SEARCH · PubMed Health

Results for “Genome, Insect”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources

PubMed2002

Genomic imprinting in Drosophila is maintained by the products of Suppressor of variegation and trithorax group, but not Polycomb group, genes.

Genomic imprinting is a form of epigenetic inheritance that is characterized by differential expression of a gene depending on its parental origin. The mini-X chromosome Dp(1;f)LJ9 in Drosophila shows this type of classical imprinting; when transmitted by the maternal parent genes on this chromosome are fully expressed, but when the chromosome is transmitted by the male parent at least three genes are subject to silencing, resulting in a variegated expression pattern. Chemical and environmental modifiers of position-effect variegation have been shown to alter the somatic maintenance of the imprint. To extend these observations, several mutations in chromatin-associated proteins were examined for their effect on imprinting on the Dp(1;f)LJ9 mini-X chromosome. Effects on establishment and maintenance were independently assessed by genetically associating the mutations in chromatin modifiers with the mini-X chromosome in either the parents, where the imprint is established, or the progeny, in which the imprint must be maintained. Nine Suppressor of variegation [ Su(var)] mutations, including alleles of the Su(var)2-5 gene, which encodes the well characterized heterochromatin-associated protein HP1, abolished maintenance but not the establishment of the imprint. Mutant alleles of two genes in the trithorax group ( trx-G), brahma and trithorax, showed a maternal-effect enhancement of the paternal imprint. Surprisingly, however, with the exception of an Enhancer of Polycomb [ E(Pc)] allele, none of the Polycomb-group ( Pc-G) mutations tested affected the imprint. Thus, the maintenance of this imprint relies on the wild-type products of Su(var) and trx-G, but not Pc-G, genes. Finally, none of the mutations tested affected the maintenance of the maternal imprint or the establishment of either the maternal or paternal imprint, suggesting that the maternal and paternal imprints depend on different molecular processes and that imprint establishment and maintenance are independently regulated.

Animals↗

PubMed2006

Insect iron binding proteins: insights from the genomes.

Sequencing of the genomes of Drosophila melanogaster, Anopheles gambiae, Apis mellifera, and Bombyx mori provided an opportunity to examine the diversity and organization of genes encoding insect transferrins (Tsf) and ferritins. Information obtained from the genomes significantly advances our knowledge of these major players in insect iron metabolism and complements the results of molecular studies on their temporal, spatial, and inducible expression pattern and regulatory mechanisms conducted in diverse insect species. Analysis of genes encoding new members of the Tsf family and non-secreted ferritin subunits allows making preliminary hypotheses about their possible functions and opens possibilities to study lesser-known aspects of insect iron homeostasis. Proteomic and gene expression studies that followed the whole genome sequencing quickly contribute to defining or better understanding of the important and diverse biological roles of Tsf and ferritin, particularly their involvement in insect's defenses against oxidative stress and infection.

Amino Acid Sequence↗

PubMed1996

Expression of a developmentally regulated gene, Mng10, in identified neurosecretory cells in the CNS of Manduca sexta.

We are interested in the molecular events underlying the development of the nervous system of Manduca sexta during the final 24 h of the pupal molt. In this article we describe a gene, Mng10, that is expressed in the abdominal nervous system of M. sexta and is developmentally regulated over this 24-h period. In situ hybridization analysis shows that the transcript is localized predominantly to a single pair of uniquely identifiable neurosecretory neurons, the NS-L1 cells in the abdominal ganglia. Mng10 is a single copy gene encoding a 229 amino acid protein with a predicted molecular mass of 26 kDa. At the amino acid level the protein shows 34% identity to the yeast transcription unit, Yer082. Northern blot analysis shows that the transcript of Mng10 is very rare, comprising about 0.001% of the poly (A)+ RNA from the CNS and is detectable at 4 h but not 24 h prior to pupal ecdysis. One of the physiological events that develops over the final 24 h of the pupal molt is the ability of the nervous system to respond to the neuropeptide eclosion hormone. In this context, it is interesting to note that the NS-L1 cells are members of the group of 50 neurons that show increased cGMP immunoreactivity when the nervous system is exposed to the neuropeptide eclosion hormone.

Amino Acid Sequence↗

PubMed2006

The pea aphid, Acyrthosiphon pisum: an emerging genomic model system for ecological, developmental and evolutionary studies.

