This project aims to elucidate the basic biochemical mechanisms behind the toxicity of Pyrenophora tritici-repentis, a fungus that causes tan spot disease of wheat. It has been shown that a protein, PtrToxA, which is the first discovered proteinaceous host-selective toxin, is responsible for disease symptoms on certain cultivars of wheat. Functionally PtrToxA is a remarkable protein, as it appears to be able to enter plant cells, enter the chloroplast, and cause cell death. Little is known about how these events occur, but given recent progress in characterizing and crystallizing the protein, the system is now poised for a major breakthrough. This collaborative three-year research program will study the PtrToxA mechanism of action through biochemical approaches supported by structural studies. Specific aims are to (1) conduct biochemical investigations of plant partner proteins involved in PtrToxA toxicity, (2) solve the three-dimensional structures of native PtrToxA and selected mutants, and (3) design, create, and characterize site-directed mutants of PtrToxA that probe biochemical mechanisms of action. Historically, toxins have been incredibly valuable tools for elucidating basic biochemical mechanisms, and similarly, this work is expected to provide insights into plant disease, to help establish an invaluable model system for toxin-induced cell death, and to uncover novel biochemical mechanisms in plants. Also, because the PtrToxA sequence appears unrelated to any known protein, the structure will contribute to efforts to map all known protein folds. From a practical perspective, this project has the potential to lead to effective tools to combat tan spot.
Broader impact: The personnel involved in the project, from undergraduates through the principle investigators, will receive unusually broad training due to the interdisciplinary nature of the project, and efforts will be made to be sure all participants are exposed to both the biochemical, cell biological, and biophysical aspects of the project.
