The spatial and temporal expression pattern of sevenless is exclusively controlled by gene-internal elements.

The sevenless gene controls the fate of a single photoreceptor cell type in the developing eye of Drosophila. Its RNA and protein accumulate transiently in a subpopulation of cells in the developing eye imaginal disc. We have used P-element transformation with different minigenes and marker gene constructs to identify cis-acting regulatory regions required for the complex sevenless expression pattern. Our results indicate that the upstream region of the sevenless gene is devoid of any detectable regulatory elements and that sequences located 3' to the transcription start site are sufficient to promote the sevenless expression pattern. These gene-internal sequences function in both orientations on heterologous promoters, also when placed at the 3' end of a lacZ reporter gene.