The use of hygromycin phosphotransferase gene (hpt) with an artificial intron to obtain marker-off transgenic plants
Since maize transposon Ac can move to a new location within genome, it has been used in removing selectable markers in transgenic plants. Previously, we have developed a marker-off system to truncate a selec marker in transgenic plants by locating one end of the transposon in the intron of the marker gene (glyphosate-tolerant epsps gene). In order to expand this technique to those marker genes without intron in this report, we created an artificial intron containing one end of the transposon to achieve marker-off. The hygromycin phosphotransferase gene (hpt) from E. coli which has been proved to be very effective marker for plant transformation was used in this study. The artificial intron which contains a 250 bp Ac 5’ end and partial sequences of the first intron of rice epsps gene was introduced into the intronless hpt gene. This modified marker gene was flanked by Ac 3’ end and transposase gene, which is under the control of the inducible promoter (PR-1a), yielding the new marker-off transposon, KH. The behavior of KH was analyzed in transgenic rice and tobacco. We determined the expression of the modified hpt gene and the transposition events in transgenic plants. The KH element thus exhibits more applications to create marker-off transgenic plants.
Key words: Ac transposase, inducible transposon, selectable marker, transgenic plants.