GENETIC-ANALYSIS OF VISUAL-SYSTEM DISORGANIZER (VID), A NEW GENE INVOLVED IN NORMAL DEVELOPMENT OF EYE AND OPTIC LOBE OF THE BRAIN IN DROSOPHILA-MELANOGASTER

A neuroanatomical screening of a collection of P-element mutagenized f lies has been carried out with the aim of finding new mutants affectin g the optic lobe of the adult brain in Drosophila melanogaster. We hav e identified a new gene that is involved in the development of the adu lt axon array in the optic ganglia and in the ommatidia assembly. We h ave named this locus visual system disorganizer (vid). Reversional mut agenesis demonstrated that the vid mutant was the result of a P-elemen t insertion in the Drosophila genome and allowed us to generate indepe ndent alleles, some of which resulted in semilethality, like the vid o riginal mutant, while the others were completely lethal. A genetic som atic mosaic analysis indicated that the vid gene is required in the ey e for its normal development by inductive-effects, This analysis also suggests an inductive effect of the vid gene on the distal portion of the optic lobe, particularly the lamina and the first optic chiasma. M oreover, the absence of mutant phenotype in the proximal region of the optic ganglia, including the medulla, the second optic chiasma, and t he lobula complex underlying mosaic eyes, is suggestive of an autonomo usly acting mechanism of the vid gene in the optic lobe. The complete or partial lethality generated by different mutations at the vid locus suggests that this gene's role may not be limited to the visual syste m, but may also affect a vital function during Drosophila development.