Search Results (83)

Sheath blight (ShB), caused by the necrotrophic fungus Rhizoctonia solani (R. solani), poses severe threats to global rice production. Developing a resistant variety with an ShB-resistance gene is one of most efficient and economical approaches to control the disease. Here, we identified a highly conserved chloroplast-localized stem-loop-binding protein encoding gene (OsCSP41b), which shows great potential in developing an ShB-resistant variety. OsCSP41b-knockout mutants exhibit chlorotic leaves and increased ShB susceptibility, whereas OsCSP41b-overexpressing lines (CSP41b-OE) display significantly enhanced resistance to R. solani, as well as to drought, and salinity stresses. Notably, CSP41b-OE lines present a completely comparable grain yield to the wild type (WT). Transcriptomic analyses reveal that chloroplast transcripts and photosynthesis-associated genes maintain observably elevated stability in CSP41b-OE plants versus WT plants following R. solani infection, which probably accounts for the enhanced ShB resistance of CSP41b-OE. Our findings nominate the OsCSP41b gene as a promising molecular target for developing a rice variety with stronger resistance to both R. solani and multi-abiotic stresses. Full article

Sclerotinia sclerotiorum, known as a typical necrotrophic pathogenic fungus, exhibits a complex pathogenic mechanism. Research on S. sclerotiorum has primarily focused on oxalic acid, pathogenicity-related enzymes, and secreted proteins. In this study, we identified a transcription factor, SsSR (S. sclerotiorum Sterol-Related transcription factor), which regulates S. sclerotiorum infection by modulating virulence through ergosterol biosynthesis. We characterized the transcriptional activity of SsSR and its downstream target gene, SsCYP51. SsSR undergoes phosphorylation induced by the host plant, subsequently regulating the expression of SsCYP51. The deletion of SsSR or SsCYP51 does not affect the growth or acid production of S. sclerotiorum, but it leads to a reduction in ergosterol, significantly diminishing virulence and impairing the stress tolerance of the hyphae. In summary, this study identifies a transcription factor, SsSR, that specifically regulates the virulence of S. sclerotiorum. SsSR upregulates the expression of SsCYP51 through phosphorylation during the infection phase, leading to the synthesis of ergosterol, which enhances hyphal stress tolerance and thereby promotes infection. Full article

The cap-binding protein complex (CBC), comprising Cbp20 and Cbp80, is crucial for gene expression, yet its role in the notorious crop pathogen Botrytis cinerea remains unclear. Immunoprecipitation coupled with LC-MS/MS demonstrated that BcCbp20 interacts with BcCbp80. Yeast two-hybrid, GST pull-down, and Split-luciferase complementation assays confirmed that the conserved RNA recognition motif (RRM, 54–127 aa) of BcCbp20 and the N-terminal MIF4G domain (1–370 aa, 1–577 aa) of BcCbp80 constitute the core interaction regions. Genetic transformation experiments revealed that BcCBP80 exerts a more dominant role than BcCBP20 in regulating hyphal morphology, growth rate, conidiophore development, and conidial yield. Furthermore, BcCBP20 and BcCBP80 differentially regulate sclerotium formation to maintain sclerotial quantity. Based on pathogenicity assays, BcCBP80 associated with infection cushion development, with this phenotypic alteration possibly being among the factors correlated with altered pathogenicity. However, the increased sensitivity of ΔBccbp20 to various stress factors may be the primary reason for the diminished pathogenicity. Taken together, these results indicate that BcCBP20 and BcCBP80 play important roles in multiple aspects of B. cinerea growth, development, stress response, and pathogenicity. Full article

