ARS | Publication request: OVEREXPRESSION OF HOST RESPONSE GENES: EFFECTS ON CELLULAR RESPONSES TO FUNGAL PATHOGENS

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 9, 1998
Publication Date: N/A

Technical Abstract: An important method for demonstrating the role in host-parasite interaction of a given gene is to clone and introduce the gene into plants. To facilitate such experiments, especially with cereals, which require time-consuming and expensive procedures to transform, we have developed a transient expression assay for rapid gene evaluation. Gene effects are evaluated by microscopic examination of living, transiently expressing hos cells in tissue inoculated with a pathogen or treated with toxins or elicitors. Genes for a rice chitinase, a maize ribosome-inhibiting protein, and an oat thaumatin-like protein (TLP) each reduced rates of infection (formation of haustoria by appressoria) by B. graminis by 48-78% of rates in controls, indicating the antifungal products of these genes strongly inhibited infection processes. However, a mutant gene for an inactive form of glucanase reduced infection by 33%, suggesting that accumulation of secreted gene products in cell walls may contribute to infection rate reduction in ways unrelated to enzymatic or other antifungal toxicity. The transient expression assay also was used to detect a gene that confers sensitivity of resistant oat cells to the host-specific toxin, victorin. We tested four genes of the H-subunit protein of glycine decarboxylase, a victorin-binding protein, cloned by J. Lorang and T. Wolpert. One of the genes significantly increased rates of cell death in toxin-treated tissues normally resistant to the toxin, pinpointing the gene for further genetic and physiological evaluation of its role in victorin sensitivity. Overall, the transient expression assay is potentially useful for evaluating a wide range of diverse plant genes postulated to influence host-parasite interaction.