Aphids display an abundance of adaptations that are not easily studied in existing model systems. Here we review the biology of a new genomic model system, the pea aphid, Acyrthosiphon pisum. We then discuss several phenomena that are particularly accessible to study in the pea aphid: the developmental genetic basis of polyphenisms, aphid-bacterial symbioses, the genetics of adaptation and mechanisms of virus transmission. The pea aphid can be maintained in the laboratory and natural populations can be studied in the field. These properties allow controlled experiments to be performed on problems of direct relevance to natural aphid populations. Combined with new genomic approaches, the pea aphid is poised to become an important model system for understanding the molecular and developmental basis of many ecologically and evolutionarily relevant problems.

Adaptation, Biological↗

PubMed2006

Genome size and determination of DNA content of the X chromosomes, autosomes, and germ line-limited chromosomes of Sciara coprophila.

The unique chromosome biology of the fungus fly Sciara coprophila has fascinated investigators for over 80 years. Male meiosis exhibits a monopolar spindle, nonrandom segregation of imprinted chromosomes and nondisjunction of the X chromosome. The unusual mechanism of sex determination requires selective elimination of X chromosomes in embryogenesis. Supernumerary (L) chromosomes are also eliminated from the soma during early cleavage divisions. Distinctive DNA puffs on the larval salivary gland chromosomes are sites of DNA amplification. As a foundation for future genome studies to explore these many unusual phenomena, we have used DNA-Feulgen cytophotometry to determine genome size from hemocyte nuclei of male (X0) and female (XX) larvae and adults. The DNA content of the X chromosome is approximately 0.05 pg DNA and the autosomal complement is approximately 0.45 pg DNA. Measurements of DNA levels for individual sperm from adults showed that the DNA contribution of the germ line-limited (L) chromosomes constitutes as much as 35% of the DNA of the male gamete. A parallel study using Sciara ocellaris, a related species lacking L chromosomes, confirmed the presence of two X chromosomes in the sperm of this species.

Animals↗

PubMed2001

A family of proteins related to Spätzle, the toll receptor ligand, are encoded in the Drosophila genome.

The Drosophila gene Spätzle encodes the activating ligand for the Toll receptor. This signaling pathway is required for dorso-ventral patterning in the early embryo and an antifungal immune response in larvae and adults. The genome sequence of Drosophila shows that there are a total of eight Toll-like receptors and these may function in other aspects of embryonic development and innate immunity. Here we describe five Drosophila homologues of Spätzle (Spz2-6) found using an iterative searching method. All five appear to encode proteins containing neurotrophin-like cystine-knot domains. In addition, most retain a characteristic intron-exon structure shared with the prototype Spätzle gene. This provides evidence that the family arose by ancient gene duplication events and indicates that the gene products may represent activating ligands for corresponding Toll receptors. Expression studies show that only Spz4 is expressed strongly in larvae and adults and thus may be involved in an ancillary antifungal response mediated by Toll-5. By contrast, Spz6 shows a complex spatial and temporally regulated expression pattern in the late embryo. Thus the new Toll/Spätzle families of signaling molecules may have important roles in other aspects of development and immunity.

Amino Acid Sequence↗

PubMed1996

Molecular, phenotypic, and expression analysis of vein, a gene required for growth of the Drosophila wing disc.

vein1 (vn1) mutants lack portions of longitudinal wing vein 4 and the anterior crossvein. Stronger alleles, originally called defective dorsal discs, show vn is also required for the growth of the wing and haltere discs, as mutants for these alleles have tiny dorsal discs. vn functions nonautonomously and encodes a secreted EGF-like protein. Here we characterize the role of vn in the imaginal wing disc by describing the expression pattern and correlating this pattern with vn mutant phenotypes and the requirement for vn. vn is expressed in wing discs in a complex and dynamic pattern. In larval wing discs vn is first expressed in the presumptive notum and later in the wing-pouch and hinge regions. There is a striking localization of vn transcripts to intervein regions which begins with a stripe of expression straddling the AP boundary in late larval discs and develops in all intervein regions after puparium formation. We isolated new vn mutations including nulls and hypomorphs. Hypomorphic vn alleles revealed region-specific requirements for vn within the wing disc. We mapped lesions caused by 10 vn mutations and defined a minimum size of 48 kb for the gene. The phenotype and expression analyses show vn has an early role in global proliferation of the wing disc and specific roles in the development of the notum, hinge, longitudinal vein 4, and all intervein regions. The role of vn in the EGF receptor signaling pathway is discussed.

