Biomedical subjects

G Periquet

Publications and source records attributed to G Periquet.

At least 37 records · Page 2Linked to original sources

PubMed1997

Biological and molecular features of the relationships between Diadromus pulchellus ascovirus, a parasitoid hymenopteran wasp (Diadromus pulchellus) and its lepidopteran host, Acrolepiopsis assectella.

The Diadromus pulchellus ascovirus (DpAV) has been isolated from laboratory strains of Diadromus pulchellus and in natural wild populations collected from the Antibes locality (southern France). The DpAV genome was found in the cells of the head, thorax and abdomen of this hymenopteran wasp. DpAV virions are present in the female genitalia and are transmitted to the nymphal lepidopteran host, Acrolepiopsis assectella, at each oviposition of the female wasp. The presence of the DpAV genome in all Diadromus somatic cells suggests that it is inherited by vertical transmission. DpAV is amplified in the host tissues during the larval development of D. pulchellus in A. assectella. Cell lysis due to amplification of the virus does not prevent the development of the hymenopteran larva. Virus amplification appears to be slower in nymphs parasitized by D. pulchellus than in nymphs artificially infected with DpAV alone. Lysis of the nymphal cells due to viral replication seems to be synchronous with egg hatching and the development of the hymenopteran larva. The features of DpAV and its relationship with the parasitoid wasp D. pulchellus during its development are compared to those of the ichnoviruses.

Animals↗

PubMed1996

Computer analyses reveal a hobo-like element in the nematode Caenorhabditis elegans, which presents a conserved transposase domain common with the Tc1-Mariner transposon family.

The present report describes the use of computer analyses to reveal a hobo-like element in the genome of Caenorhabditis elegans. This hobo-like sequence is 3039 bp long, contains two inverted terminal repeats of 25-27 bp and probably does not encoded a functional transposase. Sequence comparisons suggest that each transposase of hobo elements probably has a D(D/S)E motif. Thus the transposases of the hAT superfamily of transposons appear to be close to the other transposases and intregrases.

Amino Acid Sequence↗

PubMed1996

Transcription of four satellite DNA subfamilies in Diprion pini (Hymenoptera, Symphyta, Diprionidae).

Four satellite DNA subfamilies Ps, Pv, Pv65 and Ec, resulting from the evolution of a common ancestral motif, were isolated and characterized in the genomic DNA of Diprion pini, a phytophagous of Pinus sylvestris. Consensus sequences were 148-312 bp long. Sequence analyses revealed that these satellite subfamilies have evolved from a 45-bp ancestral motif. The amounts of each satellite in the genome (0 - 10%) and the accessibility of the DNA to restriction enzymes were sex dependent. The migration of each monomer in polyacrylamide gels and the electrophoretic migration of d(AT) n > or = 3 residues showed that all four satellite subfamilies are curved. Their transcription was analyzed using reverse transcription and the polymerase chain reaction. Three satellite DNA subfamilies were transcribed on both strands, and in both sexes. However, the female satellite DNAs seem to be more actively transcribed than those of males, indicating that transcription is not constitutive. The lack of any significant open reading frame in satellite monomers indicates that the RNA may function as structural or catalytic RNA rather than encoding protein.

Animals↗

PubMed1995

Human and other mammalian genomes contain transposons of the mariner family.

Internal fragments of the putative transposase gene of mariner-like elements (MLEs) were amplified from human, mouse, rat, chinese hamster, sheep and bovine genomic DNAs by polymerase chain reaction (PCR). The sequences identified in human, ovine and bovine genomes correspond to ancient degenerate transposons. Screening mammalian sequence libraries identified a truncated element in the human ABL gene and the sequence of its 5'-ITR was determined. This ITR sequences were used in PCR experiments with DNA from six mammalian species and detected full-sized and deleted MLEs. The presence of MLE in mammalian genomes demonstrates that they are ubiquitous mobile elements found from fungi to man. This observation strongly raises the possibility that MLE could constitute tools for the modification of eucaryotic genomes.

Amino Acid Sequence↗

PubMed1995

The genome segments of DpRV, a commensal reovirus of the wasp Diadromus pulchellus (Hymenoptera).

