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PubMed1963

Chromosomal differentiations of the lampbrush type formed by the Y chromosome in Drosophila hydei and Drosophila neohydei.

The nuclei of growing spermatocytes in Drosophila hydei and D. neohydei are characterized by the appearance of phase-specific, paired, loop-shaped structures thought to be similar to the loops in lampbrush chromosomes of amphibian oocytes. In X/O-males of D. hydei spermatogenesis is completely blocked before the first maturation division. No spermatozoa are formed in such testes. In the nuclei of X/O-spermatocytes, paired loop formations are absent. This shows the dependence of these chromosomal functional structures upon the Y chromosome. The basis of this dependence could be shown through an investigation of males with two Y chromosomes. All loop pairs are present in duplicate in XYY males. This proves that the intranuclear formations are structural modifications of the Y chromosome itself. These functional structures are species-specific and characteristically different in Drosophila hydei and D. neohydei. Reciprocal species crosses and a backcross showed that the spermatocyte nuclei of all hybrid males possess the functional structures corresponding to the species which donated the Y chromosome. This shows that the morphological character of the functional structures is also determined by the Y chromosome.

Animals↗
PubMed1988

The rosy region of Drosophila melanogaster and Drosophila simulans. I. Contrasting levels of naturally occurring DNA restriction map variation and divergence.

A 40-kb region around the rosy and snake loci was analyzed for restriction map variation among 60 lines of Drosophila melanogaster and 30 lines of Drosophila simulans collected together at a single locality in Raleigh, North Carolina. DNA sequence variation in D. simulans was estimated to be 6.3 times greater than in D. melanogaster (heterozygosities per nucleotide of 1.9% vs. 0.3%). This result stands in marked contrast to results of studies of phenotypic variation including proteins (allozymes), morphology and chromosome arrangements which are generally less variable and less geographically differentiated in D. simulans. Intraspecific polymorphism is not distributed uniformly over the 40-kb region. The level of heterozygosity per nucleotide varies more than 12-fold across the region in D. simulans, being highest over the hsc2 gene. Similar, though less extreme, variation in heterozygosity is also observed in D. melanogaster. Average interspecific divergence (corrected for intraspecific polymorphism) averaged 3.8%. The pattern of interspecific divergence over the 40-kb region shows some disparities with the spatial distribution of intraspecific variation, but is generally consistent with selective neutrality predictions: the most polymorphic regions within species are generally the most divergent between species. Sequence-length polymorphism is observed for D. melanogaster to be at levels comparable to other gene regions in this species. In contrast, no sequence length variation was observed among D. simulans chromosomes (limit of resolution approximately 100 bp). These data indicate that transposable elements play at best a minor role in the generation of naturally occurring genetic variation in D. simulans compared to D. melanogaster. We hypothesize that differences in species effective population size are the major determinant of the contrasting levels and patterns of DNA sequence and insertion/deletion variation that we report here and the patterns of allozyme and morphological variation and differentiation reported by other workers for these two species.

Animals↗
PubMed1989

In situ hybridization analysis of chromosomal homologies in Drosophila melanogaster and Drosophila virilis.

Twenty-four biotin-labeled recombinant-DNA probes which contained putative unique-sequence Drosophila melanogaster DNA were hybridized to larval salivary-gland chromosomes of D. melanogaster and Drosophila virilis. All probes hybridized to D. melanogaster chromosomes at the expected sites. However, one probe hybridized to at least 16 additional sites, and one hybridized to one additional site. Thirteen probes hybridized strongly to D. virilis chromosomes, four hybridized weakly and infrequently, and seven did not hybridize. Probes representing two multigene families (beta-tubulin and yolk-protein) hybridized as would be expected if all sites had been conserved in the two species on the same chromosomal elements. The multiple hybridization sites of a third probe which may represent a multigene family were also conserved. The results were consistent with H.J. Muller's proposal that chromosomal elements have been conserved during evolution of this genus.

Animals↗
PubMed1992

Intraspecific and interspecific variation at the y-ac-sc region of Drosophila simulans and Drosophila melanogaster.

