Plant Pathogen Resistance Research Articles

Intrinsic Natural Resistance of Various Plant Pathogens to Ipflufenoquin, a New DHODH (Dihydroorotate Dehydrogenase)-inhibiting Fungicide, in Relation to Unaltered Amino Acid Sequence of the Target Site.

In recent years, increasingly stringent pesticide regulations have made the development of new chemistries challenging. Under these regulations, the new fungicide ipflufenoquin (FRAC Code 52) was first released in Japan. Its mode of action is new; it inhibits dihydroorotate dehydrogenase (DHODH), a key enzyme in the biosynthesis of pyrimidine-based nucleotides. However, because it is a single-site inhibitor, the risk of resistance developing in pathogens must be carefully considered. The risk for dual use of DHODH inhibitors in agriculture and medicine has also become a great concern because a new antifungal olorofim is under development against human pathogens now and cross-resistance has recently been reported between ipflufenoquin and olorofim in Aspergillus fumigatus. In this study, the sensitivity to ipflufenoquin was examined in culture and in plants using "baseline" isolates, which had never been exposed to DHODH inhibitors. Isolates of Alternaria alternata, Botrytis cinerea, B. elliptica, Colletotrichum fioriniae, C. fructicola, C. nymphaeae, C. orbiculare, C. siamense, C. tropicale, C. truncatum, and Sclerotinia sclerotiorum were highly sensitive to ipflufenoquin in culture, but isolates of Coniella vitis, Corynespora cassiicola, Pseudocercospora fuligena, and Rhizoctonia solani were inherently resistant. Ipflufenoquin had low efficacy against C. cassiicola and C. vitis after inoculation of cucumber and grapevine leaves, respectively. To understand the mechanism of natural resistance, we analyzed the partial sequence of pyrE genes, which encode the DHODH enzyme, but did not find any differences in the deduced amino acids that were thought to be associated with resistance. Thus, mechanisms other than target-site mutations might be involved in the intrinsic resistance.

Propiconazole resistance phenotypes in Geotrichum candidum from South Carolina peaches are linked to point mutations in GcCYP51B gene.

Geotrichum candidum Link (1809) is a yeast-like fungus that causes sour rot of peach (Prunus persica). Outbreaks of the disease have occurred since 2021 in peach fruit kept in cold storage despite post-harvest treatments with propiconazole at a commercial farm in South Carolina (SC). A total of 58 isolates, 40 from symptomatic fruit from cold storage in Saluda County (SC packing house isolates), 11 from three SC orchards in Saluda County, Spartanburg County, and Pickens County (SC non-packing house isolates), and 7 California (CA) isolates (at least 3 from packing houses) were evaluated for propiconazole sensitivity. Mycelial growth assays revealed that 6 of 7 CA isolates had the lowest EC50 values and were considered sensitive (S) to propiconazole with an average EC50 value of 0.02 µg/ml and minimum inhibitory concentration (MIC) values >1 to < 3 µg/ml. Isolate 02J018 from CA and all SC non packing house isolates were considered reduced-sensitive (RS) to propiconazole with an average EC50 value of 0.33 µg/ml and MIC values >10 to <30 µg/ml. SC packing house isolates were considered resistant (R) to propiconazole and had an average EC50 value of 3.55 µg/ml and MIC values >300 µg/ml. Two CYP51 genes, GcCYP51A and GcCYP51B, encoding two demethylase inhibitor (DMI) target enzyme 14α-demethylases were identified, sequenced, and characterized. Two GcCYP51A and three GcCYP51B variants were found. While both GcCYP51A variants were linked to S isolates, the GcCYP51B2 variant possessing the mutation Y143F was found in RS, and the GcCYP51B3 variant possessing Y143F, E126K, and G460S mutations was identified in R isolates. The Y143F and G460S mutations had been associated with DMI fungicide resistance in other plant pathogens. No increased constitutive expression of GcCYP51A or GcCYP51B was observed in RS or R isolates. Detached fruit assays revealed that label rates of propiconazole controlled sour rot caused by S and RS but not R isolates. Our results suggest that sour rot outbreaks in a SC packing house were linked to target gene-induced propiconazole resistance in G. candidum.

