Isopentenyl transferase gene expression offers the positive selection of marker-free transgenic plant of Kalanchoe blossfeldiana

The technologies allowing the production of transgenic plants without selectable marker genes, is of great interest in public and environmental safety. For generating such marker-free transgenic plants, possibility has been offered by Multi-Auto-Transformation [MAT] vector system, which combines positive selection, using the isopentenyl transferase (ipt) gene, with a site-specific recombination that generates marker-free plants. In this study Agrobacterium tumefaciens strain EHA105 harboring an ipt-type MAT vector, pMAT21, containing lacZ, gus genes and the removable cassette in the T-DNA region was used to produce marker-free transgenic Kalanchoe blossfeldiana Poelln., employing ipt gene as the selectable marker gene. Co-cultivated explants were cultured on hormone- and selective agent-free MS medium, and 85% of the regenerated shoots showed ipt-shooty phenotype with GUS expression. Forty-one morphologically normal shoots were produced during the subculture. More than ninety percent of the normal shoots were ipt (-), gus (-) but lacZ (+) as determined by PCR analyses. These results indicate that the ipt phenotype was clearly distinguishable from non-transgenic as well as transgenic marker-free shoots. This study opens interesting perspective for the generation of marker-free transgenic K. blossfeldiana with objective useful transgene.