| Project/Area Number |
18580050
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied entomology
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| Research Institution | University of Tsukuba |
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Principal Investigator |
Taylor DeMar University of Tsukuba, Graduate School of Life and Environmental Sciences, Assistant Professor (50261772)
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| Co-Investigator(Kenkyū-buntansha) |
CHINZEI Yasuo Mie University, School of Medicine, Department of Medical Zoology, Professor (60024709)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,740,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥240,000)
Fiscal Year 2007: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2006: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | vitellosenesis / ecdsyteroids / ecdysteroid receptor / retinoid X receptor / endocrinology / ovarian develoument / egg maturation / tick / Ornithodoros moubata / ビテロジェニン |
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| Research Abstract |
A blood meal is required for reproduction in most Argasidae females. The blood meal appears to stimulate an organ in the posterior end to produce a fat body stimulating factor (FSF), which is thought to be an ecdysteroid, to induce vitellogenin (Vg) synthesis. Our studies on the relationship of vitellogenesis and ecdysteroids indicate that physiological elevation of ecdysteroids accelerates Vg synthesis, induces egg maturation and stimulates oviposltion in fed mated Ornithodoros moubata females. There are few studies on the molecular actions of ecdysteroids in hemimetabolous insects and more primitive arthropods. Therefore, we identified and analyzed the expression of the ecdysteroid receptor (EcR) and retinoid X receptor (RXR) in O. moubata mated and virgin females to further elucidate the ecdysteroid regulated mechanisms in ticks. These studies revealed the ecdysteroid (OmEcRA) receptor from O. moubata has high homology with EcRs of other arthropods, whereas OmRXR showed high homology to hard tick, crustacean and vertebrate RXRs rather than insect RXRs and USPs. OmEcR and OmRXR expression coincided with ecdysteroid titers in engorged females before Vg synthesis and egg maturation but there were some differences between mated and virgin females. Virgin females synthesize much lower concentrations of Vg and egg maturation does not occur likely because of low levels of ecdysteroids throughout the reproductive cycle, but OmRXR expression in virgin females is higher than in mated females. Further studies are needed to explain these differences between mated and virgin females. The ecdysteroid/EcR/RXR complex appears to be important in the regulation of vitellogenesis of soft ticks.
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