Costantino Benjamin F B, Bricker Daniel K, Alexandre Kelly, Shen Kate, Merriam John R, Antoniewski Christophe, Callender Jenna L, Henrich Vincent C, Presente Asaf, Andres Andrew J
School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, United States of America.
PLoS Genet. 2008 Jun 20;4(6):e1000102. doi: 10.1371/journal.pgen.1000102.
The larval salivary gland of Drosophila melanogaster synthesizes and secretes glue glycoproteins that cement developing animals to a solid surface during metamorphosis. The steroid hormone 20-hydroxyecdysone (20E) is an essential signaling molecule that modulates most of the physiological functions of the larval gland. At the end of larval development, it is known that 20E--signaling through a nuclear receptor heterodimer consisting of EcR and USP--induces the early and late puffing cascade of the polytene chromosomes and causes the exocytosis of stored glue granules into the lumen of the gland. It has also been reported that an earlier pulse of hormone induces the temporally and spatially specific transcriptional activation of the glue genes; however, the receptor responsible for triggering this response has not been characterized. Here we show that the coordinated expression of the glue genes midway through the third instar is mediated by 20E acting to induce genes of the Broad Complex (BRC) through a receptor that is not an EcR/USP heterodimer. This result is novel because it demonstrates for the first time that at least some 20E-mediated, mid-larval, developmental responses are controlled by an uncharacterized receptor that does not contain an RXR-like component.
黑腹果蝇的幼虫唾液腺合成并分泌胶糖蛋白，这些蛋白在变态发育过程中将发育中的动物黏附在固体表面。类固醇激素20-羟基蜕皮激素（20E）是一种重要的信号分子，可调节幼虫唾液腺的大多数生理功能。在幼虫发育末期，已知20E通过由EcR和USP组成的核受体异二聚体发出信号，诱导多线染色体的早期和晚期胀泡级联反应，并导致储存的胶粒向腺腔内胞吐。也有报道称，更早的激素脉冲会诱导胶基因在时间和空间上的特异性转录激活；然而，负责触发这种反应的受体尚未得到鉴定。在这里，我们表明，在三龄幼虫中期胶基因的协调表达是由20E介导的，它通过一个不是EcR/USP异二聚体的受体诱导Broad Complex（BRC）基因的表达。这一结果是新颖的，因为它首次证明，至少一些20E介导的幼虫中期发育反应是由一个未鉴定的、不含类RXR成分的受体控制的。
