Megan A Outram, Zhao Li, Michael Kuiper, Simon J Williams, Melania Figueroa, Peter N Dodds, Jana Sperschneider
{"title":"Rust Fungi Secretomes Contain Structurally Diverse Effector Families Including Cysteine-Rich Metal-Binding Proteins.","authors":"Megan A Outram, Zhao Li, Michael Kuiper, Simon J Williams, Melania Figueroa, Peter N Dodds, Jana Sperschneider","doi":"10.1094/MPMI-06-26-0062-R","DOIUrl":"https://doi.org/10.1094/MPMI-06-26-0062-R","url":null,"abstract":"<p><p>Rust fungi are significant threats to global food security, causing substantial damage to crops through their ability to evolve new strains that overcome plant resistance. These obligate biotrophs infect host plants by secreting effector proteins that manipulate host physiology to promote infection and colonisation. We used AlphaFold2 to investigate structural conservation among effector proteins for the secretomes of <i>Melampsora lini</i> and four <i>Puccinia</i> species. AlphaFold2 yielded high-confidence predictions for 45.7% of the 27,090 secreted proteins, while 19% were poor quality. Comparative analysis revealed extensive structural diversity across the rust secretomes, with all thirteen known rust Avr proteins belonging to different clusters apart from AvrSr13 and AvrSr33. Nevertheless, there were still numerous large clusters of structurally-related proteins, including 59 clusters with over 50 members each, three of which contained known Avr proteins. Of the major structural families defined in other fungi, the rust species studied here only contained FOLD and ToxA-like families. Structural analysis of cysteine-rich proteins revealed over a thousand effector candidates featuring predicted zinc-binding sites, with approximately 75% predicted to be cytoplasmic effectors. In contrast, cysteine-rich apoplastic effector candidates were characterized by a high frequency of disulfide bonds. One family of predicted metal-binding proteins was greatly expanded in <i>P. graminis</i> f. sp. <i>tritici</i> and includes AvrSr13 and AvrSr33. We confirmed that purified AvrSr13 and AvrSr22 proteins bind to zinc in vitro using biochemical assays. Taken together, structural modeling provides new avenues to study sequence-unrelated effectors and highlights the high degree of diversity in the effector repertoires of rust species.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149112182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ana Maria Bocsanczy, Sameena Ejaz Tanwir, Arianna Mangravita-Novo, David J Norman
{"title":"A LysR-Type Transcriptional Regulator Links Phosphonate Metabolism to Cool Virulence of <i>Ralstonia solanacearum</i> in Tomato.","authors":"Ana Maria Bocsanczy, Sameena Ejaz Tanwir, Arianna Mangravita-Novo, David J Norman","doi":"10.1094/MPMI-06-26-0053-R","DOIUrl":"https://doi.org/10.1094/MPMI-06-26-0053-R","url":null,"abstract":"<p><p><i>Ralstonia solanacearum</i>, the causal agent of bacterial wilt, is a major threat to solanaceous crops in tropical and subtropical regions worldwide. While most strains are pathogenic at high temperatures (>28°C), a subset can cause disease at low temperatures (16-18°C), posing a risk to temperate solanaceous crops. Previous comparative genomics of cool virulent with regular tropical strains identified candidate transcriptional regulators associated with cool virulence. In this work, we tested function in virulence to tomato at high and low temperatures of four of the candidate transcription regulators identified previously and demonstrated that a LysR-type transcriptional regulator (Rsp673_21385) in the cool-virulent strain P673 significantly contributes to virulence at 18°C but not at 30°C. This regulator is located upstream of a conserved gene cluster resembling a 2-aminoethylphosphonate (2-AEP) degradation operon. This cluster codes for an alternative pathway recently characterized. P673 was unable to utilize phosphonate as a sole carbon source, however it used 2-AEP as a source of phosphorus in a temperature dependent manner. Relative gene expression analysis of representative genes in the cluster showed significant upregulation at 18°C in the wild-type strain but not in the regulator mutant, indicating that the LysR regulator activates expression of the putative 2-AEP degradation cluster under cool temperatures. These findings reveal a novel temperature-dependent virulence factor and highlight the need to explore the regulon controlled by Rsp673_21385, providing new insights into the adaptation of <i>R. solanacearum</i> to temperate environments.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149075313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sheo Shankar Pandey, Tirtha Lamichhane, Jin Xu, Jinyun Li, Javier L Dalmendray, Ma Andrea Cruz Gatmaitan, Nian Wang