Natural populations provide valuable information and resources for addressing the genetic characterization of biological systems. Botrytis cinerea is a necrotrophic fungus that exhibits complex responses to light. Physiological analysis of B. cinerea populations from vineyards in Castilla y León (Spain) allowed for the identification of isolate Bc116. This field isolate shows a reduced pathogenicity that is conditioned by the light regime. Light also delays germination and accentuates the negative effect it exerts on the vegetative growth of B. cinerea. Bc116 also displays a marked hyperconidiation phenotype and a characteristic sclerotia production pattern. Genetic analysis demonstrates that the alternative phenotypes regarding pathogenicity, conidiation, and pattern of sclerotia production co-segregate in the progeny of crosses between isolate Bc116 and a wild-type field isolate, Bc448, showing that they are under the control of a single locus. By applying a strategy based on bulked segregant analysis, the mutation in Bc116 has been mapped to a 200 kb region on Chr14 and the analysis of this region identifies a 2 kb deletion affecting the bcltf1 gene, encoding the B. cinerea Light Responsive Transcription Factor 1 described in the reference isolate B05.10. Transformation of Bc116 with the B05.10 bcltf1 allele restored the wild-type phenotypes, providing functional evidence that the natural mutant Bc116 is altered in gene bcltf1. This study offers additional information, derived from the analysis of the genetic background of a natural mutant, on the physiological processes regulated by BcLTF1 and supports the key role of this TF in the pathogenicity and photobiology of B. cinerea. Full article

Chitinases are enzymes that catalyze the hydrolysis of chitin and play a significant biophysiological role in fungal growth, development, and pathogenesis. Valsa mali is a necrotrophic fungus that is a primary contributor to apple Valsa canker. Our study focused on the identification of chitinase gene families from V. mali and the analysis of their expression profiles during infection and nutritional growth. A phylogenetic analysis and conservation of catalytic domains were used to classify these genes into three classes, and their chromosome distribution was random. The qRT-PCR analysis identified five differentially expressed VmGH18 genes during infection and nutritional growth. GH18 chitinases use glutamate, whereas VmGH18-4 (VM1G_05900) and VmGH18-10 (VM1G_03597) use glutamine as the catalytic motif. To further test whether it can induce cell death in apple, the recombinant protein was produced in E. coli. It showed that the purified VmGH18-4 recombinant protein retained cell-death inducing activity, and it could also induce cell death in apple. But the enzyme activity shows that neither VmGH18-4 nor VmGH18-10 have chitinases enzyme activity. These results suggest that VmGH18-4 can elicit cell death in multiple plant species, while VmGH18-10 cannot. Full article

Sheath blight (ShB), caused by the necrotrophic fungus Rhizoctonia solani, is one of the most serious rice diseases worldwide. In this study, we successfully grafted salicylic acid (SA) onto mesoporous silica nanoparticles through an amide-bond coupling method, forming functionalized MSN-SA nanoparticles. Physicochemical characterization showed that the MSN-SA nanoparticles were spherical, with an average particle size of approximately 30 nm and an SA loading rate of around 7.21%. The assessment of ShB resistance revealed that both SA and MSN-OH treatments were capable of inducing resistance to a certain extent. When SA and MSN-OH were applied in combination, the resistance was further augmented, indicating an additive effect between them. Intriguingly, MSN-SA treatment (50% in Lemont) exhibited a higher and more durable control efficacy compared with SA + MSN-OH treatment (33%). Moreover, field experiments demonstrated that the MSN-SA was safe for rice, and under severe disease conditions, it could recover 16.7% of the yield loss, thus highlighting its substantial application value. Further transcriptome analysis and physicochemical assays suggested that MSN-SA released SA in a slow and continuous manner, thus persistently activating the immune response, and that MSN-SA integrated the effects of SA and MSN-OH, thereby enhancing the ShB resistance. Altogether, our results provide new perspectives and a novel nanomaterial-based immune elicitor for the green control of ShB. Full article

Citrus Alternaria brown spot caused by the necrotrophic fungal pathogen of the tangerine pathotype of Alternaria alternata causes yield losses in global tangerine production. In this study, we focus on a cytochrome P450 monooxygenase encoding gene, Aacp1, for its role in the sporulation, toxin production, and virulence of the tangerine pathotype of Alternaria alternata. Aacp1-deficient mutants (∆Aacp1) produced significantly fewer conidia than the wild-type strain. Chemical assays demonstrated that Aacp1 plays a negative role in resistance to oxidant stress and biosynthesis of ACT toxin. Virulence assays revealed that ΔAacp1 fails to induce necrotic lesions on detached Hongjv leaves. Transcriptomic analyses of WT and ΔAacp1 revealed that many metabolic process genes were regulated. Furthermore, our results revealed a previously unrecognized Aacp1 affected the expression of the gene encoding a naphthalene dioxygenase (AaNdo1) for sporulation and full virulence. Overall, this study revealed the diverse functions of cytochrome P450 monooxygenase in the phytopathogenic fungus. Full article