Genome-wide identification and expression analysis of the U-box gene family related to biotic and abiotic stresses in Coffea canephora L.

Plant U-box genes play an important role in the regulation of plant hormone signal transduction, stress tolerance, and pathogen resistance; however, their functions in coffee (Coffea canephora L.) remain largely unexplored. In this study, we identified 47 CcPUB genes in the C. canephora L. genome, clustering them into nine groups via phylogenetic tree. The CcPUB genes were unevenly distributed across the 11 chromosomes of C. canephora L., with the majority (11) on chromosome 2 and none on chromosome 8. The cis-acting elements analysis showed that CcPUB genes were involved in abiotic and biotic stresses, phytohormone responsive, and plant growth and development. RNA-seq data revealed diverse expression patterns of CcPUB genes across leaves, stems, and fruits tissues. qRT-PCR analyses under dehydration, low temperature, SA, and Colletotrichum stresses showed significant up-regulation of CcPUB2, CcPUB24, CcPUB34, and CcPUB40 in leaves. Furthermore, subcellular localization showed CcPUB2 and CcPUB34 were located in the plasma membrane and nucleus, and CcPUB24 and CcPUB40 were located in the nucleus. This study provides valuable insights into the roles of PUB genes in stress responses and phytohormone signaling in C. canephora L., and provided basis for functional characterization of PUB genes in C. canephora L.

Citrus exosome-modified exogenous dsRNA delivery reduces plant pathogen resistance and mycotoxin production

Plant-derived exosome-like nanoparticles (PENs) are crucial for intercellular communication. However, PEN-based transport of pathogenic fungal genes remains unclear. This study isolated and purified PENs from lane late navel orange citrus juice by following the sucrose gradient ultracentrifugation technique. Citrus PENs were round and oval-shaped with an average size of 154.5 ± 1.9 nm. Electroporation-based exogenous dsRNA to PENs loading efficiency remained at 6.0 %. Laser confocal microscopy was employed to investigate citrus PEN uptake by fungal spores. dsCrcB loaded PENs inhibited the CrcB gene expression in spores to alleviate Penicillium italicum resistance against prochloraz fungicide, which promoted resistant strains' mortality by 10-fold. Moreover, dsFUM21-loaded PENs suppressed the FUM21 gene expression in spores, which significantly reduced FB1 production in Fusarium proliferatum. These findings suggest that citrus PENs could potentially serve as nano-carriers to counter fungicide resistance and mycotoxin production in pathogenic plant fungi.

A 3R-MYB transcription factor is involved in Methyl Jasmonate-Induced disease resistance in Agaricus bisporus and has implications for disease resistance in Arabidopsis

IntroductionMethyl jasmonate (MeJA) and MYB transcription factors (TFs) play important roles in pathogen resistance in several plants, but MYB TFs in conjunction with MeJA-induced defense against Pseudomonas tolaasii in edible mushrooms remain unknown. ObjectivesTo investigate the role of a novel 3R-MYB transcription factor (AbMYB11) in MeJA-induced disease resistance of Agaricus bisporus and in the resistance of transgenic Arabidopsis to P. tolaasii. MethodsMushrooms were treated with MeJA alone or in combination with phenylpropanoid pathway inhibitors, and the effects of the treatments on the disease-related and physiological indicators of the mushrooms were determined to assess the role of MeJA in inducing resistance and the importance of the phenylpropanoid pathway involved. Subcellular localization, gene expression analysis, dual-luciferase reporter assay, electrophoretic mobility shift assay, and transgenic Arabidopsis experiments were performed to elucidate the molecular mechanism of AbMYB11 in regulating disease resistance. ResultsMeJA application greatly improved mushroom resistance to P. tolaasii infection, and suppression of the phenylpropanoid pathway significantly weakened this effect. MeJA treatment stimulated the accumulation of phenylpropanoid metabolites, which was accompanied by increased the activities of biosynthetic enzymes and the expression of phenylpropanoid pathway-related genes (AbPAL1, Ab4CL1, AbC4H1) and an AbPR-like gene, further confirming the critical role of the phenylpropanoid pathway in MeJA-induced responses to P. tolaasii. Importantly, AbMYB11, localized in the nucleus, was rapidly induced by MeJA treatment under P. tolaasii infection; it transcriptionally activated the phenylpropanoid pathway-related and AbPR-like genes, and AbMYB11 overexpression in Arabidopsis significantly increased the transcription of phenylpropanoid-related genes, the accumulation of total phenolics and flavonoids, and improved resistance to P. tolaasii. ConclusionThis study clarified the pivotal role of AbMYB11 as a regulator in disease resistance by modulating the phenylpropanoid pathway, providing a novel idea for the breeding of highly disease-resistant edible mushrooms and plants.

