The bZIP transcription factor PnAda1 functions as a regulator of virulence, fungicide tolerance and necrotrophy in the wheat pathogen Parastagonospora nodorum
It is shown that the understudied bZIP transcription factor PnAda1 is an important downstream component of this PnPf2-regulatory network, and current understanding of the transcriptional network underlying virulence, metabolism and stress adaptation in an important fungal wheat pathogen is expanded.
Abstract
Ada1 (All Development Altered-1) is a conserved but poorly characterised basic leucine zipper (bZIP) transcription factor found throughout filamentous fungi. In the wheat pathogen Parastagonospora nodorum, PnAda1 is required for full virulence and is transcriptionally associated with the virulence regulator PnPf2, but its biological functions remain unclear. Here, we combined comparative RNA sequencing with targeted phenotypic analyses to define the role of PnAda1 during vegetative growth and host infection. Deletion of PnAda1 did not abolish pathogenicity but delayed disease progression, with the PnAda1-deletion mutant transcriptome at 7 days post-inoculation resembling that of the wildtype SN15 at 3 days. This developmental delay was associated with impaired activation of early infection-associated genes, including putative carbohydrate-active enzymes, proteases, transporters and other host-colonisation factors. In contrast, expression of major necrotrophic effector genes was not reduced and instead remained elevated during later stages of infection, indicating that PnAda1 is required for the timely progression of infection-associated transcriptional regulation rather than direct activation of effector genes. Beyond virulence, transcriptomic and phenotypic analyses revealed roles for PnAda1 in nitrogen assimilation, carbon utilisation, abiotic stress responses and fungicide sensitivity. Notably, PnAda1 deletion increased sensitivity to succinate dehydrogenase inhibitor fungicides and reduced expression of succinate dehydrogenase subunit genes. Collectively, our findings identify PnAda1 as a broad regulator of developmental and infection-associated transitions in P. nodorum and expand current understanding of the transcriptional network underlying virulence, metabolism and stress adaptation in an important fungal wheat pathogen. IMPORTANCE Fungal pathogens of crop plants pose a major threat to global food security, and understanding how virulence is regulated may reveal new opportunities for disease control. In the wheat pathogen Parastagonospora nodorum, disease development depends on the coordinated expression of necrotrophic effectors and other infection-associated genes. The transcription factor PnPf2 is a central regulator of these virulence programs, but the downstream pathways that execute infection remain incompletely understood. Here, we show that the understudied bZIP transcription factor PnAda1 is an important downstream component of this PnPf2-regulatory network. Our findings indicate that PnAda1 coordinates processes required for successful host colonisation, including nutrient acquisition, stress tolerance and the timely deployment of infection-associated genes. By expanding our understanding of the transcriptional regulon that underpins fungal phytopathogenicity, this study provides new insight into how fungal pathogens establish disease and coordinate complex infection programs.
It is demonstrated that MrFTRP1 exerts a dual-regulatory functioning as a positive regulator of conidiation and pathogenesis but a negative regulator of environmental stress tolerance, which expands the understanding of the regulatory diversity within the C6 TF family and identifies him as a promising target for the genetic improvement of mycoinsecticides.
Chentian Jiang, Hao Wu, You-Gui Tong et al.· Journal of Invertebrate Path...· 0 citations
Fusarium graminearum, the major pathogen causing maize ear rot, severely threatens food security. Targeted gene deletion was used to characterize physiological functions of FgSRE1 in this pathogen. Transcriptomic profiling was conducted on axenic wild-type and ΔFgSRE1 cultures, plus maize ear tissues colonized by both strains. Nine core DEGs functionally annotated to transmembrane transport, membrane homeostasis and oxidative stress pathways were selected for qRT-PCR validation, including four upregulated genes encoding putative transferases and five downregulated transporter genes. Phenotypic assays revealed that the ΔFgSRE1 mutant displayed severe defects in conidial and ascospore production, along with drastically weakened pathogenicity on maize ears and leaves versus wild-type and complemented strains. qRT-PCR analysis confirmed consistent expression trends with the RNA-seq data: four putative transferase-encoding genes were up-regulated, whereas five genes related to membrane and redox transport were repressed. Together, the genetic and phenotypic results demonstrate that FgSRE1 contributes to reproductive development and virulence in F. graminearum, whereas the transcriptomic data suggest potential associations with metabolic, redox, and membrane-transport-related pathways. Our findings provide a basis for investigating the FgSRE1-associated virulence network and developing eco-friendly maize ear rot control strategies.
