Institut für Genetik (240), Universität Hohenheim, D-70593) Stuttgart, Germany. Tel.:0711/4592215, Fax:0711/4592211, E-mail:walldorf@uni-hohenheim.de,
The Drosophila gene eyeless, a Drosophila Pax6 homologue, is considered to be a master controll gene of eye development. During embryogenesis it is expressed in the eye disc primordia and later on in the undifferentiated anterior part of the eye imaginal discs. It is highly conserved between vertebrates and insects (Quiring et al., 1994, Science 265, 785-789) and most important ectopic expression results in additional eyes in different parts of the body (Halder et al., 1995, Science 267, 1788-1792). The finding that the insertion of two independent transposable element (doc and blastopia) in the eyeless alleles ey2 and eyR occurred within less than 100 bp in an intron of the gene and specifically affect eye morphogenesis suggested that the insertions might disrupt an eye-specific gene regulatory element. We investigated this in detail using reporter gene constructs. Transgenic flies carrying sequences from the complete first intron selectively express lacZ in the eye primordia of the embryo, the eye discs of the larva and in parts of the brain. Using shorter constructs it was possible to narrow down the important region to a 250 bp region near the insertion points of the transposons. In another attempt to characterize the regulatory element, the eyeless gene from Drosophila hydei was cloned and the corresponding region was sequenced. In addition to sequence conservations within the 250 bp region another region of sequence conservation was identified and the Drosophila hydei regulatory elements tested in Drosophila melanogaster by germline transformation. This analysis makes a search for trans-acting factors of eyeless possible to get an insight into the regulation of eyeless gene and to compare regulatory pathways in vertebrate and invertebrate eye development.