Pseudomonas fluorescens in plant growth promotion and biocontrol: A focus on secondary metabolites, IAA, and siderophores

Pseudomonas fluorescens, a Gram-negative bacterium abundant in soil, plays a critical role in promoting plant growth and controlling pathogens, demonstrating remarkable biocontrol capabilities. This review explores the utility of P. fluorescens and its ability to produce secondary metabolites, IAA (Indole-3-acetic acid), and siderophores, addressing agricultural challenges under the strains of climate change. It emphasizes its role as a plant growth-promoting bacterium (PGPB), synthesizing recent findings on its contributions to enhancing plant resilience, pathogen resistance, and sustainable agricultural practices. The production of secondary metabolites, IAA, and siderophores by P. fluorescens is examined for its effectiveness in biocontrol, nutrient mobilization, and hormonal regulation. These functions are critically analyzed through diverse research methodologies, including laboratory and field trials, underscoring the bacterium’s pivotal role in advancing agricultural sustainability and productivity. As the agricultural sector increasingly focuses on bio-products and the exploration of soil microorganisms, P. fluorescens emerges as a promising solution to enhance farming resilience in the face of climatic adversities.

Insights into the Complexity and Functionality of Plant Virus Protein Phosphorylation.

Phosphorylation, the most extensive and pleiotropic form of protein posttranslation modification, is central to cellular signal transduction. Throughout the extensive co-evolution of plant hosts and viruses, modifications to phosphorylation have served multiple purposes. Such modifications highlight the evolutionary trajectories of viruses and their hosts, with pivotal roles in regulation and refinement of host-virus interactions. In plant hosts, protein phosphorylation orchestrates immune responses, enhancing the activities of defense-related proteins such as kinases and transcription factors, thereby strengthening pathogen resistance in plants. Moreover, phosphorylation influences the interactions between host and viral proteins, altering viral spread and replication within host plants. In the context of plant viruses, protein phosphorylation controls key aspects of the infection cycle, including viral protein functionality and the interplay between viruses and host plant cells, leading to effects on viral accumulation and dissemination within plant tissues. Explorations of the nuances of protein phosphorylation in plant hosts and their interactions with viruses are particularly important. This review provides a systematic summary of the biological roles of the proteins of plant viruses carrying diverse genomes in regulating infection and host responses through changes in the phosphorylation status. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Interactive regulation of immune-related resistance genes with salicylic acid and jasmonic acid signaling in systemic acquired resistance in the Xanthomonas–Brassica pathosystem

