title: Analysis of the phenotypes exhibited by rudimentary-like mutants of Drosophila melanogaster.
abstract: Flies mutant for one or both of the last two enzymes of de novo pyrimidine biosynthesis express a number of phenotypes that are also expressed by mutants of the first four pathway enzymes (r and Dhod-null mutants). However, r-1 flies also express two phenotypes, mottled eyes and poor viability, that are not usually expressed by r and Dhod-null flies. Chemical determinations show that orotic acid, a substrate for the fifth pathway enzyme, accumulates in r-1 individuals but not in r and wild-type individuals. Moreover, flies simultaneously mutant for r and r-1 do not express the mottled-eye phenotype, showing that r is epistatic to r-1 for this r-1-specific phenotype. When genotypically wild-type flies are cultured on a medium containing 6-azauracil, the base of a potent inhibitor of the last enzyme of de novo pyrimidine biosynthesis, phenocopies are obtained that include the mottled-eye as well as the wing phenotypes of r-1 flies. These results support hypotheses that the phenotypes common to r, Dhod-null, and r-1 flies are consequences of uridylic acid deficiency, whereas the r-1-specific phenotypes result from orotic acid accumulation in flies lacking either or both of the last two enzymes of de novo pyrimidine biosynthesis.
mesh_terms: D000818:Animals; D002262:Carboxy-Lyases / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D005127:Eye Color; D005260:Female; D008297:Male; D009154:Mutation; D009962:Orotate Phosphoribosyltransferase / Q000172:deficiency / Q000235:genetics*; D009963:Orotic Acid / Q000032:analysis; D009964:Orotidine-5'-Phosphate Decarboxylase / Q000172:deficiency / Q000235:genetics*; D010430:Pentosyltransferases / Q000235:genetics*; D010641:Phenotype; D011743:Pyrimidines / Q000096:biosynthesis
chemical_list: D011743:Pyrimidines; D009963:Orotic Acid; D010430:Pentosyltransferases; D009962:Orotate Phosphoribosyltransferase; D002262:Carboxy-Lyases; D009964:Orotidine-5'-Phosphate Decarboxylase