Sugarcane smut, caused by Sporisorium scitamineum, is one of the most devastating diseases of sugarcane worldwide, leading to severe yield losses and long-term agricultural impacts. Integral membrane proteins are essential components of plasma membranes, playing critical roles in molecular transport, signal transduction, pathogenesis, and defense. However, their contributions to sexual mating and pathogenicity in smut fungi remain largely unknown. In this study, we sought to characterize two novel integral membrane proteins—regulation of whip and teliospore development 1 (RWTD1) and pheromone-regulated multispanning membrane protein (PRM1)—in S. scitamineum. The RWTD1 protein, which contains four transmembrane domains, showed mating-specific upregulation and localized to discrete puncta in the cytoplasm near the cell membrane. The deletion of RWTD1 in Mat-1 haploids abolished filamentous growth after sexual mating, whereas its deletion in Mat-2 haploids resulted in reduced filamentation. Transcriptome profiling revealed that, relative to the wild type, genes encoding several integral and intrinsic membrane components were differentially expressed in RWTD1 mutants, including PRM1 and DIK6, which encode putative four- and seven-transmembrane domain proteins, respectively. Deleting PRM1 recapitulated the mating defects observed in the ΔRWTD1 mutants. While RWTD1, PRM1, and DIK6 contributed to virulence, RWTD1 also functioned in symptom development and teliospore formation. Overall, our work demonstrated that the transmembrane proteins RWTD1, PRM1, and DIK6 are important contributors to virulence and sexual mating in the sugarcane smut fungus.
Aspartic proteases (APs) and G-protein-coupled receptors (GPCRs) are widespread in eukaryotes and play important roles in various cellular processes, including protein modification and cell signaling. In oomycetes, these two functional protein domains are combined into a single protein, forming a so-called bigram. However, the function of these AP-GPCR bigrams remains largely unknown. This study focuses on an AP-GPCR bigram in the devastating oomycete plant pathogen Phytophthora capsici, which is encoded by a single copy gene. Bioinformatic analyses confirmed that PcAPG encodes a membrane-associated protein with an N-terminal signal peptide, a central AP domain, and a C-terminal seven-transmembrane GPCR domain. Expression profiling revealed that PcAPG is constitutively expressed, with a significant upregulation during early host infection (1.5—12 hpi). Knocking out PcAPG using a modified CRISPR/Cas9 system resulted in mutants with only minor mycelial growth defects but severely attenuated virulence, indicating a crucial role for PcAPG in plant-pathogen interaction. Comparative transcriptomic analysis between the wild-type strain and a representative mutant suggests that PcAPG participates in regulating the expression of a suite of putative infection-related genes, potentially via a GPCR-mediated signaling pathway. Notably, in the wild-type strain, 158 genes involved in catabolic processes, such as polysaccharide degradation and hydrolase activities (e.g., alpha-galactosidase activity and arabinan catabolic process), were upregulated during infection, whereas in the mutant, these genes were not upregulated. Based on our findings it is concluded that the AP-GPCR bigram PcAPG is a key virulence factor in P. capsici with a putative role in downstream transcriptional activation of multiple catabolic enzymes thereby facilitating host colonization and invasion. This work unveils an AP-GPCR bigram as a unique signaling module in oomycete pathogens and identifies PcAPG as a promising potential target for novel management strategies against Phytophthora induced diseases.
