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PubMed2006

Retrogene movement within- and between-chromosomes in the evolution of Drosophila genomes.

Recent genomic analyses in Drosophila and mammals of inter-chromosomal retroposition have revealed that during evolution the retroposed genes that show male-biased expression tend to leave the X chromosome and opt for autosomal positions. Such a phenomenon may be a process of general, genomic and evolutionary relevance. It contributed to the unexpected overrepresentation of male-biased genes on the autosomes recently observed in microarray expression experiments. In this paper, we report our genomic analysis of within-chromosomal retroposition in Drosophila melanogaster, and compare it with the previously identified pattern of the between-chromosomal retroposition. We find that a surfeit of autosomal retroposed genes originated from parental genes located on the same chromosome, in contrast to the X chromosome in which only few genes retroposed in cis. Such an autosomal proximity effect implicates a role of the mutation process for retroposition in determining chromosomal locations of autosome-derived retroposed genes. Furthermore, this phenomenon supports the hypothesis that natural selection favors the retroposition of genes out of the X chromosome. Analyses of a large expression database for D. melanogaster genes revealed that the vast majority of the X-derived autosomal retroposed genes had evolved testis expression functions, consistent with other previous genomic analyses.

Animals↗
PubMed2003

Identification and chromosomal localization of mariner-like elements in the cabbage moth Mamestra brassicae (Lepidoptera).

A complete mariner-like element has been identified in the lepidopteran Mamestra brassicae. This element, called Mbmar, represents a new type of mariner transposon. It has a transposase similar to that of other insect mariner coding sequences but its inverted terminal repeats differ from typical mariner ones. This observation is unique since generally both mariner coding region and ITRs are evolutionarily conserved in insects. Mbmar is detectable by FISH only in the heterochromatic regions of both the sex chromosomes.

Animals↗
PubMed2001

Electron microscope mapping of the pericentric and intercalary heterochromatic regions of the polytene chromosomes of the mutant Suppressor of underreplication in Drosophila melanogaster.

Breaks and ectopic contacts in the heterochromatic regions of Drosophila melanogaster polytene chromosomes are the manifestations of the cytological effects of DNA underreplication. Their appearance makes these regions difficult to map. The Su(UR)ES gene, which controls the phenomenon, has been described recently. Mutation of this locus gives rise to new blocks of material in the pericentric heterochromatic regions and causes the disappearance of breaks and ectopic contacts in the intercalary heterochromatic regions, thereby making the banding pattern distinct and providing better opportunities for mapping of the heterochromatic regions in polytene chromosomes. Here, we present the results of an electron microscope study of the heterochromatic regions. In the wild-type salivary glands, the pericentric regions correspond to the beta-heterochromatin and do not show the banding pattern. The most conspicuous cytological effect of the Su(UR)ES mutation is the formation of a large banded chromosome fragment comprising at least 25 bands at the site where the 3L and 3R proximal arms connect. In the other pericentric regions, 20CF, 40BF and 41BC, 15, 12 and 9 new bands were revealed, respectively. A large block of densely packed material appears in the most proximal part of the fourth chromosome. An electron microscope analysis of 26 polytene chromosome regions showing the characteristic features of intercalary heterochromatin was also performed. Suppression of DNA underreplication in the mutant transforms the bands with weak spots into large single bands.

Animals↗
PubMed1980

[Relationship between an organism's radiosensitivity and its level of repair processes].

Radioresistance and repair intensity were simultaneously studied in 13 stocks of Drosophila melanogaster. The frequency of exceptional males in the progeny of X-irradiated females was used as radioresistance criterion. Repair intensity was estimated by the radiation after-effect which was determined under successive action of the radiation and elevated temperature (37 degrees C). It has been shown that the higher is the stock radioresistance, the higher are repair capacity of the stock. However, it has been revealed that relatively independent combining of radioresistance and repair intensity is possible, excluding one, "forbidden" combination: there are no organisms which are sensitive to radiation and have a high repair level. The last law appears to have a general biological nature, it is characteristic for microorganisms (Escherichia coli), plants (Vicia faba) and insects (D. melanogaster).

Animals↗
PubMed2006

Localization of Müllerian mimicry genes on a dense linkage map of Heliconius erato.

