A one-time inducible transposon for terminating selectable markers in transgenic plants

Since the maize transposon Ac can relocate to a new location within the genome, it has been used in removing selectable markers in transgenic plants. We previously developed an inducible transposon system to truncate a selectable marker in transgenic plants by locating one end of the transposon in the intron of the marker gene (glyphosate tolerant epsps gene). We have now improved upon this system by locating the other end of the transposon in the intron of the transposase gene, which is controlled by the inducible promoter (PR-1a). Treatment with salicylic acid induced transposition of this transposon, COKC, which led to both marker gene and transposase gene breakages in exons. The behavior of COKC was analyzed in singlecopy transgenic rice plants. We determined the expression of the modified transposase and epsps genes and the transposition events in transgenic plants. The COKC element thus exhibits potential as a tool to create “marker-off” transgenic plants for woody or vegetatively propagated plants species.