Pathogen-responsive immune-related genes (resistance genes [R-genes]) and hormones are crucial mediators of systemic acquired resistance (SAR). However, their integrated functions in regulating SAR signaling components in local and distal leaves remain largely unknown. To characterize SAR in the Xanthomonas campestris pv. campestris (Xcc)–Brassica napus pathosystem, the responses of R-genes, (leaf and phloem) hormone levels, H2O2 levels, and Ca2+ signaling-related genes were assessed in local and distal leaves of plants exposed to four Xcc-treatments: Non-inoculation (control), only secondary Xcc-inoculation in distal leaves (C-Xcc), only primary Xcc-inoculation in local leaves (Xcc), and both primary and secondary Xcc-inoculation (X-Xcc). The primary Xcc-inoculation provoked disease symptoms as evidenced by enlarged destructive necrosis in the local leaves of Xcc and X-Xcc plants 7 days post-inoculation. Comparing visual symptoms in distal leaves 5 days post-secondary inoculation, yellowish necrotic lesions were clearly observed in non Xcc-primed plants (C-Xcc), whereas no visual symptom was developed in Xcc-primed plants (X-Xcc), demonstrating SAR. Pathogen resistance in X-Xcc plants was characterized by distinct upregulations in expression of the PAMP-triggered immunity (PTI)-related kinase-encoding gene, BIK1, the (CC-NB-LRR-type) R-gene, ZAR1, and its signaling-related gene, NDR1, with a concurrent enhancement of the kinase-encoding gene, MAPK6, and a depression of the (TIR-NB-LRR-type) R-gene, TAO1, and its signaling-related gene, SGT1, in distal leaves. Further, in X-Xcc plants, higher salicylic acid (SA) and jasmonic acid (JA) levels, both in phloem and distal leaves, were accompanied by enhanced expressions of the SA-signaling gene, NPR3, the JA-signaling genes, LOX2 and PDF1.2, and the Ca2+-signaling genes, CAS and CBP60g. However, in distal leaves of C-Xcc plants, an increase in SA level resulted in an antagonistic depression of JA, which enhanced only SA-dependent signaling, EDS1 and NPR1. These results demonstrate that primary Xcc-inoculation in local leaves induces resistance to subsequent pathogen attack by upregulating BIK1-ZAR1-mediated synergistic interactions with SA and JA signaling as a crucial component of SAR.

Amino acid substitutions in succinate dehydrogenase complex conferring resistance to the SDHI fungicide pydiflumetofen in Cochlibolus heterostrophus causing southern corn leaf blight1

Southern corn leaf blight (SCLB) caused by Cochlibolus heterostrophus, is a widespread foliar disease that has a substantial impact on maize yield in the Huanghuaihai region of China. Pydiflumetofen (Pyd), a new succinate dehydrogenase inhibitor (SDHI), has been found as a promising fungicide for the efficient control of SCLB, however, resistance of C. heterostrophus to Pyd has not been studied well. Here, five Pyd-resistant mutants were generated through fungicide adaptation. Sequence alignment analysis revealed that these mutants primarily mutated in ChSdhB and ChSdhD, with 3 genotypes: ChSdhBH277Y, ChSdhBI279T and ChSdhDH133Y, exhibiting two distinct categories of resistance: high resistance (HR) and moderate resistance (MR), which resistance factors (RF) is 214.22 and 44.33-53.67, respectively. These mutants were more pathogenic than the wild-type parental strains, but there was a significant reduction in mycelial growth rate and sporulation in the resistant mutants, indicating a significant fitness cost associated with resistance to Pyd. In addition, this study revealed a positive cross-resistance between Pyd and another SDHI fungicide cyclobutrifluram. However, no cross-resistance was found between Pyd and other classes of fungicide, including prochloraz, fludioxonil, iprodioneand pyraclostrobin. Homology modeling and molecular docking further confirmed that point mutation of ChSdhBH277Y, ChSdhBI279T, and ChSdhDH133Y could reduce binding affinity between Pyd and its target subunits from −74.07, −74.07, −152.52 kcal mol-1 to −3.90, −4.95, −9.93 kcal/mol, respectively. These findings not only provided valuable insights for managing SCLB caused by C. heterostrophus, but also enhanced our understanding of molecular mechanism underlying plant pathogen resistance to Pyd.

Plant pathogen resistance: Understanding mechanisms and developing new strategies

Plant pathogen resistance: Understanding mechanisms and developing new strategies

Prediction of LncRNA-protein Interactions Using Auto-Encoder, SE-ResNet Models and Transfer Learning.