We report a dense genetic linkage map of Heliconius erato, a neotropical butterfly that has undergone a remarkable adaptive radiation in warningly colored mimetic wing patterns. Our study exploited natural variation segregating in a cross between H. erato etylus and H. himera to localize wing color pattern loci on a dense linkage map containing amplified fragment length polymorphisms (AFLP), microsatellites, and single-copy nuclear loci. We unambiguously identified all 20 autosomal linkage groups and the sex chromosome (Z). The map spanned a total of 1430 Haldane cM and linkage groups varied in size from 26.3 to 97.8 cM. The average distance between markers was 5.1 cM. Within this framework, we localized two major color pattern loci to narrow regions of the genome. The first gene, D, responsible for red/orange elements, had a most likely placement in a 6.7-cM region flanked by two AFLP markers on the end of a large 87.5-cM linkage group. The second locus, Sd, affects the melanic pattern on the forewing and was found within a 6.3-cM interval between flanking AFLP loci. This study complements recent linkage analysis of H. erato's comimic, H. melpomene, and forms the basis for marker-assisted physical mapping and for studies into the comparative genetic architecture of wing-pattern mimicry in Heliconius.

Adaptation, Physiological↗
PubMed2004

Y chromosome of D. pseudoobscura is not homologous to the ancestral Drosophila Y.

We report a genome-wide search of Y-linked genes in Drosophila pseudoobscura. All six identifiable orthologs of the D. melanogaster Y-linked genes have autosomal inheritance in D. pseudoobscura. Four orthologs were investigated in detail and proved to be Y-linked in D. guanche and D. bifasciata, which shows that less than 18 million years ago the ancestral Drosophila Y chromosome was translocated to an autosome in the D. pseudoobscura lineage. We found 15 genes and pseudogenes in the current Y of D. pseudoobscura, and none are shared with the D. melanogaster Y. Hence, the Y chromosome in the D. pseudoobscura lineage appears to have arisen de novo and is not homologous to the D. melanogaster Y.

Animals↗
PubMed1975

Location of nucleolar organizers in animal and plant chromosomes by means of an improved N-banding technique.

With an improved N-banding technique, the location of nucleolar organizing region was determined in 27 kinds of material including mammals, a marsupial, birds, amphibians, fishes, an insect and plants. In most cases the N-bands were clearly located on certain specific regions of chromosomes, such as the secondary constriction, satellite, centromere, telomere and heterochromatic segment, while in some species they were detected as very minute bodies distributed over many chromosomes. From the available cytological and biochemical data it was suggested that the N-bands represent certain structural non-histone proteins specifically linked to nucleolar organizers in various eukaryotic chromosomes.

Amphibians↗
PubMed2003

Male genes: X-pelled or X-cluded?

Two recent studies by Parisi et al. and Ranz et al., catalogue sex differences in gene expression across the whole genome of the fruit fly Drosophila melanogaster. Both report striking associations of sex-biased gene expression with the X chromosome. Genes with male-biased expression are depauperate on the X chromosome, whereas genes with female-biased expression show weaker evidence of being in excess. A number of evolutionary hypotheses for the expulsion or exclusion of male-biased genes from the X chromosome have been suggested. None is entirely consistent with the available evidence.

Animals↗
PubMed2002

Genetic stability of sexing strains based on the locus sw of Ceratitis capitata.

This report deals with the process of improving the stability of medfly, Ceratitis capitata, genetic sexing strains (GSS) based on the sw mutation on chromosome 2. This gene affects the rate of development as well as the eye colour and iridescence. The improved sexing strains were produced by mapping sw with deletions and then inducing and screening for new translocations with breakpoints close to the marker. The stability was assessed in large populations over many generations. Twenty-two new Y-2 translocations were identified and polytene chromosome analysis was performed to locate breakpoints. The translocation strains were ranked according to the distance of their breakpoints from sw. The map position of sw is region 20D on 2R. As data on the stability of the 22 strains accumulated, Cast 191 was shown to be the most promising as no recombination between sw and the male sex was found. After rearing the strain for 22 generations under semi-mass rearing conditions, with a population size of 15,000 adults and scoring 1000 flies per generation, only one such event was detected (estimated frequency = 3.1 x 10(-6)). Further tests are being carried out with this strain to assess its suitability as a genetic sexing strain for medfly Sterile insect technique (SIT).

Animals↗
PubMed1991

Mutagenicity and metabolism of dimethyl phthalate and its binding to epidermal and hepatic macromolecules.

