Somatic and germinal inheritance of an FLP-mediated deletion in transgenic tobacco

Site-specific recombinases are increasingly used in transgenic plants to engineer genetic rearrangements such as the removal of unwanted selectable markers and the activation or delation of expressed genes. Here a convenient vector system for the activation of transgene expression by FLP-mediated deletion of a transcription blocking sequence is presented. To investigate somatic and germinal transmission of deletion/activation events in transgenic tobacco (Nicotiana tabacum L. var. Xanthi) a derivative of this vector was constructed in which a spectinomycin resistance (SPEC) gene was introduced into plants in a silent state, separated from a CaMV 35S promoter by a GUS gene blocking sequence flanked by FLP target sites (FRTs). SPEC can therefore be activated by FLP-mediated excision of GUS. After crossing to appropriate FLP-expressing plants, heat-shock-induced FLP expression efficiently generated sectors of spectinomycin-resistant tobacco tissue. Constitutive expression of FLP resulted in activation of SPEC and loss of GUS activity in most somatic tissues of all plants carrying 35S-FLP and the target construct. One of the eight plants tested tramsmitted the recombined state to all progeny, indicative of excision activity in germinal tissue.