Green fluorescent protein as a vital elimination marker to easily screen marker-free transgenic progeny derived from plants co-transformed with a double T-DNA binary vector system

We investigated the potential of a novel double T-DNA vector for generating marker-free transgenic plants. Co-transformation methods using a double T-DNA vector or using mixture of two Agrobacterium tumefaciens strains were compared, and showed that the double T-DNA vector method could produce marker-free transgenic tobacco (Nicotiana tabacum L.) plants more efficiently. A dual marker double T-DNA vector was then constructed by assembling the green fluorescent protein (GFP) gene mgfp5 and the neomycin phosphotransferase gene nptII into the same T-DNA. The frequency of co-transformants produced by this vector was 56.3%. Co-expression of mgfp5 and nptII was found in 28 out of 29 T₁ lines, and segregation of the reporter -glucuronidase gene, gusA, from mgfp5 to nptII was found in 12 out of 29 T₁ lines. Therefore, GFP could be used as a vital marker to improve the transformation efficiency and to easily monitor the segregation of marker genes, thus facilitating screening of marker-free progeny.