As an active ingredient in insect repellents, dimethyl phthalate (DMP) had previously been shown to produce chromosomal aberrations in the livers of rats following subchronic application of the phthalate to skin. When we tested DMP in the Ames mutagenesis assay, it produced in bacterial tester strain TA100 (but not TA98) a dose-related mutagenic response that was abolished by NAD- and NADP-independent metabolism associated with rat liver microsomal preparations (S9). In a host-mediated mutagenesis assay, rats were injected ip with DMP (2 g/kg body weight); urine was collected for 24 h, extracted, and analyzed for mutagenic activity and phthalic acid-containing derivatives. The extracted urine was not mutagenic to TA100 and contained an equivalent of 1.96 mg phthalate/ml urine. More than 97% of the phthalic acid-containing derivatives present in the extracted urine consisted of the nonmutagenic metabolite of DMP, monomethyl phthalate (MMP). In vitro experiments showed that rat liver homogenates hydrolyzed 93% of carbonyl-labeled 14C-DMP (7.7 mM) to MMP in 2 h and bound 0.07 nmol of [14C]phthalate/mg liver macromolecules. By contrast, rat epidermal homogenates metabolized only 5% and bound 38-fold higher levels of carbonyl-labeled 14C-DMP (2.66 nmol/mg of macromolecules), with no detectable binding to nucleic acids. Compared to epidermis and plasma, liver had a fivefold higher rate of DMP monoesterase activity (1240 nmol/h/mg protein), which, when inhibited by 67%, resulted in a 4.4-fold increase in phthalate-bound hepatic macromolecules (0.31 vs. 0.07 nmol of carbonyl-labeled 14C-DMP/mg macromolecules). In addition to MMP, formaldehyde was produced during the metabolism of DMP by liver. When ethanol was used to inhibit the oxidation of DMP-derived methanol by hepatic homogenates, there resulted a 74% reduction in the accumulation of formaldehyde and similar reductions of 71 and 73% in the binding of methyl-labeled 14C-DMP to nucleic acids and macromolecules. (Methyl-labeled, unlike carbonyl-labeled, 14C-DMP yields a 14C-labeled methanol when hydrolyzed.) These results indicate that the DMP diester is a weak bacterial mutagen, which binds to epidermal and hepatic macromolecules other than nucleic acids, and that although the rapid hepatic metabolism of DMP to its monoester (MMP) and methanol affords protection against higher levels of phthalate binding as well as against DMP-induced bacterial mutagenesis, it also oxidizes DMP-derived methanol to formaldehyde, a metabolite that binds macromolecules, including nucleic acids.

Animals↗
PubMed2002

Comparative genome and proteome analysis of Anopheles gambiae and Drosophila melanogaster.

Comparison of the genomes and proteomes of the two diptera Anopheles gambiae and Drosophila melanogaster, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small "microsyntenic" clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected.

Animals↗
PubMed2002

Retroposed new genes out of the X in Drosophila.

New genes that originated by various molecular mechanisms are an essential component in understanding the evolution of genetic systems. We investigated the pattern of origin of the genes created by retroposition in Drosophila. We surveyed the whole Drosophila melanogaster genome for such new retrogenes and experimentally analyzed their functionality and evolutionary process. These retrogenes, functional as revealed by the analysis of expression, substitution, and population genetics, show a surprisingly asymmetric pattern in their origin. There is a significant excess of retrogenes that originate from the X chromosome and retropose to autosomes; new genes retroposed from autosomes are scarce. Further, we found that most of these X-derived autosomal retrogenes had evolved a testis expression pattern. These observations may be explained by natural selection favoring those new retrogenes that moved to autosomes and avoided the spermatogenesis X inactivation, and suggest the important role of genome position for the origin of new genes.

Animals↗
PubMed2002

The odorant-binding proteins of Drosophila melanogaster: annotation and characterization of a divergent gene family.

