Rudimentary mutants ofDrosophila melanogaster

Summary 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 eitherr ¹ orr ³⁶. 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.Ther ¹ cell lines were found to express 3–7%dihydroorotase (DHOase) activity as compared to a wildtype cell line. Reducedaspartate transcarbamylase (ATCase) activity was measured in somer ¹ cell lines whereas wildtypecarbamylphosphate synthetase (CPSase) activity is expressed in allr ¹ cell lines. Ther ³⁶ cell 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 ther ¹ cells is restored by the supplementation of the minimal medium withdihydroorotate whereas proliferation of ther ³⁶ cells is restored by supplementation with eitherdihydroorotate orcarbamylaspartate.The results demonstrate that therudimentary phenotypesr ¹ andr ³⁶ are expressed at the cellular level and that the two mutant cell types behave as cellular pyrimidine auxotrophs in vitro.     

Genetic differentiation ofDrosophila melanogaster populations as assessed by two-dimensional electrophoresis

Seven populations ofDrosophila melanogaster, representing a worldwide distribution, were compared using two-dimensional protein gel electrophoresis. A total of 611 protein spots was scored, which probably represent a sample of over 500 loci that were surveyed. Of the protein spots scored, 521 spots were found to be invariant, but another 90 spots were found to be variable among the populations. Of these variable protein spots, 12 were found to be present in only one population. All the populations, except one, had at least one protein spot restricted to itself. However, the Japanese population had by far the most, with five protein spots restricted to this one population, which has been observed in previous studies of private alleles in oriental populations. The mean genetic similarity (F) found among the seven populations was 0.965, with a range of between 0.956 and 0.977. This is similar to previous reports of lower variation found in population genetic surveys using two-dimensional electrophoresis. It was found that the historical relationships among these populations was somewhat congruent with the geographic distribution of the populations, but as in previous studies, it was not exactly coincident.     

Genetic analysis of pattern-formation in the embryo ofDrosophila melanogaster

Summary The mutationbicaudal (Bull, 1966) causes embryos to develop a longitudinal mirror image duplication of the posteriormost abdominal segments, while head and thorax are missing. These embryos occur with varying frequencies among eggs laid by mutant females, irrespective of the paternal genotype. Recombination and deletion mapping indicate thatbicaudal (bic) is a recessive, hypomorphic, maternal-effect mutation mapping at a single locus on the second chromosome ofDrosophila melanogaster close tovg (67.0±0.1). The frequency of bicaudal embryos depends on the age of the mother, her genetic constitution and the temperature at which she is raised. Best producers are very young females hemizygous forbic (bic/Df(2)vg ^B ) at 28° C. Under these conditions 80% to 90% of the eggs which differentiate can show the bicaudal embryo phenotype. Upon ageing of the mother the frequency of bicaudal embryos declines rapidly, and most of the eggs develop the normal body pattern. Temperature shift experiments suggest a temperature-sensitive period at the onset of vitellogenesis.The mutation causes several types of abnormalities in the segment pattern of theDrosophila embryo, which are interpreted as various degrees of expression of the mutant character. The most frequent abnormal phenotype is the symmetrical bicaudal embryo with one to five abdominal segments duplicated. Less frequent are asymmetrical types, in which the smaller number of segments is always in the anterior reversed part. Other phenotypes are embryos with missing or rudimentary heads, and embryos with irregular gaps in the segment pattern. In bicaudal embryos, the pole cells, formed at the posterior pole of the egg prior to blastoderm formation, are not duplicated at the anterior. The significance of thebicaudal phenotypes for embryonic pattern-formation inDrosophila is discussed.     

Detection of clones in the nervous system ofDrosophila melanogaster

Summary Mitotic recombination was induced, by X-irradiation at the blastoderm stage, in flies heterozygous for one of the temperature-sensitive paralytic mutationsshibire andtp-2. The results show that these mutations can be used to detect the presence of clones in the central nervous system through the temperature-sensitive paralysis of individual legs. Mitotic recombination can also be used to examine the effects of these mutations in the peripheral nervous system; shibire is thus shown to affect the function of sensory neurons.     