Rhizoctonia solani is a basidiomycete phytopathogenic fungus that causes rapid necrosis in a wide range of crop species, leading to substantial agricultural losses worldwide. The species complex is divided into 13 anastomosis groups (AGs) based on hyphal fusion compatibility and further subdivided by culture morphology. While R. solani classifications were shown to be independent of host specificity, it remains unclear whether different R. solani isolates share similar virulence mechanisms. Here, we investigated the infectivity of Japanese R. solani isolates on Brachypodium distachyon and barley. Two isolates, AG-1 IA (from rice) and AG-4 HG-I+II (from cauliflower), infected leaves of both plants, but only AG-4 HG-I+II infected roots. B. distachyon accessions Bd3-1 and Gaz-4 and barley cultivar ‘Morex’ exhibited enhanced resistance to both isolates compared to B. distachyon Bd21 and barley cultivars ‘Haruna Nijo’ and ‘Golden Promise’. During AG-1 IA infection, but not AG-4 HG-I+II infection, resistant Bd3-1 and Morex induced genes for salicylic acid (SA) and N-hydroxypipecolic acid (NHP) biosynthesis. Pretreatment with SA or NHP conferred resistance to AG-1 IA, but not AG-4 HG-I+II, in susceptible B. distachyon Bd21 and barley Haruna Nijo. On the leaves of susceptible Bd21 and Haruna Nijo, AG-1 IA developed extensive mycelial networks with numerous infection cushions, which are specialized infection structures well-characterized in rice sheath blight. In contrast, AG-4 HG-I+II formed dispersed mycelial masses associated with underlying necrosis. We propose that the R. solani species complex encompasses at least two distinct infection strategies: AG-1 IA exhibits a hemibiotrophic lifestyle, while AG-4 HG-I+II follows a predominantly necrotrophic strategy. Full article

Valsa mali (V. mali) is a necrotrophic fungus responsible for apple Valsa canker, which significantly diminishes apple production yields and quality in China. Our serendipitous findings revealed that genistein significantly inhibits the mycelial growth of V. mali, with an inhibition rate reaching 42.36 ± 3.22% at a concentration of 10 µg/mL. Scanning electron microscopy analysis revealed that genistein caused significant changes in the structure of V. mali, including mycelial contraction, distortion, deformity, collapse, and irregular protrusions. Transmission electron microscopy analysis revealed leakage of cellular contents, blurred cell walls, ruptured membranes, and organelle abnormalities. Genistein has been shown to increase reactive oxygen species levels in V. mali mycelia, as demonstrated by 2′,7′-dichlorofluorescin diacetate staining. This increase was associated with a decrease in superoxide dismutase activity alongside increases in catalase and peroxidase activities. These changes collectively disrupted the oxidative equilibrium, leading to the induction of oxidative stress. The transcriptomic analysis revealed 13 genes enriched in this process, linked to unsaturated fatty acid biosynthesis (three downregulated DEGs), saturated fatty acid biosynthesis (three upregulated and six downregulated DEGs), and fatty acid metabolism (four upregulated and nine downregulated DEGs). Additionally, the downregulated DEGs VMIG_07417 and VMIG_08675, which are linked to ergosterol biosynthesis, indicate possible changes in membrane composition. In conjunction with the qRT-PCR results, it is hypothesized that genistein exerts an antifungal effect on V. mali through ROS-mediated lipid peroxidation. This finding has the potential to contribute to the development of novel biological control agents for industrial crops. Full article

