Search Results (141)

Citral, an organic compound found in lemongrass (Cymbopogon citratus) oil and Litsea cubeba essential oil, has been reported to exhibit notable antifungal activity against Magnaporthe oryzae (M. oryzae), the pathogen of rice blast, which causes significant economic losses in rice production. However, the role of citral in inducing oxidative stress related to antifungal ability and its underlying regulatory networks in M. oryzae remain unclear. In this study, we investigated the oxidative effects of citral on M. oryzae and conducted transcriptomic and widely targeted metabolomic (WTM) analyses on the mycelia. The results showed that citral induced superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) activities but reduced glutathione S-transferase (GST) activity with 25% maximal effective concentration (EC₂₅) and 75% maximal effective concentration (EC₇₅). Importantly, citral at EC₇₅ reduced the activities of mitochondrial respiratory chain complex I, complex III and ATP content, while increasing the activity of mitochondrial respiratory chain complex II. In addition, citral triggered a burst of reactive oxygen species (ROS) and a loss of mitochondrial membrane potential (MMP) through the observation of fluorescence. Furthermore, RNA-seq analysis and metabolomics analysis identified a total of 466 differentially expression genes (DEGs) and 32 differential metabolites (DAMs) after the mycelia were treated with citral. The following multi-omics analysis revealed that the metabolic pathways centered on AsA, GSH and melatonin were obviously suppressed by citral, indicating a disrupted redox equilibrium in the cell. These findings provide further evidences supporting the antifungal activity of citral and offer new insights into the response of M. oryzae under oxidative stress induced by citral. Full article

Fungal diseases severely threaten global agriculture, while conventional chemical fungicides face increasing restrictions due to environmental and safety concerns. In this study, we isolated a soil-derived Bacillus stercoris strain, DXQ-1, exhibiting strong antagonistic activity against plant pathogenic fungi, notably Magnaporthe oryzae, the causal agent of rice blast. Scanning electron microscopy revealed that DXQ-1 disrupts fungal hyphae and inhibits conidial germination, with a 24 h crude broth treatment reducing germination to 83.33% and completely blocking appressoria formation. LC-MS-based metabolomic analysis identified key antifungal components, including lipids (35.83%), organic acid derivatives (22.15%), and small bioactive molecules (e.g., Leu-Pro, LPE 15:0). After optimizing fermentation conditions (LB medium, pH 7.0, 28 °C, 48 h), the broth showed >90% inhibition against M. oryzae and Nigrospora oryzae and retained high thermal (68 °C, 1 h) and UV (4 h) stability. Field trials demonstrated effective disease control and significant promotion of rice growth, increasing plant height (17.7%), fresh weight (53.3%), and dry weight (33.3%). These findings highlight DXQ-1 as a promising biocontrol agent, offering a sustainable and effective alternative for managing fungal diseases in crops. Full article

Rice blast disease, caused by the ascomycete fungus Magnaporthe oryzae (syn. Pyricularia oryzae), poses a severe threat to global rice production. Southern China, a major rice-growing region characterized by diverse agroecological conditions, faces substantial challenges from blast disease, yet our understanding of the genetic structure of M. oryzae populations in this region remains limited. Here, we analyzed 885 M. oryzae strains from 18 nurseries across four rice ecological regions in Southern China using a panel of genome-wide SNP markers. Phylogenetic and principal component analyses revealed three distinct clonal lineages: lineage I (58.19%), lineage II (21.36%), and lineage III (20.45%). Lineage I exhibited a broader geographic distribution compared to the other two lineages. Host-adapted divergence was observed across rice subspecies, with lineage III predominantly associated with japonica growing-regions, while lineages I and II mainly colonized indica rice-growing regions. Genetic diversity exhibited significant spatial heterogeneity, with the nucleotide diversity (π) ranging from 0.17 in South China to 0.32 in the Middle–Lower Yangtze River region, reflecting differential cropping systems. The predominantly negative Tajima’s D values across populations suggested recent expansion or selective sweeps, likely driven by host resistance pressures. High genetic differentiation between lineage I and other lineages contrasted with low divergence between lineages II and III, indicating distinct evolutionary trajectories. Furthermore, an uneven distribution of mating types among three genetic lineages was observed, suggesting limited sexual recombination within clonal lineages. The information obtained in this study may be beneficial in devising suitable strategies to control rice blast disease in Southern China. Full article

