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PubMed2005

Comparative analysis of BAC and whole genome shotgun sequences from an Anopheles gambiae region related to Plasmodium encapsulation.

The only natural mechanism of malaria transmission in sub-Saharan Africa is the mosquito, generally Anopheles gambiae. Blocking malaria parasite transmission by stopping the development of Plasmodium in the insect vector would provide a useful alternative to the current methods of malaria control. Toward this end, it is important to understand the molecular basis of the malaria parasite refractory phenotype in An. gambiae mosquito strains. We have selected and sequenced six bacterial artificial chromosome (BAC) clones from the Pen-1 region that is the major quantitative trait locus involved in Plasmodium encapsulation. The sequence and the annotation of five overlapping BAC clones plus one adjacent, but not contiguous clone, totaling 585kb of genomic sequence from the centromeric end of the Pen-1 region of the PEST strain were compared to that of the genome sequence of the same strain produced by the whole genome shotgun technique. This project identified 23 putative mosquito genes plus putative copies of the retrotransposable elements BEL12 and TRANSIBN1_AG in the six BAC clones. Nineteen of the predicted genes are most similar to their Drosophila melanogaster homologs while one is more closely related to vertebrate genes. Comparison of these new BAC sequences plus previously published BAC sequences to the cognate region of the assembled genome sequence identified three retrotransposons present in one sequence version but not the other. One of these elements, Indy, has not been previously described. These observations provide evidence for the recent active transposition of these elements and demonstrate the plasticity of the Anopheles genome. The BAC sequences strongly support the public whole genome shotgun assembly and automatic annotation while also demonstrating the benefit of complementary genome sequences and of human curation. Importantly, the data demonstrate the differences in the genome sequence of an individual mosquito compared to that of a hypothetical, average genome sequence generated by whole genome shotgun assembly.

Amino Acid Sequence↗

PubMed1989

Cloning and chromosomal localization of Drosophila cDNA encoding the catalytic subunit of protein phosphatase 1 alpha. High conservation between mammalian and insect sequences.

A 1.2-kb clone containing the full coding sequence of a protein phosphatase 1 catalytic subunit has been isolated from a Drosophila head cDNA library. It encodes a polypeptide of 302 amino acids with a molecular mass of 34.5 kDa. The predicted protein sequence is 92% identical (94% similar) to rabbit protein phosphatase 1 alpha (PP-1 alpha) demonstrating strict conservation of the phosphatase catalytic subunit over a considerable evolutionary distance. Abundant 1.6-kb and 2.5-kb mRNA transcripts were detected throughout Drosophila development. The clone hybridised to four sites on Drosophila salivary gland polytene chromosomes. The major site is at 87B6-12 on the right arm of chromosome 3. In addition, there are three secondary sites, one on the same chromosome at 96A2-5 and two on the X chromosome at 9C1-2 and 13C1-2. Isolation of a further cDNA clone, hybridising to 9C1-2 and encoding part of the catalytic subunit 88% similar to Drosophila PP-1 alpha, proves the existence of at least two transcriptionally active genes for protein phosphatase 1.

Amino Acid Sequence↗

PubMed2001

Wolbachia-induced incompatibility precedes other hybrid incompatibilities in Nasonia.

Wolbachia are cytoplasmically inherited bacteria that cause a number of reproductive alterations in insects, including cytoplasmic incompatibility, an incompatibility between sperm and egg that results in loss of sperm chromosomes following fertilization. Wolbachia are estimated to infect 15-20% of all insect species, and also are common in arachnids, isopods and nematodes. Therefore, Wolbachia-induced cytoplasmic incompatibility could be an important factor promoting rapid speciation in invertebrates, although this contention is controversial. Here we show that high levels of bidirectional cytoplasmic incompatibility between two closely related species of insects (the parasitic wasps Nasonia giraulti and Nasonia longicornis) preceded the evolution of other postmating reproductive barriers. The presence of Wolbachia severely reduces the frequency of hybrid offspring in interspecies crosses. However, antibiotic curing of the insects results in production of hybrids. Furthermore, F1 and F2 hybrids are completely viable and fertile, indicating the absence of F1 and F2 hybrid breakdown. Partial interspecific sexual isolation occurs, yet it is asymmetric and incomplete. Our results indicate that Wolbachia-induced reproductive isolation occurred in the early stages of speciation in this system, before the evolution of other postmating isolating mechanisms (for example, hybrid inviability and hybrid sterility).