Rice is a vital global staple crop, yet its productivity is significantly constrained by various diseases caused by pathogenic microorganisms. Developing efficient and environmentally friendly alternatives to complement or replace chemical pesticides is therefore crucial for sustainable rice production. Mesoporous silica nanoparticles have emerged as promising candidates for plant protection, owing to their unique physicochemical properties and high biocompatibility. However, the efficacy and underlying mechanisms of different mesoporous silica nanoparticles morphologies against major rice diseases remain to be fully elucidated. In this study, we synthesized two types of mesoporous silica nanoparticles with distinct morphologies–spherical (MSN) and virus-like spiky (VMSN) within a plant-absorbable size range. We systematically evaluated their protective effects against southern rice black-streaked dwarf virus (SRBSDV). The results demonstrated that both types of nanoparticles could induce viral resistance, while spherical MSN exhibited superior efficacy in pathogen suppression. Mechanistic investigations revealed that MSN and VMSN differentially up-regulated the expression of the transcription factor OsERF3, which in turn activated its downstream target gene OsRBOHE, leading to a defense-related reactive oxygen species (ROS) burst. Further genetic evidence confirmed that OsRBOHE acts as a positive regulator of rice resistance to SRBSDV. Additionally, both nanomaterials displayed favorable leaf wettability. They were efficiently absorbed and systemically translocated within rice plants, and showed no adverse effects on seed germination, seedling growth, or key agronomic traits at maturity. In conclusion, this study elucidates the molecular mechanism whereby spherical MSN functions as a potent immune primer by preferentially activating the OsERF3-OsRBOHE-ROS signaling axis. Combined with their excellent foliar delivery properties and biosafety, these findings provide a solid theoretical and practical foundation for developing sustainable, nanosilica-based crop protection strategies.
Geminiviruses employ sophisticated immune evasion strategies to incite devastating diseases, posing a significant threat to global agricultural security. A central tactic involves the subversion of chloroplast-mediated immunity via viral effectors. Here, we elucidate how the pathogenicity determinant βC1 from ageratum yellow vein China betasatellite (AYVCNB) hijacks this defense system by targeting the chloroplast-localized protein organellar single-stranded DNA-binding protein 1 (OSB1). Functionally, OSB1 acts as a positive regulator of immunity by stabilizing AGD2‐LIKE DEFENSE RESPONSE PROTEIN 1 (ALD1) and promoting pipecolic acid biosynthesis. We demonstrate that AYVCNB-encoded βC1 physically interacts with OSB1, triggering its ubiquitin-proteasome-dependent degradation and consequently abrogating the OSB1-ALD1 defense module. Parallel to this finding, our recent work revealed that βC1 from tomato yellow leaf curl China betasatellite re-localizes OSB1 from the chloroplast to the cytoplasm and promotes its degradation. These results collectively demonstrate that targeting the OSB1-ALD1 defense module represents a widespread and conserved geminivirus mechanism to subvert chloroplast immunity.
Abstract Rice false smut, caused by the ascomycete fungus Ustilaginoidea virens , is one of the most severe diseases of rice. Conventional artificial inoculation methods for rice false smut rely mainly on conidia–hyphae mixtures (CH) as inocula, which frequently result in poor reproducibility and variable disease development across experiments. Here, we established a reproducible and efficient inoculation system for rice false smut using conidia-germinated hyphae (CGH) as inoculum, in which conidia are allowed to germinate before inoculation, yielding a more uniform and physiologically active inoculum. A rice leaf-based pre-culture step markedly improved conidial production and germination, and CGH showed higher infection efficiency and more stable disease symptoms than conventional CH under both controlled and field conditions. Time-course observations further revealed that CGH-based inoculation supports the typical infection progression of U. virens in rice spikelets. Importantly, this system enabled reliable phenotyping of U. virens mutants and effectively identified resistant and susceptible rice cultivars. In addition, the high rate of diseased spikelets achieved with CGH enabled consistent sample collection for downstream molecular and multiomics analyses. Overall, this study provides a refined inoculation system and a robust platform for functional studies of the U. virens –rice pathosystem.
