A gene expression system for controllable expression of ethylene response
in a plant cell includes an activation cassette comprising a DNA-binding
domain that recognizes a response element; an ecdysone receptor ligand
binding domain; and an activation domain; and a target cassette
comprising an inducible promoter, which comprises, in operative
association, the response element and a minimal promoter responsive to
the activation domain. The inducible promoter controls the expression of
a nucleic acid sequence that encodes a selected protein that modifies
sensitivity to ethylene in the plant. Interaction among the components of
the activation cassette and target cassette, when in a plant cell, in the
presence of an inducing composition, modulates expression of the selected
protein and selectively modulates ethylene sensitivity in the plant cell.
This modulation in the expression of the protein is controlled by the
timing, the concentration and the duration of the application of the
inducing composition. Transgenic plant cells, tissues, organs and entire
plants are provided, which in the presence of the inducing composition
control ethylene sensitivity. Ethylene sensitivity and/or ethylene
production in such transgenic plants and tissues may be controlled for
purposes of manipulating ripening, flower senescence and other ethylene
sensitive functions of the plant.