Animals↗

PubMed1995

[A mutable X(Z)-chromosome isolated from a natural population of Drosophila melanogaster].

In 1986, a mutable XZ-chromosome, in which mutation at genes yellow, white, and singed were recorded, was isolated from a natural population of Drosophila melanogaster from Zaporozh'e. Visible mutations in the region garnet-forked were also detected. Mutations appeared at a rate of about 10(-4) and were probably postmeiotic. Cytological analysis showed that two types of inversions occurred independently in XZ-chromosome. Specific features of this chromosome are hypermutability of the white locus (the mutation rate was approximately 10(-3) and a hot spot for chromosomal rearrangements in the terminal segment of the X-chromosome.

Alleles↗

PubMed2006

Genomic analysis of a 1 Mb region near the telomere of Hessian fly chromosome X2 and avirulence gene vH13.

BACKGROUND: To have an insight into the Mayetiola destructor (Hessian fly) genome, we performed an in silico comparative genomic analysis utilizing genetic mapping, genomic sequence and EST sequence data along with data available from public databases. RESULTS: Chromosome walking and FISH were utilized to identify a contig of 50 BAC clones near the telomere of the short arm of Hessian fly chromosome X2 and near the avirulence gene vH13. These clones enabled us to correlate physical and genetic distance in this region of the Hessian fly genome. Sequence data from these BAC ends encompassing a 760 kb region, and a fully sequenced and assembled 42.6 kb BAC clone, was utilized to perform a comparative genomic study. In silico gene prediction combined with BLAST analyses was used to determine putative orthology to the sequenced dipteran genomes of the fruit fly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, and to infer evolutionary relationships. CONCLUSION: This initial effort enables us to advance our understanding of the structure, composition and evolution of the genome of this important agricultural pest and is an invaluable tool for a whole genome sequencing effort.

Animals↗

PubMed2005

Polygenic mutation in Drosophila melanogaster: Mapping spontaneous mutations affecting sensory bristle number.

Our ability to predict long-term responses to artificial and natural selection, and understand the mechanisms by which naturally occurring variation for quantitative traits is maintained, depends on detailed knowledge of the properties of spontaneous polygenic mutations, including the quantitative trait loci (QTL) at which mutations occur, mutation rates, and mutational effects. These parameters can be estimated by mapping QTL that cause divergence between mutation-accumulation lines that have been established from an inbred base population and selected for high and low trait values. Here, we have utilized quantitative complementation to deficiencies to map QTL at which spontaneous mutations affecting Drosophila abdominal and sternopleural bristle number have occurred in 11 replicate lines during 206 generations of divergent selection. Estimates of the numbers of mutations were consistent with diploid per-character mutation rates for bristle traits of 0.03. The ratio of the per-character mutation rate to total mutation rate (0.023) implies that >2% of the genome could affect just one bristle trait and that there must be extensive pleiotropy for quantitative phenotypes. The estimated mutational effects were not, however, additive and exhibited dependency on genetic background consistent with diminishing epistasis. However, these inferences must be tempered by the potential for epistatic interactions between spontaneous mutations and QTL affecting bristle number on the deficiency-bearing chromosomes, which could lead to overestimates in numbers of QTL and inaccurate inference of gene action.

Animals↗

PubMed1992

Insect proteins homologous to mammalian high mobility group protein 1. Characterization and DNA-binding properties.

Two chromosomal high mobility group (HMG) proteins from larvae of Chironomus thummi (Diptera) and from an epithelial cell line of Chironomus tentans were purified to homogeneity and chemically characterized. cDNA clones encoding these proteins were isolated from an expression library using an immunoscreening approach and were sequenced. The deduced amino acid sequences revealed their homology to HMG protein 1 of vertebrates. These insect proteins have therefore been designated cHMG1a and cHMG1b. They have a molecular mass of 12,915 and 12,019 kDa, respectively, and preferentially bind to AT-rich DNA. Indirect immunofluorescence microscopy with a polyclonal antibody showed the presence of cHMG1a and cHMG1b in condensed chromomeres but not in puffs, nucleoli, and cytoplasm. The cHMG1a and cHMG1b genes were both localized to a single band in region 14 of chromosome 1 of C. tentans and appear to be single copy genes. An immunologically related protein was purified from Drosophila melanogaster Kc cells. Its size and amino acid composition indicate that it is an HMG1 of D. melanogaster. On the other hand, our antibody did not recognize calf HMG1. The identification and characterization of HMG1 proteins in insects with polytene chromosomes opens new possibilities for studying function(s) of this group of chromosomal proteins.