Abstract Crop soilborne diseases caused by pathogens, such as Fusarium spp. and root-knot nematode (RKN), contribute to substantial yield losses worldwide. This study investigated the biocontrol potential of the fungivorous nematode Aphelenchoides bicaudatus isolate A23 against soilborne diseases. Isolate A23 showed strong antagonism against phytopathogenic fungi, while remaining non-pathogenic to tomato plants. Among the four soilborne pathogenic fungi tested, A. bicaudatus exhibited a pronounced feeding preference for Fusarium spp., reducing the incidence of tomato Fusarium wilt by up to 60%. Moreover, in both pot and field trials, A. bicaudatus significantly suppressed root-knot nematode attack, reflected in reduced galling index, egg masses, and egg production, thereby increasing fruit yield relative to the control. Split-root assays and qRT-PCR analysis demonstrated that root-knot nematode suppression by A. bicaudatus was primarily mediated by induced systemic resistance, involving the activation of salicylic acid-dependent defense pathways. Additionally, high-throughput amplicon sequencing indicated that A. bicaudatus inoculation reshaped the rhizosphere microbiome by enriching beneficial bacterial and fungal genera while reducing pathogen-associated taxa, such as Fusarium . Collectively, these results demonstrate that the A . bicaudatus isolate A23 is an effective biocontrol agent that acts through an integrated mechanism combining direct fungal predation, plant defense priming, and beneficial microbiome reshaping. This study establishes a foundation for using fungivorous nematodes in a multifunctional role in crop disease management.
Verticillium dahliae is a soil-borne vascular pathogen with a broad host range and the ability to survive in soil for extended periods through the formation of stress-resistant microsclerotia. It poses a major challenge to disease management and frequently causes severe Verticillium wilt in smoke tree (Cotinus coggygria) in China. Zn(II)2Cys6 transcription factors (TFs) represent a major class of fungal regulators and are involved in various biological processes, including primary and secondary metabolism, stress adaptation, and pathogenesis. In this study, we found that the deletion of VdRgt1, which belongs to Zn(II)2Cys6 TF, led to abnormal hyphal morphology, reduced vegetative growth, markedly decreased conidial production, and altered timing of microsclerotia development and melanin accumulation. Additionally, the ΔVdRgt1 mutant exhibited significantly reduced virulence and impaired colonization of C. coggygria. Transcriptome analysis indicated that VdRgt1 is involved in the regulation of carbohydrate and energy metabolism. Consistently, the ΔVdRgt1 mutant exhibited reduced ATP levels, and RT-qPCR supported a role for VdRgt1 in glucose-responsive gene regulation. Collectively, these results indicate that VdRgt1 is an important regulator in V. dahliae, coordinating hyphal development, the timing of microsclerotia development and melanin accumulation, carbon and energy metabolism, stress adaptation, and virulence.
Viral coat protein (CP)-mediated resistance represents an effective strategy that confers robust antiviral defense in plants. However, the functional relevance of this resistance mechanism during mixed infections by distinct viral species remains largely elusive. Mixed viral infections in agricultural crops frequently lead to exacerbated disease symptoms and substantial yield losses, posing a severe threat to global agricultural production. In this study, we demonstrate that expression of tomato leaf curl New Delhi virus (ToLCNDV) CP confers effective resistance against tomato yellow leaf curl China virus (TYLCCNV), another prominent geminivirus. Strikingly, the βC1 protein encoded by TYLCCNV betasatellite can fully counteract this CP-mediated resistance through direct interaction with ToLCNDV CP and promotion of its proteasome-dependent degradation. We further identified the residue Tyr110 of βC1 as essential for the interaction and subsequent CP degradation. Consequently, βC1-mediated suppression of CP resistance promotes efficient systemic infection of ToLCNDV DNA A. Collectively, our results uncover a novel mechanism by which a viral effector antagonizes viral CP-mediated host resistance during mixed viral infections, offering important insights into viral pathogenesis and the development of sustainable disease control strategies.
Nucleotide biosynthesis pathways in organisms are widely utilized in the development of antineoplastic and antifungal drugs in medical field. However, little was known about the catalytic enzymes in the pyrimidine salvage pathway of Phytophthora capsici, a major oomycete pathogen responsible for horticultural crop blight disease around the world. In current study, the functional characteristics of uridine kinase PcUK in the pyrimidine salvage pathway of P. capsici, as well as the effect of nucleoside drugs 5-Fluorouridine (5-FD), 5-Fluorouracil (5-FU), and 5-Flucytosine (5-FC) on Phytophthora pathogens were investigated. We demonstrate that 5-FD, 5-FU, and 5-FC could strongly inhibit the growth of P. capsici and P. sojae, in which the inhibition effect of 5-FD and 5-FU was dependent on the presence of PcUK. Moreover, PcUK is mainly localized at endoplasmic reticulum, and it could form homomeric complex and interact with Kelch⁃like protein Pc028643. Although uridine kinases across various Phytophthora species are highly conserved, neither deleting nor overexpressing PcUK could affect the growth and pathogenicity of P. capsici. Taken together, these results identified and characterized the uridine kinase PcUK in P. capsici, highlighting that PcUK is mainly localized at endoplasmic reticulum and its essential role in the inhibition of P. capsici by 5-FD and 5-FU.
