Relationships Between Tobacco Mosaic Virus Biosynthesis and the Nitrogen Metabolism of the Host

Abstract

1. Comparisons of the nitrogen content of TMV-infected and uninfected tobacco leaf discs at various times after inoculation show that virus synthesis is associated with a net increase in protein content. This excess protein is due to: (a) TMV, (b) an excess in insoluble protein which develops soon after inoculation and ends about 100 hours before cessation of TMV synthesis, and (c) an excess in soluble non-virus protein, which is variable in size and which only occurs during the time of virus synthesis. A deficiency in non-protein nitrogen occurs during the time when virus appears. 2. Isotope experiments with N15-labelled nutrient show that: (a) The bulk of TMV nitrogen is derived from the free ammonia of the host tissue. (b) Amino acid residues of TMV protein are not derived from the corresponding free amino acids in the host. (c) The appearance of TMV is preceded by the synthesis of an insoluble precursor of the virus which is then converted into TMV or some soluble intermediate protein. This effect is associated with a cell particulate which represents a small fraction of the total insoluble protein. (d) Infected tissue synthesizes de novo small amounts of soluble non-virus protein, which may represent intermediates in TMV synthesis. (e) Infected tissue fails to synthesize a rapidly turned-over soluble protein which is synthesized in comparable uninfected tissue. (f) TMV synthesis is preceded by a temporary enhancement of the metabolic stability of an insoluble protein component. 3. The results lead to the conclusion that TMV formation is due to diversion of some part of the host's protein-synthesizing apparatus from its normal course.

The Effects of Tobacco Mosaic Virus Synthesis on the Free Amino Acid and Amide Composition of the Host

“…occurred at 216 hours. We have previously observed similar fluctuations in the total nitrogen content of cultured leaf discs (5). No comparable common tendency occurred in infected discs; in these discs only threonine and aspartic acid showed the concentration minimum at 216 hours.…”

Relationships Between Tobacco Mosaic Virus and the Non-Virus Proteins

“…The general procedures involved in handling the plants used in this work and the culture techniques employed have been described elsewhere (2,3). The following special methods were employed in the immunochemical aspects of the experiments described below.…”

Untersuchungen über die Vermehrung und Ausbreitung des Trespenmosaikvirus (bromegrass mosaic virus) in Gerste.

“…auch bei Gerste nach Infektion mit dem Streifenmosaikvirus gefunden (ARMY und MCNF.AL 1958, MCNEAL, AFANASIEV und ARMY 1958, OHMANN-KREUTZBERG 1962. Die in vorhegenden Untersuchungen festgestellte Erhohung bei alien N-Fraktionen im direkt infizierten Gerstenblatt stimmt mit den Befunden von COMMONER, SCHIEBER und DIETZ (1953), BASLER und COM-MONER (1956) und ELBERTZHAGEN (1959) Die Infektion der Gerste mit dem TrMV fiihrte zu auffalligen Veranderungen im Stickstoffstoffwechsel der einzelnen Organe. In den direkt infizierten Primarblattern waren Eiweifi-N, Nichteiweifi-N und daher auch Gesamt-N gegenuber der gesunden KontroUe erhoht.…”