Characterization of an Autosomal Rudimentary-shaped Wing Mutation in Drosophila Melanogaster That Affects Pyrimidine Synthesis

A new autosomal mutation, rudimental (ral), which causes rudimentary-shaped wings in Drosophila melanogaster, has been isolated following ethyl methanesulfonate (EMS) mutagenesis. The wing phenotype of rudimental is identical to that of the X-linked rudimentary (r) mutation, which affects the first three enzymes in the pyrimidine biosynthetic pathway. The autosomal mutant maps very close to ebony (3-70.7) at 70.42 on the right arm of chromosome 3. Analysis of the enzyme activities of orotate phosphoribosyltransferase (OPRTase) and orotidylate decarboxylase (ODCase) indicates that the rala26a allele has less than wild-type activity for both enzymes. This result is discussed in light of the fact that the OPRTase and ODCase activities are part of an enzyme complex, as are the carbamyl phosphate synthetase (CPSase), aspartate transcarbamylase (ATCase) and dihydroorotase (DHOase) activities, which are encoded by the complex rudimentary locus. We suggest that rudimental is also a complex lucus.