Development of marker-free transformants by site-specific recombinases

To produce transgenic plants in current biotechnology, selectable marker genes are used that lead to the selectivity of transformants from non-transformed organisms. However, after the transgenic event has been occured, the presence of these genes in transformants genome is generally of no use. Moreover, the continued presence of this kind of genes in transgenic plants with their further commercialization may raise public concern. Therefore, various techniques have been developed in recent years to obtain marker free transgenic plants. In the present review are described the main strategies for removal of selective marker DNA sequences that are used in genetic engineering so far. The most popular among them is a site-specific recombination technology. The particular attention is paid to site-specific recombinase system Cre/loxP. The using of a new approach with site-specific recombinase system Cre/loxP under the control of 35S promoter to generate marker-free genetically modified plants is described.