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Elucidation of Ecdysteroid Regulated Mechanisms in Tick Reproduction

蜱繁殖中蜕皮激素调节机制的阐明

基本信息

批准号：
18580050
负责人：
Taylor DeMar
金额：
$ 2.39万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

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.

血餐是大多数软甲科雌性动物繁殖所必需的。血粉似乎刺激后端的器官产生脂肪体刺激因子（FSF），该因子被认为是蜕皮类固醇，以诱导卵黄蛋白原（Vg）的合成。本文对卵黄发生与蜕皮激素关系的研究表明，蜕皮激素的生理性升高可加速卵黄合成，诱导卵成熟，刺激产卵。蜕皮激素在半变态昆虫和更原始的节肢动物中的分子作用研究很少。因此，我们鉴定并分析了蜕皮激素受体（EcR）和维甲酸X受体（RXR）在O. moubata交配和处女雌性，以进一步阐明蜱中蜕皮类固醇的调节机制。这些研究揭示了O. moubata与其他节肢动物的EcRs有很高的同源性，而OmRXR与硬蜱、甲壳动物和脊椎动物的RXR有很高的同源性，而与昆虫的RXR和USP没有同源性。OmEcR和OmRXR的表达符合蜕皮激素滴度在饱血的女性之前Vg合成和卵成熟，但交配和处女女性之间有一些差异。处女雌性合成低得多的浓度的Vg和卵成熟不可能发生，因为在整个生殖周期的蜕皮类固醇的低水平，但OmRXR的表达处女雌性高于交配的女性。需要进一步的研究来解释交配和处女雌性之间的这些差异。蜕皮激素/EcR/RXR复合物在调节软蜱卵黄发生中起重要作用。