THE LIGHT GENE OF DROSOPHILA-MELANOGASTER ENCODES A HOMOLOG OF VPS41,A YEAST GENE INVOLVED IN CELLULAR-PROTEIN TRAFFICKING

Mutations in a number of genes affect eye colour in Drosophila melanog aster; some of these ''eye-colour'' genes have been shown to be involv ed in various aspects of cellular transport processes. In addition, co mbinations of viable mutant alleles of some of these genes, such as ca rnation (car) combined with either light (It) or deep-orange (dor) mut ants, show lethal interactions. Recently, dor was shown to be homologo us to the yeast gene PEP3 (VPS18), which is known to be involved in in tracellular trafficking. We have undertaken to extend our earlier work on the It gene, in order to examine in more detail its expression pat tern and to characterize its gene product via sequencing of a cloned c DNA. The gene appears to be expressed at relatively high levels in all stages and tissues examined, and shows strong homology to VPS41, a ge ne involved in cellular-protein trafficking in yeast and higher eukary otes. Further genetic experiments also point to a role for It in trans port processes: we describe lethal interactions between viable alleles of It and dor, as well as phenotypic interactions (reductions in eye pigment) between alleles of It and another eye-colour gene, garnet (g) , whose gene product has close homology to a subunit of the human adap tor complex, AP-3.