Tomato (Solanum lycopersicum) is a nutrient-rich vegetable crop widely cultivated worldwide. Tomato Fusarium wilt disease caused by Fusarium oxysporum f.sp. lycopersici (Fol) is a soil-borne fungal disease that leads to enormous economic losses in tomato agricultural production worldwide. The latest research on small RNA (sRNA)-mediated DNA methylation (RdDM) has highlighted its role in plant disease resistance; however, the fungal pathogen cross-kingdom sRNA that mediates host DNA methylation to counteract tomato Fusarium wilt disease has not been explored. Previously, we documented that Fol-milR1, an sRNA effector, was transported into tomato cells during the pathogen infection and hijacked the tomato immune system by binding to SlyAGO4a. Here, we further explore how Fol-milR1-SlyAGO4a participates in resistance to Fusarium wilt by regulating the DNA methylation of disease-resistant genes in tomato. The Fusarium wilt-susceptible tomato cultivar Moneymaker was infected with the water/Fol-WT/Fol-milR1_KO strain, followed by whole-genome methylation sequencing. The methylation level of Solyc08g080960 (SlyAHL) was associated with Fol-milR1 expression in tomato. The methylation type was mainly CG in the SlyAHL coding region. SlyAHL was required for wilt disease resistance by regulating reactive oxygen species (ROS) accumulation in tomato. In summary, the Fol-milR1-SlyAGO4a-SlyAHL function module, which mediates resistance to tomato wilt disease, provides a potential environmentally friendly strategy to manage it.
Fusarium head blight (FHB) poses a major threat to wheat cultivation in Korea. Given that FHB coincides with warm and wet conditions during the flowering period, climate change is projected to exacerbate the risk to wheat crops in Korea. Thus, there is an immediate need to develop effective and scientifically sound adaptation measures. A major hurdle in achieving this goal has been insufficient consideration of local agroeconomic factors and a tendency to rely on meteorological scenarios. By addressing this knowledge gap, we aimed to identify alternative wheat cultivars that can maximize yields under projected FHB epidemics. In this study, we used biophysical models and all available agroeconomic information on wheat in Korea, along with the 6th Coupled Model Intercomparison Project (CMIP6) climate change scenarios. We initially simulated the potential FHB epidemics in Korea by linking a wheat phenology model to an FHB infection model. The simulation results indicated heterogeneous projections, with substantial increases in future FHB infection risk under certain scenarios. Thereafter, using three cultivar-specific traits—heading date, FHB resistance level, and yield potential—from 40 wheat cultivars, together with projected FHB incidence, we estimated their future yields. Finally, after considering present-day market availability, the Saegeumgang cultivar, together with other yet-to-be-released cultivars, was proposed as the best alternative wheat cultivar for effective adaptation in Korea. Collectively, these results will provide scientific evidence for policymakers and agricultural stakeholders to facilitate the pragmatic selection of climate-resilient cultivars capable of adapting to the future threat of FHB.
Extracellular vesicles (EVs) are critically involved in cross-kingdom communication and plant defense mechanisms. However, their potential as delivery vehicles for exogenous antimicrobial agents remains largely unexplored. In this study, we show that EVs are essential for rice immunity against Magnaporthe oryzae, with their secretion being significantly induced upon infection. Genetic evidence from Oryza sativa Tetraspanin 7 (OsTET7) and OsTET13 overexpression lines and mutants further confirms the role of EVs in rice resistance to M. oryzae. Additionally, we demonstrate that rice-derived EVs are internalized by M. oryzae and subsequently suppress the hyphal growth. We successfully loaded the anti-fungal peptide LL37 onto rice EVs, forming stable EV-LL37 complexes, and demonstrated its efficacy in suppressing M. oryzae. These complexes displayed improved environmental stability and enhanced adhesion to leaf surfaces under stress conditions, resulting in sustained anti-fungal activity. Our results highlight the dual function of rice EVs as innate immune components and efficient nanocarriers for antimicrobial agents, providing a novel platform for crop protection strategies.
