Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, 2360102 Valparaíso, Chile.
Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, 2360102 Valparaíso, Chile;
Proc Natl Acad Sci U S A. 2021 Jul 6;118(27). doi: 10.1073/pnas.2023249118.
The daily rhythm of adult emergence of holometabolous insects is one of the first circadian rhythms to be studied. In these insects, the circadian clock imposes a daily pattern of emergence by allowing or stimulating eclosion during certain windows of time and inhibiting emergence during others, a process that has been described as "gating." Although the circadian rhythm of insect emergence provided many of the key concepts of chronobiology, little progress has been made in understanding the bases of the gating process itself, although the term "gating" suggests that it is separate from the developmental process of metamorphosis. Here, we follow the progression through the final stages of adult development with single-animal resolution and show that the circadian clock imposes a daily rhythmicity to the pattern of emergence by controlling when the insect initiates the final steps of metamorphosis itself. Circadian rhythmicity of emergence depends on the coupling between the central clock located in the brain and a peripheral clock located in the prothoracic gland (PG), an endocrine gland whose only known function is the production of the molting hormone, ecdysone. Here, we show that the clock exerts its action by regulating not the levels of ecdysone but that of its actions mediated by the ecdysone receptor. Our findings may also provide insights for understanding the mechanisms by which the daily rhythms of glucocorticoids are produced in mammals, which result from the coupling between the central clock in the suprachiasmatic nucleus and a peripheral clock located in the suprarenal gland.
昆虫完全变态的成虫每日节律是最早被研究的生物钟节律之一。在这些昆虫中，生物钟通过允许或刺激在特定时间窗口羽化，而在其他时间窗口抑制羽化，从而产生每日羽化模式，这个过程被描述为“门控”。尽管昆虫羽化的生物钟节律为时间生物学提供了许多关键概念，但对于门控过程本身的基础，几乎没有取得进展，尽管“门控”一词表明它与变态发育过程是分开的。在这里，我们以单个动物分辨率跟踪成虫发育的最后阶段，并表明生物钟通过控制昆虫自身开始变态的最后步骤的时间来对羽化模式施加每日节律。羽化的昼夜节律性取决于位于大脑中的中央时钟与位于前胸腺（PG）中的外周时钟之间的耦合，PG 是一种内分泌腺，其唯一已知的功能是产生蜕皮激素蜕皮激素。在这里，我们表明，时钟通过调节蜕皮激素受体介导的蜕皮激素的作用而不是其水平来发挥作用。我们的发现也可能为理解哺乳动物中糖皮质激素的昼夜节律产生的机制提供见解，这是由于视交叉上核中的中央时钟与位于肾上腺中的外周时钟之间的耦合产生的。