Alleles↗

PubMed1999

Different levels, but not different isoforms, of the Drosophila transcription factor DMEF2 affect distinct aspects of muscle differentiation.

mef2 genes encode alternatively spliced transcription factor isoforms that function in muscle differentiation in both Drosophila and vertebrates. Drosophila mef2 (Dmef2) has been shown to be required for the differentiation of a variety of distinct muscle types. However, many possible aspects of its function in muscle remain unexplored. There has also been no analysis in vivo of the activity of different MEF2 isoforms in any species. Our investigation centred on the role of different levels of DMEF2 in the Drosophila embryo in regulating diverse events of muscle differentiation and on the functional significance of Dmef2 alternative splicing. We used the GAL4/UAS system to both misexpress and overexpress individual DMEF2 isoforms and to rescue the different aspects of the Dmef2 mutant phenotype. Ectopic ectodermal expression of DMEF2 activated muscle gene expression and inhibited epidermal differentiation. Overexpression of DMEF2 in the mesoderm disrupted differentiation of the somatic and visceral muscle and the heart. The use of different DMEF2 levels in the rescue experiments revealed an activity range compatible with differentiation of the different muscle types: the consequence of too little or too much DMEF2 activity was disrupted differentiation. These rescue experiments also revealed that distinct DMEF2 thresholds are required for different properties within a cell and also for different cells within a muscle type and for different muscle types. Finally, each isoform functioned equivalently in these experiments, including in the stringent test of rescue of the Dmef2 mutant phenotype.

Alternative Splicing↗

PubMed2001

Alternative splicing of an amino-terminal PEVK-like region generates multiple isoforms of Drosophila projectin.

Drosophila projectin is an extremely large protein found within the muscle sarcomeric unit, parallel with the actin and myosin filaments. Projectin has been suggested as the elastic component of C-filaments in insect indirect flight muscles, which is consistent with its localization from the Z band to the tip of the A band in these muscles. Here, we describe the completion of the projectin sequence analysis, which defines projectin as a 1 MDa protein, composed of 39 immunoglobulin and 39 fibronectin III domains. This analysis led also to the identification of a domain rich in the amino acids P, E, V and K within the NH(2) terminus of projectin. The length of the projectin PEVK-like region varies from 100 to 624 amino acid residues, following a complex pattern of alternative splicing events. PEVK domains were first identified in vertebrate titin and they have been associated with the elasticity of the protein. The PEVK-like domain of the projectin isoforms in indirect flight muscles may contribute to the elastic function of the C-filaments. The synchronous projectin isoforms contain a PEVK-like region, and the possible non-elastic function(s) of this domain in synchronous muscles are discussed.

Alternative Splicing↗

PubMed2006

Polycomb silencing mechanisms and genomic programming.

Polycomb complexes, best known for their role in the epigenetic silencing of homeotic genes, are now known to regulate a large number of functions in organisms from flies to man. They control transcription activators, pattern-forming genes, maintenance of stem cells and are implicated in cell proliferation and oncogenesis. Our understanding of Polycomb mechanisms derives principally from the study of homeotic genes in Drosophila, where they act in an all-or-none fashion to silence expression in inappropriate parts of the organism. This review summarizes what has been learned from homeotic genes and examines the possible extensions of Polycomb mechanisms to allow for dynamic regulatory behavior and the reprogramming of silenced chromatin states.

Animals↗

PubMed1994

Chilo iridescent virus encodes a putative helicase belonging to a distinct family within the "DEAD/H" superfamily: implications for the evolution of large DNA viruses.