Long non-coding RNA (lncRNA) plays a crucial role in various biological processes, and mutations or imbalances of lncRNAs can lead to several diseases, including cancer, Prader-Willi syndrome, autism, Alzheimer's disease, cartilage-hair hypoplasia, and hearing loss. Understanding lncRNA-protein interactions (LPIs) is vital for elucidating basic cellular processes, human diseases, viral replication, transcription, and plant pathogen resistance. Despite the development of several LPI calculation methods, predicting LPI remains challenging, with the selection of variables and deep learning structure being the focus of LPI research. We propose a deep learning framework called AR-LPI, which extracts sequence and secondary structure features of proteins and lncRNAs. The framework utilizes an auto-encoder for feature extraction and employs SE-ResNet for prediction. Additionally, we apply transfer learning to the deep neural network SE-ResNet for predicting small-sample datasets. Through comprehensive experimental comparison, we demonstrate that the AR-LPI architecture performs better in LPI prediction. Specifically, the accuracy of AR-LPI increases by 2.86% to 94.52%, while the F-value of AR-LPI increases by 2.71% to 94.73%. Our experimental results show that the overall performance of AR-LPI is better than that of other LPI prediction tools.

Multigenerational Adaptation Can Enhance the Pathogen Resistance of Plants via Changes in Rhizosphere Microbial Community Assembly.

Plants withstand pathogen attacks by recruiting beneficial bacteria to the rhizosphere and passing their legacy on to the next generation. However, the underlying mechanisms involved in this process remain unclear. In our study, we combined microbiomic and transcriptomic analyses to reveal how the rhizosphere microbiome assembled through multiple generations and defense-related genes expressed in Arabidopsis thaliana under pathogen attack stress. Our results showed that continuous exposure to the pathogen Pseudomonas syringae pv tomato DC3000 led to improved growth and increased disease resistance in a third generation of rps2 mutant Arabidopsis thaliana. It could be attributed to the enrichment of specific rhizosphere bacteria, such as Bacillus and Bacteroides. Pathways associated with plant immunity and growth in A. thaliana, such as MAPK signaling pathways, phytohormone signal transduction, ABC transporter proteins, and flavonoid biosynthesis, were activated under the influence of rhizosphere bacterial communities. Our findings provide a scientific basis for explaining the relationship between beneficial microbes and defense-related gene expression. Understanding microbial communities and the mechanisms involved in plant responses to disease can contribute to better plant management and reduction of pesticide use.

Microbiological and Mechanism Analysis of Novel Wheat Seed Coating Agents-Induced Growth Promotion of Wheat Seedlings

TFC (10% thifluzamide–fludioxonil–clothianidin) is a novel wheat seed-coating agent. In the field, we confirmed that 10% TFC plays a positive role in preventing soil-borne diseases and promoting wheat seedling growth. However, its effects on rhizosphere microecology and the underlying molecular mechanism are not fully understood. Field trials revealed a positive effect on the biomass, plant height, and root length of wheat sharp eyespots in a Yingshang field, with 95.3% control efficiency. The effects of 10% TFC on the rhizosphere soil microbiome of young wheat plants were evaluated using high throughput sequencing technology. The results demonstrated that seed-coating agents significantly changed bacterial and fungal communities, and reduced the number of bacteria but increased the number of fungi. Sequence analysis revealed that the abundance of Proteobacteria, Actinobacteria, and Patescibacteria in bacteria and Ascomycota, Mortierellomycota, and Basidiomycota in fungi were significantly enriched, which have been reported as being beneficial for plant growth and pathogen resistance. In contrast, the abundance of Mucoromycota in fungi was reduced, and most of the related genera identified were pathogenic to plants. In this study, 15-day-old wheat plant tissues treated with 10% TFC were subjected to global transcriptome analysis by RNA sequencing to provide insights into the effects of 10% TFC on seedling growth. The comparative analysis of Triticum aestivum L. libraries identified 8286 differentially expressed genes (DEGs), of which 2290 and 5996 genes were up- and downregulated in seedling growth in the presence of 10% TFC, respectively. Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analyses were performed for up- and downregulated DEGs separately, showing that these DEGs were enriched for terms related to the phenylpropanoid biosynthesis pathway, the protein products of which promote cell differentiation and seedling growth. This research provides comprehensive insights into its effects on wheat seedling growth and the rhizosphere microecology of seed coatings and provides important insights into their regulation and into understanding the potential benefits of seed coatings in disease management and plant growth promotion.

