Fusarium Ear Blight is a devastating fungal disease of cereals and due to the
contamination of the harvested grain with a range of trichothecene mycotoxins
presents a risk to human and animal health. The re-emergence of Fusarium
graminearum on wheat and maize, the evolution of more aggressive fungal strains
and the lack of an effective control strategy, has increased the need for a greater
understanding of the disease aetiology. This project aimed to enhance the
understanding of the interaction between F. graminearum and wheat (Triticum
aestivum), through the utilisation of microscopy and molecular pathogenomics.
A detailed investigation of the infection process revealed a prolonged latent
period of intercellular infection that preceded host cell death, intracellular
colonisation and the onset of disease symptoms. Phenotypic differences in
colonisation and mycotoxin gene expression implied that hyphae within the two
phases of infection were transcriptionally distinct, while a bioinformatic analysis
described the fungal secretome. The two fungal gene-deficient strains assessed, top1
and tri5, were unable to establish symptomless infection or spread throughout the
wheat ear, in the presence or absence of mycotoxin production, suggesting the
existence of additional virulence factors.
Subsequently, a genome wide transcriptome investigation of the two phases
of infection, using both Affymetrix and RNA-sequencing technologies, revealed the
unique expression profile, and secretome, of the advancing hyphal front of the
symptomless infections. This greater understanding of the biphasic interaction will
provide a benchmark for comparison with the single gene deficient strains. Finally, a
laser capture microdissection procedure was developed to enable future cell-type
specific transcriptome experiments.
Collectively, I have discovered and developed a model of how F.
graminearum establishes symptomless and symptomatic infection. In doing so, this
study has enhanced the understanding of this non-biotrophic pathosystem, providing
many new lines of investigation, which could greatly improve crop protection
strategies