Now showing 1 - 5 of 5
  • Publication
    A small secreted protein from Zymoseptoria tritici interacts with a wheat E3 ubiquitin to promote disease
    Septoria Tritici Blotch, caused by the ascomycete fungus Zymoseptoria tritici, is a major threat to wheat production worldwide. The Z. tritici genome encodes many small, secreted proteins (ZtSSP) that likely play a key role in the successful colonisation of host tissues. However, few of these ZtSSPs have been functionally characterised for their role during infection. In this study, we identified and characterised a small, conserved cysteine-rich secreted effector from Zymoseptoria tritici which has homologues in other plant pathogens in the dothideomycetes. ZtSSP2 was expressed throughout Z. tritici infection in wheat with the highest levels observed early during infection. A yeast two-hybrid assay revealed an interaction between ZtSSP2 and wheat E3 ubiquitin ligase in yeast and this was further confirmed in planta using bimolecular fluorescence complementation, and co-immunoprecipitation. Down-regulation of this wheat E3 ligase using virus-induced gene silencing, increased the susceptibility of wheat to Septoria tritici blotch (STB). Together these results suggest that TaE3UBQ likely plays a role in plant immunity to defend against Z. tritici.
      246Scopus© Citations 8
  • Publication
    Identification and characterisation of effector proteins from Zymoseptoria tritici
    Plant pathogens are known to secrete a large number of secreted proteins termed as effectors into the host plant. These secreted effector proteins play role in the infection and manipulation of plant host defenses for aiding successful colonisation. The filamentous fungal pathogen Zymoseptoria tritici: an important pathogen of wheat, also secretes effectors that play key role during host colonisation. In this thesis, 50 Zymoseptoria tritici small secreted proteins (ZtSSPs) were identified which fulfilled all the effector characteristics including; (i) small size, (ii) presence of signal peptide, (iii) presence of cysteine residues, (iv) lack of transmembrane domain and (v) lack of functionally annotated domains. Out of these 50, 30 were cloned and characterised initially based on their ability to induce cell death in planta using a non-host plant. Five novel candidates that induce cell death in a non-host plant were selected and this cell death was shown to be independent of presence a signal peptide. All five ZtSSPs were also involved in activation of diverse defense marker genes and were found to be differentially upregulated during infection suggesting their diverse roles. One particular ZtSSP, ZtSSP2 is a well conserved effector across isolates and interacts with a wheat host ubiquitin protein. This wheat ubiquitin possess a RING finger E3 ligase domain and plays a key role in ubiquitin mediated cellular processes. The expression of wheat ubiquitin ligase showed that its expression is downregulated at early and late stages of Z. tritici infection, suggesting involvement of this ubiquitin in host defense responses. To explore different system for effector characterisation the grass B. distachyon was used as a non-host model to study non-host defense and the potential for Z. tritici effector screening. In conclusion secreted effectors of Z. tritici play a key role in host defense manipulation. This study on Z. tritici candidate effectors has provided the identification of a wheat host effector target and further insights into the plant-pathogen interaction between Z. tritici, host plant wheat as well as with the non-hosts N. benthamiana and B. distachyon.
      269
  • Publication
    Wheat Encodes Small, Secreted Proteins That Contribute to Resistance to Septoria Tritici Blotch
    During plant–pathogen interactions, pathogens secrete many rapidly evolving, small secreted proteins (SSPs) that can modify plant defense and permit pathogens to colonize plant tissue. The fungal pathogen Zymoseptoria tritici is the causal agent of Septoria tritici blotch (STB), one of the most important foliar diseases of wheat, globally. Z. tritici is a strictly apoplastic pathogen that can secrete numerous proteins into the apoplast of wheat leaves to promote infection. We sought to determine if, during STB infection, wheat also secretes small proteins into the apoplast to mediate the recognition of pathogen proteins and/or induce defense responses. To explore this, we developed an SSP-discovery pipeline to identify small, secreted proteins from wheat genomic data. Using this pipeline, we identified 6,998 SSPs, representing 2.3% of all proteins encoded by the wheat genome. We then mined a microarray dataset, detailing a resistant and susceptible host response to STB, and identified 141 Z. tritici- responsive SSPs, representing 4.7% of all proteins encoded by Z. tritici – responsive genes. We demonstrate that a subset of these SSPs have a functional signal peptide and can interact with Z. tritici SSPs. Transiently silencing two of these wheat SSPs using virus-induced gene silencing (VIGS) shows an increase in susceptibility to STB, confirming their role in defense against Z. tritici.
      35Scopus© Citations 12
  • Publication
    Isolate specific responses of the non-host grass Brachypodium distachyon to the fungal pathogen Zymoseptoria tritici, compared to wheat
    Septoria tritici blotch (STB) is an important foliar disease of wheat that is caused by the fungal pathogen Zymoseptoria tritici. The grass Brachypodium distachyon has been used previously as a model system for cereal-pathogen interactions. In this study, we examined the non-host resistance (NHR) response of B. distachyon to two different Z. tritici isolates in comparison to wheat. These isolates vary in aggressiveness on wheat cv. Remus displaying significant differences in disease and pycnidia coverage. Using microscopy, we found that similar isolate specific responses were observed for H2O2 accumulation and cell death in both wheat and B. distachyon. Despite this, induction of isolate specific patterns of defence gene expression by Z. tritici did differ between B. distachyon and wheat. Our results suggest that phenylalanine ammonia lyase (PAL) expression may be important for NHR in B. distachyon while pathogenesis-related (PR) genes and expression of genes regulating reactive oxygen species (ROS) may be important to limit disease in wheat. Future studies of the B. distachyon-Z. tritici interaction may allow identification of conserved plant immunity targets which are responsible for the isolate specific responses observed in both plant species.
      338Scopus© Citations 1
  • Publication
    Taxonomically Restricted Wheat Genes Interact With Small Secreted Fungal Proteins and Enhance Resistance to Septoria Tritici Blotch Disease
    Understanding the nuances of host/pathogen interactions are paramount if we wish to effectively control cereal diseases. In the case of the wheat/Zymoseptoria tritici interaction that leads to Septoria tritici blotch (STB) disease, a 10,000-year-old conflict has led to considerable armaments being developed on both sides which are not reflected in conventional model systems. Taxonomically restricted genes (TRGs) have evolved in wheat to better allow it to cope with stress caused by fungal pathogens, and Z. tritici has evolved specialized effectors which allow it to manipulate its’ host. A microarray focused on the latent phase response of a resistant wheat cultivar (cv. Stigg) and susceptible wheat cultivar (cv. Gallant) to Z. tritici infection was mined for TRGs within the Poaceae. From this analysis, we identified two TRGs that were significantly upregulated in response to Z. tritici infection, Septoria-responsive TRG6 and 7 (TaSRTRG6 and TaSRTRG7). Virus induced silencing of these genes resulted in an increased susceptibility to STB disease in cvs. Gallant and Stigg, and significantly so in the latter (2.5-fold increase in STB disease). In silico and localization studies categorized TaSRTRG6 as a secreted protein and TaSRTRG7 as an intracellular protein. Yeast two-hybrid analysis and biofluorescent complementation studies demonstrated that both TaSRTRG6 and TaSRTRG7 can interact with small proteins secreted by Z. tritici (potential effector candidates). Thus we conclude that TRGs are an important part of the wheat-Z. tritici co-evolution story and potential candidates for modulating STB resistance.
      15Scopus© Citations 10