VIEW ARTICLE

Prevention of the Hypersensitive Reaction in Tobacco by Proteinaceous Constituents of Pseudomonas solanacearum. Luis Sequeira, Department of Plant Pathology, University of Wisconsin, Madison 53706; Sheila Aist(2), and Virginia Ainslie(3). (2)(3)Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 62:536-541. Accepted for publication 13 December 1971. DOI: 10.1094/Phyto-62-536.

The hypersensitive reaction (HR) induced in tobacco leaves by the introduction of many incompatible bacteria can be delayed or prevented by prior infiltration with heat-killed cells of Pseudomonas solanacearum. A protective response, similar to that obtained with heat-killed cells, was induced by both soluble and insoluble (cell wall) fractions from disrupted bacteria. Purification of cell wall polysaccharides removed the protective properties from the insoluble fraction. The active component of the soluble fraction was precipitated with ethanol, (NH₄) ₂SO₄, or trichloroacetic acid. Addition of four volumes of ethanol gave the most active precipitate. When resuspended in citrate buffer and infiltrated in tobacco leaves, substances in the ethanol fraction induced a protective effect within 7 hr after infiltration. The protective effect moved to nontreated leaf areas when sufficient time (48 hr) was allowed before leaves were challenged with live cells. The active component of the ethanol fraction was destroyed by pronase, trypsin, and hot trichloroacetic acid, but was remarkably resistant to high temperatures, being completely destroyed only after prolonged autoclaving. Partial purification of proteinaceous constituents by chromatography on DEAE-Sephadex and Sephadex G-200 yielded an active fraction associated with a major protein peak. Separation of this fraction by gel electrofocusing on carrier ampholytes yielded several protein bands. Although partial protection against the HR was associated with one of the major bands, the results were not consistent, presumably due to toxicity of the carrier.