The RXR homolog ultraspiracle is an essential component of the Drosophila ecdysone receptor.
The RXR homolog ultraspiracle is an essential component of the Drosophila ecdysone receptor.
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发表时间：
1998-12
期刊：
影响因子：
4.6
通讯作者：
B. L. Hall;C. Thummel
中科院分区：
文献类型：
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作者：
B. L. Hall;C. Thummel
类固醇激素蜕皮激素的脉冲在昆虫发育过程中作为关键的时间信号，协调主要的胚胎后发育转变，包括蜕皮和变态。体外研究表明，EcR蜕皮激素受体的活性需要RXR异源二聚体伴侣，由超螺旋（usp）位点编码。我们在这里表明，usp在三岁中期的幼虫中没有明显的作用，当一个调节等级为动物的变态开始做准备时。相反，三龄幼虫需要usp来对触发蛹形成的蜕皮激素脉冲做出适当的发育和转录反应。usp突变体的影像盘开始发育，但不延长或分化，幼虫的中肠和唾液腺不能经历程序性细胞死亡，成虫的中肠不能形成。与这些发育表型一致的是，usp突变体在蜕皮激素调节的基因表达中表现出多效性缺陷。Usp突变体也在蛹形成时再现幼虫蜕皮的各个方面，形成多余的角质层。这些观察结果表明，体内蜕皮激素受体活性需要usp，表明EcR/ usp异源二聚体在变态开始时以特定阶段的方式发挥作用，并暗示usp在幼虫发育过程中对蜕皮激素脉冲的反应中决定蜕皮或产卵。
Pulses of the steroid hormone ecdysone function as key temporal signals during insect development, coordinating the major postembryonic developmental transitions, including molting and metamorphosis. In vitro studies have demonstrated that the EcR ecdysone receptor requires an RXR heterodimer partner for its activity, encoded by the ultraspiracle (usp) locus. We show here that usp exerts no apparent function in mid-third instar larvae, when a regulatory hierarchy prepares the animal for the onset of metamorphosis. Rather, usp is required in late third instar larvae for appropriate developmental and transcriptional responses to the ecdysone pulse that triggers puparium formation. The imaginal discs in usp mutants begin to evert but do not elongate or differentiate, the larval midgut and salivary glands fail to undergo programmed cell death and the adult midgut fails to form. Consistent with these developmental phenotypes, usp mutants show pleiotropic defects in ecdysone-regulated gene expression at the larval-prepupal transition. usp mutants also recapitulate aspects of a larval molt at puparium formation, forming a supernumerary cuticle. These observations indicate that usp is required for ecdysone receptor activity in vivo, demonstrate that the EcR/USP heterodimer functions in a stage-specific manner during the onset of metamorphosis and implicate a role for usp in the decision to molt or pupariate in response to ecdysone pulses during larval development.