Rice tungro bacilliform virus: transcription and translation in protoplasts.

Protoplasts from cell suspension cultures of Oryza sativa (monocot) and Orychophragmus violaceus (dicot) support transcription from the rice tungro bacilliform virus (RTBV) promoter and translation of the resulting mRNA despite the presence of a long leader sequence with strong secondary structure and 12 short open reading frames. Transcriptional elements located both upstream and downstream of the transcription initiation site are defined by deletion analysis and the functional TATA motif is determined. Expression of an open reading frame downstream of the entire leader is more efficient than that downstream of truncated derivatives. For optimal expression sequences in the 5' and 3' parts of the leader are required.