oxysporum f. sp.lini in the combined treatment. Discussion: This research provides insights into the protective effects of AMF, revealing the pre-symbiotic gene expression profile of flax in response to mutualism in comparison with pathogenicity. Potential target genes for crop improvement were identified, especially defense related genes. [ABSTRACT FROM AUTHOR]

Over three-quarters of Earth's surface exhibits extreme environments where life thrives under harsh physicochemical conditions. While prokaryotes have often been investigated in these environments, only recent studies have revealed the remarkable adaptability of eukaryotes, in particular fungi. This study explored the mycobiota of two meromictic hypersaline lakes, Ursu and Fără Fund, in Transylvania (Romania). The intrinsic and extrinsic fungal diversity was assessed using amplicon sequencing of environmental DNA samples from sediments, water columns, surrounding soils, and an associated rivulet. The fungal communities, illustrated by the 18S rRNA gene and ITS2 region, exhibited contrasting patterns between the lakes. The ITS2 region assessed better than the 18S rRNA gene the fungal diversity. The ITS2 data showed that Ascomycota was the most abundant fungal group identified in both lakes, followed by Aphelidiomycota, Chytridiomycota, and Basidiomycota. Despite similar α-diversity levels, significant differences in fungal community structure were observed between the lakes, correlated with salinity, total organic carbon, total nitrogen, and ammonium. Taxonomic profiling revealed depth-specific variations, with Saccharomycetes prevalent in Ursu Lake's deeper layers and Lecanoromycetes prevalent in the Fără Fund Lake. The functional annotation using FungalTraits revealed diverse ecological roles within the fungal communities. Lichenized fungi were dominant in Fără Fund Lake, while saprotrophs were abundant in Ursu Lake. Additionally, wood and soil saprotrophs, along with plant pathogens, were more prevalent in the surrounding soils, rivulet, and surface water layers. A global overview of the trophic relations in each studied niche was impossible to establish due to the unconnected graphs corresponding to the trophic interactions of the analyzed fungi. Plotting the unweighted connected subgraphs at the genus level suggests that salinity made the studied niches similar for the identified taxa. This study shed light on the understudied fungal diversity, distribution, and ecological functions in hypersaline environments. [ABSTRACT FROM AUTHOR]

Polyamines (PAs), which are aliphatic polycationic compounds with a low molecular weight, are found in all living organisms and play essential roles in plant–pathogen interactions. Putrescine, spermidine, and spermine, the most common PAs in nature, respond to and function differently in plants and pathogens during their interactions. While plants use certain PAs to enhance their immunity, pathogens exploit PAs to facilitate successful invasion. In this review, we compile recent studies on the roles of PAs in plant–pathogen interactions, providing a comprehensive overview of their roles in both plant defense and pathogen pathogenicity. A thorough understanding of the functions of PAs and conjugated PAs highlights their potential applications in fungicide development. The creation of new fungicides and compounds derived from PAs demonstrates their promising potential for further research and innovation in this field. [ABSTRACT FROM AUTHOR]

The genus Elsinoe contains many aggressive pathogens of a wide range of plants, many of which are economically important. These fungal pathogens cause serious scab diseases affecting various plant parts, impacting plant vigour, yield and market value. While studies on Elsinoe species have predominantly focused on their taxonomy, there is a conspicuous gap in knowledge of these fungi from a plant pathology perspective. In this review, we draw together and critically evaluate the existing, but rather fragmented, research on the taxonomic status, phylogenetic relationships, host range, as well as the biology and epidemiology of Elsinoe species. Our aim is primarily to augment the existing understanding of the global significance of Elsinoe species, and furthermore, to shed light on the escalating prominence of scab diseases caused by species in a fungal genus that has been known for over 100 years but remains relatively poorly understood and somewhat enigmatic. [ABSTRACT FROM AUTHOR]

Trichoderma spp. is known for its ability to enhance plant growth and suppress disease, but the mechanisms for its interaction with host plants and pathogens remain unclear. This study investigated the transcriptomics and metabolomics of peanut plants (Arachis hypogaea L.) inoculated with Trichoderma harzianum QT20045, in the absence and presence of the stem rot pathogen Sclerotium rolfsii JN3011. Under the condition without pathogen stress, the peanut seedlings inoculated with QT20045 showed improved root length and plant weight, increased indole acetic acid (IAA) production, and reduced ethylene level, with more active 1-aminocyclopropane-1-carboxylate acid (ACC) synthase (ACS) and ACC oxidase (ACO), compared with the non-inoculated control. Under the pathogen stress, the biocontrol efficacy of QT20045 against S. rolfsii was 78.51%, with a similar effect on plant growth, and IAA and ethylene metabolisms to the condition with no biotic stress. Transcriptomic analysis of peanut root revealed that Trichoderma inoculation upregulated the expression of certain genes in the IAA family but downregulated the genes in the ACO family (AhACO1 and AhACO) and ACS family (AhACS3 and AhACS1) consistently in the absence and presence of pathogens. During pathogen stress, QT20045 inoculation leads to the downregulation of the genes in the pectinesterase family to keep the host plant's cell wall stable, along with upregulation of the AhSUMM2 gene to activate plant defense responses. In vitro antagonistic test confirmed that QT20045 suppressed S. rolfsii growth through mechanisms of mycelial entanglement, papillary protrusions, and decomposition. Our findings highlight that Trichoderma inoculation is a promising tool for sustainable agriculture, offering multiple benefits from pathogen control to enhanced plant growth and soil health. [ABSTRACT FROM AUTHOR]

AbstractBotrytis cinerea, an airborne plant pathogen, holds the potential to synthesize sesquiterpenes, which have been used for the industrial production of abscisic acid. Previously, through our genetic technology, we obtained strain ZX2, whose main product 1´,4´-trans-ABA-diol is physiologically active in plants. In this study, 50 L of fed fermentation was carried out with ZX2 strain to study the stability of expression of TUA, TUB, ATC, EF-1, GAPDH, UCE and GTP genes. Four kinds of software (GeNorm, NormFinder, BestKeeper and Delta Ct) were used to analyze the expression stability of candidate genes, and finally the best reference gene was screened by RefFinder. Based on the results, the ACT was the most stable gene. It was used to normalize the expression levels of two genes related to 1´,4´-trans-ABA-diol production (hmgr and bcaba3) when fed-batch fermentation. Guide the selection of appropriate internal reference genes during the fermentation process to accurately quantify the relative transcription levels of target genes in B.cinerea ZX2. [ABSTRACT FROM AUTHOR]