Rudimentary Locus Research Articles

Rudimentary locus of Drosophila melanogaster: partial purification of a carbamylphosphate synthase--aspartate transcarbamylase--dihydroorotase complex.

Glutamine-dependent CPSase, ATCase, and DHOase from Drosophila, the first three enzymes in pyrimidine biosynthesis, show coordinate variation in activity throughout development. The three activities were highest in first instar larvae and decreased as development proceeded. The three activities cosediment in sucrose gradients as a single peak with a relative sedimentation coefficient of approximately 30S. CPSase, ATCase, and DHOase copurify during (NH4)2SO4 fractionation and during DEAE-cellulose and hydroxylapatite chromatography.

A genetic and biochemical analysis of the temperature sensitive, normal-winged alleles of the rudimentary locus of Drosophila melanogaster.

The genetic and biochemical characteristics of a particular class of mutants at the rudimentary locus are described. The mutants are pyrimidine auxotrophs, like classical rudimentary alleles, but they are unique in that they do not alter the size or shape of the wing (Falk and Nash 1974b). Aspartate transcarbamylase and dihydroorotase activities have been measured in seven different normal-winged mutants, and the results indicate that these strains are enzymologically "leaky" mutants. Previous studies have shown that three genetic functions (corresponding to the first three enzymes of pyrimidine synthesis) are associated with the rudimentary locus. Four of the seven mutants appear to affect all three of these functions. Each of the four is temperature sensitive, and a biochemical analysis of the temperature sensitivity of one of these mutants, (r)pyr1-3, suggests that a process affecting the synthesis or assembly of these enzymes is altered at high temperatures.

Genetic mosaics of the rudimentary locus of Drosophila melanogaster: A genetical investigation into the physiology of pyrimidine synthesis

Genetic mosaics have been utilized to investigate each of the three pleiotropic effects which result from mutation of the rudimentary locus. The wing abnormality results from a requirement for endogenous pyrimidine synthesis within the wing imaginal disk itself. Mosaic analysis indicates the defect in the wing can be rescued by pyrimidine synthesis any place within the imaginal disk and that no more than 10% of the cells of the disk need be genetically capable of producing pyrimidines. This requirement for endogenous synthesis is probably the result of a reduction or complete elimination of pyrimidine uptake at a particular stage during development. Ovary transplantations indicate that the sterility of homozygous rudimentary females results from a requirement for pyrimidine synthesis within the ovary itself, and mosaic analysis of the auxotrophic phenotype indicates that survival of larvae on pyrimidine-free medium depends on pyrimidine synthesis within a variety of different tissues.

Phosphonacetyl-L-aspartate: An aspartate transcarbamylase inhibitor causing larval death and rudimentary wing phenocopies in Drosophila melanogaster

Phosphonacetyl-L-aspartate, an inhibitor and transition state analogue of aspartate transcarbamylase, has been found to cause rudimentary wing phenocopies and larval death in Drosophila melanogaster. We believe this compound may prove useful as a selection agent for regulatory mutations at the rudimentary locus.

Pyrimidine auxotrophy and the complementation map of the rudimentary locus of Drosophila melanogaster.

The complementation pattern of twelve rudimentary mutations have been analyzed at two different levels. When analyzed on the basis of complementation for a wing abnormality the mutations can be divided into three groups, each of which is believed to affect the activity of one of the first three enzymes of pyrimidine synthesis (Norby, 1973; Jarry and Falk, 1974; Rawls and Fristrom, 1975). However, when the mutants are analyzed for complementation on the basis of a second phenotype, pyrimidine auxotrophy, the distinction between two of these three groups is not evident. The disparity in the two patterns probably reflects a different threshold of gene activity required for the detection of an auxotrophic phenotype as compared to that at which a wing abnormality is detectable. The biochemical basis of these results is interpreted in light of recent data suggesting that at least the first two enzymes of pyrimidine synthesis are contained within a single multifunctional protein complex (Soderholm et al., 1975).

Pyrimidine auxotrophy in Drosophila

Eleven reduced-winged and nine normal-winged pyrimidine requiring mutants of Drosophila melanogaster are characterised. All map close to the rudimentary locus (54.5, chromosome 1). On the basis of complementation studies with wing abnormalities, all the reduced-winged mutants prove to be rudimentary alleles. All twenty mutants are partially dominant as auxotrophs; the validity of complementation tests to establish their allelic nature with respect to the auxotrophic phenotype is, therefore, somewhat questionable. However, complementation tests using low-level pyrimidine nucleoside supplementation indicate that at least seven of the normal-winged mutants are rudimentary isoalleles.

Functional diversity within the rudimentary locus of Drosophila melanogaster.

The rudimentary locus of Drosophila melanogaster is shown to be at least bifunctional. Mutants in different regions of the locus have either no CPSase or no ATCase activity; some mutants lack both activities. The results are discussed in correlation with the complementation and genetic map of the locus.

The effects of inversions and the C(3)G mutation on intragenic recombination in Drosophila.

SUMMARYThe effects of heterozygous inversions and of theC(3)Gmutation on recombination between alleles of the rudimentary locus ofDrosophila melanogasterwere analysed. It is shown that the presence of either of these genetic alterations significantly changes the frequency and type of intragenic recombinants which are produced.