Genetic regulation of theAchaete-scute complex ofDrosophila melanogaster

Summary Mutants in two loci,hairy (h ⁺) andextramacrochaetae (emc ⁺), produce phenotypes corresponding to an excess of function of theachaete-scute complex (AS-C), that is, they cause the appearance of extra chaetae. These mutants, although recessive in normal flies, become dominant in the presence of extra doses of AS-C. Here we study the interactions between these three genes, in an attempt to elucidate their relationships. The results show that the insufficiency produced byh oremc mutants can be titrated by altering the number of copies of AS-C. Moreover, excess of function of AS-C produced by derepression mutants within the complex (Hairy-wing) can also be titrated by altering the number of wild type copies of⁺ oremc ⁺. These specific interactions indicate that bothh ⁺ andemc ⁺ code for repressors of AS-C that interact with theachaete andscute region of the complex respectively.     

Recent origin for a thermostable alcohol dehydrogenase allele ofDrosophila melanogaster

Summary The nucleotide sequence of theFast-Chateau Douglas isolate of the thermostable alcohol dehydrogenase allele is compared with the sequences of theSlow andFast alleles ofDrosophila melanogaster. Conceptual translation of theFChD sequence indicates that the thermostable polypeptide has the diagnostic FAST amino acid replacement at residue 192 and an additional replacement of serine for proline at residue 214. This suggests aFast origin for the thermostableAdh allele. However, some of the biochemical properties of the FCHD protein resemble those of the SLOW rather than the FAST polypeptides. The serine for proline replacement confers upon the thermostable polypeptide substrate specificities and some kinetic parameters similar to the SLOW protein. The same replacement substitution within the third coding exon also appears to alter the ADH protein concentration to a level similar to the SLOW polypeptide and the probable effect is at the level of mRNA concentration. The low level of nucleotide sequence variation, other than that leading to the amino acid substitution, suggests a recent origin for the thermostable allele. The time since divergence of theFChD sequence fromFast is estimated to be approximately 260,000–470,000 years.     

Effects of mutations at thestambh A locus ofDrosophila melanogaster

We report novel findings on the cytogenetic location, functional complexity and maternal and germline roles of thestambh A locus ofDrosophila melanogaster. stmA is localized to polytene bands 44D1.2 on 2R.stmA mutations are of two types: temperature-sensitive (ts) adult and larval paralytic or unconditional embryonic or larval lethal. Twelve alleles reported in this study fall into two intragenic complementing groups suggesting thatstmA is a complex locus with more than one functional domain. Some unconditional embryonic lethal alleles show a ‘neurogenic’ phenotype of cuticle loss accompanied by neural hypertrophy. It is shown that embryos of ts paralytic alleles also show mild neural hypertrophy at permissive temperatures while short exposure to heat induces severe cuticle loss in these embryos.stmA exerts a maternal influence over heat-induced cuticle loss. Unconditional embryonic lethal alleles ofstmA are also germline lethal.     

Cell lines from imaginal discs ofDrosophila melanogaster

Summary New cell lines, designated as ML-DmDl≈10, were established from dissociated imaginal discs ofDrosophila melanogaster. The culture medium was prepared by mixing in a 1:1 ratio Cross and Sang’s M3(BF) medium, supplemented with 10% heat inactivated fetal bovine serum (FBS), with the supernatant of a primary embryonic cell culture made in the M3(BF) medium and supplementing this mixture with insulin. One cell line was established in the medium containing larval hemolymph instead of the primary culture supernatan, and another was established in fresh M3(BF) medium supplemented with insulin and FBS. In these mediums, imaginal disc cells first formed aggregates and cellular vesicles within a few weeks followed by the proliferation of thin-layered cells around them after about 1 mo. Ten cell lines have so far been established from two kinds of imaginal discs and disc mixtures. The ploidy of these cell lines was predominantly diploid. Population doubling time was about 50 to 70 h at 3 to 10 mo. after initiation of the culture. When the cell aggregates formed in vitro were implanted in metamorphosing larvae, they differentiated at high frequency into adult cuticular strutures in the early phase of the primary culture. This differentiation of aggregates was also observed, though at low frequency, in a culture maintained by dilution-transfer for 6 to 15 mo. in vitro.     

Hybrid dysgenesis in natural populations ofDrosophila melanogaster in Japan

The P-M system of hybrid dysgenesis inDrosophila melanogaster was investigated on the basis of gonadal dysgenesis, using 1,590 strains from 28 natural populations in Japan, and 20 populations from Southeast Asia, the Pacific area and Africa. Strong P strains were found sporadically in several populations in Japan. Few strong M strains were observed. Q strains were present at a high frequency in most populations. Thus, most populations in these areas were regarded as Q populations. The distribution of the P element and the evolution of P, Q and M populations are also discussed.     