Amino Acid Sequence↗

PubMed1992

Genetics of sexual isolation in females of the Drosophila simulans species complex.

Genetic analysis of hybrids between Drosophila simulans and D. sechellia shows that sexual isolation in females is caused by at least two genes, one on each major autosome, while the X chromosome has no effect. These results are similar to those of a previous study of hybrids between D. simulans and another sibling species, D. mauritiana. In this latter hybridization, each arm of the second chromosome carries genes causing sexual isolation in females, implying a total divergence of at least three loci. The genetic similarity between the D. simulans/D. mauritiana and D. simulans/D. sechellia hybridizations probably results from independent evolution and not phylogenetic artifacts, because the dominance relationships and behavioural interactions differ between the two hybridizations. The lack of an X-chromosome effect on sexual isolation contrasts with genetic studies of post-zygotic reproductive isolation, which invariably show strong effects of this chromosome.

Animals↗

PubMed1999

Transposable element interactions in insects: crossmobilization of hobo and Hermes.

There are four non-drosophilid insect gene vector systems available that have been constructed from the short inverted repeat-type transposable elements Minos, piggyBac, mariner and Hermes. These elements (with the possible exception of piggyBac) are members of transposable element families that appear to be widespread in nature. Because these transposable element families are large it is possible that an insect species targeted for transformation will contain related transposable elements. The data presented here begin to address directly the question of interaction between diverged but related members of transposable element families. We tested the ability of the hAT elements hobo and Hermes to interact and cause crossmobilization. Using plasmid-based and chromosome-based element mobility assays we found that the terminal sequences of hobo and Hermes were almost equally good substrates for hobo transposase. However, this ability to crossmobilize was not reciprocal. Hermes transposase was only rarely able to cause the excision of hobo elements from plasmids and was never observed from germline chromosomes. These results have important implications for transgenic insect studies in the future.

Animals↗

PubMed1998

Imprinted control of gene activity in Drosophila.

Genetic imprinting is defined as a reversible, differential marking of genes or chromosomes that is determined by the sex of the parent from whom the genetic material is inherited [1]. Imprinting was first observed in insects where, in some species, most notably among the coccoids (scale insects and allies), the differential marking of paternally and maternally transmitted chromosome sets leads to inactivation or elimination of paternal chromosomes [2]. Imprinting is also widespread in plants and mammals [3,4], in which paternally and maternally inherited alleles may be differentially expressed. Despite imprinting having been discovered in insects, clear examples of parental imprinting are scarce in the model insect species Drosophila melanogaster. We describe a case of imprint-mediated control of gene expression in Drosophila. The imprinted gene - the white+ eye-color gene - is expressed at a low level when transmitted by males, and at a high level when transmitted by females. Thus, in common with coccoids, Drosophila is capable of generating an imprint, and can respond to that imprint by silencing the paternal allele.

Animals↗

PubMed2002

Roads to polyploidy: the megakaryocyte example.

Polyploidy, recognized by multiple copies of the haploid chromosome number, has been described in plants, insects, and in mammalian cells such as, the platelet precursors, the megakaryocytes. Several of these cell types reach high ploidy via a different cell cycle. Megakaryocytes undergo an endomitotic cell cycle, which consists of an S phase interrupted by a gap, during which the cells enter mitosis but skip anaphase B and cytokinesis. Here, we review the mechanisms that lead to this cell cycle and to polyploidy in megakaryocytes, while also comparing them to those described for other systems in which high ploidy is achieved. Overall, polyploidy is associated with an orchestrated change in expression of several genes, of which, some may be a result of high ploidy and hence a determinant of a new cell physiology, while others are inducers of polyploidization. Future studies will aim to further explore these two groups of genes.

Animals↗

PubMed1994

Polytene chromosomes of monogenic and amphogenic Chrysomya species (Calliphoridae, Diptera): analysis of banding patterns and in situ hybridization with Drosophila sex determining gene sequences.

