SEARCH · PubMed Health

Results for “WASPS”

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 1,711 records · Page 95Linked to original sources

PubMed1990

Parasitoid virus-like particles destroy Drosophila cellular immunity.

Parasitoid wasps must avoid the destructive effects of the host's cellular defense system in order to exploit the host hemocoel as a suitable environment for their survival. To protect their eggs from encapsulation by Drosophila melanogaster blood cells, Leptopilina heterotoma females inject a factor that selectively destroys lamellocytes, the type of Drosophila blood cell involved in recognition and encapsulation of large foreign objects. Other types of host blood cells, including the phagocytic plasmatocytes, remain functional. This report demonstrates that the destructive factor for lamellocytes is a virus-like particle (VLP) stored in the reservoir of an accessory gland associated with the female wasp reproductive system. We show that VLPs enter Drosophila blood cells in vitro. VLPs are found free in the cytoplasm of lamellocytes but are confined to phagocytic vesicles of plasmatocytes. As lamellocytes are susceptible to the VLP infection and plasmatocytes are not, we conclude that the mode of VLP entry and its disposition in the cytoplasm determine the fate of the infected host blood cell.

Animals↗

PubMed1998

A protein with protective properties against the cellular defense reactions in insects.

The molecular mechanism of how insects recognize intruding microorganisms and parasites and distinguish them from own body structures is not well known. We explored evolutionary adaptations in an insect parasitoid host interaction to identify components that interfere with the recognition of foreign objects and cellular encapsulation. Because some parasitoids provide protection for the developing wasp in the absence of an overt suppression of the insect host defense, we analyzed the surface of eggs and symbiotic viruses for protective properties. Here we report on the molecular cloning of a 32-kDa protein (Crp32) that is one of the major protective components. It is produced in the calyx cells of the female wasp ovaries and attached to the surface of the egg and other particles including polydnaviruses. The recombinant protein confers protection to coated objects in a cellular encapsulation assay suggesting that a layer of Crp32 may prevent cellular encapsulation reactions by a local inactivation of the host defense system.

Amino Acid Sequence↗

PubMed2005

Sociality and the rate of molecular evolution.

The molecular clock does not tick at a uniform rate in all taxa but may be influenced by species characteristics. Eusocial species (those with reproductive division of labor) have been predicted to have faster rates of molecular evolution than their nonsocial relatives because of greatly reduced effective population size; if most individuals in a population are nonreproductive and only one or few queens produce all the offspring, then eusocial animals could have much lower effective population sizes than their solitary relatives, which should increase the rate of substitution of "nearly neutral" mutations. An earlier study reported faster rates in eusocial honeybees and vespid wasps but failed to correct for phylogenetic nonindependence or to distinguish between potential causes of rate variation. Because sociality has evolved independently in many different lineages, it is possible to conduct a more wide-ranging study to test the generality of the relationship. We have conducted a comparative analysis of 25 phylogenetically independent pairs of social lineages and their nonsocial relatives, including bees, wasps, ants, termites, shrimps, and mole rats, using a range of available DNA sequences (mitochondrial and nuclear DNA coding for proteins and RNAs, and nontranslated sequences). By including a wide range of social taxa, we were able to test whether there is a general influence of sociality on rates of molecular evolution and to test specific predictions of the hypothesis: (1) that social species have faster rates because they have reduced effective population sizes; (2) that mitochondrial genes would show a greater effect of sociality than nuclear genes; and (3) that rates of molecular evolution should be correlated with the degree of sociality. We find no consistent pattern in rates of molecular evolution between social and nonsocial lineages and no evidence that mitochondrial genes show faster rates in social taxa. However, we show that the most highly eusocial Hymenoptera do have faster rates than their nonsocial relatives. We also find that social parasites (that utilize the workers from related species to produce their own offspring) have faster rates than their social relatives, which is consistent with an effect of lower effective population size on rate of molecular evolution. Our results illustrate the importance of allowing for phylogenetic nonindependence when conducting investigations of determinants of variation in rate of molecular evolution.

Animals↗

PubMedDate not supplied

Visible mutation induction in Mormoniella by low frequency ultrasonic energy.

