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Karki, Sujit Jung
Preferred name
Karki, Sujit Jung
Official Name
Karki, Sujit Jung
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Now showing 1 - 3 of 3
- PublicationIdentification and characterisation of effector proteins from Zymoseptoria tritici(2019)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.
64 - PublicationIsolate specific responses of the non-host grass Brachypodium distachyon to the fungal pathogen Zymoseptoria tritici, compared to wheat(American Phytopathological Society, 2021-02)
; ; ; ; ; 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.176Scopus© Citations 1 - PublicationA small secreted protein from Zymoseptoria tritici interacts with a wheat E3 ubiquitin to promote disease(Oxford University Press, 2021-02-02)
; ; ; ; ; ; ; ; 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.99Scopus© Citations 4