A 2.2-kb region including the ac gene of Drosophila simulans has been sequenced. Interspecific divergence between Drosophila melanogaster and D. simulans was estimated as 0.0695 and 0.0558 for silent and for all sites, respectively. Estimated silent site divergence for the ac region is comparable to that estimated for other regions of the genome between these species, indicating that silent sites of the ac region are not under significantly stronger functional constraint. Intraspecific variation in both species was also investigated. Restriction-site and length polymorphism in the ac region of D. simulans has been investigated for 103 X chromosome lines sampled from three natural populations in Spain using eight four-cutter restriction enzymes. Neither restriction-site nor length variation was detected in the three populations surveyed. In D. melanogaster restriction-site and length polymorphism in all major transcription units of the y-ac-sc region (23.1-kb region) has been studied using four four-cutter restriction enzymes for 245 X chromosome lines sampled from 10 natural populations (seven from Europe, two from North America and one from Japan). Fourteen restriction-site and 28 length polymorphisms were detected. There was some indication of population subdivision for North American vs. European samples of D. melanogaster. The frequency spectrum of restriction-site polymorphisms in European populations was skewed toward rarer frequencies than predicted by the neutral theory. Comparison of silent site variation at this telomeric region with that in the Adh 5'-flanking region showed a reduced level of heterozygosity in the y-ac-sc region. Since interspecific silent divergence is not reduced in the y-ac-sc region as compared to other regions, the reduction in standing levels of variation at this telomeric locus in both D. simulans and D. melanogaster is most easily explained by a hitchhiking effect of linked selected substitutions.

Amino Acid Sequence↗
PubMed1992

A comprehensive study of genic variation in natural populations of Drosophila melanogaster. VI. Patterns and processes of genic divergence between D. melanogaster and its sibling species, Drosophila simulans.

We present here an extensive set of data on allelic differences between homologous proteins of Drosophila melanogaster and its sibling species, Drosophila simulans, obtained by nondenaturing one-dimensional, and denaturing two-dimensional gel electrophoresis. The data suggest that, for these two species, (1) approximately 10% of protein-coding loci have no alleles in common in our sample, (2) the extent of genic variation at a locus (mean heterozygosity) within a species is not correlated with the extent of divergence (Nei's genetic distance) at that locus between species, and (3) significant heterogeneity of divergence rates exists for different structural/functional classes of loci. These results are discussed in the context of the dynamics of genetic variation within and between species.

Alleles↗
PubMed1996

Regulation of the gene Sex-lethal: a comparative analysis of Drosophila melanogaster and Drosophila subobscura.

The Drosophila gene Sex-lethal (Sxl) controls the processes of sex determination and dosage compensation. A Drosophila subobscura genomic fragment containing all the exons and the late and early promotors in the Sxl gene of D. melanogaster was isolated. Early Sxl expression in D. subobscura seems to be controlled at the transcriptional level, possibly by the X:A signal. In the region upstream of the early Sxl transcription initiation site are two conserved regions suggested to be involved in the early activation of Sxl. Late Sxl expression in D. subobscura produces four transcripts in adult females and males. In males, the transcripts have an additional exon which contains three translational stop codons so that a truncated, presumably nonfunctional Sxl protein is produced. The Sxl pre-mRNA of D. subobscura lacks the poly-U sequence presented at the polypirimidine tract of the 3' splice site of the male-specific exon present in D. melanogaster. Introns 2 and 3 contain the Sxl-binding poly-U stretches, whose localization in intron 2 varies but in intron 3 is conserved. The Sxl protein is fully conserved at the amino acid level in both species.

Amino Acid Sequence↗
PubMed1997

Dominant mutations of Drosophila MAP kinase kinase and their activities in Drosophila and yeast MAP kinase cascades.