Trichoderma spp., Metarhizium spp., and Bacillus spp. are commonly used as biocontrol microorganisms domestically and internationally. However, microbial pesticides currently prepared from single living microorganisms have problems such as a short shelf life, particularly under stressful environment conditions. Secondary metabolites produced from biocontrol microorganisms are comparatively stable when used under field conditions. This study screened the optimal combination of biocontrol metabolites, referred to as TMB, composed of culture filtrates from certain isolates of Trichoderma asperellum 10264, Bacillus subtilis S4-4-10, and Metarhizium anisopliae 3.11962 (1:4:1 (v/v)). RNA-seq analysis and transmission electron microscope observations were carried out to identify the major functions of the most effective culture filtrates against Magnaporthe oryzae (the pathogen causing rice blast disease) and Chilo suppressalis (an insect pest in rice cultivation). TMB was found to disrupt the midgut subcellular structure of C. suppressalis larvae and inhibit the expression of genes related to immunity, membrane components, protein synthesis, and other functions in C. suppressalis larvae and M. oryzae, thereby interfering with their normal growth, reproduction, and infection potential in rice. In addition, TMB was also able to promote rice growth and trigger host defense responses against infections by the target pests and pathogens. In summary, TMB generated different inhibitory activities against multiple targets in C. suppressalis and M. oryzae and induced plant immunity in rice. Therefore, it can be used as a new environmentally friendly agent or alternative to control rice pests and diseases. Full article

Magnaporthe oryzae (M. oryzae) is a phytopathogenic fungus that inflicts damage on vital crops, particularly rice. Its asexual reproduction leads to the generation of numerous conidia, which is a critical factor contributing to the prevalence of rice blast disease. However, the molecules regulating the asexual reproduction of M. oryzae are unknown. In our study, to identify the molecules capable of regulating the asexual reproduction of M. oryzae, compositions of the complete medium (CM) were screened. Results showed that acid-hydrolyzed casein (AHC) could remarkably promote conidial production. One M. oryzae conidiation inducer was isolated from AHC using high-performance liquid chromatography (HPLC) under the guidance of bioassay. Its structure was further elucidated as a decapeptide compound (pyroGlu-EQNQEQPIR) by LC-MS/MS, chemical synthesis, and conidium-inducing assays, named M. oryzae conidiation inducer decapeptide (MCIDP). MCIDP could significantly promote the conidiation of M. oryzae and two other filamentous ascomycetes (Botrytis cinerea and Fusarium graminearum). The Mps1 MAPK cascade signaling pathway is crucial for conidiation, and the effect of MCIDP on this pathway was investigated to elucidate the mechanism underlying conidiation enhancement. qRT-PCR analysis demonstrated that MCIDP could remarkably upregulate the gene expression within the Mps1 MAPK cascade signaling pathway, especially the WSC2, WSC3, PKC1, MKK1, MPS1, and MIG1. Furthermore, the ΔMowsc1, ΔMowsc2, ΔMowsc3, and ΔMomid2 mutant strains were constructed. Bioassay results showed that MCIDP failed to promote conidial formation and hyphal growth in these mutant strains. These findings indicate that MCIDP promotes conidiation of M. oryzae by modulating the Mps1 MAPK signaling pathway. Full article

Rice blast disease is a major threat to rice yields. Sustainable control relies on resistant varieties, where plant immunity is triggered by pattern recognition receptors like receptor-like proteins (RLPs). The rice RLP chitin-elicitor binding protin (CEBiP) recognizes fungal chitin and confers blast resistance to pathogen Magnaporthe oryzae. However, understanding of the broader signaling and metabolomic pathways associated with CEBiP activation remains limited. Here, we performed an integrated transcriptomic and metabolomic analysis of the rice Zhonghua 11 genotype and CEBiP knockout plants. Both plants were infected with M. oryzae, and infected leaves were harvested at 24, 48, and 72 hpi for RNA sequencing and Liquid Chromatography-Tandem Mass Spectrometry analysis. Transcriptomics identified a total of 655 genes that were differentially regulated upon knockout of CEBiP; they were mainly related to diterpenoid/phenylpropanoid biosynthesis, nitrogen metabolism, the mitogen-activated protein kinasesignaling pathway, plant–pathogen interaction, and plant hormone signal transduction. The presence of a large number of pathogenesis-related protein 1 family genes indicates the key role of salicylic acid (SA) in CEBiP immunity. Metabolomics detected a total of 962 differentially accumulated metabolites and highlights the roles of caffeine and glutathione metabolism in CEBiP-mediated immunity. Since caffeine and glutathione metabolism can regulate SA signaling, we propose that SA signaling plays a central role in the CEBiP immune function. Full article

