Department of Biological Sciences, Graduate School of Science, Osaka University, Machikaneyama, 560-0043 Toyonaka, Osaka, Japan
Department of Biological Sciences, Graduate School of Science, Osaka University, Machikaneyama, 560-0043 Toyonaka, Osaka, Japan.
Proc Natl Acad Sci U S A. 2021 Mar 2;118(9). doi: 10.1073/pnas.2018823118.
Animals show photoperiodic responses in physiology and behavior to adapt to seasonal changes. Recent genetic analyses have demonstrated the significance of circadian clock genes in these responses. However, the importance of clock genes in photoperiodic responses at the cellular level and the physiological roles of the cellular responses are poorly understood. The bean bug shows a clear photoperiodic response in its reproduction. In the bug, the pars intercerebralis (PI) is an important brain region for promoting oviposition. Here, we analyzed the role of the photoperiodic neuronal response and its relationship with clock genes, focusing on PI neurons. Large PI neurons exhibited photoperiodic firing changes, and high firing activities were primarily found under photoperiodic conditions suitable for oviposition. RNA interference-mediated knockdown of the clock gene abolished the photoperiodic response in PI neurons, as well as the response in ovarian development. To clarify whether the photoperiodic response in the PI was dependent on ovarian development, we performed an ovariectomy experiment. Ovariectomy did not have significant effects on the firing activity of PI neurons. Finally, we identified the output molecules of the PI neurons and analyzed the relevance of the output signals in oviposition. PI neurons express multiple neuropeptides-insulin-like peptides and diuretic hormone 44-and RNA interference of these neuropeptides reduced oviposition. Our results suggest that oviposition-promoting peptidergic neurons in the PI exhibit a circadian clock-dependent photoperiodic firing response, which contributes to the photoperiodic promotion of oviposition.
动物在生理和行为上表现出光周期反应，以适应季节性变化。最近的遗传分析表明，生物钟基因在这些反应中具有重要意义。然而，时钟基因在细胞水平的光周期反应中的重要性以及细胞反应的生理作用还知之甚少。豆象在其繁殖中表现出明显的光周期反应。在这种昆虫中，脑间核（PI）是促进产卵的重要脑区。在这里，我们分析了光周期神经元反应的作用及其与生物钟基因的关系，重点是 PI 神经元。大型 PI 神经元表现出光周期放电变化，高放电活动主要出现在适合产卵的光周期条件下。RNA 干扰介导的生物钟基因 敲低消除了 PI 神经元的光周期反应，以及卵巢发育的反应。为了阐明 PI 中的光周期反应是否依赖于卵巢发育，我们进行了卵巢切除术实验。卵巢切除术对 PI 神经元的放电活动没有显著影响。最后，我们鉴定了 PI 神经元的输出分子，并分析了输出信号在产卵中的相关性。PI 神经元表达多种神经肽——胰岛素样肽和利尿激素 44——这些神经肽的 RNA 干扰降低了产卵。我们的结果表明，PI 中促进产卵的肽能神经元表现出生物钟基因依赖性的光周期放电反应，这有助于光周期促进产卵。
