| Summary: | Fungal plant pathogens are a threat to food security, destroying enough crops annually to feed over 8% of the world’s rapidly growing population. Zymoseptoria tritici, a filamentous ascomycete, is responsible for Septoria Leaf Blotch disease on wheat. This devastating disease is associated with huge financial costs and yield losses. Current management strategies such as partially resistant wheat cultivars and fungicides do not provide sufficient control of this pathogen, and new strategies are urgently needed.
An effector protein essential for Z. tritici virulence on wheat, Zt3LysM, may provide a useful target for future control methods. This effector sequesters chitin fragments, masking the pathogen from host immune detection, and also protects against host defences. While many advances have been made in understanding its biology, little is known about what triggers Zt3LysM expression and how this is regulated.
In this project, strains expressing GFP under the control of the Zt3LysM promoter were used to explore potential triggers for its expression. A close association between the transition to hyphal growth and Zt3LysM expression was found, along with putative genetic factors influencing expression. Zt3LysM expression was also found to be linked to the cell wall integrity pathway, with Slt2 knockouts showing reduced expression of this effector. The impact of chitin masking and perception were explored through RNA sequencing, which showed a temporal delay in infection progress and related gene expression in both pathogen and host during infection with a strain showing reduced virulence and Zt3LysM expression. Finally, through BLASTP analysis and a pipeline to identify putative effectors, Zt3LysM-like secreted proteins were identified throughout much of the fungal kingdom, across a range of lifestyles. By investigating the mechanisms by which Z. tritici pathogenesis occurs, targets for future control methods can be identified and explored, with the aim of reducing harm caused by this devastating pathogen in the future.
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