The Use of Virus Induced Gene Silencing to Investigate Septoria Leaf Blotch in Wheat

Septoria leaf blotch, caused by the fungal pathogen Zymoseptoria tritici, is one of the most damaging diseases of wheat (Triticum aestivum), a crop plant of significant worldwide importance. Using the system of Virus-Induced Gene Silencing, to create transient knockdowns of target genes, a novel wheat gene, TaR1, was identified as playing a key role in the host response to this pathogen. Silencing this gene leads to the earlier onset of disease symptoms, but reduced reproduction of the causal pathogen. Sequence analysis, confocal microscopy and protein-protein interaction assays were used to determine that the protein TaR1 localises the nucleus, where its function involves the binding of histones. Precisely, TaR1 is able to bind the Histone 3 subunit, specifically methylated on Lysine 4. Through this action, the host defence response is delayed, and successful pathogen colonisation is promoted. It is hypothesised that this is an example of the pathogen ‘hi-jacking’ TaR1 from its original function, in order to complete its lifecycle.