IN-VIVO CHARACTERIZATION OF TRANSCRIPTIONAL REGULATORY SEQUENCES INVOLVED IN THE DEFENSE-ASSOCIATED EXPRESSION OF THE TOBACCO RETROTRANSPOSON TNT1

The expression of the tobacco retrotransposon Tnt 1 is induced by woun ding, pathogen infections as well as microbial elicitors and abiotic f actors known to induce the plant defence response. We report here that the LTR U3 region is sufficient to mediate transcriptional activation by biotic and abiotic elicitors in stable transgenic conditions. We h ave used in vivo footprinting techniques in order to analyse the cis-r egulatory elements of the LTR U3 region that mediate the induction of Tnt1 expression. Our results indicate that a tandemly repeated short e lement, named BII box, is involved in the transcriptional activation o f the tobacco retrotransposon Tnt1 in association with the plant defen ce signaling cascade.