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Alterations in Structural Proteins from Chloroplast Membranes of Bacterially Induced Hypersensitive Tobacco Leaves. Jeng -sheng Huang, Graduate Assistant, Department of Plant Pathology, University of Missouri, Columbia 65201; Robert N. Goodman, Professor, Department of Plant Pathology, University of Missouri, Columbia 65201. Phytopathology 62:1428-1434. Accepted for publication 26 June 1972. DOI: 10.1094/Phyto-62-1428.

Chloroplasts were isolated from tobacco leaf tissues, by homogenization and differential centrifugation, 20 min, 3 and 6 hr after infiltration with water or 108 cells/ml of Erwinia amylovora. Chloroplast membranes were prepared from isolated chloroplasts by sonication. Structural proteins (SP) were isolated from the membranes by extraction with acetone, solubilized with sodium dodecyl sulfate, and precipitated with ammonium sulfate. All SP preparations migrated as a single boundary during ultracentrifugation, and exhibited absorption maxima at 280 and minima at 250 nm. The SP isolated from tissues 20 min after infiltration with bacteria and from water-infiltrated tissues had similar optical density (OD), OD280/OD250 ratios, and electrophoretic patterns. The SP isolated from leaf tissues 3 and 6 hr after bacterial infiltration had increased OD, decreased OD280/OD250 ratios, and two new protein bands in electrophoretic profiles. All SP preparations were insoluble in water but able to bind lecithin; however, the SP isolated from tobacco leaf tissue 3 and 6 hr after infiltration with E. amylovora had decreased solubilities in 0.1 N NaOH and sodium dodecyl sulfate + urea solutions and decreased lecithin-binding capacity. The mole percent of nonpolar amino acids of structural protein decreased as a consequence of hypersensitive reaction. The changes in OD280/OD250 ratios, solubility, phosphatide binding, and amino acid composition suggest that alteration of SP occurs during the development of the hypersensitive reaction.

Additional keywords: Nicotiana tabacum.