Efficient Transposition of the Retrotransposon Tnt1 in Cucumber (Cucumis sativus L.)

Tnt1 is an active retrotransposon originally identified in tobacco (Nicotiana tabacum L.) (Grandbastien et al., 1989), but its transposition activity could be activated through tissue culture in other plant species. The insertions are stable and inheritable in the progeny, which has made it a valuable and versatile tool for developing insertional mutagenesis libraries in several plant species. Here, we explored its utility for mutagenesis in cucumber (Cucumis sativus L.). T3 Tnt1 transgenic cucumber plants were subjected to tissue culture to regenerate self-pollinated progeny. With PCR and analyses and Southern hybridization, we found regenerated plants maintained the original Tnt1 insertion and created new insertions suggesting characteristic re-transposition activity of Tnt1 during this process. Using genome walking, some flanking sequences of Tnt1 insertions were recovered in regenerated plants. The results demonstrated that Tnt1 could be stably inherited and re-transposable during tissue culture in cucumber and that it is feasible to use for developing an insertional mutagenesis library for cucumber. Keywords: cucumber, Tnt1, retrotransposon, tissue culture, mutagenesis library