2001 Fiscal Year Final Research Report Summary
Molecular Mechanisms Regulating Tick Vitellogenesis
| Project/Area Number |
12660040
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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 |
植物保護
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| Research Institution | University of Tsukuba |
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Principal Investigator |
Taylor DeMar University ofTsukuba, Institute of Agriculture and Forestry, Foreign Professor, 農林学系, その他 (50261772)
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| Co-Investigator(Kenkyū-buntansha) |
CHINZEI Yasuo Mie University, School of Medicine, Department of Medical Zoology, Professor, 医学部・医動物教室, 教授 (60024709)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Edvsteroid Receptor / Vitellogenesis / Soft Tick / Ornithodoros moubata / Ecdvsone / Vitellogenin / Endocrinology / DNA |
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| Research Abstract |
Our research has concentrated on characterization of vitellogenin (Vg) and elucidation of mechanisms regulating the expression of this protein in a soft tick. Vg synthesized in the fat body is carried by the hemolymph to the ovary and incorporated into the oocytes as vitellin (Vn). Previous studies have shown two factors, vitellogenesis-inducing factor (VIF) and fat body stimulating factor (FSF), regulate Vg synthesis. VIF is a peptide and FSF appears to be a steroid. Injection of high concentrations of ecdysteroids stimulates an increase in Vg tilers of unfed females. Analysis of ecdysteroid titers in the hemolymph, whole body and reproductive tracts of virgin and mated fed females indicate ecdysteroids regulate reproduction in ticks. Ecdysteroid and Vg concentrations remain at low levels, oocytes do not mature and no oviposition occurs in virgin females. On the other hand, three and four distinct ecdysteroid peaks are seen in mated female hemolymph and whole body extracts, respectively. The first peak coincides with the beginning of FSF secretion. The second, a large broad peak, coincides with absorption of Vg into the oocytes. The third peak, a small peak, occurs at the start of oviposition. The fourth large broad peak, only in the whole body, appears to be due to ecdysteroids in the reproductive tract. Experiments are underway to identify the ecdysteroid (EcR) and retinoid X (RXR) receptors of O. moubata. These studies indicate there are at least three isoforms of ecdysteroid receptors (EcR) in this tick. Expression of the ecdysteroid receptor genes during the different phases of vitellogenesis is under investigation now. The full sequence of the vitellogenin gene has not yet been completely analyzed, but when completed will allow us to determine if this gene has an ecdysteroid responsive element and to investigate vitellogenesis more carefully.
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Research Products
(2 results)