Biological and Behavioral Effects of Heavy Metals in Drosophila melanogaster Adults and Larvae

Heavy metals are essential components of biological systems but are extremely toxic at high doses. As a result, we hypothesized that perception of heavy metals through gustation may exist in Drosophila melanogaster. In this study, we investigated the behavioral effects of iron, copper, zinc, and cadmium on D. melanogaster gustation, oviposition, and pupation-site selection. In addition, we examined the biological effects of heavy metals on the fruit fly survival and reproductive success. Our results illustrate that D. melanogaster responds behaviorally to the presence of high concentrations of heavy metals in food. All metals acted as repellents to the fruit flies at high doses, with the egg-laying and feeding of the female flies significantly decreasing. Furthermore, supplementation of heavy metals in the culture medium reduced survival to the adult stage and shortened the life span of adult flies. From these observations, we speculate that D. melanogaster avoidance behavior towards high concentrations of heavy metals may have a positive effect on their survival and reproductive success in nature, particularly in the presence of metal-contaminated food sources.     

Complete replication of DNA in polytene nuclei of salivary glands ofDrosophila melanogaster

Summary Combined cytophotometric and autoradiographic experiments are performed on individual polytene salivary gland nuclei of X/X-female and X/Y-male larvae ofDrosophila melanogaster, DNA measurements of unlabeled nuclei reveal complete douplings of all 4C DNA quantity during polytenization. These new data do not agree with the hypothesis of heterochromatic underreplication.     

Differing amounts of genetic polymorphism in testes and male accessory glands ofDrosophila melanogaster andDrosophila simulans

We surveyed genetic polymorphism by two-dimensional gel electrophoresis of male reproductive tract proteins in 20 isofemale lines each ofDrosophila melanogaster andDrosophila simulans. After classifying 244 such proteins ofDrosophila melanogaster and 271 ofDrosophila simulans by their distribution between testes and accessory glands within the reproductive tract, significant correlations were found between genetic polymorphism and tissue distribution. In both species, gland-specific proteins were significantly more polymorphic than testis-specific proteins, as well as those found in both testes and glands. Simultaneously, inDrosophila simulans, proteins found in roughly equivalent relative abundance in both testes and glands were significantly less variable than gland-specific and testis-specific proteins, as well as those with a quantitative difference in relative abundance between testes and glands. These correlations may reflect general differences in variability between extracellular and intracellular proteins and between proteins with broad as opposed to tissue-specific distributions.We thank the Natural Sciences and Engineering Research Council of Canada for financial support (Grant A0235 to R.S.S.).     

Molecular characteristics of the heterochromatic I elements from a reactive strain ofDrosophila melanogaster

Summary There are two categories of strains inDrosophila melanogaster with respect to the I-R system of hybrid dysgenesis. The inducer strains contain particular transposable elements named I factors. They are not present in the strains of the other category called reactive (R) strains. Defective I elements are present in the pericentromeric regions of both categories of strains. This last subfamily of I sequences has not yet been described in detail and little is known about its origin. In this paper, we report that the defective I elements display an average of 94% of sequence identity with each other and with the transposable I factor. The results suggest that they cannot be the progenitors of the present day I factors, but that each of these two subfamilies started to evolve independently several million years ago. Furthermore, the sequence comparison of these I elements with an active I factor fromDrosophila teissieri provides useful information about when the deleted I elements became immobilized.     

Distribution of polymorphic gene duplication at theGpdh locus in natural populations ofDrosophila melanogaster

Summary The glycerol-3-phosphate dehydrogenase (GPDH, E. C. 1.1.1.8) gene ofDrosophila melanogaster contains a tandem duplication of a 4.5-kb-long DNA fragment. Survey of theGpdh gene region by the Southern blot analysis revealed the following features of this gene duplication: (1) The duplication was not observed in chromosome lines that carryIn(2L)t, a cosmopolitan chromosomal inversion in this species. The duplication and the inversion are in linkage disequilibrium. (2) The duplication is polymorphic in the Japan and US natural populations examined. Its frequency is 0.26 on an average inIn(2L)t-free chromosomes. (3) Triplication is absent or has not become frequent in the populations surveyed. Possible evolutionary factors of this duplication polymorphism are discussed.     

