New Transformation Method (MATVS) Regeneration of Transgenic Plants Through Internal Manipulation of Plant Hormone, 1997 Biological Sciences Symposium Proceedings

We have developed a new transformation method: MAT (Multi-Auto-Transformation) Vector System in which a chimeric ipt gene, inserted into the maize transposable element AC (pNPI106)( l), and the yeast site-specific-recombination system pSR1 (pNPI132)(2), is used as a selectable marker for transformation (called for “hit & run cassette”). Th e ipt gene is coded for the enzyme isopentenyl transferase which catalyses cytokinin synthesis, and causes proliferation of transgenic cells and differentiation of adventitious buds. When transformed by MAT vectors, transgenic plants (tobacco, aspen) are auto-regenerated on the hormone-free medium, develop a lot of shoots and lose apical dominance. Therefore, We can visually identif y transgenic plants as ESP (extreme shooty phenotype). When subsequent excision of “hit & run cassette” occurs, normal shoots extend from ESP shoots. Therefore we can select marker-free transgenic plants as normal shoots without sexual crosses or seed production. The MAT vector system provides an alternate approach to regenerate some recalcitrant plant species for transformation, through internal manipulation of cytokinin-to- auxin ratio, and also enables us to produce marker-free transgenic plants without sexual crosses and seed production for pyramid of multiple genes into a vegetably propagated crop by repeated transformation.