Figure 5.

Strategy of using chemicals or heat to induce SMG-removal in transgenic plants. (A) The T-DNA contains an inducible promoter (IP) and a cre recombinase gene (Rec) that is transformed into a plant and reside at locus 1, while the second T-DNA cassette containing the SMG and GOI is transformed and integrates on locus 2. When the induce agent (heat or chemicals) is applied, Cre recombinase protein is produced and excises at the two loxP sites, which removes the P₁-SMG-T₁ fragment. If locus 1 and locus 2 are unlinked, SMG-free transgenic plants can be obtained after segregation in the subsequent generation. (B) Autoexcision scheme. In the autoexcision strategy, the SMG and the cre recombinase gene [which uses an inducible promoter (IP)] are constructed within two loxP sites. Once the inducible promoter is activated, the whole unit within the two loxP sites is removed altogether. Abbreviations. RB: T-DNA right border, LB: T-DNA left border, GOI: gene of interest, SMG: selectable marker gene, IP: inducible promoter, P₁ and P₂: promoters, T, T₁ and T₂: terminators.