The promoter of the TLC1.1 retrotransposon from Solanum chilense is activated by multiple stress-related signaling molecules

Marcela Salazar, Enrique González, José A. Casaretto, and Simón Ruiz-Lara. Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Casilla 747, Talca, ChileThe LTR retrotransposons are the most abundant mobile elements in the plant genome and seem to play an important role in genome reorganization induced by environmental challenges. Their success in this function depends on the ability of their promoters to respond to different signaling pathways that regulate plant adaptation to biotic and abiotic stresses. The promoter of the TLC1.1 retrotransposon from Solanum chilense contains two primary ethylene-responsive elements (PERE boxes) that are essential for its response to ethylene and for the stress-induced expression. Here, we describe that a 270 bp fragment (P270), derivative of this retroelement promoter, is also able to activate the transcription of the GUS reporter gene in transgenic plants in response to salicylic acid (SA), abscisic acid (ABA), methyl jasmonate (MeJA), hydrogen peroxide (H2O2) and the synthetic auxin 2,4-D. PERE box-dependent and independent routes are involved in the response of P270 to these signal molecules. MeJA, H2O2 and 2,4-D activate this promoter through cis-acting elements other than PERE boxes, whereas ABA and SA act via a PERE box-independent pathway but require this element for maximal activation. Three putative cis-acting elements MRE, GCN4 and GT1/TCA identified in the P270 promoter may be involved in the PERE box-independent activation pathway. These results suggest that the promoter of TLC1.1 may act as an integrator of different signal transduction pathways, allowing this member of the TLC1 retrotransposon family to be activated in response to multiples challenges