The complete genome structure and synthesis of infectious RNA from clones of tomato bushy stunt virus

Abstract

The complete sequence of the genome of the cherry strain of tomato bushy stunt virus (TBSV), a member of the tombusvirus group, was determined. A full-length clone of the genome containing a bacteriophage T7 RNA polymerase promoter was assembled from partial cDNA clones. In vitro transcripts of the genome, either with or without a 5' cap structure, were highly infectious. In addition, a genomic clone modified to contain an EcoRI restriction site as a signature mutation was infectious. Five genes are encoded by the TBSV genome. The first ORF from the 5' terminus encodes a p33 protein as well as a p92 product translated by read-through of the amber terminator for p33. The capsid protein gene resides internally, and two ORFs for proteins of 19 and 22 kDa reside at the 3' terminus. These last three genes are expressed from two subgenomic RNAs. The genomic organization of TBSV agrees with previous models for tombusviruses. Computer alignments of TBSV proteins with those of two other tombusviruses suggest greater relatedness among the members of this group than previously reported.