Mating behavior in Drosophila melanogaster males heterozygous for the dominant temperature-sensitive lethal mutation

The influence of two mutations on the mate success of Drosophila melanogaster males was studied. Dominant temperature-sensitive lethal mutations l(2)M167DTS and l(2)M65DTS were used in experiments. Both these mutations are recessive lethals in homozygote. Individuals l(2)M65DTS and l(2)M167DTS die at 17 and 28 degrees C, respectively. The mate success of l(2)M65DTS males is much lower than that of normal males. In the experiments conducted in autumn, l(2)M167DTS males were always at advantage, whatever their age. In the winter experiments, they were only at advantage at the age of 2-3 and 15-17 days. For l(2)M167DTS males, a relationship has been established between the mate success and t degrees, and season. The role of behavioural pleiotropic effects of mutations on the probability of their fixation in a population is discussed.     

Mutual correction of faulty PCNA subunits in temperature-sensitive lethal mus209 mutants of Drosophila melanogaster

Proliferating cell nuclear antigen (PCNA) functions in DNA replication as a processivity factor for polymerases delta and epsilon, and in multiple DNA repair processes. We describe two temperature-sensitive lethal alleles (mus209(B1) and mus209(2735)) of the Drosophila PCNA gene that, at temperatures permissive for growth, result in hypersensitivity to DNA-damaging agents, suppression of position-effect variegation, and female sterility in which ovaries are underdeveloped and do not produce eggs. We show by mosaic analysis that the sterility of mus209(B1) is partly due to a failure of germ-line cells to proliferate. Strikingly, mus209(B1) and mus209(2735) interact to restore partial fertility to heteroallelic females, revealing additional roles for PCNA in ovarian development, meiotic recombination, and embryogenesis. We further show that, although mus209(B1) and mus209(2735) homozygotes are each defective in repair of transposase-induced DNA double-strand breaks in somatic cells, this defect is substantially reversed in the heteroallelic mutant genotype. These novel mutations map to adjacent sites on the three-dimensional structure of PCNA, which was unexpected in the context of this observed interallelic complementation. These mutations, as well as four others we describe, reveal new relationships between the structure and function of PCNA.     

Genetic and biochemical characterization of phosphofructokinase from Drosophila melanogaster

Phosphofructokinase (PFK;EC 2.7.1.11) activity in Drosophila melanogaster is controlled by a single dosage-sensitive region of the genome between 45F and 47E of chromosome IIR. Only a single form of PFK was detected electrophoretically in both adults and larvae. Nearly 90% of the PFK activity in adults is localized to the thorax. Purification of the enzyme was hampered by the extreme lability of Drosophila PFK; however, a 36-fold partial purification was achieved.     

wiser tsl : a recessive X-linked temperature-sensitive lethal mutation that affects the wings and the eyes in Drosophila melanogaster

In this study, we characterize a recessive X-linked temperature-sensitive mutation of the gene CG32711. The mutation, named wiser ^tsl (wings scalloped-eyes rough), was isolated from a dysgenic cross and is due to a natural P element insertion within the 5′ regulatory region of the gene. Mutant (wiser ^tsl ) individuals exhibit wing notching, rough eyes, tarsal malformations and reduced life-span. At 29°C they die at larval and late pharate stages or during eclosion. The CG32711 (wiser) gene is mainly expressed in the ventral midline cells, the peripheral neural system, the hemocytes and the tracheal system of embryos. It is also expressed in nurse cells of adult female ovaries. Our results show that the wiser gene is alternatively spliced generating two mRNAs, which share the same open reading frame, while western analysis identified two protein isoforms. Their expression pattern depends on the stage of development and the culture temperature. wiser ^tsl and wild-type individuals display different expression patterns of the two isoforms and this difference most probably accounts for the mutant phenotype. Our results indicate that wiser is a vital gene for the development of Drosophila melanogaster which has no orthologs outside the Drosophilidae. Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession nos. bankit1003537 EU071463–bankit1003860 EU071464.     