Magnaporthe oryzae serves as a model organism for studying the molecular biology of filamentous fungi and the pathogenic mechanisms of fungal pathogens. It also poses a significant threat to rice production in China. Bax inhibitor-1 (Bi-1), a protein with evolutionary conservation, functions as an inhibitor of programmed cell death induced by the proapoptotic protein Bax. Despite the widespread presence of Bi-1 proteins in hyphal fungi, their biological functions have not been extensively characterized. Here, we characterized the function of MoBI-1, a putative Bax-inhibitor protein in M. oryzae, which is located in the mitochondria and participates in conidiation, stress adaptation, and pathogenicity. Further investigations revealed that MoBi-1 is also essential for the regulation of mitochondrial energy metabolism. Remarkably, experimental evidence indicates that MoBi-1 does not seem to function in inhibiting Bax-induced programmed cell death, thus lacking inherent Bax inhibitory function, which broadens the existing understanding of Bax inhibitor-1’s function and provides significant new insights into the disease-causing mechanisms of M. oryzae. Full article

Rice blast caused by Magnaporthe oryzae pathotype is the worst disease that leads to serious food insecurity globally. Understanding rice blast disease pathogenesis is therefore essential for the development of a blast disease mitigation strategy. Reverse phosphorylation mediated by phosphatases performs a vital function in the activation of diverse biological mechanisms within eukaryotic. However, little has been reported on the roles of PP2Cs in the virulence of blast fungus. In this current work, we deployed functional genomics and biochemical approaches to characterize type 2C protein phosphatase MoPtc6 in blast fungus. Deletion of MoPTC6 led to a drastic reduction in conidiophore development, conidia production, hyphal growth, and stress tolerance. Western blotting assay demonstrated that the phosphorylation level of MoOsm1 was decreased while MoMps1 was increased in the MoPtc6 deletion mutant, and comparative transcriptome assay revealed a higher number of expressed genes between mutant and wild type. Localization assay confirmed that MoPtc6 is sub-localized in the cytoplasm of mycelia, spores, and in the appressoria of M. oryzae. Furthermore, disruption of MoPTC6 impaired appressoria turgor pressure and glycogen utilization; more findings revealed attenuation of hyphal penetration and virulence upon deletion of MoPTC6. Generally, present findings suggested the role of MoPtc6 in the growth and virulence of M. oryzae. Full article

The avirulence (AVR) genes of the filamentous ascomycete fungus Magnaporthe oryzae (M. oryzae) are known to mutate rapidly under a higher selection pressure, allowing the pathogen to evade recognition by rice resistance (R) genes. Understanding the geographic distribution and natural variation of AVR genes is critical for the rational utilization and prolonging of the effectiveness of R genes. In this study, a total of 1060 M. oryzae strains collected from 19 rice blast nurseries in 13 provinces across southern China were subjected to presence/absence variation (PAV), genetic variation, and virulence analyses of the AVR-Pita1 gene. PCR amplification results indicated that AVR-Pita1 was present in only 57.45% of the blast strains, with significant geographic variation in distribution frequency. Specifically, the highest frequency (100%) was observed in strains from Chengmai, Hainan, while the lowest (1.79%) was observed in strains from Baoshan, Yunnan. A sequencing analysis identified 29 haplotypes of AVR-Pita1, characterized by insertions, deletions, and base substitutions. A phylogenetic analysis indicated that haplotypes of AVR-Pita1 identified in this study were clustered into one clade. A further amino acid sequence analysis of these haplotypes led to the identification of 25 protein variants. Notably, four haplotypes of AVR-Pita1 exhibited pathogenicity toward its corresponding rice R gene, PtrA. Additionally, we performed allele profiling of Ptr in a collection of elite parental lines that are widely used in rice breeding in southern China and found that the functional Ptr alleles (PtrA, PtrB, and PtrC) accounted for over 70%. Full article

