Tobacco mosaic virus RNA as genetic determinant: genesis of a discovery.

Abstract

It is generally held that the American geneticists Alfred Hershey and Martha Chase were the first to elucidate, in 1952, the genetic functions of phage DNA. The discovery of the genetic functions of RNA in a plant virus (Tobacco mosaic virus, TMV) is commonly attributed to the American plant virologist Heinz Fraenkel-Conrat, and to the Germans Alfred Gierer and Gerhard Schramm, who came to the same conclusion independently in 1956. In reality, the first understandings dated back to about 1940, when several scientists discovered that TMV infectivity was closely related to the presence of undamaged RNA in the virus particles. A very important but underestimated contribution came from the English group of Roy Markham, Kenneth Smith and Richard Matthews in 1948. This group purified and characterized an isometric plant virus, Turnip yellow mosaic virus, and first showed that virus infectivity depended on the presence of the RNA, concluding that nucleic acid was essential for virus multiplication. This finding was confirmed by the same group one year later but it laid neglected. After a five year period, in which several groups attempted to solve the question of the function of TMV RNA, the American electron microscopist Roger Hart offered, in 1955, further direct evidence which correlated RNA to TMV infectivity. One year later, three research groups (Fraenkel-Conrat; Gierer and Schramm; Max Lauffer, David Trkule and Anne Buzzell) obtained evidence that put an end to the question, which was (and is) fundamental to molecular Genetics because it demonstrated that RNA can function independently of DNA.