The complete nucleotide sequences of the five double-stranded RNA genome segments of the Diadromus pulchellus reovirus (DpRV) have been determined. They consist of 985, 1240, 1318, 1652, and 4230 bp. Each segment contains at least one putative open reading frame encoding 33-, 40-, 45-, 49-, and 148-kDa proteins, respectively. The proteins have no significant similarities with sequences in data banks. Analysis of these segments and of two other previously published segments revealed the presence of degenerate consensus inverted repeats at both ends (5'-rCAAUUUUnnACU...AGUAAAAAAAUnrG-3'). The biological, structural, and genomic features of DpRV suggest that this virus is related to members of the Orthoreovirus genus.

Amino Acid Sequence↗

PubMed1995

Spread of the autonomous transposable element hobo in the genome of Drosophila melanogaster.

The transposable element hobo has been introduced into the previously empty Drosophila melanogaster strain Hikone so that its dynamics can be followed and it can be compared with the P element. Five transformed lines were followed over 58 generations. The results were highly dependent on the culture temperature, the spread of hobo element being more efficient at 25 degrees C. The multiplication of hobo sequences resulted in a change in the features of these lines in the hobo system of hybrid dysgenesis. The number of hobo elements remained low (two to seven copies) and the insertions always corresponded to complete sequences. Our findings suggest that, despite their genetic similarities, P and hobo elements differ in many aspects, such as mobility and regulation mechanisms.

Animals↗

PubMed1994

A member of the reoviridae (DpRV) has a ploidy-specific genomic segment in the wasp Diadromus pulchellus (Hymenoptera).

Wild and laboratory populations of the parasitoid wasp Diadromus pulchellus are infected with a new member of the reoviridae (DpRV) described in this paper. The particles of this virus possess two capsid shells (diameters: 35 and 70 nm) made up of 11 proteins. The virus is present mainly in the gut of the wasp, with smaller quantities in its venom gland. The genome of virus particles purified from haploid insects (functional males) contains 10 segments, whereas virus from diploid insects (females and sterile diploid males) contains a supernumerary 3.33-kb segment. The sequence of this dsRNA segment revealed that it is a triplicated 1050-bp motif which is 97.5% similar to the 5' region of one of the 10 basic segments, the 3.80-kb segment.

Amino Acid Sequence↗

PubMed1994

Mariner-like elements in hymenopteran species: insertion site and distribution.

Copies of mariner-like element (MLE) transposons in two species, the bumble bee, Bombus terrestris, and the ant, Myrmica ruginodis, were sequenced. The full-sized elements are 1250 bp long in both species and include 28-bp inverted terminal repeats. The five copies sequenced were approximately 75% similar to a mariner element (peach) of Drosophila mauritiana. The distribution of MLE in 27 hymenopteran species was studied by PCR and Southern blot hybridization; 93% of the species contained one or more of the four major forms of the element. They are inserted in their host genomes, in the middle of a degenerated 30-bp palindrome, which is itself located in an 85-bp conserved region with a purine-rich tail at one of its ends. The hymenopteran MLEs lie in a specific insertion site, suggesting that this region is conserved. It is thus possible that this region may be a selectively neutral insertion site, which would explain why these elements are widespread in hymenopteran genomes and are not eliminated by male haploidy.

Animals↗

PubMed1994

The evolutionary genetics of the hobo transposable element in the Drosophila melanogaster complex.

Hobo elements are a family of transposable elements found in Drosophila melanogaster and its three sibling species: D. simulans, D. mauritiana and D. sechellia. Studies in D. melanogaster have shown that hobo may be mobilized, and that the genetic effects of such mobilizations included the general features of hybrid dysgenesis: mutations, chromosomal rearrangements and gonadal dysgenis in F1 individuals. At the evolutionary level some hobo-hybridizing sequences have also been found in the other members of the melanogaster subgroup and in many members of the related montium subgroup. Surveys of older collected strains of D. melanogaster suggest that complete hobo elements were absent prior to 50 years ago and that they have recently been introduced into this species by horizontal transfer. In this paper we review our findings and those of others, in order to precisely describe the geographical distribution and the evolutionary history of hobo in the D. melanogaster complex. Studies of the DNA sequences reveal a different level of divergence between the group D. melanogaster, D. simulans and D. mauritiana and the fourth species D. sechellia. The hypothesis of multiple transfers in the recent past into the D. melanogaster complex from a common outside source is discussed.

