The invention provides a method for selectively controlling the
transcription of a gene of interest, comprising producing one or more
plants that express either a first, a second, or both the first and
second genetic constructs. The first genetic construct comprises a first
regulator region operatively linked to a gene of interest and at least
one repressor sequence capable of controlling the activity of the first
regulatory region. The second genetic construct comprises a second
regulator region in operative association with a nucleic acid molecule,
or a derivative thereof, encoding a repressor protein, the repressor
protein exhibiting both repressor operator sequence binding activity and
repressor activity. The first and second genetic constructs may reside on
separate vectors, or the vector may comprise both the first and second
genetic constructs comprised as just defined. If the first and second
constructs reside within separate plants, then the first plant and the
second plant are crossed to obtain progeny, so that the progeny comprise
both the first genetic construct and the second genetic construct. The
progeny of this cross are characterized in that the expression of the
second genetic construct represses expression of the gene of interest.
The first and second regulatory regions may be either the same or
different and may be selected from the group consisting of a constitutive
promoter, an inducible promoter, a tissue specific promoter, and a
developmental promoter. if the plant comprises the vector that comprises
both the first and second genetic construct, or if a plant has been
co-transformed with the first and second genetic construct so that both
the first and second genetic constructs may be expressed in the same
plant, then it is preferred that the first and second regulatory regions
are different. The first regulatory region may comprise a constitutive
promoter, an inducible promoter, a tissue specific promoter, or a
developmental promoter. The second regulatory region may comprise an
inducible promoter, a tissue specific promoter, or a developmental
promoter.