XVI International Botanical Congess

The tobacco Tnt1 element is one of the few active plant retrotransposons. Its transcription is induced by pathogen attacks and factors, such as fungal extracts used for protoplast isolation, and is correlated to plant defense responses. We have used the S-SAP strategy to analyze Tnt1 distribution in its host genomes, and to test for Tnt1 transposition in tobacco plants regenerated from leaf tissue culture and from protoplast culture. Tissue culture poorly induces Tnt1 transposition, but fungal extracts used for protoplast isolation activate Tnt1 transposition in more than 25% of the regenerated plants. Our results indicate that Tnt1 transposition is correlated to transcription, and show that factors of pathogen origin are able to generate genomic variability in plants.