Selectable gene auto-excision via a cold inducible ‘gene deletor’ system

Selectable marker genes are necessary tools for selecting transformants during transgenic plant production. However, once transformation is accomplished, the presence of these selectable marker genes is no longer necessary and can even be undesirable. Here we describe the successful excision of selectable genes from transgenic plants via the use of a cold inducible ‘gene deletor’ system. During a transformation procedure in tobacco, transgenic plants obtained by selection on kanamycin medium and identified by GUS staining and PCR method. Some shoots regenerated form transgenic tobacco leaves, after cold inducing, were screened for selective marker excision using GUS staining and PCR method, and all the exogenous genes were found to have been eliminated. About 28 - 94% of regenerated plants were marker-free. This excision system, mediated by the cold inducible ‘genedeletor’ system to eliminate a selectable marker gene can be very readily adopted and used to efficiently generate marker-free transgenic plants.