The complete nucleotide sequence of the EcoRI DNA fragment M (7099 bp; 0.310-0.345 map units) of the genome of insect iridescent virus type 6--Chilo iridescent virus (CIV)--was determined. A 606 codon open reading frame located in this region encoded a protein (p69) related to a distinct family of putative DNA and/or RNA helicases belonging to the "DEAD/H" superfamily. Unique sequence signatures were derived that allowed selective retrieval of the putative helicases of the new family from amino acid sequence databases. The family includes yeast, Drosophila, mammalian, and bacterial proteins involved in transcription regulation and in repair of damaged DNA. It is hypothesized that p69 of CIV may be a DNA or RNA helicase possibly involved in viral transcription. A distant relationship was observed to exist between this family of helicases and another group of proteins that consists of putative helicases of poxviruses, African swine fever virus, and yeast mitochondrial plasmids. It is shown that p69 of CIV is much more closely related to cellular helicases than any of the other known viral helicases. Phylogenetic analysis suggested an independent origin for the p69 gene and the genes encoding other viral helicases.

Amino Acid Sequence↗

PubMed1994

Molecular analysis of a candidate gene for the reproductive isolation between sibling species of Drosophila.

The X-linked gene Hmr in Drosophila melanogaster, when mutated, rescues otherwise inviable interspecific hybrids from crosses between D. melanogaster and any of its three most closely related species D. simulans, D. mauritiana and D. sechellia. DNA from the site of a breakpoint at the putative locus of the gene has been cloned, and results of transcription and sequence analyses are presented. Three distinct mRNAs are transcribed from this locus, two of which are abundantly expressed throughout life. A third transcript, which is larger but rarer, appears to be disrupted by at least one of the two known mutations of Hmr. The gene encodes a mitochondrial ADP/ATP translocator protein, which plays an essential role in maintaining metabolic energy. Analysis of several cDNAs suggested that the rescue of hybrids may be dependent on mutations in the variable 3' end region of this gene, affecting the level and/or the stability of the largest messenger RNA.

Amino Acid Sequence↗

PubMed2005

Transposable element orientation bias in the Drosophila melanogaster genome.

Nonrandom distributions of transposable elements can be generated by a variety of genomic features. Using the full D. melanogaster genome as a model, we characterize the orientations of different classes of transposable elements in relation to the directionality of genes. DNA-mediated transposable elements are more likely to be in the same orientation as neighboring genes when they occur in the nontranscribed region's that flank genes. However, RNA-mediated transposable elements located in an intron are more often oriented in the direction opposite to that of the host gene. These orientation biases are strongest for genes with highly biased codon usage, probably reflecting the ability of such loci to respond to weak positive or negative selection. The leading hypothesis for selection against transposable elements in the coding orientation proposes that transcription termination poly(A) signal motifs within retroelements interfere with normal gene transcription. However, after accounting for differences in base composition between the strands, we find no evidence for global selection against spurious transcription termination signals in introns. We therefore conclude that premature termination of host gene transcription due to the presence of poly(A) signal motifs in retroelements might only partially explain strand-specific detrimental effects in the D. melanogaster genome.

Animals↗

PubMed2006

Fine-scale crossover rate heterogeneity in Drosophila pseudoobscura.

Broad-scale differences in crossover rate across the genome have been characterized in most genomes studied. Fine-scale differences, however, have only been examined in a few taxa, such as Arabidopsis, yeast, humans, and mice. No prior studies have directly looked for fine-scale recombination rate heterogeneity in Drosophila. We produced 370 Drosophila pseudoobscura containing a crossover event within the 2-megabase (MB) region between the genes yellow and white. We then examined 19 intervals within this region and determined where the crossovers occurred. We found that recombination events occur nonrandomly on a small scale and that mild "hotspots" of a few kilobases exist in Drosophila. Among the regions studied, recombination rates varied from 1.4 to 52 cM/MB. We also observed a trend toward high codon bias in regions of high recombination. Finally, we identified a significantly positive correlation between recombination rate and simple repeats, as well as the motif CACAC. These sequence features may contribute to broad-scale variation in crossover rate and, thus, shed light on features associated with crossover rate heterogeneity at a genome-wide scale.

Animals↗

PubMed2006

Abundance and chromosomal distribution of six Drosophila buzzatii transposons: BuT1, BuT2, BuT3, BuT4, BuT5, and BuT6.