Low frequency ultrasonic energy was utilized in an attempt to induce visible mutations in the parasitoid wasp Mormoniella vitripennis (Walker). Ultrasonic exposure at a frequency of 20,000 cycles per second was accomplished in aqueous medium with a commercially obtained energy source. Among the 22,396 progeny of exposed males and females, 63 phenotypically changed wasps were recovered. Three of these changes from exposed males and two from exposed females proved to be genetically transmissible. No transmissible changes were found among 4,739 control progeny. This study demonstrates that low frequency ultrasound may be used as an effective mutagenic agent with this organism, and suggests that it may have applications with other genetic systems.

Animals↗

PubMed2001

Possible horizontal transfer of a transposable element from host to parasitoid.

Full-length mariner-like elements (MLEs) were identified from both a parasitoid wasp, Ascogaster reticulatus, and its moth host, Adoxophyes honmai. MLEs were detected in two related Tortricid moths, but not in another Ascogaster species. The MLEs of A. reticulatus and A. honmai were 97.6% identical in DNA sequence. This high similarity suggests a recent horizontal transfer, probably from the moth host to the wasp parasitoid, facilitated by the intimacy of the host-parasitoid relationship.

Amino Acid Sequence↗

PubMed1997

Phylogenetic analysis of a retrotransposon with implications for strong evolutionary constraints on reverse transcriptase.

This study examines the evolutionary dynamics of a retrotransposon in a group of parasitoid wasps. A region containing the reverse transcriptase (RT) domain was sequenced for 43 elements from the genomes of nine different wasp species. Phylogenetic analysis of the elements revealed concordance with taxonomic classification of the host species, and the pattern was consistent with that expected for vertical transmission of a multicopy element during differentiation of the species. Twenty-three of the 43 elements had comparable intact open reading frames in the amplified region, and these were used in an analysis of evolutionary constraint on the amino acid sequence. As previously documented for retroelements, closely related elements exhibited nearly equal substitution rates at nonsynonymous and synonymous sites, but relative nonsynonymous substitution rates decreased as increasingly divergent elements were compared. A statistical test indicated that the decrease was not due to saturation of weakly selected sites. The pattern is most likely caused by a "pseudogene effect." Individual elements are not subject to purifying selection, and therefore, synonymous and nonsynonymous substitutions accumulate at equal rates. Comparisons among closely related elements are influenced strongly by this pseudogene evolution, whereas comparisons among distantly related elements reveal selection on the actively replicating lineages connecting the elements. These distant comparisons more accurately reflect the constraints on the amino acid sequence, and the comparisons among elements in this study indicated strong constraints on RT.

Amino Acid Sequence↗

PubMed1998

Hierarchical analysis of variation in the mitochondrial 16S rRNA gene among Hymenoptera.

Nucleotide sequences from a 434-bp region of the 16S rRNA gene were analyzed for 65 taxa of Hymenoptera (ants, bees, wasps, parasitoid wasps, sawflies) to examine the patterns of variation within the gene fragment and the taxonomic levels for which it shows maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. As previously reported for many holometabolous insects, the 16S data reported here for Hymenoptera are highly AT-rich and exhibit strong site-to-site variation in substitution rate. More precise estimates of the shape parameter (alpha) of the gamma distribution and the proportion of invariant sites were obtained in this study by employing a reference phylogeny and utilizing maximum-likelihood estimation. The effectiveness of this approach to recovering expected phylogenies of selected hymenopteran taxa has been tested against the use of maximum parsimony. This study finds that the 16S gene is most informative for phylogenetic analysis at two different levels: among closely related species or populations, and among tribes, subfamilies, and families. Maximization of the phylogenetic signal extracted from the 16S gene at higher taxonomic levels may require consideration of the base composition bias and the site-to-site rate variation in a maximum-likelihood framework.

Animals↗

PubMed2000

Drosophila resistance genes to parasitoids: chromosomal location and linkage analysis.

Insect hosts can survive infection by parasitoids using the encapsulation phenomenon. In Drosophila melanogaster the abilities to encapsulate the wasp species Leptopilina boulardi and Asobara tabida each involve one major gene. Both resistance genes have been precisely localized on the second chromosome, 35 centimorgans apart. This result clearly demonstrates the involvement of at least two separate genetic systems in Drosophila resistance to parasitoid wasps. The resistance genes to L. boulardi and A. tabida are not clustered as opposed to many plant resistance genes to pathogens cloned to date.