Background: Hazelnut (Corylus), a significant woody oil tree species in economic forests, faces production constraints due to biotic stresses, with Hazelnut Husk Brown Rot, caused by the pathogenic necrotrophic fungus Botrytis cinerea (B. cinerea), being the most severe. To date, limited information is available regarding the resistance of hazelnuts to B. cinerea. To better understand the mechanisms of resistance to B. cinerea. in hazelnut, we conducted metabolomics and WGCNA analyses of a B. cinerea-resistant Ping’ou hybrid hazelnut variety (Dawei; DW) and a susceptible variety (Qiuxiang; QX). Methods: In this study, metabolomics and weighted gene co-expression network analysis (WGCNA, weighted correlation network analysis) were applied to elucidate the resistance mechanisms underlying different hazelnut varieties to B. cinerea. Our study focused on the metabolome profiles of DW and QX plants after 72 h of B. cinerea infection. Results: Venn analysis of QX_0 vs. DW_0 and QX_72 vs. DW_72 revealed 120 differential accumulation metabolites (DAMs) that were upregulated. Among these metabolites, the concentrations of flavonoids and phenolic acids in DW were significantly higher than those in QX, respectively, suggesting that the elevated levels of these compounds contribute substantially to the resistance of hazelnut against B. cinerea. 3,4-hydroxyphenyllactic acid and phloretin were significantly more abundant in accumulation in DW than in QX after infection by B. cinerea. Conclusions: This study provides that the elevated levels of these compounds (flavonoids and phenolic acids) contribute substantially to the resistance of hazelnut against B. cinerea. Furthermore, 3,4-hydroxyphenyllactic acid and phloretin were identified as pivotal metabolites in modulating the resistance of hazelnut to B. cinerea. Through WGCNA analyses, we identified four transcription factors (WRKY19, HSFC1, ERF071, and RAP2-1) that are most likely to regulate the synthesis of 3,4-dihydroxyphenyllactic acid and phloretin. This study provides crucial insights for further investigation into the regulatory network of metabolites associated with hazelnut resistance to B. cinerea. Full article

Microscopic evidence demonstrated a strictly biotrophic lifestyle of the scab fungus Venturia inaequalis on growing apple leaves and characterised its hemibiotrophy as the combination of biotrophy and saprotrophy not described before. The pathogen–host interface was characterised by the formation of knob-like structures of the fungal stroma appressed to epidermal cells as early as 1 day after host penetration, very thin fan-shaped cells covering large parts of the host cell lumen, and enzymatic cuticle penetration from the subcuticular space limited to the protruding conidiophores. The V. inaequalis cell wall had numerous orifices, facilitating intimate contact with the host tissue. Pathogen-induced modifications of host cells included partial degradation of the cell wall, transition of epidermal cells into transfer cells, modification of epidermal pit fields to manipulate the flow of nutrients and other compounds, and formation of globular protuberances of mesophyll cells without contact with the pathogen. The non-haustorial biotrophy was characterised by enlarged areas of intimate contact with host cells, often mediated by a matrix between the pathogen and plant structures. The new microscopic evidence and information on the pathogens’ biochemistry and secretome from the literature gave rise to a model of the lifestyle of V. inaequalis, lacking a necrotrophic stage that covers and explains its holomorphic development. Full article

Fungi have played a pivotal role in human history, from the dangers of fungal toxins to the revolutionary discovery of penicillin. Fungal secondary metabolites (SMs), such as polyketides (PKs) and terpenes, have attracted considerable interest due to their diverse biological activities. Botrytis deweyae, an endophytic fungus, exhibits behaviors that are notably distinct from those of its necrotrophic relatives within the genus Botrytis. This study explores the importance of terpenes and PK gene clusters and their conservation between species. In addition, new putative biosynthetic gene clusters corresponding to those families were identified. Consequently, the new PKS BdPKS22-26 were also identified in other Botrytis species and other fungi. In addition, those new gene clusters identified in this work show differences in the degree of conservation and are phylogenetically closely related to some of the 21 PKSs previously described in the reference strain Botrytis cinerea B05.10. Moreover, a new gene cluster related to terpenes in B. deweyae B1 and B. cinerea B05.10 was also identified that had never been detected before. This new gene cluster is well conserved among other Botrytis species in many phylogenetically distant fungal lineages. Understanding the genetic basis and conservation of these putative biosynthetic gene clusters sheds light on the metabolic potential and ecological roles of B. deweyae and related fungal species. Full article

