1993 Fiscal Year Final Research Report Summary
Regulation of host defense reaction gy parasitoid
| Project/Area Number |
04660046
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
植物保護
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| Research Institution | Nagoya University |
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Principal Investigator |
TANAKA Toshiharu Nagoya University, School of Agricultural Sciences, Associate Prof., 農学部, 助教授 (30227152)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Host regulation / polydnavirus / venom / Encapsulation / Defense reaction / Parasitoid |
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| Research Abstract |
Both eggs and larvae of parasitoids can avoid defense reaction of hosts when parasitization occurred in suitable host. In this project, the reason why eggs and larvae are not encapsulated in the hemocoel of host was anslysed in Pseudaletia-Cotesiakariyai system. To examine the change of the ability of encapsulation by parasitization, Sephadex beads as foreign substance were injected into hosts. Thickness of encapsulation layr around Sephadex beads decreased with lapse of days after oviposition. Its decreasing thickness seems to depend on two causes : decreasing of number of hemocytes or change of receptor hemocytes to discriminate the foreigh substances. However, completely depression of number of hemocytes made the parasitoid disadvantage because of easy infection by bacteria. Counting of total hemocyte made clear that number of hemocytes decreased to 1/5 compared with one of unparasitized hosts in one days after parasitization, was maintained until emerge of parasitoid. Decreasing the number of hemocytes for a short term in parasitized host was caused by both polydnavirus and venom, which was injected into the host at the time of oviposition. Artificial injection of both polydnavirus and venom caused reduced number of hemocytes within 1 hr post-injection. Attached hemocytes on glass plate were so related with processing of encapsulation against foreign materials. Number of attached hemocytes was also decreased with lapse of days after oviposition. A fewer granulocyte in hemocyte fraction separated by parcoll gradient was observed with lapse of days after parasitization. Sephadex beads coated with venom were hard to be encapsulated by hemocytes preconditioned with polydnavirus and venom 6 h before injection in in vitro incubation system. These results suggested that during egg stage, eggs coated with venom was hard to be distinguished as foreign substance. Additionally, at the same time, the number of hemocytes was decreased by the function of both polydnavirus an
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