Detection of a subgenomic mRNA for gene V, the putative reverse transcriptase gene of cauliflower mosaic virus

Polypeptides synthesized in vitro in rabbit reticulocyte lysates, directed by poly(A)+ RNA isolated from turnip leaves infected with cauliflower mosaic virus (CaMV), were analysed by polyacrylamide gel electrophoresis. Following translation of virus-specific RNA purified by hybrid-selection using CaMV DNA immobilized on DBM papers, the polypeptides observed included the viral gene VI inclusion body protein P62, and a larger product, P75, together with several smaller polypeptides. By translating RNA hybrid-selected with restriction fragments encompassing the CaMV genome, a mRNA for P75 has been mapped to gene V. These results, together with sucrose gradient ultracentrifugation studies, suggest that a CaMV gene V mRNA is a sub-genomic transcript of approximately 2.5Kb and 22S. The expression strategy of the CaMV genome is discussed in the light of our findings.