X. TMV STUDIES IN GENETIC CODING 491 



serological relationship between the product and anti-TMV serum was 

 detected. A detailed analysis of the labeled material produced under the 

 influence of TMV-RNA was thereupon initiated. When unlabeled TMV- 

 protein was added as carrier after the incubation and subsequently 

 reisolated by column chromatography, it contained and retained a 

 significant fraction of the counts, if TJMV-RNA had been present during 

 the reaction, but much less if another RNA or no RNA had been present. 

 Upon tryptic degradation of the protein and separation of the typical 

 peptides, the counts were found distributed in characteristic manner; 

 thus, with phenylalanine or tyrosine as labeled amino acids the radio- 

 activity was predominantly associated with the peptides known to carry 

 the respective amino acid. These data seemed to establish rather firmly 

 that a protein resembling TMV-protein was made by the cell-free 

 E. coli enzyme system under the influence of TMV-RNA. However, one 

 test suggested that there was something wrong with much of the product. 

 While the carrier protein reisolated from control reaction mixtures com- 

 bined with TMV-RNA in the usual way under the conditions of re- 

 constitution, the protein carrying what was presumed to be newly 

 synthesized TMV-protein formed very little stable virus. This strong inter- 

 ference with the reconstitution reaction by the small amount of "product" 

 present may be tentatively interpreted as evidence that a good part of 

 this protein carried a structural imperfection which prevented it from 

 participating normally in the aggregation reaction which leads to rod 

 formation. If one thinks of the typically aggregating protein units as 

 analogous to bivalent antibody molecules, then the in vitro synthesized 

 protein might be regarded as monovalent. Such a mental image would 

 readily explain the marked interference of the latter with the reconstitu- 

 tion reaction. 



To conclude this review of a number of quite recent and preliminary 

 results, it now appears that TMV-RNA can act as messenger and evoke 

 in a completely foreign system the synthesis of a protein which shows 

 very great resemblance to TMV-protein in serological, chromatographic, 

 and amino acid sequential tenns, but probably differs in some as yet 

 unknown feature necessary for the specific native conformation which 

 enables TMV-protein to form rods (Tsugita et al. 1962b). 



V. Natural Strains of TMV 



A. SYMPTOMATOLOGY OF TMV AND ITS STRAINS 



Plant virus diseases in general are either systemic, i.e., they spread 

 throughout the plant, or they result in localized damage. In the case of 

 TMV, different varieties of tobacco and other hosts respond typically in 



