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At least 973 records · Page 54Linked to original sources
PubMed2003

Does a deletion in a virus-like particle protein have pleiotropic effects on the reproductive biology of a parasitoid wasp?

Endoparasitoid insects have evolved mechanisms to counteract host immune defences. At oviposition, the endoparasitoid Venturia canescens injects virus-like particles (VLPs) together with the egg that interfere with the immune system of the host. These prevent encapsulation of the parasitoid egg. It has been shown that the gene coding for one of the VLP proteins exists in two variants (called Repeat-Plus (RP) and Repeat-Minus (RM)). Previous observations suggested that these variants induce pleiotropic effects on the reproductive biology of the female resulting, in an impeded transfer of eggs from the ovarioles to the oviducts in RM females, and in alterations in the egg laying sequence. We show that RM females from another geographical locality do not exhibit any phenotypic alteration of the reproductive biology. By showing a lack of association between VLP alleles and the reproductive phenotypic characteristics in a given strain, our results do not support the hypothesis of pleiotropic effects. Conversely, the results suggest that different genes code for the VLPs and for the reproductive biology characteristics. Different phenomena such as linkage, the action of pathogens, etc. could explain the association between characters that is observed in some strains.

Animals↗
PubMed2006

Effects of venom/calyx fluid from the endoparasitic wasp Cotesia plutellae on the hemocytes of its host Plutella xylostella in vitro.

Crude venom and calyx fluid from Cotesia plutellae (Hymenoptera Braconidae) were assayed for biological activity toward hemocytes of Plutella xylostella (Lepidoptera Plutellidae). Venom from C. plutellae displayed high activity toward the spreading of plasmatocytes of P. xylostella early in the incubation period, and the inhibition was more severe as the concentration of venom increased. However, most inhibited hemocytes spread normally after being incubated for 4h. No effects were found toward granular cells from the host. Additionally, the venom from C. plutellae had some lethal effects on hemocytes of P. xylostella at high concentrations. In contrast, when incubated with different concentrations of calyx fluid, the spreading of some hemocytes was inhibited, some began to disintegrate, and some were badly damaged with only the nucleus left. After 4h, the majority of hemocytes died. The same results were observed when hemocytes were incubated in calyx fluid together with venom. These results show that calyx fluid from C. plutellae may play a major role in the suppression of the host immune system, whereas venom from C. plutellae has a limited effect on hemocytes and probably synergizes the effect of calyx fluid or polydnavirus.

Animals↗
PubMed2003

Lipogenesis in an adult parasitic wasp.

The goal of this study was to determine the extent of lipogenesis in the parasitoid Eupelmus vuilletti (Hymenoptera: Eupelmidae). Carbohydrate and lipid metabolism were followed in glucose-fed and starved females over 3 days. Fed females increased their glycogen level, while maintaining their lipid level. Starved females used most of their glycogen, while maintaining their lipid level too. Thus, females either use exclusively sugars to preserve their lipid reserves, or maintained a steady renewal of lipids through lipogenesis. The incorporation of radioactively marked glucose into lipids showed however that lipogenesis did not occur at a sufficient level to increase lipid reserves and to compensate for lipid use. This result has important implications for understanding nutrients allocation strategy in this species as the amount of lipids is almost totally fixed upon the emergence. From an evolutionary perspective, we call for detailed physiological studies of lipogenesis in a wide range of adult hymenopterans, as the absence of lipogenesis could be common to all of Aculatea.

Animals↗
PubMed2004

A molecular phylogeny of eurytomid wasps inferred from DNA sequence data of 28S, 18S, 16S, and COI genes.

Using partial DNA sequence data from nuclear 28S and 18S genes and mitochondrial 16S and COI genes, we reconstructed a phylogeny of the family Eurytomidae. Both maximum parsimony and Bayesian methods were employed. The analysis revealed a significant incongruence between the mitochondrial genes and the nuclear genes, and we chose the results from the nuclear genes as our preferred hypothesis. Our phylogeny suggested that the family Eurytomidae is not a monophyletic group; neither are the genera Eurytoma and Bruchophagus. The monophyly of genera Sycophila and Plutarchia was well supported, as was the close association of the genera Aiolomorphus, Tenuipetiolus, Bephratelloides, and Phylloxeroxenus. Our phylogeny also revealed an anticipated pattern, in which species groups from the genera Eurytoma and Bruchophagus are often more closely related to other small genera than to other species groups of the same genus. Subsequent taxonomic revisions include elevating the subfamily Rileyinae to a family status and the divisions of the genera Eurytoma and Bruchophagus.

Animals↗
PubMed2004

Dynamics of chemical mimicry in the social parasite wasp Polistes semenowi (Hymenoptera: Vespidae).

Chemical cues are so important in the recognition mechanism of social insects that most social parasites (which rely on hosts to rear their brood) have been documented as overcoming the mechanism by which colony residents recognize non-nestmates, by mimicking the odour of the usurped colony. We simulated in the laboratory the process by which the obligate social parasite, Polistes semenowi, invades nests of the host species, Polistes dominulus, in the field and analysed the epicuticular lipid layer before and after host nest usurpation. The experiment documents that P. semenowi social parasites have an epicuticular hydrocarbon pattern which is very similar to that of their host but, after entering host colonies, parasites mimic the odour of the colonies they invade, to the point that they perfectly match the hydrocarbon profile peculiar to the colony they entered. However, both before and after host nest invasion, parasites show a tendency to possess diluted recognition cues with respect to their hosts.

Animals↗
PubMed1996

Neuroactive polyamine wasp toxins: nuclear magnetic resonance spectroscopic analysis of the protolytic properties of philanthotoxin-343.

Acid-base properties (pKa values and proton distribution patterns) of philanthotoxin-343(PhTX-343) were investigated by 1H and 13C NMR titration. Chemical shift data and the total ionization shifts were used to assign carbon atoms of the polyamine chain. Nonlinear analysis of the 13C NMR titration curves gave four pKa values (pK1 8.5, pK2 9.5, pK3 10.4, pK4 11.4) and the intrinsic chemical shifts of the non-, mono-, di-, tri-, and tetraprotonated forms. The changes of intrinsic chemical shifts enabled analysis of the deprotonation sequence of fully protonated PhTX-343. The results of analysis of the 13C NMR titration curves were supported by 1H NMR data obtained from two-dimensional 1H, 13C chemical shift correlation experiments. Thus, the first deprotonation mainly takes place at the inner amino group. The phenol group is deprotonated in the second and third deprotonation steps. The preferential deprotonation of the inner amino group is also apparent in the deprotonated form. The monoprotonated form carries a practically fully ionized phenol group and the proton shared between the three amino groups. This characteristic is in agreement with existing data on polyamines. At physiological pH, the tetraprotonated form of PhTX-343 predominates, but the proportion of the triprotonated form becomes significant at low ionic strength. The terminal, primary amino group, which has been shown to be essential for biological activity, remains practically fully protonated at biologically relevant pH values, and this charge is likely to participate in the receptor-binding event. Protonation of the central amino group does not appear to be necessary for biological activity.

Carbon Isotopes↗