Improved FLP Recombinase, FLPe, Efficiently Removes Marker Gene from Transgene Locus Developed by Cre-lox Mediated Site-Specific Gene Integration in Rice

Site-specific recombination systems, such as FLP-FRT and Cre-lox, carry out precise recombination reactions on their respective targets in plant cells. This has led to the development of two important applications in plant biotechnology: marker-gene deletion and site-specific gene integration. To draw benefits of both applications, it is necessary to implement them in a single transformation process. In order to develop this new process, the present study evaluated the efficiency of FLP-FRT system for excising marker gene from the transgene locus developed by Cre-lox mediated site-specific integration in rice. Two different FLP recombinases, the wild-type FLP (FLPwt) and its thermostable derivative, FLPe, were used for the excision of marker gene flanked by FLP recombination targets (FRT). While marker excision mediated by FLPwt was undetectable, use of FLPe resulted in efficient marker excision in a number of transgenic lines, with the relative efficiency reaching up to similar to 100%. Thus, thermo-stability of FLP recombinase in rice cells is critical for efficient site-specific recombination, and use of FLPe offers practical solutions to FLP-FRT-based biotechnology applications in plants.