The role of RiPP proteins in plant pathogenic fungi

Abstract

The ascomycete fungus, Zymoseptoria tritici, has risen in prevalence and significance in the past few decades, overtaking wheat pathogens such as Stagonospora nodorum for the title of most prevalent foliar wheat pathogen in the UK and Europe – as well as several other countries worldwide. Losses to the pathogen can be significant, as such, the fungus and its associated disease, Septoria tritici blotch, presents a huge threat to global wheat production and food security given the dietary importance of wheat grain. Zymoseptoria tritici infection of wheat includes a biotrophic-like latent phase and necrotrophic stage, however, the transition between the two is currently poorly understood, and assumed to involve fungal effectors which trigger the plant hypersensitive response. Equally, fungal ribosomally synthesised and post-translationally modified peptides (RiPPs) are under-researched, despite the RiPP victorin contributing to Cochliobolus victoriae virulence on Vb oat cultivars.

This thesis explores a fungal RiPP from Z. tritici, the biosynthetic pathway of which has been characterised bioinformatically with knockout strains produced for future experimental confirmation of the method predicted in this work. Bioinformatic investigation also proved informative regarding RiPP repeat variation between strains of the same species and in identifying novel RiPP producers entirely. Attempts were made to understand the function of the RiPP, to determine whether it was involved in pathogenicity, as with victorin, this however remains elusive. Although the Zymoseptoria RiPP does not have a clear role in virulence given that null mutants were fully virulent, results from this work demonstrated the impact of the environment on the wheat-Zymoseptoria interaction, demonstrating the multiple routes that can be explored to control Z. tritici.

Overall, this work has extended our understanding of Zymoseptoria tritici – by examining the environmental conditions conducive or inconducive to infection – and its RiPP, with this also contributing to our knowledge of fungal RiPPs more widely.

Date of Award	5 Dec 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Gary Foster (Supervisor) & Andy M Bailey (Supervisor)