Protein phosphatases are crucial enzymes that regulate key cellular processes such as the cell cycle, gene transcription, and translation in eukaryotes. Seven PP2C protein phosphatases have been identified in Magnaporthe oryzae. However, their synergistic roles in the pathology and physiology of M. oryzae remain poorly investigated. By qRT-PCR analysis, we found that PTC1 and PTC2 are significantly upregulated in the PTC5 deletion mutant. The double deletion of the MoPTC5/MoPTC1 and MoPTC5/MoPTC2 genes significantly reduced hyphal growth, conidiophore formation, sporulation, and virulence in M. oryzae. In addition, the double-knockout mutants were increasingly sensitive to different osmotic, oxidative, and cell wall stresses. Western blot analysis revealed that MoPtc5 plays a synergistic function with MoPtc1 and MoPtc2 in the regulation of MoMps1 and MoOsm1 phosphorylation levels. Lastly, appressorium formation and turgor generation were remarkably affected in the ΔMoptc5ΔMoptc1 and ΔMoptc5ΔMoptc2 double-deletion mutants. These findings demonstrate the overlapping roles of PP2c protein phosphatase in the fungal development and pathogenesis of M. oryzae. Full article

Rice brown spot disease, caused by Bipolaris oryzae, is a significant fungal disease that poses a major threat to global rice production. Despite its widespread impact, genomic studies of B. oryzae remain limited, particularly those involving high-quality genomic data. In this study, we performed whole-genome sequencing of the B. oryzae strain RBD1, which was isolated from the demonstration field for upland rice cultivation in Haozhiba Village, Lancang County, Pu’er City, Yunnan Province, China, using a combination of second-generation Illumina sequencing and third-generation Single-Molecule Real-Time (SMRT) sequencing. The assembled genome was 37.5 Mb in size with a G + C content of 49.39%, containing 42 contigs with a contig N50 of 2.0 Mb. Genomic analysis identified genes related to carbon, nitrogen, and lipid metabolism, highlighting the strain’s metabolic flexibility under diverse environmental conditions and host interactions. Additionally, we identified pathogenicity-related genes involved in MAPK signaling, G protein signaling, and oxidative stress responses. Under 1.2 M sorbitol-induced osmotic stress, we observed significant differences in growth responses between RBD1 and the rice blast fungus Magnaporthe oryzae H7. Transcriptomic analysis using Illumina sequencing revealed that RBD1 responds to osmotic stress by enhancing carbohydrate metabolism, fatty acid degradation, and amino acid synthesis, while H7 primarily relies on protein synthesis to enhance growth tolerance. This study provides a valuable foundation for understanding the pathogenic mechanisms of rice brown spot and future disease control strategies. Full article

Unique genes refer to genes specific to a particular organism and play crucial roles in the biological functions, evolutionary processes, and adaptations to external environments. However, the roles of unique genes in plant pathogenic fungi remain largely unexplored. In this study, we identified a novel unique gene in the rice blast fungus Magnaporthe oryzae, named MoUNG (M. oryzae unique gene), through T-DNA insertion mutagenesis. The disruption of the MoUNG promoter region in the T-DNA insertion mutant (T30-104) led to an almost loss of MoUNG expression. MoUNG has no functional domains and lacks homologues in other organism. It is highly expressed during the early-infection stage between 16 and 32 h post-inoculation (HPI), in contrast to its expression in mycelia and at the later infection stage of 48 HPI. Notably, attempts to knock out MoUNG were unsuccessful, so we examined the T30-104 mutant and found it showed significantly reduced growth, conidiation, and pathogenicity. Introducing the full-length MoUNG with its promoter into T30-104 restored these phenotypic defects. Additionally, subcellular localization assays revealed that MoUNG exhibits a dot-like distribution within the cytoplasm of mycelium, conidium, appressorium, and invasive hypha. Furthermore, knock-down of MoUNG produced results similar to those observed with the insertion mutation. In conclusion, we identified a novel unique gene MoUNG in M. oryzae and demonstrated its involvement in growth, conidiation, and pathogenicity. Full article