Animals↗

PubMed2002

Caste totipotency and conflict in a large-colony social insect.

In most social insects with large, complex colonies workers and queens are morphologically quite distinct. This means that caste determination must occur prior to adulthood. However workers and queens in the swarm-founding epiponine wasps are often morphologically indistinguishable, or nearly so, suggesting that caste determination in these wasps could be quite different. To determine the extent of caste lability in the epiponine, Parachartergus colobopterus, we removed all the queens from one colony and all but one from another colony. Worker aggression diminished after queen removal. A week later the colony with no queens had a new, young cohort of mated queens. These must have been either adults or pupae at the time of queen removal, and so could not have been fed any differently from workers. Relatedness patterns confirmed that these new queens would normally have been workers and not queens. A model of inclusive fitness interests shows that workers ought to suppress new queen production, except at low queen numbers, a prediction supported by our empirical results. The patterns of social conflict over queenship resulting from swarm founding in a many-queen society may help to explain the unusually weak caste differentiation in the epiponines.

Animals↗

PubMed2003

Pollinator attraction in a sexually deceptive orchid by means of unconventional chemicals.

Ophrys flowers mimic virgin females of their pollinators, and thereby attract males for pollination. Stimulated by scent, the males attempt to copulate with flower labella and thereby ensure pollination. Here, we show for the first time, to our knowledge, that pollinator attraction in sexually deceptive orchids may be based on a few specific chemical compounds. Ophrys speculum flowers produce many volatiles, including trace amounts of (omega-1)-hydroxy and (omega-1)-oxo acids, especially 9-hydroxydecanoic acid. These compounds, which are novel in plants, prove to be the major components of the female sex pheromone in the scoliid wasp Campsoscolia ciliata, and stimulate male copulatory behaviour in this pollinator species. The specificity of the signal depends primarily on the structure and enantiomeric composition of the oxygenated acids, which is the same in wasps and in the orchids. The overall composition of the blend differs significantly between the orchid and its pollinator and is of secondary importance. 9-Hydroxydecanoic acid is a rarely occurring compound that until now has been identified only in honeybees. Contrary to the standard hypothesis that Ophrys flowers produce only 'second-class attractivity compounds' and are neglected once the pollinator females are present, we show that flowers are more attractive to the males than are their own females.

Animals↗

PubMed2003

Relative importance of predators and parasitoids for cereal aphid control.

Field experiments with manipulations of natural enemies of plant-feeding insects may show how a diverse enemy group ensures an important ecosystem function such as naturally occurring biological pest control. We studied cereal aphid populations in winter wheat under experimentally reduced densities of: (i) ground-dwelling generalist predators (mostly spiders, carabid and staphylinid beetles); (ii) flying predators (coccinellid beetles, syrphid flies, gall midges, etc.) and parasitoids (aphidiid wasps), and a combination of (i) and (ii), compared with open controls. Aphid populations were 18% higher at reduced densities of ground-dwelling predators, 70% higher when flying predators and parasitoids were removed, and 172% higher on the removal of both enemy groups. Parasitoid wasps probably had the strongest effect, as flying predators occurred only in negligible densities. The great importance of parasitism is a new finding for aphid control in cereal fields. In conclusion, a more detailed knowledge of the mechanisms of natural pest control would help to develop environmentally sound crop management with reduced pesticide applications.

Animals↗

PubMed1986

Molecular analysis of Campoletis sonorensis virus DNA in the lepidopteran host Heliothis virescens.

Nucleic acid hybridization techniques were used to analyse the fate of Campoletis sonorensis virus (CsV) DNAs in naturally parasitized and virus-injected Heliothis virescens larvae. Viral DNA persisted in injected H. virescens larvae from 0 to 10 days post-injection but no increase in the amount of viral DNA could be detected. Similarly, no increase in the amount of viral DNA was detected in naturally parasitized H. virescens larvae before the development of the C. sonorensis pupae. However, a dramatic increase of viral DNA was detected in pharate and newly emerged (0 to 48 h) adult C. sonorensis wasps. The results from these in vivo molecular analyses suggest that CsV replication does not occur in naturally parasitized or virus-injected H. virescens and that viral replication may be restricted to tissues of C. sonorensis wasps.

