Binding sites of Drosophila melanogaster sex peptide pheromones

Drosophila melanogaster sex peptide (SP) and Ductus ejaculatorius peptide (DUP99B) are male pheromones transferred in the seminal fluid to the female during copulation. Both reduce sexual receptivity and stimulate oviposition in females. The presence of high-affinity SP and DUP99B binding sites in the female were investigated by incubation of cryostat tissue sections with (125)I-iodinated peptides and subsequent autoradiography. We found that in adult females radiolabeled SP and DUP99B bind to peripheral nerves, the subesophageal ganglion, the cervical connective, to discrete parts of the thoracic ganglion, and to the genital tract. Weak and uniform labeling was detected in the neuropil of the brain and the thoracic ganglion. The labeling pattern in the nervous system suggests binding of the peptides to sensory afferents or glial cells. Scatchard analysis of the binding of (125)I-DUP99B to antennal nerves yielded a dissociation constant K(d) of 6.4 nM. Competition experiments with peptide fragments show that the peptides bind with their homologous C-terminal regions. Binding sites in the nervous system of females are established throughout sexual maturation. Prominent binding of the peptides to afferent nerves suggests modification of sensory input.     

A single mutation alters production and discrimination of Drosophila sex pheromones

The evolution of communication is a fundamental biological problem. The genetic control of the signal and its reception must be tightly coadapted, especially in inter-individual sexual communication. However, there is very little experimental evidence for tight genetic linkage connecting the emission of a signal and its reception. We found that a single genomic transposon inserted in the desatl gene of Drosophila melanogaster simultaneously affected the emission and the perception of sex-specific signals. This mutation greatly decreased the production of unsaturated hydrocarbons on the cuticle of mature flies of both sexes. These substances represent the sex pheromones necessary for mate discrimination: control males could not discriminate the sex of mutant desatl flies. Moreover, mutant males were unable to discriminate the sex pheromones of con-trol flies. Expression of desatl was found in the peripheral tissues that produce and detect sex pheromones.Excision of the transposon rescued both the production and discrimination phenotypes, but the two effects did not always coincide. This indicates that the emission and perception of pheromones are coded by differ-ent products of the same gene, reflecting the pleiotropic activity of desatl .     

A male-specific lethal mutation in Drosophila melanogaster that transforms sex.

Sex-lethal, male-specific allele #1 (Sxl^M#1, 1–19.2) is a dominant, X-linked mutation that is lethal to males. It has no effect in females other than to rescue them from the otherwise lethal maternal effect of the autosomal mutation, daughterless. From a study of the effects of Sxl^M#1 on the development of sexually mosaic flies (gynandromorphs), it was observed that this lethal mutation can cause genetically male (haplo-X) tissue to differentiate as if it were female. With respect to its effect on sexual differentiation, the mutation transformer (tra, 3–45) is epistatic to Sxl^M#1, though the lethal effects of Sxl^M#1 are not modified by tra. In addition to its effect on sexual differentiation, Sxl^M#1 reduces the size of haplo-X imaginal disc and histoblast derivatives in general in a cell autonomous fashion. The viability of gynandromorphs with Sxl^M#1 tissue is very low, and the surviving mosaics have relatively little haplo-X tissue, suggesting that there is no single localized “lethal focus” for this mutation. The relationship between Sxl and daughterless is discussed, as well as the possible involvement of the Sxl locus in X-chromosome dosage compensation.     

Interaction of dopamine, female pheromones, locomotion and sex behavior in Drosophila melanogaster

The regulation of female hydrocarbons and courtship behavior by dopamine and their relationship with locomotion, were investigated in Drosophila melanogaster. Ddc mutants and wild-type female flies treated with tyrosine hydroxylase inhibitors (alpha-methyltyrosine or 3-iodotyrosine) had fewer diene hydrocarbons (female pheromones) and there was a total (Ddc), partial (alpha-methyltyrosine) or no (3-iodotyrosine) rescue of hydrocarbon pattern after dopamine ingestion. There was a correlation between female pheromone level and male courtship intensity for these dopamine-depleted or rescued flies. Female locomotion was decreased in flies treated with tyrosine hydroxylase inhibitors and restored by dopamine, showing that decreased mobility of the female has little importance on male courtship. However, male courtship was inhibited by an increased mobility of dopamine-supplemented females. Tanning, which is altered in dopamine-deficient flies and in tan and ebony mutants, seemed to have no significant influence on female pheromones. Females with increased quantities of dopamine (by ingestion) exhibited larger quantities of pheromones. However, Catsup mutants did not, probably as a result of defects in the epidermis. The Dat mutation, which resulted in more dopamine being produced in the brain, showed no pheromone modification. Together, these data show a complex interaction between dopamine, female hydrocarbons, locomotion and male courtship behavior.     