Rice is exposed to attacks by the three most destructive pathogens, Magnaporthe oryzae (M. oryzae), Xanthomonas oryzae pv. oryzae (Xoo), and Rhizoctonia solani (R. solani), which cause substantial yield losses and severely threaten food security. To cope with pathogenic infections, rice has evolved diverse molecular mechanisms to respond to a wide range of pathogens. Among these strategies, plant microRNAs (miRNAs), endogenous single-stranded short non-coding RNA molecules, have emerged as promising candidates in coordinating plant–pathogen interactions. MiRNAs can modulate target gene expression at the post-transcriptional level through mRNA cleavage and/or translational inhibition. In rare instances, they also influence gene expression at the transcriptional level through DNA methylation. In recent years, substantial advancements have been achieved in the investigation of microRNA-mediated molecular mechanisms in rice immunity. Therefore, we attempt to summarize the current advances of immune signaling mechanisms in rice–pathogen interactions that are regulated by osa-miRNAs, including their functions and molecular mechanisms. We also focus on recent findings concerning the role of osa-miRNAs that respond to M. oryzae, Xoo, and R. solani, respectively. These insights enhance our understanding of how the mechanisms of osa-miRNAs mediate rice immunity and may facilitate the development of improved strategies for breeding pathogen-resistant rice varieties. Full article

Rice blast disease, caused by Magnaporthe oryzae (M. oryzae), is a significant threat to global rice production. Conventional methods for disease management face limitations, emphasizing the importance of sustainable alternatives. In this study, two rice cultivars with different blast resistant abilities, the susceptible variety CO39 and the resistant variety Pi4b, were used as materials to study the effects of Piriformospora indica (Pi) on the resistance to M. oryzae infection and rice growth. The in vitro tests revealed no direct antagonistic interaction between Pi and M. oryzae. However, the in vivo experiments showed that Pi promoted plant growth by increasing root and shoot length, chlorophyll content, and nitrogen uptake, particularly in CO39 during pathogen infection. Pi inoculation also significantly reduced disease severity, which was indicated by smaller lesion areas and shorter lesion lengths in both cultivars but a more pronounced effect in CO39. This occurred due to the decreasing levels of MDA and the modulating activity of antioxidant enzymes in Pi-inoculated rice plants. At the early stage of M. oryzae infection, the expression of the ethylene signaling gene OsEIN2 and the gibberellin biosynthesis gene OsGA20ox1 in Pi-inoculated CO39 decreased but significantly increased in both rice cultivars at the later stage. The reverse was found for the pathogenesis-related (PR) genes OsPR10 and OsPBZ1 and the blast-resistant genes OsBRG1, OsBRG2, and OsBRW1, suggesting early growth suppression for rice resilience to blast followed by a later shift back to growth. Meanwhile, Pi inoculation increased OsCesA9 expression in rice to strengthen cell walls and establish the primary defense barrier against M. oryzae and upregulated the expression of OsNPR1 without a significant difference in CO39 but downregulated it in Pi4b to activate PR genes to enhance plant resistance. In summary, these results underscore the potential of Pi as a sustainable biological control agent for rice blast disease, which is particularly beneficial for blast-susceptible rice cultivars. Full article

Magnaporthe oryzae causes devastating rice blast disease, significantly impacting rice production in many countries. Among the many known resistance (R) genes, Piz-t confers broad-spectrum resistance to M. oryzae isolates and encodes a nucleotide-binding site leucine-rich repeat receptor (NLR). Although Piz-t-interacting proteins and those in the signal transduction pathway have been identified over the last decade, the Piz-t-mediated resistance has not been fully understood at the transcriptomic and metabolomic levels. In this study, we performed transcriptomic and metabolomic analyses in the Piz-t plants after inoculation with M. oryzae. The transcriptomic analysis identified a total of 15,571 differentially expressed genes (DEGs) from infected Piz-t and wild-type plants, with 2791 being Piz-t-specific. K-means clustering, GO term analysis, and KEGG enrichment pathway analyses of the total DEGs identified five groups of DEGs with distinct gene expression patterns at different time points post inoculation. GO term analysis of the 2791 Piz-t-specific DEGs revealed that pathways related to DNA organization, gene expression regulation, and cell division were highly enriched in the group, especially at early infection stages. The gene expression patterns in the transcriptomic datasets were well correlated with the metabolomic profiling. Broad-spectrum “pathway-level” metabolomic analyses indicated that terpenoid, phenylpropanoid, flavonoid, fatty acid, amino acid, glycolysis/TCA, and phenylalanine pathways were altered in the Piz-t plants after M. oryzae infection. This study offers new insights into the molecular dynamics of transcripts and metabolites in R-gene-mediated resistance against M. oryzae and provides candidates for enhancing rice blast resistance through the engineering of metabolic pathways. Full article