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Endoparasitoid Wasp (endoparasitoid + wasp)
Selected AbstractsDetailed characterization of polydnavirus immunoevasive proteins in an endoparasitoid waspFEBS JOURNAL, Issue 10 2002Kohjiro Tanaka Polydnaviruses are a unique group of insect viruses in terms of their obligate and symbiotic associations with some parasitic wasps. The Cotesia kariyai polydnavirus (CkPDV) replicates only in ovarian calyx cells of C. kariyai female wasps and is injected into the wasp's host, the armyworm Pseudaletia separata, along with the eggs. A previous study indicated the possibility that one of the CkPDV surface proteins mediates immunoevasion by the wasp from the encapsulation reaction of the host insect's hemocytes. This protein was named immunoevasive protein (IEP). The present studies substantially confirmed the previous observation by showing that an anti-IEP IgG neutralizes immunoevasive activity on the wasp eggs. Further, we isolated the IEP homologue (IEP-2) cDNA and IEP (IEP-1) cDNA, sequenced them and found that both are cysteine-rich proteins, each containing epidermal growth factor (EGF)-like repeats. IEP genes were not found to reside in the CkPDV genome, but in the wasp chromosomal DNA. IEPs are synthesized in the female reproductive tract and their expression was detected from 4 days after pupation, 1 day later than expression of the virus capsid proteins. In situ hybridization and immunocytochemistry indicated that the lateral oviduct cells of the reproductive tracts produce IEP-1/IEP-2 mRNAs and secrete the proteins into the oviduct. These data suggest that the expression pattern and localization of IEPs are different from other components of CkPDV virions. [source] N-terminal tail of a viral histone H4 encoded in Cotesia plutellae bracovirus is essential to suppress gene expression of host histone H4INSECT MOLECULAR BIOLOGY, Issue 1 2009W. Gad Abstract An endoparasitoid wasp, Cotesia plutellae, possesses a symbiotic bracovirus (CpBV), which facilitates parasitism of a specific host, such as larvae of the diamondback moth, Plutella xylostella. A viral histone H4 (CpBV-H4) has been found in the CpBV genome and its gene product plays a role in impairing the host insect cellular immune response. Based on its high similarity to histone H4 of P. xylostella apart from its extended N-terminal tail, it has been suspected to alter host gene expression. Histone subunits were purified from parasitized P. xylostella larvae and found to contain both host and viral H4s, confirming a previous report of a possible epigenetic mode of action. Moreover, this study showed that the host H4 levels in the parasitized larvae clearly decreased during the parasitization period, whereas CpBV-H4 levels maintained a significant level without significant changes. To understand the decrease of host H4 levels, transcription levels of host H4 were monitored by quantitative reverse-transcriptase PCR (RT-PCR) and showed a significant decrease in parasitized P. xylostella larvae, whereas no significant change of the mRNA level was detected in nonparasitized larvae. This transcriptional control of host H4 expression was also observed by inducing transient expression of CpBV-H4 in nonparasitized P. xylostella. Moreover, co-injection of CpBV-H4 and its specific double-stranded RNA recovered the host H4 expression level. To identify a functional domain of CpBV-H4 involved in the transcriptional control, the extended N-terminal tail of CpBV-H4 was removed by preparing a truncated viral H4 construct in an expression vector by deleting the N-terminal tail of 38 amino acid residues and inducing its expression in nonparasitized P. xylostella larvae. The truncated CpBV-H4 clearly lost its inhibitory effects on host H4 transcription. Moreover, the presence of CpBV-H4 affects the spreading of host haemocytes by an epigenetic effect, which is at least partly restored in larvae expressing the truncated version of CpBV-H4. This study suggests that the viral H4 encoded in CpBV can alter host gene expression with its extended N-terminal tail. [source] Altered actin polymerization of Plutella xylostella (L.) in response to ovarian calyx components of an endoparasitoid Cotesia plutellae (Kurdjumov)PHYSIOLOGICAL ENTOMOLOGY, Issue 2 2009MADANAGOPAL NALINI AbstractCotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae), a solitary braconid endoparasitoid wasp, parasitizes the diamondback moth Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) by suppressing the host defense response, thereby resulting in successful parasitization. During parasitization, ovarian calyx fluid is also delivered into the haemocoel of the host along with the wasp egg. The effect of calyx fluid constituents on haemocyte-spreading behaviour of P. xylostella is analysed by measuring F-actin development in the haemocytes. For this purpose, the calyx fluid of C. plutellae is separated into ovarian protein and C. plutellae bracovirus (CpBV). The ovarian protein consists of a wide range of molecular weight proteins, which are apparently different from those of CpBV. When nonparasitized P. xylostella haemocytes are incubated with either ovarian protein or CpBV for 1 or 2 h, haemocytes lose their responsiveness to a cytokine, plasmatocyte-spreading peptide, in a dose-dependent manner for each calyx component and fail to exhibit haemocyte-spreading behaviour. Some CpBV genes are expressed within 1 h of parasitization. The inhibition of haemocyte-spreading could be explained by measuring F-actin contents, in which parasitization by C. plutellae inhibits F-actin development in the haemocytes of P. xylostella. Either ovarian protein or CpBV could inhibit F-actin development in the nonparasitized haemocytes. In addition, co-incubation of ovarian protein and CpBV results in significant additive inhibition of both haemocyte-spreading and F-actin development in the haemocytes in response to cytokine. These results suggest that both components of C. plutellae calyx fluid function in a synergistic manner, leading to immunosuppression during the early stage of parasitization. [source] Venom of Pteromalus puparum (Hymenoptera: Pteromalidae) induced endocrine changes in the hemolymph of its host, Pieris rapae (Lepidoptera: Pieridae)ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 1 2009Jia-Ying Zhu Abstract Pteromalus puparum is a predominant endoparasitoid wasp of Pieris rapae. Its venom is the only active factor injected into host associated with oviposition. In this report, we explored whether the venom alone from this wasp affects the endocrine system of its host or not. We monitored the changes of hemolymph juvenile hormone (JH; only JH III detected), ecdysteroid, and juvenile hormone esterase activity (JHE) over 72,h in parasitized and venom-microinjected P. rapae pupae. Non-parasitized and PBS-microinjected P. rapae served as controls. Results showed that JH titers were significantly higher in parasitized and venom-microinjected pupae than that in control pupae during 24 to 72,h. After 12,h, JH titers were significantly promoted by parasitization and venom microinjection. JHE activities of non-parasitized and PBS-microinjected pupae were significantly higher than that of parasitized and venom-microinjected pupae, which was with a peak at 12,h (parasitized pupae) or 24,h (venom-microinjected pupae) during 6 to 48 and 12 to 36,h, respectively. The hemolymph titers of ecdysteroid in non-parasitized and PBS-microinjected pupae increased rapidly during 12 to 36,h with a peak at 36,h, and were higher than treatments before 48,h, while presenting a significant difference at 24 to 48,h between the treatments and controls. The results demonstrate that venom alone of this parasitoid wasp can disrupt its host's endocrine system. © 2009 Wiley Periodicals, Inc. [source] | |||||||||||||