Abstract Fatty acid ω-hydroxyacid/fatty alcohol hydroxycinnamoyl transferase (FHT) is a key enzyme involved in suberin biosynthesis. The phytohormone abscisic acid (ABA) positively regulates suberin formation by promoting FHT expression, however the role of FHT regulated by ABA in viral infection remains unclear. Immunoprecipitation coupled with mass spectrometry (IP-MS) screening indicated that NbFHT interacting with the coat protein (CP) of cucumber green mottle mosaic virus (CGMMV). This interaction was further confirmed by bimolecular fluorescence complementation (BiFC) assay and co-immunoprecipitation (Co-IP) assays. Quantitative real-time polymerase chain reaction (qPCR) analysis revealed that the NbFHT gene expression was induced during CGMMV infection. Virus-induced gene silencing (VIGS) and overexpression analysis further demonstrated that NbFHT in Nicotiana benthamiana enhances host resistance to CGMMV. Notably, NbFHT interferes with the CGMMV CP self-interaction and promotes CP degradation. Moreover, exogenous ABA treatment significantly stabilized NbFHT and accelerated CP degradation, contributing to the increased resistance to CGMMV. Collectively, this study makes a unique contribution by shedding light on the previously unexplored relationship between the suberin synthesis-related enzyme FHT and ABA during viral infection.
Abstract Puccinia triticina Eriks. (Pt) is a basidiomycete fungal pathogen causing wheat leaf rust, a significant global threat to wheat production, leading to substantial yield losses in susceptible cultivars. Traditional management strategies, including planting resistant cultivars and deploying fungicides, are increasingly challenged by this pathogen’s rapid evolution and emergence of new virulent races. Recent interest has focused on mycoviruses, viruses that infect fungi, for their potential roles in biological control and influencing fungal population dynamics. This study investigates the virome of 117 Pt isolates collected across Canada when inoculated onto the susceptible wheat cultivar Thatcher. The total RNA was isolated from infected leaf tissues and metatranscriptome analysis followed by manual filtering steps revealed 37 unique viral species at the amino-acid (AA) level with the identity ranging from 30.4% to 100% across 6 viral families and unclassified viruses. High-throughput sequencing and RT-PCR amplification from germinated urediniospores mats confirmed the presence of putative mycoviruses, which could provide insights into their impact on the biology and epidemiology of Pt. Additionally, among the 37 viral species, we describe 17 novel viruses with high divergence based on the amino acid similarity from known viral species. This study reveals a diverse virome associated with P. triticina across Canada, highlighting the potential influence of mycoviruses on the pathogen’s biology, evolution, and epidemiology. This represents the first step toward opening new avenues for innovative management strategies against wheat leaf rust.
Abstract Phytoalexins are low-molecular-weight antimicrobials that plants synthesize de novo upon pathogen attack, forming a frontline chemical defense arsenal. Despite decades of study, the genetic basis and regulatory mechanisms governing their biosynthesis have remained surprisingly fragmentary. A landmark study by Wang et al. (Cell, 2026, https://doi.org/10.1016/j.cell.2026.04.021 ) closes this gap for the fungicidal sesquiterpenoid debneyol by elucidating its complete three-enzyme dominated biosynthesis pathway (EAS–EAE–EH1) from farnesyl pyrophosphate, identifying the Solanaceae-specific miR1919–MCD1 module as a regulatory switch, and revealing that MCD1 functions as a metabolic organizer—a scaffold protein that enhances EAS–EAE association and EAE catalytic efficiency while competitively directing substrate flux away from the capsidiol branch toward debneyol synthesis. This metabolic channeling mechanism contributes to rapid, broad-spectrum disease resistance against fungal, viral, and bacterial pathogens. Inducible expression of MCD1 under the TBF1::uORFs promoter achieves disease resistance while minimizing the fitness costs associated with constitutive defense activation (Xu et al. 2017). This work uncovers a genetic framework for phytoalexin-mediated chemical defense, reveals metabolic organizers as a new class of immune regulators, and offers a novel strategy for engineering disease-resistant crops and microbial production of bioactive phytoalexins.
