Introduction of the tobacco retrotransposon Tto1 into diploid potato.

The tobacco retrotransposon Tto1 is one of the few known active retrotransposons, and its transposition in tobacco, rice and Arabidopsis has been reported to be activated by tissue culture. We introduced Tto1 into a diploid potato by means of Agrobacterium-mediated transformation and obtained two transformed plants carrying Tto1. We then induced plant regeneration via callus formation from leaf explants of Tto1-transformed plants and determined the copy number of Tto1 in the regenerants. A drastic increase in the number of Tto1 copies was not observed. Transcripts of Tto1 were detected in the leaf but not in the callus, suggesting that the transposition of Tto1 may not be activated by tissue culture in potato. The results indicated that the potato is a recalcitrant plant with respect to Tto1 transposition and that the behavior of Tto1 can differ depending on the host plant.