Production of marker-free transgenic Nierembergia caerulea using MAT vector system

Agrobacterium tumefaciens strain EHA105 harboring an ipt-type MAT vector, pNPI132, was used to produce morphologically normal transgenic Nierembergia caerulea cv. Mont Blanc employing ipt gene as the selectable marker gene. beta-glucuronidase (GUS) gene was used as model gene of interest. The MAT vector system is a positive selection system that gives the advantage of regeneration to the transgenic cells without killing the non-transgenic cells. Infected explants were cultured on hormone- and antibiotic-free MS medium, and 65% of the regenerated shoots developed ipt shooty phenotype-morphologically abnormal shoots, within approximately 3 months after co-cultivation. Twenty morphologically normal shoots were produced from 12 transgenic ipt shoots 7 months after co-cultivation. The normal shoots rooted well on hormone-free MS medium. Ninety percent of the normal shoots were ipt (-), GUS(+) and excision(+) as determined by PCR and Southern blot analyses. These results indicate that ipt-type MAT vector system can be used successfully in Nierembergia to produce marker-free transgenic plants without using phytohormones and selective chemical agents.