Separable cis-acting control elements for expression of the white gene of Drosophila.

The white gene of Drosophila is required for the pigmentation of the eyes, ocelli, Malpighian tubules and testis sheath. We have examined the regulation of white expression in germ line transformants that carry the mRNA-coding sequences of white flanked by varying amounts of the sequences normally located adjacent to them. A segment with as little as 1.9 kb of 5'- and 2.1 kb of 3'-flanking DNA was expressed to give essentially wild-type pigmentation in all of these tissues and interacted in trans with the zeste-1 allele. In contrast, transformants having segments with 1.1 kb of 5'-flanking DNA had reduced levels of pigment in their eyes, no detectable pigment in their testes and did not interact with zeste-1. The eyes, Malpighian tubules and ocelli of transformants with as little as 0.4 kb of 5'-flanking DNA were pigmented and the eye pigmentation exhibited dosage compensation. We conclude that there are sequence elements present in the region from 1.1 to 1.9 kb upstream from the 5' end of the white transcript which are required for expression in the testes and interaction of white and zeste-1. The same or other elements in this region appear to augment the pigmentation of the eye.