1999 Fiscal Year Final Research Report Summary
Molecular Studies on the Regulation of Tick Vitellogenesis and Expression of Hormone Receptors
| Project/Area Number |
10660043
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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 of Tsukuba, Institute of Agriculture and Forestry Foreign Professor, (生物資源学類)農林学系, 外国人教師 (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) |
1998 – 1999
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| Keywords | Edysteroid Receptor / Vitellogenesis / Soft Tick / Ornithodoros moubata / Ecdysone / RXR / Endocrinology / DNA |
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| Research Abstract |
Over the past several years we have concentrated our efforts on characterization of vitellogenin (Vg) and elucidation of mechanisms regulating the expression of this protein in the soft ticks. Vg is synthesized in the fat body, carried by the hemolymph to the ovary and undergoes proteolysis to become vitellin (Vn). Vn is then incorporated into the oocytes. Previous studies have shown a peptide, vitellogenesis-inducing factor (VIF), produced by the synganglion, stimulates a tissue in the posterior half to produce a second factor, fat body stimulating factor (FSF), which stimulates the fat body to produce Vg. We speculate this second factor to be a steroid. Injection of high concentrations of ecdysteroids stimulates an increase in Vg titers of unfed females and analysis of ecdysteroid titers in the hemolymph indicates a role for ecdysteroids in the regulation of vitellogenesis. To clarify this role, experiments are underway to identify the ecdysteroid (EcR) and retinoid X (RXR) receptors of O. moubata. Analysis of clones produced by PCR of tick genomic DNA revealed partial sequences similar to the DNA binding domains of insect EcR and USP receptors. The partial sequences similar to the DNA binding domains of the EcR receptors showed 100% homology to the ixodid tick, Amblyomma americanum, 83% to Bombyx mori and 85% to the human FXR receptor. The products from PCR with the USP primers showed homologies of 93, 95 and 85% with the DNA binding domains of A. americanum, B. mori and human RXR receptors, respectively. In addition, separate clones showed 94, 89 and 87% homologies to the DNA binding domains of Drospholia melongaster seven-up, HR3 and HR78 nuclear orphan receptor genes.
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