A cytological and genetic study of oogenesis in Drosophila melanogaster

A newly derived collection of 98 autosomal recessive female-sterile (fs) lines induced by ethyl methanesulfonate (EMS) in Drosophila melanogaster has been studied genetically and cytologically. By the use of phenotype and complementation tests, the 98 fs lines were resolved into 19 fs genes on the 2nd chromosome and 17 fs genes on the 3rd chromosome. Nearly half of the fs lines turned out to be replicates of noninduced fs mutant loci that preexisted in the EMS-treated files.Systematizing these fs genes according to their phenotypic and morphological defects focuses attention on their relevance to five major aspects of oogenesis: (1) the developmental organization of the ovary, (2) the synthesis and deposition of yolk material, (3) the formation of the chorion, (4) the control of egg-laying, and (5) the construction of the internal milieu of the ovarian oocyte for normal embryogenesis.The results of this study demonstrate that a systematic collection and characterization of fs mutants can provide the genetic tools needed to study the complex interactions which proceed undetected during normal oogenesis.     

A genetic suppressor of two dominant temperature-sensitive lethal proteasome mutants of Drosophila melanogaster is itself a mutated proteasome subunit gene

Two dominant temperature-sensitive (DTS) lethal mutants of Drosophila melanogaster are Pros26(1) and Prosbeta2(1), previously known as DTS5 and DTS7. Heterozygotes for either mutant die as pupae when raised at 29 degrees , but are normally viable and fertile at 25 degrees . Previous studies have identified these as missense mutations in the genes encoding the beta6 and beta2 subunits of the 20S proteasome, respectively. In an effort to isolate additional proteasome-related mutants a screen for dominant suppressors of Pros26(1) was carried out, resulting in the identification of Pros25(SuDTS) [originally called Su(DTS)], a missense mutation in the gene encoding the 20S proteasome alpha2 subunit. Pros25(SuDTS) acts in a dominant manner to rescue both Pros26(1) and Prosbeta2(1) from their DTS lethal phenotypes. Using an in vivo protein degradation assay it was shown that this suppression occurs by counteracting the dominant-negative effect of the DTS mutant on proteasome activity. Pros25(SuDTS) is a recessive polyphasic lethal at ambient temperatures. The effects of these mutants on larval neuroblast mitosis were also examined. While Prosbeta2(1) shows a modest increase in the number of defective mitotic figures, there were no defects seen with the other two mutants, other than slightly reduced mitotic indexes.     

A histological and ultrastructural analysis of developmental defects produced by the mutation,lethal(1)myospheroid,in Drosophila melanogaster

The recessive embryonic lethal, lethal(1)myospheroid, is located at 21.7 map units on the X chromosome in Drosophila melanogaster. Embryos hemizygous for this mutation appear to develop normally until the time of the first muscular contractions. Due to the physical stress of these initial contractions, dramatic tissue separations occur, which characterize the phenotype of this mutation. The dorsal suture separates with the herniation of midgut and nervous tissue, and the somatic and visceral muscles retract from their sites of attachment. An ultrastructural examination of the development of the muscle attachment sites in these embryos indicates that in 1(1)mys embryos there is a delay in the formation of normal cell-cell attachments. At the muscle-tendon cell junction, the deposition of the apparently normal extracellular matrix of this desmosomal attachment occurs considerably later in development than normal. The 1(1)mys locus apparently makes a product which is either defective, made more slowly, or produced in smaller amounts than normal. The 1(1)mys product is probably necessary for the production of a component of the extracellular matrix of cell-cell attachments.     

Characterization of conditionally expressed mutants affecting age-specific survival in inbred lines of Drosophila melanogaster: lethal conditions and temperature-sensitive periods

The specific genetic basis of inbreeding depression is poorly understood. To address this question, two conditionally expressed lethal effects that were found to cause line-specific life span reductions in two separate inbred lines of Drosophila melanogaster were characterized phenotypically and genetically in terms of whether the accelerated mortality effects are dominant or recessive. The mortality effect in one line (I4) is potentially a temperature-sensitive semilethal that expresses in adult males only and is partially dominant. The other line (I10) responds as one would expect for a recessive lethal. It requires a cold shock for expression and is cold sensitive. Flies exhibiting this lethal condition responded as pupae and freshly eclosed imagoes. The effect is recessive in both males and females. The expression of the lethal effects in both lines is highly dependent upon environmental conditions. These results will serve as a basis for more detailed and mechanistic genetic research on inbreeding depression and are relevant to sex- and environment-specific effects on life span observed in quantitative trait loci studies using inbred lines.     