Eight alleles of Dsor1 encoding a Drosophila homologue of mitogen-activated protein (MAP) kinase kinase were obtained as dominant suppressors of the MAP kinase kinase kinase D raf. These Dsor1 alleles themselves showed no obvious phenotypic consequences nor any effect on the viability of the flies, although they were highly sensitive to upstream signals and strongly interacted with gain-of-function mutations of upstream factors. They suppressed mutations for receptor tyrosine kinases (RTKs); torso (tor), sevenless (sev) and to a lesser extent Drosophila EGF receptor (DER). Furthermore, the Dsor1 alleles showed no significant interaction with gain-of-function mutations of DER. The observed difference in activity of the Dsor1 alleles among the RTK pathways suggests Dsor1 is one of the components of the pathway that regulates signal specificity. Expression of Dsor1 in budding yeast demonstrated that Dsor1 can activate yeast MAP kinase homologues if a proper activator of Dsor1 is coexpressed. Nucleotide sequencing of the Dsor1 mutant genes revealed that most of the mutations are associated with amino acid changes at highly conserved residues in the kinase domain. The results suggest that they function as suppressors due to increased reactivity to upstream factors.

Alleles↗
PubMedDate not supplied

Evolutionary rearrangement of the amylase genomic regions between Drosophila melanogaster and Drosophila pseudoobscura.

Two Drosophila pseudoobscura genomic clones have sequence similarity to the Drosophila melanogaster amylase region that maps to the 53CD region on the D. melanogaster cytogenetic map. The two clones with similarity to amylase map to sections 73A and 78C of the D. pseudoobscura third chromosome cytogenetic map. The complete sequences of both the 73A and 78C regions were compared to the D. melanogaster genome to determine if the coding region for amylase is present in both regions and to determine the evolutionary mechanism responsible for the observed distribution of the amylase gene or genes. The D. pseudoobscura 73A and 78C linkage groups are conserved with the D. melanogaster 41E and 53CD regions, respectively. The amylase gene, however, has not maintained its conserved linkage between the two species. These data indicate that amylase has moved via a transposition event in the D. melanogaster or D. pseudoobscura lineage. The predicted genes within the 73A and 78C regions show patterns of molecular evolution in synonymous and nonsynonymous sites that are consistent with previous studies of these two species.

Amylases↗
PubMed1987

Heat shock loci 93D of Drosophila melanogaster and 48B of Drosophila hydei exhibit a common structural and transcriptional pattern.

A comparison of gene structure, sequence, and transcription pattern of heat shock loci 93D of Drosophila melanogaster and 48B of Drosophila hydei has been performed. Both heat shock loci consist of an unique region that is flanked by an internally repetitive element. Different members of these elements are highly conserved, repeat unit length, however, and primary sequence diverged totally. Whereas the overall gene structure in both species is substantially related, sequence conservation is only observed at very few sites in the unique region. These represent primarily sequences that are identified as regulatory elements for faithful transcription and processing. The number and size of transcripts obtained from heat shock locus 48B in third instar larvae closely resembles the pattern of heat shock locus 93D. Thus their quite alike structure and transcription pattern suggest strongly a conserved hitherto unknown function.

Animals↗
PubMed1997

The evolution of small gene clusters: evidence for an independent origin of the maltase gene cluster in Drosophila virilis and Drosophila melanogaster.

We analyzed a 5,770-bp genomic region of Drosophila virilis that contains a cluster of two maltase genes showing sequence similarity with genes in a cluster of three maltase genes previously identified in Drosophila melanogaster. The D. virilis maltase genes are designated Mav1 and Mav2. In addition to being different in gene number, the cluster of genes in D. virilis differs dramatically in intron-exon structure from the maltase genes in D. melanogaster, the transcriptional orientation of the genes in the cluster also differs between the species. Our findings support a model in which the maltase gene cluster in D. virilis and D. melanogaster evolved independently. Furthermore, while in D. melanogaster the maltase gene cluster lies only 10 kb distant from the larval cuticle gene cluster, the maltase and larval cuticle gene clusters in D. virilis are located very far apart and on a different chromosome than that expected from the known chromosome arm homologies between D. virilis and D. melanogaster. A region of the genome containing the maltase and larval cuticle gene clusters appears to have been relocated between nonhomologous chromosomes.

Aedes↗
PubMed1998

Microsatellite variation in Drosophila melanogaster and Drosophila simulans: a reciprocal test of the ascertainment bias hypothesis.

