[Stress activation and genomic impact of plant retrotransposons].

Retrotransposons are mobile genetic elements that amplify via reverse transcription of an RNA intermediate. They insert at different positions in host genomes, can be amplified to high copy number and are an important source of genetic diversity. The tobacco TntlA retrotransposon is activated by stresses of pathogen origin, and regulatory sequences involved in this activation are similar to those of various stress responsive plant genes. Tnt1A belongs to an ancient family present in various Solanaceous species, and composed of populations of closely related elements that differ in their expression conditions. This expression is often observed in response to stress, but with specificities that differ sensibly for each population, possibly refecting an adaptative response of ancestral populations to different stimuli, during the radiation of Solanaceous species and genera. Microbial factors efficiently stimulate Tnt1A amplification, reinforcing the hypothesis that environmental challenges can generate genetic modifications. In addition, TntlA transposition preferentially targets genic regions, suggesting that the activity of transposable elements can modulate genic functions and represent a natural source of phenotypic diversity.