| Ptr ToxA, produced by races 1 and 2 of Pyrenophora tritici-repentis, the causal agent of tan spot, is a host-selective toxin that is specific for certain wheat genotypes. The toxin causes necrosis development in wheat with the TSN1 gene and has been associated with high virulence in this system. The object of this research were to develop an understanding of biochemical and molecular events associated with necrosis development in the host. Bioassays based on electrolyte leakage from toxin-treated wheat demonstrated that toxin action requires active host metabolism. In those experiments, electrolyte leakage failed to develop in wheat leaves when experiments were performed at 4 degree or when leave were treated with inhibitors of eukaryotic translation and mRNA synthesis. In other experiments, calcium channel blockers and inhibitors of protein kinases and protein phosphatases reduced or blocked toxin action. Collectively, these data indicated that toxin activates a form of programmed cell death in the host.; Ptr ToxA is a protein that contains the amino acid sequence RGD at amino acids 140--142. Exogenous RGD tripeptide reduced toxin action by 68%; the control peptide RGES had no effect on toxin action. The current model holds that toxin receptor on cell membrane might direct the activity of signaling mechanisms. |
