This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Collendavelloo, J. Articles by Fritig, B. Search for Related Content PubMed PubMed Citation Articles by Collendavelloo, J. Articles by Fritig, B. Agricola Articles by Collendavelloo, J. Articles by Fritig, B.

Articles

Plant Disease and the Regulation of Enzymes Involved in Lignification

Increased Rate of De Novo Synthesis of the Three Tobacco O-Methyltransferases during the Hypersensitive Response to Infection by Tobacco Mosaic Virus

Institut de Biologie Moléculaire et Cellulaire du Centre National de la Recherche Scientifique, 15, rue Descartes, 67000 Strasbourg, France

The mechanism underlying the increase of activity of the three O-methyltransferases of tobacco (Nicotiana tabacum) after infection by tobacco mosaic virus (TMV) has been investigated with a density-labeling method. The three O-methyltransferases from healthy or TMV-infected leaves fed with H₂O or ²H₂O were purified by ion-exchange chromatography and their mean buoyant densities were calculated from their respective distribution profiles after centrifugation to equilibrium on RbCl gradients. Densities were corrected with respect to the mean buoyant density of a radioactive density marker prepared from tobacco leaves floated on a solution containing L-[³H]leucine and selected on a preparative gradient for its density close to those of the O-methyltransferases. The introduction of ²H into the pool of amino acids from which the enzymic proteins were synthesized was monitored. By measurement of the labeling of -galactosidase synthesized by bacteria from the plant amino acids, it was shown that infection did not alter the rate of labeling of the pool of amino acids. The buoyant-density values of the three O-methyltransferases were determined, and density-labeled enzymes from healthy and infected materials were compared. The largest density shifts from the native enzyme were measured for O-methyltransferases from infected leaves. These results show that the increase in activity of the three enzymes after infection is due to the stimulation of the rate of de novo synthesis of enzyme proteins.