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United States Department of Agriculture

Agricultural Research Service

Research Project: CHARACTERIZATION OF HOST-PATHOGEN INTERACTIONS IN BARLEY AND WHEAT Title: SnTox3 Acts in Effector Triggered Susceptibility to Induce Disease on Wheat Carrying the Snn3 Gene

Authors
item Liu, Zhaohui -
item Faris, Justin
item Oliver, Richard -
item Tan, Kar-Chun -
item Solomon, Peter -
item Mcdonald, Megan -
item Mcdonald, Bruce -
item Nunez, Alberto
item Lu, Shunwen
item Rasmussen, Jack -
item Friesen, Timothy

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 2009
Publication Date: September 18, 2009
Citation: Liu, Z., Faris, J.D., Oliver, R.P., Tan, K., Solomon, P.S., Mcdonald, M.C., Mcdonald, B.A., Nunez, A., Lu, S., Rasmussen, J.B., Friesen, T.L. 2009. SnTox3 Acts in Effector Triggered Susceptibility to Induce Disease on Wheat Carrying the Snn3 Gene. PLoS Pathogens. 5:(9) 1-15

Interpretive Summary: The necrotrophic fungus Stagonospora nodorum produces multiple toxins that are effective in causing disease. Here, we report the characterization of the SnTox3-producing gene, designated SnTox3, as well as the initial characterization of the SnTox3 protein. In order to verify the action of this toxin we transferred the SnTox3 gene into yeast to show that SnTox3 encodes the SnTox3 protein which interacts with the corresponding wheat susceptibility gene Snn3. Transformation of a non pathogenic S. nodorum isolate with SnTox3 indicated that expression of the SnTox3 gene is sufficient to render an avirulent isolate virulent in the presence of Snn3. SnTox3 disruption mutants are deficient in the production of SnTox3 and consequently are avirulent on the Snn3 differential wheat line BG220. SnTox3 is present in 58% of a worldwide collection of 929 isolates. The cloning of SnTox3 provides a critical tool for the investigation of the S. nodorum-wheat interaction, but also for the general characterization of necrotroph-plant interactions.

Technical Abstract: The necrotrophic fungus Stagonospora nodorum produces multiple proteinaceous host-selective toxins (HSTs) which act as effectors of pathogenicity. Here, we report the molecular cloning and functional characterization of the SnTox3-producing gene, designated SnTox3, as well as the initial characterization of the SnTox3 protein. SnTox3 is a 693 bp intron-free gene with little obvious homology to other known genes. Using heterologous expression in Pichia pastoris and transformation into an avirulent S. nodorum isolate we show that SnTox3 encodes the SnTox3 protein which interacts with the wheat sensitivity/susceptibility gene Snn3. Transformation of an avirulent S. nodorum isolate with SnTox3 indicates that it is sufficient to render an avirulent isolate virulent in the presence of Snn3. SnTox3 disruption mutants are deficient in the production of SnTox3 and consequently are avirulent on the Snn3 differential wheat line BG220. The predicted immature SnTox3 protein is 25.8 kDa in size. A 20 amino acid signal sequence as well as a possible pro sequence are predicted. Six cysteine residues in the protein are predicted to form disulfide bonds and are shown to be important for SnTox3 activity. An analysis of genetic diversity revealed that SnTox3 is present in 58% of a worldwide collection of 929 isolates and occurs as twelve nucleotide haplotypes resulting in four amino acid haplotypes. The cloning of SnTox3 provides a critical tool for the investigation of the S. nodorum-wheat interaction, but also for the general characterization of necrotroph-plant interactions.

Last Modified: 10/25/2014
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