Abstract Mycoviruses are widely distributed across major fungal clades and have significant potential as biocontrol agents, particularly in phytopathogenic fungi, which cause substantial economic losses in agricultural production. Fusarium pseudograminearum, a prominent causal agent of wheat crown rot worldwide, remains underexplored with respect to its associated mycoviral species. To explore the mycovirome of F. pseudograminearum, metatranscriptomic sequencing was performed on 400 isolates of this fungal pathogen in this study. A diverse array of 80 contigs associated with mycovirus species was identified, of which 34 represent novel species. Genome-type analysis revealed 52 positive-sense single-stranded RNA (+ssRNA), 18 negative-sense ssRNA (-ssRNA), and 10 double-stranded RNA (dsRNA) viruses. Classification using BLASTp and phylogenetic analysis of RNA-dependent RNA polymerase (RdRp) sequences placed these mycoviruses into 12 distinct evolutionary lineages. Mitoviruses constituted nearly half (47.5%) of the identified mycoviruses, while phenuiviruses accounted for 11.25%. Intriguingly, multiple mycoviruses shared homology with plant viruses, suggesting possible evolutionary links. This study provides the first comprehensive mycovirome analysis of F. pseudograminearum, uncovering substantial viral diversity. The findings expand our understanding of mycoviral communities and offer new perspectives for studying virus evolution.
Abstract The Major Facilitator Superfamily (MFS) is an extensive group that plays important roles in nutrient and metabolite transport, drug resistance, and nerve signaling. To explore the potential roles of MFS transporters in Magnaporthe oryzae, we identified and characterized two MFS transporters, MoMfs1 and MoMfs3, from the rice blast fungus M. oryzae. Targeted gene disruption revealed that both transporters are involved in fungal development and the efflux of fungicides. Moreover, the MoMFS1 and MoMFS3 mutants exhibited decreased extracellular peroxidase and laccase activities, likely due to reduced production or secretion of these enzymes. Interestingly, the ∆Momfs3 mutant showed reduced pathogenicity and limited expansion of invasive hyphae, indicating that MoMfs3 plays a critical role in pathogenicity. Metabolic analysis identified 537 down-regulated metabolites and 17 specific compounds, including toxins, antibacterial substances, and biotin, suggesting that MoMfs3 is involved in the secretion of secondary metabolites. In summary, our findings illustrate that MFS transporters are important for the development of M. oryzae throughout the disease cycle by selectively modulating specific transporters.
Abstract Fusarium head blight (FHB), caused by Fusarium graminearum, severely reduces wheat yield and grain quality due to deoxynivalenol (DON) contamination. To develop sustainable alternatives to synthetic fungicides, we evaluated the antifungal activity of tea infusion. It significantly inhibited F. graminearum mycelial growth, conidiation, and germination. Transmission electron microscopy revealed hyphal cell wall thickening and deformation, enlarged vacuoles, and protoplasmic leakage, leading to cell death. Transcriptomic analysis showed that tea infusion disrupts ribosome biogenesis, tRNA methylation, hydrolase activity, and pathogenesis-related pathways. Among the differentially expressed genes, Fg014, encoding a hydrolase, was downregulated. Functional characterization of the ΔFg014 mutant revealed reduced radial growth, impaired host penetration, and attenuated virulence on wheat spikes and maize silks, along with decreased trichothecene biosynthesis (Tri) gene expression and DON production. Notably, tea infusion application suppressed disease development and DON accumulation in wheat without inducing pathogenesis-related (PR) gene expression, indicating that its effect stems from direct antifungal activity rather than host defense activation. Although individual tea components—epigallocatechin gallate (EGCG), caffeine, L-theanine, and theobromine—inhibited fungal growth, their efficacy was lower than that of the full tea infusion, suggesting synergistic interactions among constituents. Collectively, tea infusion suppresses F. graminearum by targeting multiple cellular and virulence pathways, supporting its potential as an environmentally friendly strategy for green control of FHB in sustainable agriculture.
