Assessing European wheat sensitivities to Parastagonospora nodorum necrotrophic effectors and fine-mapping the Snn3-B1 locus conferring sensitivity to the effector SnTox3

Rowena Downie, Laura Bouvet, Eiko Furuki, Nick Gosman, Keith Gardner, Ian Mackay, Camila Campos Mantello, Greg Mellers, Huyen Phan, Gemma Rose, Kar-Chun Tan, Richard Oliver, James Cockram

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Abstract

Here, we evaluate the expression of the proteinaceous effectors ToxA and ToxB, produced by the necrotrophic fungal pathogen Pyrenophora tritici-repentis, which confer tan spot disease susceptibility on wheat. These necrotrophic effectors were expressed in two heterologous systems: Escherichia coli and Pichia pastoris. The E. coli SHuffle system was demonstrated to be superior to P. pastoris in generating high-levels of recombinant proteins that were soluble and stable. In addition, protein extracts from P. pastoris induced non-specific chlorosis on wheat, postulated to be caused by co-purified glucanases secreted by the host. Up to 79.6 μg/ml of ToxB was obtained using the SHuffle system in the absence of the native signal peptide, whilst the ToxA yield was considerably lower at 3.2 μg/ml. Results indicated that a histidine tag at the ToxA C-terminus interfered with effector functionality. Heterologously expressed ToxA and ToxB were tested on a panel of Australian cereals, including 122 varieties of bread wheat, 16 durum, 20 triticale and 5 barley varieties, as well as common plant model species including tobacco and Arabidopsis thaliana. A varying degree of effector sensitivities was observed, with a higher ToxB sensitivity and prevalence in the durum and triticale varieties. ToxB-induced chlorosis was also detected on barley. The heterologous expression of effectors that are easily scalable, will facilitate effector-assisted selection of varieties in wheat breeding programs as well as the investigation of P. tritici-repentis effectors in host and non-host interactions.
Original languageEnglish
Article number881
Number of pages12
JournalFrontiers in Plant Science
Volume9
Early online date4 Jul 2018
DOIs
Publication statusFirst published - 4 Jul 2018
Externally publishedYes

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Keywords

  • wheat
  • MAGIC
  • Plant breeding
  • Plant disease

Cite this

Downie, R., Bouvet, L., Furuki, E., Gosman, N., Gardner, K., Mackay, I., Campos Mantello, C., Mellers, G., Phan, H., Rose, G., Tan, K-C., Oliver, R., & Cockram, J. (2018). Assessing European wheat sensitivities to Parastagonospora nodorum necrotrophic effectors and fine-mapping the Snn3-B1 locus conferring sensitivity to the effector SnTox3. Frontiers in Plant Science, 9, [881]. https://doi.org/10.3389/fpls.2018.00881