Elucidating the structural basis of effector induced susceptibility in the Parastagonospora nodorum–wheat interaction

MA Outram1, XM Zhao1, S Breen2, PS Solomon2, B Kobe1 and SJ Williams2

  1. School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
  2. Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, Australia

Parastagonospora nodorum, the causal agent of Septoria Nodorum Blotch, is a major necrotrophic fungal pathogen of wheat worldwide. P. nodorum secretes small cysteine-rich proteinaceous effectors (ToxA, Tox1 and Tox3) that interact with corresponding dominant host sensitivity gene products, promoting cell death and rendering the plant susceptible to disease. Whilst it is now understood that these effectors are required for the development of disease, there is little understanding of their function. Using yeast two-hybrid and co-immunoprecipitation assays the effector protein Tox3 has been shown to interact with basic and acidic wheat pathogenesis-related 1 (PR1) proteins. To understand the structural basis of this interaction we have developed protein expression and purification systems for the production of Tox3 and wheat PR1 proteins. We present here the in-solution biophysical characterisation of Tox3 and wheat PR1 proteins using multi-angle light scattering coupled with size-exclusion chromatography. We further present the first crystal structure of an acidic wheat PR1 protein. This data provides structural and mechanistic insights into the interaction between Tox3 and wheat PR1 proteins.