GLASS ENCODES A SITE-SPECIFIC DNA-BINDING PROTEIN THAT IS REGULATED IN RESPONSE TO POSITIONAL SIGNALS IN THE DEVELOPING DROSOPHILA EYE

The glass gene encodes a zinc finger protein required for normal photoreceptor cell development in Drosophila. We show that glass transcripts are present in the third-instar eye-imaginal disc starting in the morphogenetic furrow and extending to the posterior margin of the disc; glass protein is detected in the nuclei of all cells in this region. We also show that glass encodes a site-specific DNA-binding protein. A 27-bp glass-binding site can confer glass-dependent expression on a reporter gene in developing photoreceptor cells, the particular subset of glass-expressing cells known to require glass function. This specificity may represent a regulation of glass protein activity after cells are recruited to the photoreceptor cell fate.