title: Rudimentary mutants ofDrosophila melanogaster : Isolation and characterization of pyrimidine auxotrophic cell lines.
abstract: The X-linkedrudimentary (r) mutants ofDrosophila melanogaster are pyrimidine auxotrophs and require exogenous pyrimidines (Nørby, 1970; Falk, 1976). We have established a set ofrudimentary cell lines that are derived from embryos, homozygous for eitherr1orr36. The enzymatic activities of the pyrimidine synthesizing enzymes were measured in the mutant lines. We have further investigated the nutritional requirements of the mutant cells in vitro by using a pyrimidine free culture medium.Ther1cell lines were found to express 3-7%dihydroorotase (DHOase) activity as compared to a wildtype cell line. Reducedaspartate transcarbamylase (ATCase) activity was measured in somer1cell lines whereas wildtypecarbamylphosphate synthetase (CPSase) activity is expressed in allr1cell lines. Ther36cell line expresses wildtype activity ofDHOase andCPSase. ATCase activity was found to be reduced to 10% of the wildtype activity.The mutant cell lines do not proliferate in pyrimidine free minimal medium and cell proliferation is obtained by the addition of crude RNA. Proliferation of ther1cells is restored by the supplementation of the minimal medium withdihydroorotate whereas proliferation of ther36cells is restored by supplementation with eitherdihydroorotate orcarbamylaspartate.The results demonstrate that therudimentary phenotypesr1andr36are expressed at the cellular level and that the two mutant cell types behave as cellular pyrimidine auxotrophs in vitro.
authors.affiliation: Department of Cell Biology, Biozentrum, University of Basel, Klingelbergstr. 70, CH-4056, Basel, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Regenass
authors.affiliation: Department of Cell Biology, Biozentrum, University of Basel, Klingelbergstr. 70, CH-4056, Basel, Switzerland.
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Bernhard
keywords: Drosophila melanogaster; Pyrimidine biosynthesis; rudimentary mutants