The dominant Drop eye mutations of Drosophila melanogaster define two loci implicated in normal eye development (original) (raw)

1994, MGG Molecular & General Genetics

The three existing dominant gain-of-function Drop alleles, Dr 1, Dr vi° and Dr we, previously assumed to define a single locus, severely disrupt eye development. Genetic analysis of ethylmethanesulphonate (EMS) and irradiation-induced revertants revealed that the Drop mutations define two loci: the Drop locus, which is defined by the Dr I and Dr M~° mutants, and a separate locus defined by the Dr We mutation, which has been renamed Wedge. The majority of the Dr 1 and Dr M*° revertants are embryonic lethal in trans, mutant embryos exhibiting trachea that fail to join the Filzk6rper, thus revealing a role for the Drop gene in embryogenesis. Clonal analysis of lethal revertant alleles suggests a role for both genes in eye development. In the Drop homozygous mutant clones, the outer photoreceptor cells R1-R6 develop aberrantly. Wedge, however, is not required by the developing photoreceptor cells but its absence does disrupt normal ommatidial alignment. Although the Drop and nearby string loci were shown to be genetically distinct, both Dr ~ and Dr M~° were found to interact in trans with lesions at the string locus, causing loss and derangement of bristles and loss of neuromuscular coordination.