Abstract Minor cereal crops of Poaceae (MCCP) are crucial regional crops in China. Currently, little is known about the diversity, multilocus phylogeny, and pathogenicity of helminthosporioid fungi associated with MCCP leaf spots in China. However, emerging leaf spot diseases have become a serious problem threatening the MCCP industry. This study aims to enhance understanding of the pathogen populations causing leaf spot diseases of MCCP, focusing on their pathogenic diversity, pathogenicity, and fungicide sensitivity. A total of 176 samples with typical leaf spot symptoms were meticulously collected from five different minor cereal crops (oat, barley, common millet, foxtail millet, and sorghum), and 135 pure isolates were obtained. Based on morphology, phylogenetic analyses, and pathogenicity tests, these pathogens belonged to six species across three genera: three Bipolaris species (B. sorokiniana, B. variabilis, and B. yamadae), two Curvularia species (C. plantarum and C. spicifera), and one Exserohilum species (E. monoceras). Among these, B. sorokiniana (25.2%) and B. variabilis (27.4%) were the predominant species, whereas B. yamadae (11.9%), C. plantarum (9.6%), C. spicifera (17.0%), and E. monoceras (8.9%) showed lower prevalence. In this study, we describe nine leaf spot diseases of MCCP caused by six helminthosporioid fungi. Notably, five novel leaf spot diseases on MCCP are reported for the first time, including those caused by B. variabilis on common millet (44.8%), foxtail millet (100.0%), and sorghum (53.6%); C. plantarum on sorghum (46.4%); and E. monoceras on oat (25.0%). Furthermore, oat leaf spot caused by C. spicifera is reported for the first time in China. Our findings represent the most comprehensive study on the genera Bipolaris, Curvularia, and Exserohilum associated with MCCP leaf spots in China. Fungicide sensitivity assays and control efficacy assessments demonstrated that fludioxonil and prochloraz exhibited high efficacy against the nine leaf spot diseases, with control efficacies ranging from 70.9% to 79.5% and 71.7% to 82.2%, respectively. The results confirm six helminthosporioid fungi as the causal agents of nine leaf spot diseases on MCCP. Fludioxonil and prochloraz are valuable choices for fungicide rotation programmes to manage these diseases.
Ustilaginoidea virens, the causal agent of rice false smut, produces a variety of mycotoxins, including ustilaginoidins, which are highly toxic and harmful to humans and animals. The Ugs gene cluster has been identified to be responsible for ustilaginoidin biosynthesis in U. virens. However, little is yet known about how ustilaginoidin biosynthetic genes are transcriptionally regulated in U. virens. In this study, we reveal that the transcription factor calcineurin-responsive zinc finger 1 (CRZ1) is a major regulator of ustilaginoidin biosynthesis in U. virens. Notably, a novel calcineurin-dependent response element (CDRE) has been identified for CRZ1 in U. virens and is enriched in the promoters of ustilaginoidin synthesis genes, including Pks1 and UgsH. Electrophoretic mobility shift assay and chromatin immunoprecipitation-PCR analysis demonstrated that UvCRZ1 activates the expression of Pks1 and UgsH through directly binding CDREs in their promoters. We further find that UvCRZ1 is important for vegetative growth, conidiogenesis, conidial development, virulence, and mycotoxin biosynthesis in U. virens. Consistently, transcriptome analysis revealed that UvCRZ1 positively regulates the expression of genes involved in pathogenesis, secondary metabolism, and energy metabolism. These findings deepen the understanding of the regulatory mechanisms underlying virulence and mycotoxin biosynthesis, particularly ustilaginoidin production, in phytopathogenic fungi.