DNA Replication↗

PubMed1994

Polydnavirus infection inhibits synthesis of an insect plasma protein, arylphorin.

The wasp Campoletis sonorensis injects a segmented, double-stranded DNA polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. After parasitization, CsPDV protects the wasp egg and larva by selectively disabling the host's cellular immune response. Other host physiological systems including growth and development are affected to the apparent benefit of the parasite. To begin the characterization of the biochemical effects and mode of action of CsPDV on host growth, the titre of a developmentally regulated insect storage protein, arylphorin, was studied. Parasitized or virus-infected insects had substantially less circulating arylphorin than control insects. Fat bodies from parasitized larvae also synthesized less arylphorin in vitro. However, Northern blots of total RNA from parasitized and non-parasitized, control insects showed that the arylphorin transcript level was unaffected by parasitization suggesting a biochemical block at the translational level. In vitro translation followed by immunoprecipitation of arylphorin indicated that the mRNA was present and translatable at equal levels in both parasitized and control insects. Injection of purified virus elicited the response observed in naturally parasitized larvae, demonstrating that the effect on arylphorin synthesis is mediated, either directly or indirectly, by polydnavirus gene product(s).

Animals↗

PubMed1996

Isolation and characterization of a member of the cysteine-rich gene family from Campoletis sonorensis polydnavirus.

The endoparasitic wasp Campoletis sonorensis injects a symbiotic polydnavirus into its host Heliothis virescens. Viral gene expression protects the wasp egg and larva from encapsulation by host haemocytes. Three related C. sonorensis polydnavirus (CsPDV) genes, which are expressed in parasitized H. virescens, have been previously isolated and grouped into a cysteine-rich gene family. In this report, a CsPDV gene encoding an abundant 1.4 kb mRNA expressed in parasitized insects was isolated and mapped to viral segment V (15.2 kb) by Southern blotting and PCR. The VHv1.4 cDNA is 1338 bp long and has an ORF that encodes 322 amino acids with two complete and one partial cysteine motifs. Similar to other characterized CsPDV cysteine motifs, the VHv1.4 motifs are also characterized by six cysteines at conserved positions and variable inter-cysteine amino acids. DNA sequence analyses show that the VHv1.4 gene shares regions of significant identity (73-97%) with the VHv1.1 gene, a member of the cysteine-rich gene family. The VHv1.4 and the VHv1.1 proteins are 62% identical overall; at the N termini including the signal peptide and the N-terminal cysteine motif the identity is greater (90%). Unlike other CsPDV cysteine-rich genes, the VHv1.4 cDNA has two conserved domains (77% identical in nucleotides, 55% identical in amino acids) that presumably result from the duplication of a portion of the gene. The VHv1.4 gene has four introns with splicing sites located at positions similar to VHv11.1 introns. Introns 2 and 3, located in the first and second domains respectively, have greater identity (97%) than the flanking exon sequences (77%). We propose, based on the evidence presented in this paper, that the VHv1.4 gene is a new member of the cysteine-rich polydnavirus gene family.

Amino Acid Sequence↗

PubMed2002

Characterization of Chelonus inanitus polydnavirus segments: sequences and analysis, excision site and demonstration of clustering.

Polydnaviruses (genera Ichnovirus and Bracovirus) have a segmented genome of circular double-stranded DNA molecules, replicate in the ovary of parasitic wasps and are essential for successful parasitism of the host. Here we show the first detailed analysis of various segments of a bracovirus, the Chelonus inanitus virus (CiV). Four segments were sequenced and two of them, CiV12 and CiV14, were found to be closely related while CiV14.5 and CiV16.8 were unrelated. CiV12, CiV14.5 and CiV16.8 are unique while CiV14 occurs also nested in another larger segment. All four segments are predicted to contain genes and predictions could be substantiated in most cases. Comparison with databases revealed no significant similarities at either the nucleotide or amino acid level. Inverted repeats with identities between 77% and 92% and lengths between 26 bp and 100 bp were found on all segments outside of predicted genes. Hybridization experiments indicate that CiV12 and CiV14 are both flanked by other virus segments, suggesting that proviral CiV segments are clustered in the genome of the wasp. The integration/excision site of CiV14 was analysed and compared to that of CiV12. On both termini of proviral CiV12 and CiV14 as well as in the excised circular molecule and the rejoined DNA a very similar repeat of 14 bp was found. A model to illustrate where the terminal repeats might recombine to yield the circular molecule is presented. Excision of CiV12 and CiV14 is restricted to the female and sets in at a very specific time-point in pupal-adult development.

