Hemibiotrophic fungi of the genus Colletotrichum provide valuable systems for studying plant immunity and pathogen lifestyle transitions; however, compatible and incompatible interactions have rarely been compared within the same host species. Here, we show that Arabidopsis thaliana exhibits contrasting responses to two phylogenetically distinct hemibiotrophic fungi, Colletotrichum coccodes KACC40803 and Colletotrichum scovillei KC05. Multilocus phylogenetic analyses using ITS , ACT , GAPDH , and TUB2 sequences confirmed their taxonomic identities. The two fungi also differed morphologically, particularly in colony characteristics and appressorial structures. Inoculation of Arabidopsis leaves with C. coccodes caused progressive chlorosis, necrotic lesions, extensive fungal colonization, acervulus formation, and increasing fungal biomass, indicating a compatible susceptible interaction. Host defense-related genes associated with salicylic acid– and jasmonic acid–mediated pathways were suppressed during infection. By contrast, C . scovillei induced restricted lesion development, rapid accumulation of callose and reactive oxygen species, localized plasma membrane disruption, and strong induction of defense-related genes in Arabidopsis leaves, consistent with an incompatible hypersensitive response (HR)–like cell death. Fungal biomass remained low throughout infection, demonstrating effective restriction of colonization. Together, these findings establish a dual Arabidopsis – Colletotrichum pathosystem that enables comparative analysis of susceptibility and HR-like resistance within a single host, providing a tractable model for dissecting host specificity, immune signaling, and regulated cell death during hemibiotrophic infection. Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
Plant-parasitic nematodes are a diverse group collectively capable of infecting most major crops. Among the most damaging are the cyst nematodes, which can remain dormant in the soil for decades as infection-competent, developmentally arrested, second-stage juveniles in eggs. Hatching is stimulated by a variety of factors. However, the impact of hatching factor responsiveness on nematode morphology, physiology, gene expression, and infection biology has not been explored. We examined the impact of hatching time on the beet cyst nematode, Heterodera schachtii . We found that late hatchers invaded host roots and established feeding sites in greater numbers than early hatchers. We demonstrate variation in baseline parasitism gene expression and in responsiveness of genes to effectostimulins—small, plant-derived molecules that upregulate parasitism genes. Three quarters of effectostimulin-induced transcriptional changes were also modulated, either positively or negatively, by hatching time. Although there were no observable morphological differences between early- and late-hatching nematodes on their day of hatching, the late hatchers displayed signs of faster utilization of internal energy reserves after 7 days at 4°C, as evidenced by less body area attributed to fat, than early hatchers. Finally, we found no evidence of substantive genetic differences between early and late hatchers—they were representative of a single population, despite the observed differences in infection, gene expression, and physiology. Taken together, nongenetic differences likely drive late hatchers to more rapidly utilize their internal energy reserves, to be differentially responsive to host-derived signals, and to be ultimately more infective than their early-hatching counterparts. Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .
