Characterisation of LTR sequences involved in the protoplast specific expression of the tobacco Tnt1 retrotransposon

Abstract

The tobacco Tntl retrotransposon is the only plant retrotransposon that 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 Tntl expression in tobacco protoplasts. We show that LTR sequences upstream of the TATA box are sufficient to confer protoplast-dependent induction to a heterologous promoter. We also show that this region contains two short activator elements, and that one of these sequences, BlI, interacts with protoplast-specific nuclear factors.

The rice Rim2 transcript accumulates in response to Magnaporthe grisea and its predicted protein product shares similarity with TNP2-like proteins encoded by CACTA transposons

“…The sequence GGCATTTGGC found from position )125 to )116 is very similar to the BI core sequence found in Tnt1 (Casacuberta and Grandbastien 1993), although the BI-like sequence is located downstream of the BII-like region instead of upstream as observed in Tnt1 (Fig. 3; Casacuberta and Grandbastien 1993). Four motifs with the sequences (T)TGAC(C) that are identical to the consensus of the elicitor-responsive elements found in the promoters of the parsley PR-1 genes (Rushton et al 1996) and the maize PRms gene (Ravento s et al 1995) were found in the distal upstream region from )683 to )426 (Fig.…”

“…3). The sequence GGCATTTGGC found from position )125 to )116 is very similar to the BI core sequence found in Tnt1 (Casacuberta and Grandbastien 1993), although the BI-like sequence is located downstream of the BII-like region instead of upstream as observed in Tnt1 (Fig. 3; Casacuberta and Grandbastien 1993).…”

“…The sequence of the BII motif (CCAACC-N 7 -CT) is similar to a well-characterized motif, named the H-box (CCTACC-N 7 -CT) involved in the transcriptional activation of the chalcone synthase promoter. An element named BI with the core sequence GGCATGTGC, upstream of the BII elements, resembles G-box related sequences (Casacuberta and Grandbastien 1993;Vernhettes et al 1997). These results suggest that transcriptional activation of plant retrotransposons is activated by stress, and activation is under the control of cis-regulatory sequences similar to those of plant defense genes (Grandbastien 1998).…”

Involvement of Ethylene in Stress-Induced Expression of the TLC1.1 Retrotransposon from Lycopersicon chilense Dun.

“…Whereas the 5.3-kb RNA would correspond to the expected size of a full-length TLC1.1 transcript, the nature of the 6-kb RNA is unclear. Nevertheless, longer hybridizing transcripts have also been reported in RNA-blot analysis with the Tnt1 retrotransposon probe (Casacuberta and Grandbastien, 1993), indicating that this longer transcript might correspond to a TLC1.1-derived RNA. The effect of drought and salt stresses on TLC1.1 expression was analyzed by RT-PCR and compared with the expression of the L. chilense endochitinase and H1 histone-like genes, both reported to be induced by drought (Chen et al, 1994;Wei and O'Connell, 1996).…”

“…Signals controlling retrotransposon expression of these elements are located within the 5# LTR and the adjacent untranslated region. Several cis-acting elements corresponding to tandem repeated sequences and specific DNA motifs have been identified in the LTR U3 domains and have been shown to be involved in the induction of retrotransposon transcription by biotic and abiotic stress factors (Casacuberta and Grandbastien, 1993;Grandbastien et al, 1997;Vernhettes et al, 1997;Grandbastien, 1998;Takeda et al, 1998Takeda et al, , 1999. Within this region, high variability is indeed observed among the different subfamilies of plant retrotransposons, a trait that has been recently associated with the ability of these promoters to respond to different stressassociated signaling molecules (Marillonnet and Wessler, 1998;Vernhettes et al, 1998;Araujo et al, 2001).…”