Amino Acid Sequence↗

PubMed1994

Invasion of the hobo transposable element studied by in situ hybridization on polytene chromosomes of Drosophila melanogaster.

The invasion kinetics of hobo transposable element in the Drosophila melanogaster genome was studied by in situ hybridization on the polytene chromosomes. Six independent lines of Drosophila melanogaster flies that had been previously transformed by microinjection of the pHFL1 plasmid containing a complete hobo element were followed over 50 generations. We observed that hobo elements were scattered on each of the chromosome arms, with more insertion sites on the 3R arm. The total number of insertion sites remains quite small, between four and six, at generation 52. On the 2R arm, a short inversion appeared once at generation 52. Most of the integration sites reported here were already described for several transposons but some of them appear to be hotspots for hobo elements.

Animals↗

PubMed1994

Horizontal transmission versus ancient origin: mariner in the witness box.

The transposable element mariner has been found in many species of Drosophilidae, several groups of Arthropods, and more recently in Platyhelminthes as well as in a phytopathogenic fungus. In the family Drosophilidae, the distribution of mariner among species shows many gaps, and its geographical distribution among endemic species is restricted to Asia and Africa. Among mariner elements in species within and outside the Drosophilidae, the similarities in nucleotide sequence and the amino acid sequence of the putative transposase reveal many phylogenetic inconsistencies compared with the conventional phylogeny of the host species. This paper discusses the contrasting hypotheses of horizontal transfer versus ancestral origin proposed to explain these results.

Africa↗

PubMed1994

Sequencing and gene expression of hypodermins A, B, C in larval stages of Hypoderma lineatum.

The cDNAs of hypodermins, enzymes secreted by the larvae of the parasitic fly Hypoderma lineatum, were sequenced. Four cDNA clones were isolated, one encoding hypodermin A (HA), one encoding hypodermin C (HC), and the two others encoding proteins related to hypodermin B (HB). The amino acid sequences deduced from the nucleotide sequences confirmed that these enzymes are serine proteases. HA and one of the HB proteins had potential N-linked glycosylation sites. Analysis of hypodermin protein, RNA and DNA at different larval stages indicated that protein overexpression is regulated transcriptionally for HA and HB, and by transcriptional and DNA amplification for HC.

Amino Acid Sequence↗

PubMed1993

Evolution of the Drosophila melanogaster-sigma virus system in natural populations from Languedoc (southern France).

An analysis of natural populations of Drosophila melanogaster in a southern French region (Languedoc) was started in 1983, concerning two non Mendelian systems: the P-M system of transposable elements and the sigma virus. This virus is not contagious, but only transmitted through gametes; it is usually present in a minority of individuals in natural populations. The first data collected revealed unexpectedly clear and fast-evolving phenomena; they also gave evidence of some interesting correlations between the two systems. This paper presents all the results gathered from 1983 to 1991 in the Drosophila-sigma system. Striking correlations were observed for three interconnected parameters: frequency of infected flies, frequency of an allele of the fly giving resistance to the virus, and adaptation of the virus to this allele. This adaptation consisted of a qualitative step (change of viral type) followed by quantitative variation (better adaptation to the allele). This analysis also showed, firstly, that the evolution of natural populations differs completely in Languedoc from the rest of France; secondly, that three geographical zones where selective forces worked differently persisted over time in Languedoc.

Adaptation, Physiological↗

PubMed1993

The occurrence of the transposable element pogo in Drosophila melanogaster.

We examined the genomic occurrence of the transposable element pogo in over 120 strains of Drosophila melanogaster, from around the world and from different eras. All had multiple copies of a 2.1 kilobase (kb) pogo element, and multiple copies of several size classes between 1.0 and 1.8 kb. There were differences between strains in intensities or presences of deletion-derivative size classes, suggesting current or recent mobility in the species. We were unable to find any pogo-hybridization in eight other species in the genus, in three subgenera, or in the related Scaptomyza pallida. The pogo element may be a 'middle-aged' element in the genome of D. melanogaster, having entered the species since its divergence from its sibling species, but long before the P and hobo elements.