{"title":"Chloroplast-Associated ROS Signaling Shapes Tissue-Specific Pathogenicity Mechanisms of <i>Candidatus</i> Liberibacter asiaticus in Leaf and Root.","authors":"Sheo Shankar Pandey, Tirtha Lamichhane, Jin Xu, Jinyun Li, Javier L Dalmendray, Ma Andrea Cruz Gatmaitan, Nian Wang","doi":"10.1094/MPMI-06-26-0060-R","DOIUrl":"https://doi.org/10.1094/MPMI-06-26-0060-R","url":null,"abstract":"<p><p>The phloem-colonizing bacterial pathogen <i>Candidatus</i> Liberibacter asiaticus (CLas) causes the devastating citrus Huanglongbing (HLB). Despite the important roles of roots, how CLas affects roots remains largely unknown. Here we dissected host responses in leaf and root at different time points after CLas inoculation. Our data showed that CLas triggers less reactive oxygen species (ROS) accumulation and phloem callose deposition, which are known to contribute to HLB symptom development in leaves, in roots than leaves. Increased chloroplastic ROS accumulation was detected in CLas-infected leaf compared to uninfected controls, which may explain the increased ROS levels in leaves than roots infected by CLas. qRT-PCR and RNA-seq analyses showed global induction of immune related pathways in both roots and leaves, whereas photosynthesis related pathways were only downregulated in leaves, but not in roots, by CLas infection. The differential expression pattern related to immunity and photosynthesis in the leaf and root tissues suggests that chloroplasts might be involved in the differences in ROS accumulation and callose deposition. Root cell death was observed in HLB symptomatic trees regardless of CLas infection status of roots. Significantly more starch accumulation was first observed in CLas positive leaves than healthy controls followed by starch depletion in CLas positive roots later, suggesting a causative relationship between them. Taken together, root cell death caused by CLas infection maybe caused by carbon starvation rather than via a similar mechanism as in leaves. Our data suggests chloroplasts play a critical role in the different pathogenicity mechanisms of CLas in leaf and root.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149062820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nam Khoa Nguyen, Anh Cong Pham, Dongping Liu, Byung Kook Hwang, Nam-Soo Jwa
{"title":"Differential Susceptibility and HR-Like Resistance Responses in <i>Arabidopsis thaliana</i> to <i>Colletotrichum coccodes</i> and <i>Colletotrichum scovillei</i>.","authors":"Nam Khoa Nguyen, Anh Cong Pham, Dongping Liu, Byung Kook Hwang, Nam-Soo Jwa","doi":"10.1094/MPMI-05-26-0040-SC","DOIUrl":"https://doi.org/10.1094/MPMI-05-26-0040-SC","url":null,"abstract":"<p><p>Hemibiotrophic fungi of the genus <i>Colletotrichum</i> 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 <i>Arabidopsis thaliana</i> exhibits contrasting responses to two phylogenetically distinct hemibiotrophic fungi, <i>Colletotrichum coccodes</i> KACC40803 and <i>Colletotrichum scovillei</i> KC05. Multilocus phylogenetic analyses using <i>ITS</i>, <i>ACT</i>, <i>GAPDH</i>, and <i>TUB2</i> sequences confirmed their taxonomic identities. The two fungi also differed morphologically, particularly in colony characteristics and appressorial structures. Inoculation of <i>Arabidopsis</i> leaves with <i>Colletotrichum coccodes</i> 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, <i>Colletotrichum scovillei</i> induced restricted lesion development, rapid accumulation of callose and reactive oxygen species, localized plasma membrane disruption, and strong induction of defense-related genes in <i>Arabidopsis</i> 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 <i>Arabidopsis-Colletotrichum</i> 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.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148977251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mason Rugen-Hankey, Priya Desikan, George Harpum, Chongjing Xia, Victor Hugo Moura de Souza, Unnati Sonawala, Lida Derevnina, Beth Molloy, Anika Damm, Sebastian Eves-van den Akker
