Structure of the 19 S RNA transcript encoded by the cauliflower mosaic virus genome.

Turnip leaves infected with cauliflower mosaic virus accumulate several virus-derived RNA species. These include a large transcript (>25 S) and a 19 S transcript. R-looping and diazo-cellulose filter hybridization techniques show that the 19 S RNA is derived from a contiguous segment of the CaMV genome which includes EcoR1-b and -d DNA fragments. This region encodes the synthesis of a nonvirion protein called P66. The 3' end of the 19 S transcript is polyadenylated and terminates near the single strand break in the alpha-strand of the genome. The 5' end of the transcript starts in or near the EcoR1-d fragment, near position zero on the map described by Hull and Howell (1978).