Arabidopsis LIM proteins are named after the initials of three proteins Lin-11, Isl-1, and MEC-3, which belong to a class of transcription factors that play an important role in the developmental regulation of eukaryotes and are also involved in a variety of life processes, including gene transcription, the construction of the cytoskeleton, signal transduction, and metabolic regulation. Plant LIM proteins have been shown to regulate actin bundling in different cells, but their role in immunity remains elusive. Mitogen-activated protein kinases (MAPKs) are a family of conserved serine/threonine protein kinases that link upstream receptors to their downstream targets. Pathogens produce pathogen-associated molecular patterns (PAMPs) that trigger the activation of MAPK cascades in plants. Recently, we conducted a large-scale phosphoproteomic analysis of PAMP-induced Arabidopsis plants to identify putative MAPK targets. One of the identified phospho-proteins was WLIM2A, an Arabidopsis LIM protein. In this study, we investigated the role of WLIM2A in plant immunity. We employed a reverse-genetics approach and generated wlim2a knockout lines using CRISPR-Cas9 technology. We also generated complementation and phosphosite-mutated WLIM2A expression lines in the wlim2a background. The wlim2a lines were compromised in their response to Pseudomonas syringae Pst DC3000 but showed enhanced resistance to the necrotrophic fungus Botrytis cinereae. Transcriptome analyses of wlim2a mutants revealed the deregulation of immune hormone biosynthesis and signaling of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) pathways. The wlim2a mutants also exhibited altered stomatal phenotypes. Analysis of plants expressing WLIM2A variants of the phospho-dead or phospho-mimicking MAPK phosphorylation site showed opposing stomatal behavior and resistance phenotypes in response to Pst DC3000 infection, proving that phosphorylation of WLIM2A plays a crucial role in plant immunity. Overall, these data demonstrate that phosphorylation of WLIM2A by MAPKs regulates Arabidopsis responses to plant pathogens. Full article

Sheath blight (ShB) is the most serious disease of rice (Oryza sativa L.), caused by the soil-borne fungus Rhizoctonia solani Kühn (R. solani). It poses a significant threat to global rice productivity, resulting in approximately 50% annual yield loss. Managing ShB is particularly challenging due to the broad host range of the pathogen, its necrotrophic nature, the emergence of new races, and the limited availability of highly resistant germplasm. In this study, we conducted QTL mapping using an F₂ population derived from a cross between a partially resistant accession (IRGC81941A) of Oryza nivara and the susceptible rice cultivar Punjab rice 121 (PR121). Our analysis identified 29 QTLs for ShB resistance, collectively explaining a phenotypic variance ranging from 4.70 to 48.05%. Notably, a cluster of four QTLs (qRLH1.1, qRLH1.2, qRLH1.5, and qRLH1.8) on chromosome 1 consistently exhibit a resistant response against R. solani. These QTLs span from 0.096 to 420.1 Kb on the rice reference genome and contain several important genes, including Ser/Thr protein kinase, auxin-responsive protein, protease inhibitor/seed storage/LTP family protein, MLO domain-containing protein, disease-responsive protein, thaumatin-like protein, Avr9/Cf9-eliciting protein, and various transcription factors. Additionally, simple sequence repeats (SSR) markers RM212 and RM246 linked to these QTLs effectively distinguish resistant and susceptible rice cultivars, showing great promise for marker-assisted selection programs. Furthermore, our study identified pre-breeding lines in the advanced backcrossed population that exhibited superior agronomic traits and sheath blight resistance compared to the recurrent parent. These promising lines hold significant potential for enhancing the sheath blight resistance in elite cultivars through targeted improvement efforts. Full article

Botrytis cinerea is a necrotrophic fungus that causes considerable economic losses in commercial crops. Fungi of the genus Botrytis exhibit great morphological and genetic variability, ranging from non-sporogenic and non-infective isolates to highly virulent sporogenic ones. There is growing interest in the different isolates in terms of their methodological applications aimed at gaining a deeper understanding of the biology of these fungal species for more efficient control of the infections they cause. This article describes an improvement in the protoplast production protocol from non-sporogenic isolates, resulting in viable protoplasts with regenerating capacity. The method improvements consist of a two-day incubation period with mycelium plugs and orbital shaking. Special mention is made of our preference for the VinoTaste Pro enzyme in the KC buffer as a replacement for Glucanex, as it enhances the efficacy of protoplast isolation in B459 and B371 isolates. The methodology described here has proven to be very useful for biotechnological applications such as genetic transformations mediated by the CRISPR/Cas9 tool. Full article