CHARACTERIZATION OF LTR SEQUENCES INVOLVED IN THE PROTOPLAST SPECIFICEXPRESSION OF THE TOBACCO TNT1 RETROTRANSPOSON

The tobacco Tnt1 retrotransposon is the only plant retrotransposon tha t has been shown to be transcriptionally active, and its transcription is strongly induced when preparing leaf-derived protoplasts. We have analysed in this paper the LTR sequences important for Tnt1 expression in tobacco protoplasts. We show that LTR sequences upstream of the TA TA box are sufficient to confer protoplast-dependent induction to a he terologous promoter. We also show that this region contains two short activator elements, and that one of these sequences, BII, interacts wi th protoplast-specific nuclear factors.