Discovery of novel piperidine-containing thymol derivatives as potent antifungal agents for crop protection.

Plant fungal diseases pose a significant threat to crop production. The extensive use of chemical pesticides has led to growing environmental safety risks and pesticide resistance of various plant pathogens. Therefore, it is an urgent task to explore novel eco-friendly fungicidal agents with high efficacy to combat fungal infection. In this study, we rationally designed a series of novel thymol derivatives by incorporation of the sulfonamide moiety and evaluated their biological activities against plant pathogenic fungi. The bioassay results underscored the remarkable in vitro antifungal activity of compounds 5m and 5t against Phytophthora capsici (P. capsici), with EC50 values of 8.420 and 8.414 μg/mL, respectively. Their efficacies were superior to that of widely used commercial fungicides azoxystrobin (AZO, 20.649 μg/mL) and cabendazim (CAB, 251.625 μg/mL). Furthermore, compound 5v exhibited excellent in vitro antifungal activity against Sclerotinia sclerotiorum (S. sclerotiorum), with an EC50 value of 12.829 μg/mL, significantly outperforming AZO (63.629 μg/mL). In vivo bioassays demonstrated the impactful activity of compound 5v against S. sclerotiorum, achieving over 98% curative and protective efficacies at the concentration of 200 μg/mL. Further mechanistic investigations unveiled that compound 5v induced mycelial shrinkage and collapse in S. sclerotiorum, resulting in organelle damage and the accumulation of antioxidant enzyme activity. The significant antifungal efficacy of the prepared thymol derivatives shall encourage further exploration of compound 5v as a promising candidate to develop novel fungicides for crop protection. © 2024 Society of Chemical Industry.

A biostimulant yeast, Hanseniaspora opuntiae, modifies Arabidopsis thaliana root architecture and improves the plant defense response against Botrytis cinerea

Main conclusionThe biostimulant Hanseniaspora opuntiae regulates Arabidopsis thaliana root development and resistance to Botrytis cinerea.Beneficial microbes can increase plant nutrient accessibility and uptake, promote abiotic stress tolerance, and enhance disease resistance, while pathogenic microorganisms cause plant disease, affecting cellular homeostasis and leading to cell death in the most critical cases. Commonly, plants use specialized pattern recognition receptors to perceive beneficial or pathogen microorganisms. Although bacteria have been the most studied plant-associated beneficial microbes, the analysis of yeasts is receiving less attention. This study assessed the role of Hanseniaspora opuntiae, a fermentative yeast isolated from cacao musts, during Arabidopsis thaliana growth, development, and defense response to fungal pathogens. We evaluated the A. thaliana–H. opuntiae interaction using direct and indirect in vitro systems. Arabidopsis growth was significantly increased seven days post-inoculation with H. opuntiae during indirect interaction. Moreover, we observed that H. opuntiae cells had a strong auxin-like effect in A. thaliana root development during in vitro interaction. We show that 3-methyl-1-butanol and ethanol are the main volatile compounds produced by H. opuntiae. Subsequently, it was determined that A. thaliana plants inoculated with H. opuntiae have a long-lasting and systemic effect against Botrytis cinerea infection, but independently of auxin, ethylene, salicylic acid, or jasmonic acid pathways. Our results demonstrate that H. opuntiae is an important biostimulant that acts by regulating plant development and pathogen resistance through different hormone-related responses.

