Origin and Messenger Activity of Two Small RNA Species Found in Particles of Tobacco Rattle Virus Strain SYM

Abstract
Summary Nucleoprotein preparations of tobacco rattle virus (TRV) strain SYM contain particles of four modal lengths. Particles of length 188 nm and 101 nm contain RNA-1 and RNA-2 respectively. Those of length 57 nm and 48 nm contain RNA molecules that are not required for infectivity but include specific sequences derived from both RNA-1 and RNA-2. No products attributable to translation of RNA-2 were obtained in reticulocyte lysates, whereas RNA-2 of other TRV strains serves as messenger RNA for virus coat protein. In strain SYM, one of the smaller RNA species, RNA-3 (mol. wt. 0.6 × 106, 1750 nucleotides), was translated in vitro to give coat protein, and is apparently a subgenomic messenger RNA derived from RNA-2. The other small RNA species, RNA-4 (mol. wt. 0.54 × 106, 1550 nucleotides), was translated into a polypeptide of apparent mol. wt. 29000, unrelated to coat protein. It is suggested that RNA-4 is a subgenomic messenger RNA derived from RNA-1.