The effects of spontaneous mutation on competitive fitness in Drosophila melanogaster

Abstract We have analysed the effect of 288 generations of mutation accumulation (MA) on chromosome II competitive fitness in 21 full‐sib lines of Drosophila melanogaster and in a large control population, all derived from the same isogenic base. The rate of mean log‐fitness decline and that of increase of the between‐line variance were consistent with a low rate (λ ≈ 0.03 per gamete and generation), and moderate average fitness effect [E(s) ≈ 0.1] of deleterious mutation. Subsequently, crosses were made between pairs of MA lines, and these were maintained with effective size on the order of a few tens. In these crosses, MA recombinant chromosomes quickly recovered to about the average fitness level of control chromosomes. Thus, deleterious mutations responsible for the fitness decline were efficiently selected against in relatively small populations, confirming that their effects were larger than a few percent.     

Germ-line sex determination in Drosophila melanogaster

In Drosophila melanogaster, the mechanism of sex determination is substantially different in the germ line and in the soma. In the germ line, the process is not completely cell-autonomous, but requires some signals from the soma. Only some of the genes involved in somatic sex determination are also needed for germ cell development. Recent genetic studies have identified loci required for germ-line sex determination.     

Control of female pheromones in Drosophila melanogaster by homeotic genes

We have investigated the role of the Antennapedia and Bithorax complexes (ANT-C and BX-C) on the production of cuticular hydrocarbons in Drosophila melanogaster. In males, there is little, if any, influence of these complexes on the hydrocarbon pattern. In females, there are large and opposite effects of these complexes on diene production: two ANT-C mutations cause an increase in diene production and a reduction of monoenes, whereas most BX-C mutations result in a decrease in dienes and an increase in monoenes, although their sum remains constant. The effect is the highest in Mcp and iab6 females. It is suggested that a factor originating from the prothorax might activate the conversion of monoenes to dienes in females. The abdomen seems to have a crucial role in the production or control of pheromones: abdominal segments four to seven have the main effects, with a most dramatic effect for segments four and five.     

A mutation affecting larval muscle development in Drosophila melanogaster

The phenotypic analysis of a new spontaneous recessive lethal mutation of Drosophila melanogaster is described. The lethal(2)thin mutation maps at 85.6 on chromosome 2 and produces a characteristic long, thin puparium due to an inability to shorten the larval form prior to pupariation. Histological examination of larval muscles and behavioural studies support the hypothesis that the mutation affects the striated structure of the larval muscles in late larval stages. Lethality largely occurs due to an inability to perform the movements necessary for pupation, although there is evidence for larval and possibly embryonic lethal phases.     

Whole-genome effects of ethyl methanesulfonate-induced mutation on nine quantitative traits in outbred Drosophila melanogaster

We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to approximately 100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20 degrees and by 0.04% at 25 degrees, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.     

A mosaic analysis of the apterous mutation in Drosophila melanogaster

An analysis of three phenotypes expressed by the apterous-four (ap⁴) mutant of Drosophila melanogaster has been carried out in $\text{ap}{}^4\text{ap}{}^{\mathrm{+}}$ mosaic adults. The wing and haltere deficiency phenotype was found to be autonomous for entirely mutant structures. However, small patches of mutant anterior and posterior wing margin cells can exist in mosaic wings. Examples of duplicated and triplicated lengths of bristle rows were often found associated with the existing mutant patches. About 20% of the mosaics expressed the phenotype of precocious adult death, dying 30–40 hr after eclosion. The focus for this phenotype was located in the posterior region of the abdomen, and a strong correlation was found between expression of this phenotype and the presence of mutant Malpighian tubules. The focus for juvenile hormone deficiency in ap⁴ adults was located near that for precocious adult death; in fact, the two foci may be identical. It is suggested that defective functioning of ap⁴ adult Malpighian tubules results in abnormal hemolymph leading to early death. Inadequate juvenile hormone secretion could result indirectly from impaired glandular functioning attributable to abnormal adult hemolymph.     

