Marker-Free Targeted Transformation

There are many transformation methods available for stable integration of a desirable gene into plant cells. In transformation, variable numbers of desired genes together with marker genes are randomly inserted into the plant genome. Therefore, cumbersome screening procedures are required to identify transgenic plants with a single copy of transgenes at appropriate expression levels. However, the lack of reproducibility of expression levels limits studies of both the gene expression and physiological effects of transgenes. And remaining of marker genes precludes retransformation with the same marker system and can raise safety and public concerns. The targeting approach is the best way to solve this problem. In this chapter, we focus on the application of site-specific recombination systems for introducing a desirable gene into a predefined site in a plant genome. Furthermore, we discuss an approach for removing a marker gene from targeted transgenic plants.