In many animals, progression of developmental stages is temporally controlled by steroid hormones. In Drosophila, the level of ecdysone titer oscillates and developmental stage transitions, such as larval molting and metamorphosis, are induced at each of ecdysone peaks. Ecdysone titer also peaks at the stage of mid‐embryogenesis and the embryonic ecdysone is necessary for morphogenesis of several organs, although the regulatory mechanisms of embryonic organogenesis dependent on ecdysone signaling are still open questions. In this study, we find that absence or interruption of embryonic ecdysone signaling caused multiple defects in the tracheal system, including decrease in luminal protein deposition, uneven dilation of the dorsal trunk and loss of terminal branches. We also reveal that an ecdysone‐inducible gene polished rice (pri) is essential for tip cell fate decision in dorsal branches. As over‐expression of pri can restore the defects caused by disturbance of ecdysone biosynthesis, pri functions as one of the major mediators of embryonic ecdysone signal in tracheogenesis. These results demonstrate that ecdysone and its downstream target pri play essential roles in tracheal development by modulating cell fate decision.

中文翻译：

---

精米介导果蝇胚胎器官发生的蜕皮激素依赖性控制

在许多动物中，发育阶段的进程是由类固醇激素暂时控制的。在果蝇中，蜕皮激素滴度的水平振荡和发育阶段转变，例如幼虫蜕皮和变态，在每个蜕皮激素峰处被诱导。蜕皮激素滴度也在胚胎发生中期达到峰值，并且胚胎蜕皮激素对于多个器官的形态发生是必需的，尽管依赖于蜕皮激素信号传导的胚胎器官发生的调节机制仍然是悬而未决的问题。在这项研究中，我们发现胚胎蜕皮激素信号的缺失或中断会导致气管系统出现多种缺陷，包括管腔蛋白质沉积减少、背干不均匀扩张和终末分支丢失。我们还揭示了一种蜕皮激素诱导基因精米（pri) 对于背侧分支的尖端细胞命运决定至关重要。由于pri的过表达可以修复蜕皮激素生物合成障碍引起的缺陷，pri在气管发生中作为胚胎蜕皮激素信号的主要介质之一发挥作用。这些结果表明蜕皮激素及其下游靶标pri通过调节细胞命运决定在气管发育中发挥重要作用。