ARS | Publication request: Identification of ToxA-Interacting Proteins Suggests a Possible Role for Pathogenesis-Related Protein 1(PR-1) in Mediating Stagonospora Nodorum-wheat Interactions

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 7, 2009
Publication Date: July 19, 2009
Citation: Lu, S., Friesen, T.L., Faris, J.D. 2009. Identification of ToxA-Interacting Proteins Suggests a Possible Role for Pathogenesis-Related Protein 1(PR-1) in Mediating Stagonospora Nodorum-wheat Interactions. Meeting Abstract. p. 97.

Technical Abstract: ToxA is a proteinaceous host-selective toxin produced by the wheat fungal pathogens Stagonospora nodorum and Pyrenophora tritici-repentis. Sensitivity to the toxin and susceptibility to the fungus are both controlled by a single dominant gene (Tsn1) in the host. Map-based cloning has revealed that Tsn1 encodes a protein belonging to the NBS-LRR family of plant disease resistance proteins (Faris et al., unpublished). The pathway(s) connecting activities of ToxA and Tsn1 is still unknown although it has been reported that ToxA may interact with two unrelated chloroplastic proteins (Manning et al., 2007; Tai et al., 2007). By using the yeast two-hybrid system, we have identified two additional ToxA-interacting proteins (TaPR-1a-1 and TaPR-1a-2) that are members of the pathogenesis-related protein 1 family known to be extracellularly located and associated with hypersensitive response/disease resistance pathways. TaPR-1a-1 and a-2 proteins are highly similar (89% identity) and both contain the conserved SCP-like extracellular protein domain and an N-terminal signal peptide. Preliminary experiments indicate that TaPR-1a-1 and a-2 are expressed in uninfected wheat with expression levels differing between susceptible and resistant lines. More interestingly, in the early stages (12/24h after inoculation) of infection by a ToxA-producing isolate, TaPR-1a-1 and a-2 appear to be up-regulated in susceptible wheat but not in resistant wheat. These findings raise the possibility that PR-1a-1 and a-2 may play important roles in mediating host-pathogen interactions by binding directly to ToxA. The characterization of ToxA-PR-1a-1/2 interactions and downstream pathways will help us answer the question of how a plant disease resistance gene like Tsn1 governs disease susceptibility in the S. nodorum-wheat interaction.