Animals↗

PubMed1993

DNA insertions as a component of the evolution of unique satellite DNA families in two genera of parasitoid wasps: Diadromus and Eupelmus (Hymenoptera).

In the two parasitoid wasps, Diadromus collaris and Eupelmus orientalis, the satellite DNAs were each found to consist wholly or largely of a single family (5%-7% of the genome). Several clones of each family were obtained and sequenced. The repeat unit in each species is characterized by both the repetition of a basic motif and the presence of an inserted sequence. Sequence comparisons with satellite DNA from D. pulchellus and E. vuilleti provide plausible scenarios for the evolution of the satellite DNA in each genus. Palindromes and A-rich tracts in each consensus sequence suggest the formation, in vivo, of hairpin structures and bend centers that may play a role in heterochromatin condensation in insects. The insertions in the repeat units of each species also contain these structural features, suggesting that maintenance of these insertions requires constraints similar to those pertaining to the rest of the satellite-DNA unit.

Animals↗

PubMed1992

Comparative evolution of P-M system and infection by the sigma virus in French and Spanish populations of Drosophila melanogaster.

In 1983, an extensive survey of populations of D. melanogaster was started in a southern French region (Languedoc) in two non-Mendelian systems: the P-M system of transposable elements and the hereditary Rhabdovirus sigma. Unexpectedly fast-evolving phenomena were observed and interesting correlations were noted, giving similar geographical pattern to the region in both systems. For these reasons, the analysis was continued and extended towards the north (Rhône Valley) and the south (Spain). In the P-M system, all the Languedoc populations evolved from 1983 to 1991 towards the Q type which is characteristic of the Rhône Valley populations. In contrast, M' strains are currently observed in the southernmost French populations and in all Spanish ones, so that there is a clear pattern in their geographical distribution. The frequency of flies infected by the sigma virus dramatically increased from 1983 to 1988 in Languedoc; this increase was clearly correlated with some viral characteristics. But, in northern France, similar characteristics did not trigger any increase in the frequency of infected flies. The data presented here show that the distinctive features of Languedoc extend northwards through the Rhône Valley up to Lyon and disappears southwards before the Spanish border.

Alleles↗

PubMed1992

Mitotic and salivary gland chromosome analyses in the Musca domestica L. (house fly) (Diptera: Muscidae).

The mitotic chromosomes in Musca domestica consist of five pairs of autosomes and an X, Y sex chromosome pair. They respond to C-banding with procentric bands on all autosomes and deep staining over most of the X and Y chromosomes. Polytene chromosomes were previously found in several larval and pupal tissue of Musca domestica. Polytene chromosome reference maps of the two sexual and the five autosomal chromosomes of Musca domestica from salivary gland cells are shown. Characteristic features of each chromosome are described identifying areas that are difficult to analyse.

Animals↗

PubMed1991

Genetic and molecular analyses of vgal: a spontaneous and unstable mutation at the vestigial locus in Drosophila melanogaster.

We describe herein, a new unstable mutant of the vestigial locus, isolated from a French natural population. From this mutant vestigial almost (vgal) wild-type flies (vgal+) and extreme vg phenotypes (vge) arose spontaneously without genomic shock. The occurrence of vgal+ or vge alleles depends mostly on the breeding temperature; vgal+ revertants arose principally at low temperature (21 degrees C) and vge at 28 degrees C. These events occur mainly in the male germ line and the phenomenon appears to be premeiotic. Our results with in situ hybridization experiments and Southern blots show that the vgal mutation is due to a 2 kb DNA insertion, which is a deleted hobo element. Genetic and molecular analyses show that two distinct events may underly the wild-type revertants. One is the excision of the resident hobo element, the other a further deletion (about 300 bp in the example characterized herein). The vge mutation is probably due to a deletion of vestigial sequences flanking the hobo insertion.

Alleles↗