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 (Quiring et al., 1994, Science 265, 785-789; Halder et al., 1995, Science 267, 1788-1792). In contrast to its function in eye development, nothing is known about its function in the central nervous system. During embryogenesis eyeless is expressed in the nervous system from stage 9 on until the end of embryogenesis. In addition it is also expressed in the brain. Using various nervous system markers we are in the process to identify the eyeless expressing cells in the nervous system. The regulatory element responsible for the nervous system expression was identified in the first intron of the gene, but is only functional when the intron was reversed in orientation. This allowed us to generate ey-Gal4 lines with this element to misexpress other gene products in the eyeless expressing cells in the nervous system in the future. By sequence comparisons with the corresponding intron region of the Drosophila hydei eyeless gene four well conserved sequence elements were identified. Their importance was tested using reporter gene constructs. A 700 bp fragment from Drosophila melanogaster having all four conserved regions reproduces the complete nervous system expression, whereas shorter constructs with only three conserved regions result in expression in fewer cells. The corresponding Drosophila hydei region also gives rise to the embryonic nervous system expression when tested in Drosophila melanogaster. We are now in the process to identify if some of the sequences necessary for the correct expression of eyeless in the nervous system of Drosophila are conserved during evolution.