The abundance and chromosomal distribution of six class-II transposable elements (TEs) of Drosophila buzzatii have been analyzed by Southern blotting and in situ hybridization. These six transposons had been previously found at the breakpoints of inversions 2j and 2q ( 7 ) of D. buzzatii. These two polymorphic inversions were generated by an ectopic recombination event between two copies of Galileo, a Foldback element. The four breakpoints became hotspots for TE insertions after the generation of the inversion and the transposons analyzed in this work are considered to be secondary invaders of these regions. Insertions of the six transposons are present in the euchromatin but show an increased density in the pericentromeric euchromatin-heterochromatin transition region and the dot chromosome. They are also more abundant in the inverted segments of chromosome 2 rearrangements. We further observed that the accumulation of TE insertions varies between elements and is correlated between dot, proximal regions, and inverted segments. These observations fully agree with previous data in Drosophila melanogaster and support recombination rate as the chief force explaining the chromosomal distribution of TEs.

Animals↗

PubMed2006

Molecular characterization and genomic distribution of Isis: a new retrotransposon of Drosophila buzzatii.

A new transposable element, Isis, is identified as a LTR retrotransposon in Drosophila buzzatii. DNA sequence analysis shows that Isis contains three long ORFs similar to gag, pol and env genes of retroviruses. The ORF1 exhibits sequence homology to matrix, capsid and nucleocapsid gag proteins and ORF2 encodes a putative protease (PR), a reverse transcriptase (RT), an Rnase H (RH) and an integrase (IN) region. The analysis of a putative env product, encoded by the env ORF3, shows a degenerated protein containing several stop codons. The molecular study of the putative proteins coded by this new element shows striking similarities to both Ulysses and Osvaldo elements, two LTR retrotransposons, present in D. virilis and D. buzzatii, respectively. Comparisons of the predicted Isis RT to several known retrotransposons show strong phylogenetic relationships to gypsy-like elements, particulary to Ulysses retrotransposon. Studies of Isis chromosomal distribution show a strong hybridization signal in centromeric and pericentromeric regions, and a scattered distribution along all chromosomal arms. The existence of insertional polymorphisms between different strains and high molecular weight bands by Southern blot suggests the existence of full-sized copies that have been active recently. The presence of euchromatic insertion sites coincident between Isis and Osvaldo could indicate preferential insertion sites of Osvaldo element into Isis sequence or vice versa. Moreover, the presence of Isis in different species of the buzzatii complex indicates the ancient origin of this element.

Animals↗

PubMed2007

Copper homeostasis gene discovery in Drosophila melanogaster.

Recent studies have shown a high level of conservation between Drosophila melanogaster and mammalian copper homeostasis mechanisms. These studies have also demonstrated the efficiency with which this species can be used to characterize novel genes, at both the cellular and whole organism level. As a versatile and inexpensive model organism, Drosophila is also particularly useful for gene discovery applications and thus has the potential to be extremely useful in identifying novel copper homeostasis genes and putative disease genes. In order to assess the suitability of Drosophila for this purpose, three screening approaches have been investigated. These include an analysis of the global transcriptional response to copper in both adult flies and an embryonic cell line using DNA microarray analysis. Two mutagenesis-based screens were also utilized. Several candidate copper homeostasis genes have been identified through this work. In addition, the results of each screen were carefully analyzed to identify any factors influencing efficiency and sensitivity. These are discussed here with the aim of maximizing the efficiency of future screens and the most suitable approaches are outlined. Building on this information, there is great potential for the further use of Drosophila for copper homeostasis gene discovery.

Animals↗

PubMed2006

Mobilization of a hobo-related sequence in the genome of Drosophila simulans.

The hobo transposable element can occur under three forms in the Drosophila genome: as a complete element (also called canonical), as internally deleted copies, or as hobo-related sequences (relics). Some evidence indicated that canonical elements and internally deleted copies are recent acquisitions of Drosophila genomes, while the "relics" are old components, normally degenerated and immobile. Here we present the characterization of a hobo-related sequence, found in the genome of a hypermutable strain of D. simulans, which insertion into the white locus raised a de novo white mutation. It is a shorter hobo related element presenting, overall, roughly 18% of divergence at the DNA level from the canonical hobo, with many indels that make clear this element is defective. However, its ITRs and flanking regions are extremely conserved. This is the first hobo "relic" showed to be mobilizable. We suggest, and point up some evidences, toward the idea that this sequence could have been mobilized by the canonical element. The presence of a similar "relic" element in D. sechellia allows us to suggest that these elements have been maintained mobilizable since the time of divergence between these species.

ATP-Binding Cassette Transporters↗