Animals↗

PubMed2002

Characterization of Campoletis sonorensis ichnovirus segment I genes as members of the repeat element gene family.

Campoletis sonorensis ichnovirus (CsIV) is a symbiotic virus associated with the endoparasitic wasp C. sonorensis. The virus is injected into the wasp's host, Heliothis virescens, during oviposition. One CsIV gene has been identified as a repeat element (rep) gene and encodes a ubiquitous imperfectly conserved 540 bp sequence. We report the sequencing and mapping of a rep-containing segment, segment I, that hybridizes to a known rep sequence from segment O(1). Analysis of this 8.6 kbp segment identified three ORFs having high similarity to the 540 bp rep sequence. All three rep sequence ORFs were expressed in parasitized H. virescens as well as in C. sonorensis tissues. Two of these rep genes, I 0.9 and I 1.1, have single copies of the 540 bp repeat sequence, while the third rep gene, I 1.2, has two imperfect copies, which are more similar to each other than to sequences on the segment I single-motif genes. Like the CsIV BHv 0.9 rep gene, the segment I rep genes lack introns and a signal peptide, suggesting that they are not secreted. Based on their similarity in nucleotide sequence, predicted amino acid sequence and gene structure, the three segment I repeat-containing genes, I 0.9, I 1.1 and I 1.2, are new members of the rep gene family.

Amino Acid Sequence↗

PubMed2003

Polydnavirus particle proteins with similarities to molecular chaperones, heat-shock protein 70 and calreticulin.

Multipartite nucleic acid-containing virus-like particles, known as polydnaviruses, are special structures produced by female parasitoid wasps to deliver wasp components into the body of their host at oviposition. The particles confer protection for the developing parasitoid by passive and active means. Although several genes expressed from the circular DNA of these particles have been identified from various host-parasitoid systems, there is not much known about the structural proteins of these particles. Here we report on two genes encoding Cotesia rubecula particle proteins with similarities to molecular chaperones, calreticulin and heat-shock protein 70.

Amino Acid Sequence↗

PubMed2005

Cloning, characterization and analysis by RNA interference of various genes of the Chelonus inanitus polydnavirus.

Successful parasitism of some endoparasitic wasps depends on an obligately symbiotic association with polydnaviruses. These unique viruses have a segmented genome consisting of circles of double-stranded (ds) DNA and do not replicate in the parasitized host. They are produced in the wasp's ovary and injected into the host along with the egg. Chelonus inanitus is an egg-larval parasitoid; its polydnavirus (CiV) has been shown to protect the parasitoid larva from the host's immune system and to induce developmental arrest in the prepupal stage. The genome of CiV consists of at least 10-12 segments and five have been sequenced up to now. Here, the complete (CiV12g2) or partial (CiV12g1, CiV16.8g1) cloning of three new CiV genes is reported. All three occur only on one viral segment and have no similarity to other known polydnavirus genes, with the exception of a high similarity of CiV12g1 to CiV14g1 and CiV12g2 to CiV14g2. Furthermore, the first attempt of in vivo application of RNA interference to study the function of polydnavirus genes is shown. Injection of dsRNA of two late- and one early- and late-expressed CiV genes into CiV/venom-containing host eggs partially rescued last-instar larvae from developmental arrest. Injection of the same dsRNAs into parasitized eggs partially reduced parasitoid survival, mainly by preventing the successful emergence of the parasitoid from the host. These viral genes thus seem to be involved in inducing developmental arrest and in keeping the cuticle soft, which appears to be necessary for parasitoid emergence and host feeding.

Amino Acid Sequence↗