Standard maps for the five banded polytene chromosomes found in trichogen cell nuclei of the monogenic blowfly Chrysomya rufifacies and the amphogenic Chrysomya pinguis are presented. The chromosomes are highly homologous in the two species; differences in banding patterns are predominantly caused by one pericentric and ten paracentric inversions. In chromosome 5 of the amphogenic Chrysomya phaonis, also analysed in this paper, an additional paracentric inversion was observed. The distribution of species specific inversions indicates that the monogenic C. rufifacies is phylogenetically older than the amphogenic species. The maternal sex realizer locus F'/f on polytene chromosome 5 of C. rufifacies is not associated with a structural heterozygosity. Chromosome pair 6 of C. rufifacies and the sex chromosome pair of C. pinguis are under-replicated in polytene nuclei; they consist of irregular chromatin granules, frequently associated with nucleolus material. Evolution of heteromorphic sex chromosomes in Chrysomya is probably correlated with heterochromatin accumulation. A search for sex determining genes in Chrysomya was initiated using sex determining sequences from Drosophila melanogaster for in situ hybridization. The polytene band 41A1 on chromosome 5 of monogenic and amphogenic Chrysomya species contains sequences homologous to the maternal sex determining gene daughterless (da). Homology to the zygotic gene Sex-lethal (Sxl) of Drosophila is detected in band 39A1 on chromosome 5 of C. rufifacies. The findings reported here are the first evidence for a possible homology between the da gene of Drosophila and the maternal sex realizer F' of C. rufifacies. An hypothesis for the evolution of the maternal effect sex determination of C. rufifacies is proposed.

Animals↗

PubMed1997

[Developmental genes].

In the present review article, we have attempted to define and class the so called "developmental genes". This designation applies to genes whose activity is involved in lineage determination, in differentiation pathways or in the modes of tissue or organ formation. A special emphasis has been given to genes controlling the body plan in the course of development. Three main subclasses of such genes are described: genes involved in very early development by establishing the anteroposterior or dorso-ventral axes of the embryo (or of the insect larva); segmentation genes; homeotic genes containing an homeodomain (HD) motif and homeotic-related genes (with a "LIM" or "PAX" motif). While classical (HD containing) homeotic genes were initially discovered and studied in drosophila, their general occurrence in many other species, particularly in vertebrates was soon reported. They are characterized phylogenetically speaking, by a high degree of sequence similarities and chromosomal organization, although their number appears much greater in vertebrates than in insects due to successive duplication and chromosomal distribution events. In vertebrates they are essentially involved in the development of the central nervous system. Large varieties of genes with "LIM" or "PAX" motifs have been reported, and many subclasses can be distinguished depending upon the presence or absence of distinct peptidic motifs within the genes under concern. The peptidic domains encoded by the LIM motifs include "Zn finger" containing varieties which are involved in protein-protein interactions. The roles of genes with a LIM motif vary according to the type of sub-variety (organization of the central nervous system; axonal distribution of peripheric nerves at distinct levels of the spinal cord, control of tissue differentiation, etc.). "Pax" genes include a DNA binding domain (encoded by the "paired" motif) with variable sequences and organization, which is sometime in the vicinity of an homeodomain. Generally speaking "Pax" genes behave like controlling elements in the development of the brain or of tissues derived from the neural crest.

Animals↗

PubMed1996

Hermes, a functional non-Drosophilid insect gene vector from Musca domestica.

Hermes is a short inverted repeat-type transposable element from the house fly, Musca domestica. Using an extra-chromosomal transpositional recombination assay, we show that Hermes elements can accurately transpose in M. domestica embryos. To test the ability of Hermes to function in species distantly related to M. domestica we used a nonautonomous Hermes element containing the Drosophila melanogaster while (w+) gene and created D. melanogaster germline transformants. Transgenic G1 insects were recovered from 34.6% of the fertile G0 adults developing from microinjected w- embryos. This transformation rate is comparable with that observed using P or hobo vectors in D. melanogaster, however, many instances of multiple-element insertions and large clusters were observed. Genetic mapping, Southern blotting, polytene chromosome in situ hybridization and DNA sequence analyses confirmed that Hermes elements were chromosomally integrated in transgenic insects. Our data demonstrate that Hermes elements transpose at high rates in D. melanogaster and may be an effective gene vector and gene-tagging agent in this species and distantly related species of medical and agricultural importance.

Animals↗

PubMed2004

A physically anchored genetic map and linkage to avirulence reveals recombination suppression over the proximal region of Hessian fly chromosome A2.