The effect of fat body on the differentiation in vitro of wing imaginal discs ofDrosophila melanogaster

Summary The effect of suboptimal levels of -ecdysone on the differentiation in vitro ofDrosophila melanogaster wing discs was enhanced by the addition of larval fat body to the cultures. However, similar experiments with -ecdysome showed no enhancement. It is suggested that a partial conversion of -ecdysone to -ecdysone by the fat body may well account for these results.     

Patterns of protein synthesis in salivary glands ofDrosophila melanogaster during larval and prepupal development

Summary Patterns of protein synthesis in the salivary glands ofDrosophila melanogaster have been studied throughout late larval and prepupal development by pulse labelling the tissues with³⁵S-methionine. Specific changes to the pattern of proteins synthesized during development are found and the significance of these changes is discussed in view of the known changes in gene (puffing) activity which occur at the same times. We review the problem of salivary gland function in prepupalDrosophila.     

A cluster of esterase genes on chromosome 3R ofDrosophila melanogaster includes homologues of esterase genes conferring insecticide resistance inLucilia cuprina

We identify an esterase isozyme inDrosophila melanogaster, EST 23, which shares biochemical, physiological, and genetic properties with esterase E3, which is involved in resistance to organophosphate insecticides inLucilia cuprina. Like E3, theD. melanogaster EST 23 is a membrane-bound -esterase which migrates slowly toward the anode at pH 6.8. Both enzymes have similar preferences for substrates with shorter acid side chain lengths. Furthermore, on the basis of their high sensitivity to inhibition by paraoxon and their insensitivity to inhibition by eserine sulfate, both enzymes were classified as subclass I carboxylesterases. The activity of each enzyme peaks early in development and, again, in the adult stage. Both enzymes are found in the male reproductive system and larval and adult digestive tissues, the latter being consistent with a role for these enzymes in organophosphate resistance. Fine structure deficiency mapping localizedEst 23 to cytological region 84D3 to E1-2 on the right arm of chromosome 3. Moreover, we show that the genes encoding three other esterase phenotypes also map to the same region; these phenotypes involve allozymic differences in EST 9 (formerly EST C), ali-esterase activity, defined by the hydrolysis of methyl butyrate, and malathion carboxylesterase activity, defined by hydrolysis of the organophosphate malathion. This cluster corresponds closely to that encompassing E3 and malathion carboxylesterase on chromosome 4 inL. cuprina, the homologue of chromosome 3R inD. melanogaster.     

Oviposition preference for novel versus normal food resources in laboratory populations ofDrosophila melanogaster

Female fecundity, oviposition preference and specificity on one normal and two novel food media were assayed on four laboratory populations ofDrosophila melanogaster, revealing considerable among- and within-population variation in oviposition preference. Overall, there was a significant tendency of females to prefer novel media to their normal banana food as an oviposition substrate. Specificity in the populations was fairly high, implying that a large proportion of females tended to lay the majority of their eggs on the preferred medium. The results showed that oviposition preference for a given food medium could be affected by the alternative provided, and that, consequently, oviposition preference for a given food medium versus another cannot be predicted based upon a knowledge of what the preference for each of the two media was versus a common third medium. Specificity, on the other hand, was not significantly affected by the type of alternative food media provided in a given trial. Moreover, comparison of results from fecundity and oviposition preference assays also showed that the egg laying behaviour ofDrosophila females in response to different food media may be different in choice versus no-choice situations. Thus, a substrate on which fecundity is higher than on another, when assayed in a no-choice situation, may not be preferred over the other substrate when a choice between the two is provided to the ovipositing females. The latter two results point to possible complexity in the responses of females to various oviposition substrates based upon the overall setting of the assay, including the alternative substrates present for egg laying.     

Geographical variation in encapsulation ability ofDrosophila melanogaster larvae and evidence for parasitoid-specific components

Summary The ability ofDrosophila melanogaster larvae in Europe to encapsulate the eggs of their most important parasitoids,Asobara tabida andLeptopilina boulardi, shows a large amount of geographical variation. Interestingly, encapsulation ability againstA. tabida is not correlated with encapsulation ability againstL. boulardi. This indicates that the encapsulation system ofD. melanogaster larvae has parasitoid-specific components. The variation in encapsulation ability can only partly be explained by the incidence of parasitism on the larvae. This means that factors other than the two parasitoid species must be selection pressures on the encapsulation ability ofD. melanogaster larvae.