REGULATION OF EXPRESSION OF THE TOBACCO TNT1 RETROTRANSPOSON IN HETEROLOGOUS SPECIES FOLLOWING PATHOGEN-RELATED STRESSES

Transcriptional regulation of the tobacco retrotransposon Tnt1 was mon itored in Arabidopsis thaliana and Lycopersicon esculentum. In these t wo heterologous host species, Tnt1 expression is developmentally regul ated, and its tissue-specific pattern of transcription is similar to t hat observed in tobacco, with the exception that Tnt1 is expressed in their flowers. Induction of Tnt1 by microbial elicitors, previously fo und in tobacco, is maintained in Arabidopsis and tomato. Tnt1 activati on is not strictly dependent upon a Hypersensitive Response-like necro tic response, but also occurs in a plant-pathogen compatible interacti on triggered by viral or bacterial infections. The putative role of Tn t1 in generating genetic variability in its host plant is discussed.