Analysis of five near-complete genome assemblies of the tomato pathogen Cladosporium fulvum uncovers additional accessory chromosomes and structural variations induced by transposable elements effecting the loss of avirulence genes

BackgroundFungal plant pathogens have dynamic genomes that allow them to rapidly adapt to adverse conditions and overcome host resistance. One way by which this dynamic genome plasticity is expressed is through effector gene loss, which enables plant pathogens to overcome recognition by cognate resistance genes in the host. However, the exact nature of these loses remains elusive in many fungi. This includes the tomato pathogen Cladosporium fulvum, which is the first fungal plant pathogen from which avirulence (Avr) genes were ever cloned and in which loss of Avr genes is often reported as a means of overcoming recognition by cognate tomato Cf resistance genes. A recent near-complete reference genome assembly of C. fulvum isolate Race 5 revealed a compartmentalized genome architecture and the presence of an accessory chromosome, thereby creating a basis for studying genome plasticity in fungal plant pathogens and its impact on avirulence genes.ResultsHere, we obtained near-complete genome assemblies of four additional C. fulvum isolates. The genome assemblies had similar sizes (66.96 to 67.78 Mb), number of predicted genes (14,895 to 14,981), and estimated completeness (98.8 to 98.9%). Comparative analysis that included the genome of isolate Race 5 revealed high levels of synteny and colinearity, which extended to the density and distribution of repetitive elements and of repeat-induced point (RIP) mutations across homologous chromosomes. Nonetheless, structural variations, likely mediated by transposable elements and effecting the deletion of the avirulence genes Avr4E, Avr5, and Avr9, were also identified. The isolates further shared a core set of 13 chromosomes, but two accessory chromosomes were identified as well. Accessory chromosomes were significantly smaller in size, and one carried pseudogenized copies of two effector genes. Whole-genome alignments further revealed genomic islands of near-zero nucleotide diversity interspersed with islands of high nucleotide diversity that co-localized with repeat-rich regions. These regions were likely generated by RIP, which generally asymmetrically affected the genome of C. fulvum.ConclusionsOur results reveal new evolutionary aspects of the C. fulvum genome and provide new insights on the importance of genomic structural variations in overcoming host resistance in fungal plant pathogens.

Plant Growth Promotion and Stress Tolerance Enhancement through Inoculation with Bacillus proteolyticus OSUB18.

The isolation of B. proteolyticus OSUB18 from switchgrass unveiled its significant potential in both the enhancement of plant growth and the suppression of plant diseases in our previous study. The elucidation of the related mechanisms governing this intricate plant-microbe interaction involved the utilization of the model plant Arabidopsis thaliana. In our comprehensive study on Arabidopsis, OSUB18 treatment was found to significantly alter root architecture and enhance plant growth under various abiotic stresses. An RNA-seq analysis revealed that OSUB18 modified gene expression, notably upregulating the genes involved in glucosinolate biosynthesis and plant defense, while downregulating those related to flavonoid biosynthesis and wound response. Importantly, OSUB18 also induces systemic resistance in Arabidopsis against a spectrum of bacterial and fungal pathogens and exhibits antagonistic effects on phytopathogenic bacteria, fungi, and oomycetes, highlighting its potential as a beneficial agent in plant stress management and pathogen resistance. Overall, our findings substantiate that OSUB18 exerts a stimulatory influence on plant growth and health, potentially attributed to the remodeling of root architecture, defense signaling, and the comprehensive mitigation of various biotic and abiotic stresses.

Genetic variation of drug target CYP51 conferring resistance to ergosterol biosynthesis inhibitors in Botrytis cinerea, causing lily gray mould