Resistance in wheat (Triticum aestivum) to the Hessian fly (Mayetiola destructor), a major insect pest of wheat, is based on a gene-for-gene interaction. Close linkage (3 +/- 2 cM) was discovered between Hessian fly avirulence genes vH3 and vH5. Bulked segregant analysis revealed two DNA markers (28-178 and 23-201) within 10 cM of these loci and only 3 +/- 2 cM apart. However, 28-178 was located in the middle of the short arm of Hessian fly chromosome A2 whereas 23-201 was located in the middle of the long arm of chromosome A2, suggesting the presence of severe recombination suppression over its proximal region. To further test that possibility, an AFLP-based genetic map of the Hessian fly genome was constructed. Fluorescence in situ hybridization of 20 markers on the genetic map to the polytene chromosomes of the Hessian fly indicated good correspondence between the linkage groups and the four Hessian fly chromosomes. The physically anchored genetic map is the first of any gall midge species. The proximal region of mitotic chromosome A2 makes up 30% of its length but corresponded to <3% of the chromosome A2 genetic map.

Animals↗

PubMed1985

Is human X chromosome inactivation a sex-determining device?

The evolutionary function of X chromosome inactivation is thought to be dosage compensation. However, there is, at present, little evidence to suggest that most X chromosome-linked genes require such compensation. Another view--that X chromosome inactivation may be related to sex determination--is examined here. Consider a hypothetical DNA sequence regulating a major structural gene concerned with the determination of maleness. If this regulatory sequence occurs in both X and Y chromosomes and if its copy number in the Y chromosome is significantly greater than in the X chromosome, then the male-determining properties of the Y chromosome could be attributed to this higher copy number. On the other hand, if the Y chromosome has the same copy number of this sequence as the X chromosome, it is difficult to see how determination of two sexes would occur under such circumstances because XX and XY genomes would then be indistinguishable in this regard. Such a situation seems to occur in the human species with respect to the banded krait minor satellite, a repetitious DNA sequence associated with sex determination. This apparent difficulty may be resolved if X chromosome inactivation renders regulatory as well as structural genes nonfunctional and thereby brings about a significant reduction in the effective copy number of X chromosome-linked DNA sequences concerned with sex determination. It is suggested that X chromosome inactivation brings about, in this manner, a critical inequality between XX and XY embryos and that sex determination in humans is a consequence of this inequality. An analogous situation appears to exist in certain insects in which inactivation of a haploid set of chromosomes (and presumably, therefore, a 50% reduction in the effective copy number of most genes) is associated with maleness. If this line of reasoning is correct, it would suggest that sex determination may be the primary function of X chromosome inactivation.

Animals↗

PubMed1994

Drosophila melanogaster genes encoding three troponin-C isoforms and a calmodulin-related protein.

Using low-stringency hybridization and polymerase chain reaction (PCR)-based DNA amplification, we have isolated three Drosophila melanogaster genes that encode troponin-C isoforms and one specifying a protein that is closely related to calmodulin. Two of the troponin-C genes, located within the 47D and 73F subdivisions of chromosomes 2 and 3, respectively, encode very closely related isoforms. That specified by the 47D gene accumulates almost exclusively in larval muscles, while that encoded by the 73F gene is present in both larvae and adults. The third gene, located within the 41C subdivision of chromosome 2, encodes a more distantly related troponin-C isoform that accumulates only within adults. The gene that encodes the calmodulin-related protein is located within the 97A subdivision of chromosome three. The protein encoded by this gene has a different primary sequence from that of conventional calmodulin, which is specified by a gene located within the 49A subdivision of chromosome 2. Our report is the first to describe insect troponin-C isoforms and further avails genetic methods for investigating the in vivo functions of the troponin-C/myosin light-chain/calmodulin protein superfamily.

Amino Acid Sequence↗

PubMed2002

Photographic polytene chromosome maps for Glossina morsitans submorsitans (Diptera: Glossinidae): cytogenetic analysis of a colony with sex-ratio distortion.

Photographic polytene chromosome maps from trichogen cells of pharate adult Glossina morsitans submorsitans were constructed. Using the standard system employed to map polytene chromosomes of Drosophila, the characteristic landmarks were described for the X chromosome and the two autosomes (L1 and L2). Sex-ratio distortion, which is expressed in male G. m. submorsitans, was found to be associated with an X chromosome (X8) that contains three inversions in each arm. Preliminary data indicate no differences in the fecundity of X(A)X(A) and X(A)X(B) females, but there are indications that G. m. submorsitans in colonies originating from Burkina Faso and Nigeria have genes on the autosomes and (or) the Y chromosome that suppress expression of sex-ratio distortion.

Animals↗