{"title":"Better Late than Never: The Impact of Hatching Time on <i>Heterodera schachtii</i> Parasitism.","authors":"Mason Rugen-Hankey, Priya Desikan, George Harpum, Chongjing Xia, Victor Hugo Moura de Souza, Unnati Sonawala, Lida Derevnina, Beth Molloy, Anika Damm, Sebastian Eves-van den Akker","doi":"10.1094/MPMI-06-26-0057-R","DOIUrl":"https://doi.org/10.1094/MPMI-06-26-0057-R","url":null,"abstract":"<p><p>Plant-parasitic nematodes are a diverse group collectively capable of infecting most major crops. Amongst 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, <i>Heterodera schachtii</i>. 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 which upregulate parasitism genes. Three quarters of effectostimulin-induced transcriptional changes were also modulated, either positively or negatively, by hatching time. While there were no observable morphological differences between early and late hatching nematodes on their day of hatching, the late hatchers displayed signs of faster utilisation 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, non-genetic differences likely drive late hatchers to more rapidly utilise their internal energy reserves, to be differentially responsive to host-derived signals, and to be ultimately more infective than their early hatching counterparts.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148944752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Structural Phylogenetics Identifies Conserved Effector Families and Cell Death-Inducing Proteins from <i>Cercospora zeina</i>.","authors":"Trystan Nadasen, Ingo Hein, Dave K Berger","doi":"10.1094/MPMI-05-26-0048-R","DOIUrl":"https://doi.org/10.1094/MPMI-05-26-0048-R","url":null,"abstract":"<p><p><i>Cercospora zeina</i> causes gray leaf spot disease on maize in Africa. As a foliar fungal pathogen, <i>C. zeina</i> 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 <i>C. zeina</i> and to assign putative functions to <i>C. zeina</i> 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 <i>Nicotiana benthamiana</i>. It was therefore hypothesized that <i>C. zeina</i> 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 <i>C. zeina</i> effectors were selected for biological validation. Transient expression of <i>C. zeina</i> effectors from these families induced cell death in <i>N. benthamiana</i>. These <i>C. zeina</i> 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 <i>C. zeina</i>.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148881092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"3-Methylpentanoic Acid Controls Wheat Blast Disease by Disrupting Cell Wall Integrity and Putatively Targeting UDP-Glucose 4-Epimerase.","authors":"Md Shahrear Parvaj Sujon, Soharth Hasnat, Rojana Binte Azad, Dipali Rani Gupta, Tofazzal Islam","doi":"10.1094/MPMI-05-26-0049-R","DOIUrl":"https://doi.org/10.1094/MPMI-05-26-0049-R","url":null,"abstract":"<p><p>Wheat blast, caused by <i>Magnaporthe oryzae Triticum</i> (<i>MoT</i>), is a devastating fungal disease threatening global food security. Emergence of fungicide-resistant <i>MoT</i> 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 <i>Bacillus safensis</i> NI2B against <i>MoT</i>. In vitro assays demonstrated that 3-MP inhibits <i>MoT</i> 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<sup>+</sup>-associated Rossmann fold of UGE, sterically hindering substrate access and perturbing NAD<sup>+</sup> orientation. RT-qPCR expression analysis was consistent with this model, showing a biphasic response characterized by early induction followed by significant repression of <i>UGE</i> 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.</p>","PeriodicalId":19009,"journal":{"name":"Molecular Plant-microbe Interactions","volume":" ","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148881097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}