Mapping of the red clover necrotic mosaic virus subgenomic RNA.

The red clover necrotic mosaic dianthovirus capsid protein is expressed in vivo from a subgenomic RNA (sgRNA) identical to the 3'-terminal 1.5 kb of RNA-1. The 5' leader sequence of the capsid protein sgRNA is 62 nucleotides, contains a 14-nucleotide putative promoter sequence homologous to the RNA-1 5' terminus, and exhibits a high level of similarity with the tobacco mosaic virus 5' leader translational enhancer element omega. Analysis of the RNA-1 secondary structure, in the region adjacent to the position where the 5' end of the sgRNA was mapped, predicts a stable stem-loop which includes the putative sgRNA promoter element. It is suggested that this structure is important for recognition of the sgRNA transcriptional initiation from the full-length negative-sense RNA-1.