Abstract: Compositions and methods are provided for the production and selection of transgenic plants and plant parts, for increasing the transformation frequency of a plant or plant part, and for regulating the expression of a transgene, such as a herbicide tolerance polynucleotide. The methods and compositions allow for the delay in the expression of herbicide tolerance polynucleotides until a point in development during which herbicide selection is more efficient. Compositions comprise polynucleotide constructs comprising an excision cassette that separates a transgene, such as a herbicide tolerance polynucleotide, from its promoter and host cells comprising the same. The excision cassette comprises a polynucleotide encoding a site-specific recombinase operably linked to an inducible promoter and expression of the recombinase leads to excision of the excision cassette and expression of the transgene.

Abstract: Compositions and methods are provided for the production and selection of transgenic plants and plant parts, for increasing the transformation frequency of a plant or plant part, and for regulating the expression of a transgene, such as a herbicide tolerance polynucleotide. The methods and compositions allow for the delay in the expression of herbicide tolerance polynucleotides until a point in development during which herbicide selection is more efficient. Compositions comprise polynucleotide constructs comprising an excision cassette that separates a transgene, such as a herbicide tolerance polynucleotide, from its promoter and host cells comprising the same. The excision cassette comprises a polynucleotide encoding a site-specific recombinase operably linked to an inducible promoter and expression of the recombinase leads to excision of the excision cassette and expression of the transgene.