Insect odorant-binding proteins (OBPs) are thought to facilitate the delivery of hydrophobic odorants, such as sex pheromones or food odors, to receptors on sensory neurons. Increasingly, OBP family members are also being found in non-sensory tissues where they might carry other types of small hydrophobic molecules. They are identifiable by four or six conserved Cys residues and contain six alpha-helices which enclose a hydrophobic ligand-binding pocket. Through exhaustive BLAST searches we have increased the total number of OBPs identified in Drosophila melanogaster to 38, and have amplified the DNA complementary to RNA corresponding to 21 of these by reverse transcriptase polymerase chain reaction. Isoforms frequently share less than 30% amino acid identity and appear to have radically changed since the separation of the major insect orders. However, their sequences are consistent with known OBP structures. Most are located in clusters of between four and 14 genes and several were unusual in that they contained additions, deletions, or fusions. These hexa-helical insect OBPs are structurally unrelated to the functionally analogous lipocalin-like beta-barrel OBPs of vertebrates. As only two lipocalin-like proteins have been found in D. melanogaster, these helical proteins appear to be the dominant carrier of small hydrophobic molecules in insects.

Amino Acid Sequence↗
PubMed1998

DLG3, the gene encoding human neuroendocrine Dlg (NE-Dlg), is located within the 1.8-Mb dystonia-parkinsonism region at Xq13.1.

Neuroendocrine-Dlg (NE-Dlg) is a member of the discs-large-related (DLG) subfamily of the membrane-associated guanylate kinase-related protein family. Based on evidence from model systems, this protein appears to be critical for synaptogenesis, acting as a site-specific organizational center for integral membrane proteins and their downstream signaling molecules associated with the cytoskeleton. NE-Dlg also directly interacts with the colorectal tumor suppressor adenomatous polyposis coli, suggesting that it may play a role in regulating cell proliferation in epithelial cells. To explore the genetic control of NE-Dlg, we developed a physical map of the chromosome region containing DLG3, the locus encoding NE-Dlg. Using human-hamster radiation hybrid mapping panels, we mapped DLG3 to Xq13.1 and established a sequence-tagged site marker map of the surrounding region. We then developed a yeast artificial chromosome (YAC) contig for this region. Encompassing approximately 2.0 Mb contained within five overlapping YACs, this contig also includes the dystonia-parkinsonism syndrome (DYT3) locus. The close proximity of DLG3 to the DYT3 region suggests that the gene encoding NE-Dlg is a candidate locus for this neurological disorder.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Genetic and molecular analysis of a set of unstable white mutants in Drosophila melanogaster.

Two related unstable mutants at the white locus of Drosophila melanogaster show different interactions with the zeste1 mutant: one mutated white gene becomes repressed in males, whereas the other is unaffected by z1. By use of Southern blot techniques and by constructing genomic lambda-libraries, molecular analyses of the white regions of these two strains were performed. The results showed a single difference at a site 2.5 kb (kilobases) downstream of the white transcription unit. In both strains, FB (foldback) elements were integrated at this site, but the repressed strain also harboured a 4 kb NOF (Nofretete) element. No other restriction site polymorphisms between the two strains were observed within a 120 kb region surrounding the white gene. The extent of twelve white deletions and twelve white transpositions deriving from these unstable strains was analysed by in situ hybridisation and Southern blot techniques. The results revealed that the distal breakpoint of all aberrations coincided with the insertion site of the mobile elements, but that the centromere proximal breakpoints varied. The mechanisms for the instability and the interaction with the zeste1 mutant are discussed.

Animals↗
PubMed1997

High mobility group proteins cHMG1a, cHMG1b, and cHMGI are distinctly distributed in chromosomes and differentially expressed during ecdysone dependent cell differentiation.

The mammalian high mobility group proteins HMGI/Y and HMG1/2 are thought to play an architectural role in assembly of nucleoprotein structures. Counterparts to these proteins have recently been found in the cells of the Dipteran insect Chironomus. In this report we investigate the distribution of three abundant HMG proteins in interphase giant chromosomes of the midge, Chironomus. By means of the indirect immunofluorescence technique the cHMG1b and cHMGI proteins were localized in chromosomal puffs, suggesting their involvement in the organization of transcriptionally active chromatin. In contrast, the highly abundant protein cHMG1a was rather uniformly distributed in the chromosomes. The cHMGI protein, but not cHMG1a or cHMG1b, was detected in nucleoli, which may indicate a role in the transcription of ribosomal genes. The regions of the interphase chromosomes containing AT-rich DNA did not contain higher levels of the cHMGI and cHMG1b proteins. A correlation between the specific location of these proteins in chromatin and their synthesis and turnover rates was observed.

Amino Acid Sequence↗