Lin-Ru Shen, Hongyan Hui, Lei Guo et al.· Journal of Fungi· 0 citations
Colletotrichum fructicola, the primary causal agent of Glomerella leaf spot (GLS), is a destructive fungal pathogen of apple, whose underlying pathogenic mechanisms remain largely unknown. A previous transcriptomic analysis of infected leaves indicated induction of the transcription factor CfMBZ1. This study confirmed that CfMBZ1 is highly expressed in conidia and during early infection. To elucidate its function, we generated a ΔCfMBZ1 deletion mutant via homologous recombination. Phenotypic analysis revealed that ΔCfMBZ1 lost pathogenicity on apple leaves due to a blockage in appressorium-mediated host penetration, despite retaining the ability to form penetration pegs on cellophane. However, extension of invasive hyphae and necrotrophic growth in wounded apple fruit were unaffected. The mutant also exhibited defects in maintaining the integrity of the cell wall and cell membrane, as well as in tolerating oxidative and acid–base stress. Comparative transcriptome analysis suggested that CfMBZ1 regulates appressorium-mediated penetration by modulating genes involved in peroxisome biogenesis, lipid droplet metabolism, and other penetration-related pathways. Our findings reveal that CfMBZ1 plays a critical role in the pathogenesis of Glomerella leaf spot caused by C. fructicola.
Wenkui Liu, Wenxin Shi, Yecan Pan et al.· Phytopathology Research· 0 citations
Plant-fungus-virus tripartite interactions represent complex ecological systems in which mutualistic endophytes can influence host physiology, yet the molecular basis of endophyte-mediated defence remains poorly understood. Here, we demonstrate that the endophytic fungus Penicillium pinophilum EU0013 suppresses the yellow strain of cucumber mosaic virus (CMV-Y) in Solanum lycopersicum and Nicotiana benthamiana. CMV-Y infection induced pronounced oxidative and hormonal perturbations, which were mitigated by P. pinophilum colonisation. Endophyte-associated plants exhibited early accumulation of jasmonate intermediates, consistent with the activation of jasmonate signalling. This response promoted the degradation of jasmonate-ZIM-domain proteins and release of core JA-responsive transcription factors. Virus-induced gene silencing identified MYC2 as a key regulator required for endophyte-mediated antiviral protection, with WRKY17 contributing to defence modulation. In parallel, transcriptome analysis revealed the upregulation of a Dicer-like gene, indicating enhanced engagement of RNA silencing, a primary antiviral mechanism targeting viral RNA. This coordinated activation occurred alongside significant induction of pathogenesis-related proteins, particularly PR9, and improved control of reactive oxygen species. Salicylic acid-responsive defences showed a host-modulated pattern, with PR1 induced by CMV and PR2/PR5 preferentially enhanced in endophyte-associated plants. Collectively, these findings demonstrate that P. pinophilum enhances antiviral immunity through coordinated defence integration pathways, providing a framework for endophyte-based viral disease management.
S. Ibiang, I. Galis, Hideki Kondo et al.· Plant, Cell and Environment· 0 citations
Wheat leaf rust, caused by the biotrophic fungus Puccinia triticina (Pt), is a major threat to global wheat production. Fungal pathogens often deploy plant cell wall-degrading enzymes to breach host barriers, with glycoside hydrolases (GHs) providing hydrolytic activity and carbohydrate-binding modules (CBMs) enabling substrate recognition. However, research on their specific roles in the leaf rust fungus remains limited. Here, we functionally characterized two Pt genes, PtGH1 and PtCBM1. PtCBM1, a carbohydrate-binding module protein, binds cellulose and potentiates cellulase activity despite lacking hydrolase activity, whereas PtGH1 encodes a β-glucanase secreted via a non-classical pathway. Both proteins suppress Bax-induced cell death in Nicotiana benthamiana, suggesting immune-suppressive activity. Silencing either of the two genes in wheat via host-induced gene silencing significantly reduced fungal virulence, impaired hyphal growth, and enhanced host defense. Together, these findings identify PtGH1and PtCBM1 as distinct virulence factors that act through complementary mechanisms, involving physical facilitation and enzymatic degradation of host cell walls. This dual strategy illustrates how the leaf rust fungus overcomes host immunity and provides potential molecular targets for developing durable wheat resistance.
Yanan Lu, Keyan Wu, Jinyang Li et al.· Phytopathology Research· 0 citations