Interspecific comparisons of microsatellite loci have repeatedly shown that the loci are longer and more variable in the species from which they are derived (the focal species) than are homologous loci in other (nonfocal) species. There is debate as to whether this is due to directional evolution or to an ascertainment bias during the cloning and locus selection processes. This study tests these hypotheses by performing a reciprocal study. Eighteen perfect dinucleotide microsatellite loci identified from a Drosophila simulans library screen and 18 previously identified in an identical Drosophila melanogaster library screen were used to survey natural populations of each species. No difference between focal and nonfocal species was observed for mean PCR fragment length. However, heterozygosity and number of alleles were significantly higher in the focal species than in the nonfocal species. The most common allele in the Zimbabwe population of both species was sequenced for 31 of the 36 loci. The length of the longest stretch of perfect repeat units is, on average, longer in the focal species than in the non-focal species. There is a positive correlation between the length of the longest stretch of perfect repeats and heterozygosity. The difference in heterozygosity can thus be explained by a reduction in the length of the longest stretch of perfect repeats in the nonfocal species. Furthermore, flanking-sequence length difference was noted between the two species at 58% of the loci sequenced. These data do not support the predictions of the directional-evolution hypothesis; however, consistent with the ascertainment bias hypothesis, the lower variability in nonfocal species is an artifact of the microsatellite cloning and isolation process. Our results also suggest that the magnitude of ascertainment bias for repeat unit length is a function of the microsatellite size distribution in the genomes of different species.

Animals↗
PubMed2002

Variable modes of inheritance of morphometrical traits in hybrids between Drosophila melanogaster and Drosophila simulans.

We investigated body-size inheritance in interspecific sterile hybrids by crossing a Drosophila simulans strain with 13 strains of Drosophila melanogaster, which were of various origins and chosen for their broad range of genetic variation. A highly significant parent-offspring correlation was observed, showing that the D. melanogaster genes for size are still expressed in a hybrid background. Superimposed on to this additive inheritance, the size of hybrids was always less than the mid-parent value. This phenomenon, which at first sight might be described as dominance or overdominance, is more precisely interpreted as a consequence of a hybrid breakdown, that is, a dysfunction of the parental genes for size when put to work together. This interpretation is enforced by the fact that phenotypic variability was much more prevalent in hybrids than in parents. We also analysed body pigmentation inheritance in the same crosses and got a very different picture. There was no increase in the phenotypic variance of F(1) hybrids and only a low parent-offspring correlation. Apparent overdominance could be observed but in opposite directions, with no evidence of hybrid breakdown. Our data point to the possibility of analysing a diversity of quantitative traits in interspecific hybrids, and indicate that breakdown might be restricted to some traits only.

Animals↗
PubMed1985

Regulated expression of a Drosophila melanogaster heat shock locus after stable integration in a Drosophila hydei cell line.

DNA-mediated cotransformation has been used to transfer a Drosophila melanogaster heat shock locus into cultured Drosophila hydei cells by use of the copia-based selectable vector pCV2gpt and of pMH10A, a cloned 87A7 heat shock locus encoding a mutant heat shock protein (hsp). Transformed lines contain between 50 and 200 copies of both plasmids, each separately organized as a head-to-tail concatemer which is stably maintained in the transformed lines. Exposure of the cotransformants to heat shock temperatures induces the regulated expression of the hsp RNA and the mutant hsp in all the lines analyzed.

Animals↗
PubMed1994

Tiggrin, a novel Drosophila extracellular matrix protein that functions as a ligand for Drosophila alpha PS2 beta PS integrins.

Genetic and other studies of Drosophila integrins have implicated these extracellular matrix receptors in various morphogenetic events, but identification of their endogenous ligands has been elusive. We report the biochemical purification and cloning of tiggrin, a novel extracellular matrix protein from Drosophila. This 255 x 10(3) M(r) polypeptide contains the potential integrin recognition sequence Arg-Gly-Asp (RGD) and 16 repeats of a novel 73-77 amino acid motif. The tiggrin gene is at chromosome locus 26D1-2 and is expressed by embryonic hemocytes and fat body cells. Tiggrin protein is detected in matrices, especially at muscle attachment sites that also strongly express integrins. Tiggrin-coated surfaces support primary embryo cell culture and provide excellent substrates for alpha PS2 beta PS integrin-mediated cell spreading. Soluble RGD-peptides inhibit this cell spreading.