Interactive effects of social environment,age and sex on immune responses in Drosophila melanogaster

Social environments have been shown to have multiple effects on individual immune responses. For example, increased social contact might signal greater infection risk and prompt a prophylactic upregulation of immunity. This differential investment of resources may in part explain why social environments affect ageing and lifespan. Our previous work using Drosophila melanogaster showed that single‐sex social contact reduced lifespan for both sexes. Here, we assess how social interactions (isolation or contact) affect susceptibility to infection, phagocytotic activity and expression of a subset of immune‐ and stress‐related genes in young and old flies of both sexes. Social contact had a neutral, or even improved, effect on post‐infection lifespan in older flies and reduced the expression of stress response genes in females; however, it reduced phagocytotic activity. Overall, the effects of social environment were complex and largely subtle and do not indicate a consistent effect. Together, these findings indicate that social contact in D. melanogaster does not have a predictable impact on immune responses and does not simply trade‐off immune investment with lifespan.     

Developmental effects of monensin on Drosophila melanogaster

Extracellular matrix and membrane proteins and their correct secretion probably are key elements in morphogenesis and differentiation in Drosophila. In this study, we have analysed the effects of monensin, a Na⁺-H⁺-ionophore which blocks normal secretion, applied during cellular blastoderm formation on further development. Normal cell morphology and intercellular contacts are lost and the extracellular matrix becomes disorganized. Gastrulation is blocked and abnormal foldings can be observed. Cuticle phenotypes showed different degrees of ventral, dorsal, head and posterior defects. The results are discussed in the context of what is known about membrane and extracellular matrix proteins in Drosophila.     

Hypoxia induces major effects on cell cycle kinetics and protein expression in Drosophila melanogaster embryos

Hypoxia induces a stereotypic response in Drosophila melanogaster embryos: depending on the time of hypoxia, embryos arrest cell cycle activity either at metaphase or just before S phase. To understand the mechanisms underlying hypoxia-induced arrest, two kinds of experiments were conducted. First, embryos carrying a kinesin-green fluorescent protein construct, which permits in vivo confocal microscopic visualization of the cell cycle, showed a dose-response relation between O2 level and cell cycle length. For example, mild hypoxia (Po2 approximately 55 Torr) had no apparent effect on cell cycle length, whereas severe hypoxia (Po2 approximately 25-35 Torr) or anoxia (Po2 = 0 Torr) arrested the cell cycle. Second, we utilized Drosophila embryos carrying a heat shock promoter driving the string (cdc25) gene (HS-STG3), which permits synchronization of embryos before the start of mitosis. Under conditions of anoxia, we induced a stabilization or an increase in the expression of several G1/S (e.g., dE2F1, RBF2) and G2/M (e.g., cyclin A, cyclin B, dWee1) proteins. This study suggests that, in fruit fly embryos, 1) there is a dose-dependent relationship between cell cycle length and O2 levels in fruit fly embryos, and 2) stabilized cyclin A and E2F1 are likely to be the mediators of hypoxia-induced arrest at metaphase and pre-S phase.     

Consistent effects of a major QTL for thermal resistance in field-released Drosophila melanogaster

Molecular genetic markers can be used to identify quantitative trait loci (QTL) for thermal resistance and this has allowed characterization of a major QTL for knockdown resistance to high temperature in Drosophila melanogaster. The QTL showed trade-off associations with cold resistance under laboratory conditions. However, assays of thermal tolerance conducted in the laboratory may not necessarily reflect performance at varying temperatures in the field. Here we tested if lines with different genotypes in this QTL show different thermal performance under high and low temperatures in the field using a release recapture assay. We found that lines carrying the QTL genotype for high thermal tolerance were significantly better at locating resources in the field releases under hot temperatures while the QTL line carrying the contrasting genotype were superior at cold temperatures. Further, we studied copulatory success between the different QTL genotypes at different temperatures. We found higher copulatory success in males of the high tolerance QTL genotype under hot temperature conditions, while there was no difference in females at cold temperatures. The results allow relating components of field fitness at different environmental temperatures with genotypic variation in a QTL for thermal tolerance.     

Estimation of microsatellite mutation rates in Drosophila melanogaster

Microsatellite mutations were studied in a set of 175 mutation accumulation lines, all of them independently derived from a completely homozygous population of Drosophila melanogaster and maintained under strong inbreeding during 80 generations. We assayed 28 microsatellites and detected two mutations. One mutation consisted of a single addition of a dinucleotide repeat and the other was a deletion of five trinucleotide repeats. The average mutation rate was 5.1 x 10(-6), in full agreement with previous estimates from two different sets of mutation accumulation lines.