Reversible alteration in the neuromuscular junctions of Drosophila melanogaster bearing a temperature-sensitive mutation, shibire

In this study we report a relationship between the ultrastruct of the neuromuscular junctions of tibial muscles and the temperature-induced paralysis in shibire flies. There is a decrease in the number of synaptic vesicles of neuromuscular junctions in flies which are held at or above 29 degrees. Shortly after return to 22 degrees C, the synaptic vesicles are again present in large numbers. Prior treatment with tetrodotoxin or barbiturate protects the junctions from the temperature change in morphology.     

The dominant temperature-sensitive lethal DTS7 of Drosophila melanogaster encodes an altered 20S proteasome beta-type subunit.

Proteasomes are multicatalytic complexes that function as the major proteolytic machinery in regulated protein degradation. The eukaryotic 20S proteasome proteolytic core structure comprises 14 different subunits: 7 alpha-type and 7 beta-type. DTS7 is a dominant temperature-sensitive (DTS) lethal mutation at 29 degrees that also acts as a recessive lethal at ambient temperatures. DTS7 maps to cytological position 71AB. Molecular characterization of DTS7 reveals that this is caused by a missense mutation in a beta-type subunit gene, beta2. A previously characterized DTS mutant, l(3)73Ai1, results from a missense mutation in another beta-type subunit gene, beta6. These two mutants share a very similar phenotype, show a strong allele-specific genetic interaction, and are rescued by the same extragenic suppressor, Su(DTS)-1. We propose that these mutants might act as "poison subunits," disrupting proteasome function in a dosage-dependent manner, and suggest how they may interact on the basis of the structure of the yeast 20S proteasome.     

Genetic and enzymatic characterization of a conditional lethal mutant of Escherichia coli K12 with a temperature-sensitive DNA ligase

$\text{TAU}$ts7 an Escherichia coli 15 strain with a thermolabile DNA ligase, has previously been shown to be a temperature-sensitive conditional lethal mutant that is sensitive to methyl methane sulfonate and to ultraviolet irradiation; it also accumulates 10 S DNA fragments to an abnormal extent. When the ligase mutation is transferred to a wild-type E. coli K12 strain, the strain becomes temperature sensitive for growth and displays the same characteristics as $\text{TAU}$ts7. These findings show that a functional DNA ligase is essential for normal DNA replication and repair in E. coli.     

Isolation and characterization of X-linked lethal mutants affecting differentiation of the imaginal discs in Drosophila melanogaster

Summary Twenty-seven late larval or early pupal lethal mutations were isolated for the X-chromosome, some of which showed structural and/or functional deficiencies of the imaginal discs. The mutants were grouped according to the size and morphology of their discs as follows: 1. discs normal: 18 mutants. 2. discs small: 2 mutants. 3. discs degenerate: 4 mutants. 4. discless: 1 mutant. 5. discs heterogeneous: 2 mutants. Preliminary characterization of the mutants included a study of disc morphology, puparium formation and pupal molt, in vivo and in vitro evagination of the imaginal discs, autonomy of the mutation in the disc tissue (differentiation after transplantation and gynander mosaicism test). Possible relations between disc morphology and the former characteristics are discussed.     

Synchronized endocytosis studied in the oocyte of a temperature-sensitive mutant of Drosophila melanogaster

Summary This study demonstrates that endocytosis in the oocyte of Drosophila melanogaster is reversibly blocked at the stage of pit formation by the temperature-sensitive, single-gene mutant, shibire ^ts1. Uptake of horseradish peroxidase conjugated with wheat-germ agglutinin was observed to be normal in mutant oocytes at 19°C, but was blocked at 29°C. After 10 min at 29°C, there was a build-up of coated pits along invaginations of the plasma membrane. Also, the endosomal compartment consisting of tubules, bulbs, and small yolk spheres, disappeared. Lowering the temperature to 19°C after 10 min at 29°C released a synchronized wave of endocytosis into a cytoplasm cleared of uptake-related organelles. By observing this synchronized wave after exposure to 19°C for varying durations, we determined that endocytosis proceeds as follows: coated pits/vesiclestubulessmall yolk spheresmature yolk spheres. The observations suggest that these organelles transform one into another within this sequence.