Gray mould caused by Botrytis cinerea poses a threat to Lily (Lilium spp.), an important plant with both medicinal and ornamental value, during pre- and post-harvest stages. Ergosterol biosynthesis inhibitors (EBIs) have been widely registered to control gray mould caused by B. cinerea in various plants over a prolonged period of time, yet no instances of resistance of B. cinerea to EBIs have been detected in the field. In this study, the field B. cinerea EBIs-resistant populations were detected from the diseased lily flowers. The CYP51 protein, which is the target of EBIs, was found to have G461S or R464K substitutions in these resistant strains. To further verify whether the G461S or R464K substitutions of CYP51 confer the resistance to EBIs in B. cinerea, the mutants carrying the G461S or R464K substitutions of CYP51 were generated from EBIs-sensitive wild type strains via site-directed mutagenesis. The G461S or R464K substitutions indeed resulted in decreased sensitivity of B. cinerea to EBIs. Meanwhile, the mutants conferring the S461G or K464R substitutions of CYP51 were generated from the field EBIs-resistant strains, and the significant increase in sensitivity to EBIs were observed in these mutants. Furthermore, the G461S or R464K substitutions suffered to fitness penalty in mycelial growth and virulence, but improved sporulation capability. Molecular docking analysis furtherly demonstrated that the CYP51 protein, carrying the G461S or R464K substitutions, exhibited reduced binding affinity with tebuconazole. To the best of our knowledge, it is the first report that G461S or R464K substitutions in CYP51 leading to field resistance to EBIs in B. cinerea. These findings not only provided valuable insights for managing lily gray mould caused B. cinerea, but also enhance our understanding of molecular mechanism underlying plant pathogen resistance to EBIs.

Exogenous Melatonin Regulates Plant‐Disease Interaction by Inducing Maize Resistance and Decreasing the Pathogenicity of Fusarium graminearum

AbstractPlants cannot avoid environmental challenges and are constantly threatened by diverse biotic and abiotic stresses. However, plants have developed a unique immune system to defend themselves against the invasion of various pathogens. Melatonin, N‐acetyl‐5‐methoxytryptamine has positive physiological effects in plants that are involved in disease resistance. The processes underlying melatonin‐induced pathogen resistance in plants are still unknown. The current study explores how melatonin regulates the plant‐disease interaction in maize. The results showed that 400 μM melatonin strongly reduced the disease lesion on maize stalks by 1.5 cm and corn by 4.0 cm caused by Fusarium graminearum PH‐1. Furthermore, after treatment with melatonin, the plant defense enzymes like SOD significantly increased, while POD and APX significantly decreased compared to the control. In addition, melatonin can also improve maize's innate immunity, which is mediated by melatonin treatments through the salicylic acid signaling pathway, and up‐regulate the defense‐associated expression of PR1, LOX1, OXR, serPIN, and WIPI genes in maize. Melatonin not only inhibits the disease in the maize stalks and corn, but also down‐regulates the deoxynivalenol (DON) production‐related expression of genes Tri1, Tri4, Tri5, and Tri6 in maize. Overall, this study sheds new light on the mechanisms by which melatonin regulates antioxidant enzymes and defense‐related genes involved in plant immunity to effectively suppress plant diseases.

Red light activates H2O2 signal involved in powdery mildew resistance in oriental melon seedlings

Melon is one of the most important horticultural crops in Asia. Powdery mildew (PM) is frequently occurred in facility cultivation, which seriously affects its yield and fruit quality of melon. Light signal is the basis of plant growth and development, and appropriate red light (RL) plays an important role in regulating the resistance of plant pathogens. Reactive oxygen species (ROS) also have been shown to be participated in plant defence against pathogen infection. However, whether light is involved in PM resistance through ROS remains unclear. Here, we found that RL+PM treatment significantly enhanced the resistance of PM in melon seedlings, improved NADPH oxidase activity, upregulated respiratory burst oxidase homologue 1 (RBOHD) expression, and increased hydrogen peroxide (H2O2) level. Compared with the PM treatment alone, diphenylene iodonium (DPI)+PM treatment significantly enhanced the sensitivity to PM in melon seedlings and weakened the effect of RL-induced PM resistance. Further studies showed that silencing CmRBOHD significantly inhibited the RL-induced PM resistance by inhibiting H2O2 synthesis. In addition, CmWRKY50 could activate CmRBOHD expression by binding to the promoter of CmRBOHD. Taken together, the results suggest that RL can increase endogenous H2O2 levels and induce the initiation of defence through activation of CmWRKY50, and therefore, when plants are subjected to pathogen stress, higher H2O2 levels in the plants are beneficial for organizing the invasion of pathogens and enhancing powdery mildew resistance.