Investigating transcription factors in wheat defence against Zymoseptoria tritici fungus.

Zymoseptoria tritici (Septoria) is a devastating fungal pathogen of wheat, causing yield losses of up to 50%. It is classed as a major pathogen threat within the EU. Finding new resistance breeding targets is of upmost importance due to Septoria’s ability to evolve resistance quickly. During this project I used Virus Induced Gene Silencing (VIGS) to study WRKY transcription factors. I identified two that, when silenced, caused a change in Septoria’s infection phenotype, TaWRKY19 and TaWRKY9. TaWRKY19 is a resistance factor whereas TaWRKY9 is a susceptibility factor. To further study the defence network I performed a Yeast 1 Hybrid (Y1H) experiment to identify TFs that bound to TaWRKY19’s and TaWRKY9’s promoter. Through this screen I found multiple potential binders. I focussed on one, TabZIP2, which bound to TaWRKY19’s promoter. Further silencing and infection experiment revealed TabZIP2 to be a susceptibility factor. qRT-PCR experiments were used to study the relationship between TaWRKY19 and TabZIP2, these showed that TabZIP2 appears to be a negative regulator of TaWRKY19 expression. Results from this thesis offer three potential breeding targets for Septoria resistant wheat, with further TFs also identified for further experimentation.