Phytopathogenic fungi must contend with host immune responses to successfully colonize plants. These responses include the production of heterogenous antimicrobial compounds (phytoalexins), which plants deploy to intoxicate infecting microbes. Among these host defense compounds are the coumarins, a family of aromatic lactones widely present in dicotyledonous plants (dicots). The fungal necrotroph Botrytis cinerea (gray mold) infects a plethora of dicots, causing large losses in the produce, viticulture, and ornamental flower industries. B. cinerea detoxifies numerous host defense compounds to support its virulence, including the coumarin scopoletin. However, B. cinerea coumarin detoxification factors have remained uncharacterized. Here, we employed transcriptomics in scopoletin-treated B. cinerea followed by heterologous expression of scopoletin-induced genes in budding yeast (Saccharomyces cerevisiae) to identify a reductase, BCIN14g01070 (Bcsaf1), which B. cinerea deploys to degrade scopoletin. Using liquid chromatography-tandem mass spectrometry, we demonstrate that Bcsaf1 reduces a carbon-carbon double bond within the coumarin backbone, converting coumarins to their nontoxic melilotic acid derivatives. We further show that Bcsaf1 orthologs are present in numerous fungi of the family Sclerotiniaceae and that an ortholog from another notorious phytopathogen, Sclerotinia sclerotiorum (white mold), possesses similar coumarin detoxification capacity. We constructed ΔBcsaf1 mutants that displayed compromised scopoletin degradation and increased scopoletin susceptibility. The ΔBcsaf1 mutants further displayed reduced virulence in Nicotiana tabacum (tobacco), which exerts a scopoletin defense response, whereas their virulence was only modestly compromised in Helianthus annuus (sunflower) seedlings, which produce much less scopoletin. Thus, Bcsaf1 is an important virulence factor that counters host coumarins to support B. cinerea infection. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Wheat blast, caused by Magnaporthe oryzae Triticum (MoT), is a devastating fungal disease threatening global food security. Emergence of fungicide-resistant MoT populations necessitates safe, eco-friendly alternatives. This study evaluates the biorational potential of 3-methylpentanoic acid (3-MP), a volatile organic compound (VOC) produced by Bacillus safensis NI2B against MoT. In vitro assays demonstrated that 3-MP inhibits MoT mycelial growth, conidiogenesis, conidial germination, and appressorium formation in a dose-dependent manner, achieving complete suppression at 100-125 µM. Furthermore, detached leaf, seedling, and spike assays revealed robust preventive and curative efficacy, indicating strong translational potential for wheat blast management. Mechanistic analyses indicated reduced fungal cellular viability following 3-MP treatment, as confirmed by fluorescein diacetate staining. In silico molecular docking and dynamics simulations predicted that 3-MP putatively interacts with UDP-glucose 4-epimerase (UGE), a key enzyme in galactose metabolism and cell wall integrity. 3-MP binds stably within the NAD+-associated Rossmann fold of UGE, sterically hindering substrate access and perturbing NAD+ orientation. RT-qPCR expression analysis was consistent with this model, showing a biphasic response characterized by early induction followed by significant repression of UGE transcripts, which aligns with disrupted UDP-glucose metabolism and impaired cell wall biosynthesis. Collectively, this study establishes 3-MP as a potent biocontrol agent and provides preliminary mechanistic insights into its antifungal activity associated with UGE perturbation. These findings offer a promising molecular framework for developing VOC-based integrated pest management strategies against wheat blast.
Cercospora zeina causes gray leaf spot disease on maize in Africa. As a foliar fungal pathogen, C. zeina relies on effectors to facilitate successful infection and colonization of its host. Predicting effector function is therefore essential for understanding the molecular mechanisms underlying this plant-pathogen interaction. Although effector functions are typically predicted using sequence-based analyses, many effectors are subject to strong selection pressure and exhibit high sequence diversity, reducing the accuracy of such predictions. In this study, a structural phylogenetics approach was employed to identify effector structural families in C. zeina and to assign putative functions to C. zeina candidate secreted effector proteins based on their structural clustering with functionally characterized effectors from related phytopathogens. Twenty-two effector structural families were identified, several of which contained effectors shown to induce cell death in Nicotiana benthamiana. It was therefore hypothesized that C. zeina effectors belonging to these structural families would exhibit similar functions. Three families containing cell death-inducing effectors ZtCDI1, MgNLP, VdPEVD1with high structural similarity and low sequence identity to C. zeina effectors were selected for biological validation. Transient expression of C. zeina effectors from these families induced cell death in N. benthamiana. These C. zeina structural analogs were expressed in either the latent (CDI1-like) or necrotrophic (NLP-like, PevD1-like) phase of GLS disease in maize. This work shows that structural phylogenetics can be employed to predict effector function and identify structurally related, cell death-inducing effectors with divergent amino acid sequences in C. zeina.
