Developmental specificity of a bidirectional moth chorion promoter in transgenic Drosophila.

The developmentally specific activity of the 326-bp promoter that is shared by the paired 18 and 401 chorion genes of the silkmoth Antheraea pernyi was studied in transgenic Drosophila melanogaster. Bidirectional activity of this promoter is demonstrated in a novel dual reporter vector, containing lacZ on one side and CAT on the other. The single chorion-specific hexamer of this promoter, TCACGT, is essential for expression in both orientations; even single-base substitutions (at positions 2 or 4 of the hexamer) suppress expression. With both reporter genes, ovarian expression is greater from the 401 side of the promoter, although the difference between the two sides is greater for the CAT gene. The intact promoter fragment (which includes some 5' untranslated sequences) is expressed with a high degree of tissue specificity, but a central 184-bp fragment derived from it is also active ectopically in parts of the internal male genitalia. Strong spatial as well as temporal regulation is evident with both the intact promoter and its 184-bp subfragment, assayed in either orientation.