Amino Acid Sequence↗
PubMed1975

[Study of the vertical transmission and horizontal transmission of "Drosophila melanogaster" and "Drosophila immigrans" picornavirus (author's transl)].

The contamination of drosophila eggs, of larvae of the 3 instars and of adults, was studied using several strains of P and C viruses of D. melanogaster and of iota virus of D. immigrans. The infected adults contaminated other flies if they were rich in viral particles and if the contact was long enough. Infection of the adults occurred in the presence of concentrated viral suspensions. The larvae were easily infected when they grew in contaminated media; the more sensitive stage was the first instar. Transovarian transmission was observed only in naturally infected flies propagating viruses of serotype I or III. C viruses were not hereditarily transmitted. Persistence of the Picornaviruses of drosophila populations can be explained by the additive effects of the 3 mechanisms of contamination.

Animals↗
PubMed1996

Vitellogenetic defects in hybrids of the species pair Drosophila virilis and Drosophila texana.

In interspecific matings between the species Drosophila virilis and Drosophila texana, female sterility can be observed in F2 backcross females and in F2 hybrid females. The results presented in this report show that the female sterility, whenever it exists, is due to prevention of vitellogenin synthesis in the fat body, but other abnormalities such as defects with the hybrid ovaries are not excluded. The observation that sterility appears among females from backcrosses suggests that incompatibilities between interspecific genes may cause female sterility even in the presence of a complete habloid genome from one or the other species. Yet, the parallel observation that female sterility appears only in hybrid females with recombinant chromosomes indicates that sterility results when conspecific combinations of genes on the same chromosome are broken by interspecific recombination.

Animals↗
PubMed2000

Evolutionary change of codon usage for the histone gene family in Drosophila melanogaster and Drosophila hydei.

The nucleotide divergence in the protein-coding region for replication-dependent and replication-independent histone 3 and 4 genes of Drosophila melanogaster and Drosophila hydei occurred mostly at the synonymous site. Therefore, the pattern of codon usage was analyzed in the two species, considering the genomic codon bias, which is proposed for estimating the genomic composition pressure in the protein-coding regions. The results indicated that the codon usage in the histone gene family could be explained mostly by the genomic codon bias. However, biases for Ala and Arg were commonly observed for the histone 3 and histone 4 gene families, and biases for Ser, Leu, and Glu were observed in a gene-specific manner. This suggests that both genomic codon bias and gene- or codon-specific bias are responsible for the nucleotide differentiation in the protein-coding region of the histone genes.

Animals↗
PubMed1990

Inversion polymorphism in populations of Drosophila sulphurigaster albostrigata and Drosophila nasuta albomicans from Phuket, Thailand.

Two species of the Drosophila nasuta subgroup of the Drosophila immigrans group, D. sulphurigaster albostrigata and D. nasuta albomicans were investigated in this study. Collections of both species were made from Phuket, Thailand. Both species have similar salivary chromosomes, with four autosomal arms and one sex chromosome arm, and both are highly polymorphic for paracentric inversions. D.s. albostrigata accounted for the majority of the isolines collected and exhibited the greater number of inversions. One inversion, C14 was common to both species, indicating common ancestry. A non-random distribution of inversions was observed on the proximal end of chromosome III in both D.s. albostrigata and D. n. albomicans. An inter-collection comparison revealed that both rigid and flexible chromosomal polymorphism were operating in the two species, with a seasonal variation noted for one inversion in D. s. albostrigata. A non-random association of two inversions was observed in D. n. albomicans. Based on a comparison of the indices of crossing over, both D. s. albostrigata and D. n. albomicans were found to be more heterozygous than in previous studies, with D. n. albomicans appearing to have evolved further than D. s. albostrigata.

Animals↗