Cotranslational disassembly increases the efficiency of expression of TMV RNA in wheat germ cell-free extracts.

Cotranslational disassembly of tobacco mosaic virus (TMV) particles in the rabbit reticulocyte lysate has recently been demonstrated (T.M.A. Wilson, Virology, in press). A similar phenomenon in wheat germ extracts is now reported. However, in contrast to the reticulocyte lysate, wheat germ cell-free extracts respond approximately three times more efficiently to pH 8 treated TMV particles than to conventional TMV RNA templates prepared by phenol extraction. Dose-response curves indicate that this behaviour is reproducible over a wide range of exogenous RNA or virus concentrations (equivalent to 6 to 400 microg/ml RNA). Enhanced synthesis of the large (126K) virus-specific polypeptide is observed in translations programmed with virus particles. These results probably reflect the protective influence of the capsid protein during protein synthesis in a cell-free extract containing ribonuclease activity. This environment may be similar to that which confronts the virus within the cells of infected host plants.