Nakagawa Marika, Okano Keiko, Saratani Yuya, Shoji Yosuke, Okano Toshiyuki
Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, Waseda University, TWIns, Wakamatsucho 2-2, Shinjuku-Ku, Tokyo, 162-8480, Japan.
Zoological Lett. 2022 Jun 7;8(1):8. doi: 10.1186/s40851-022-00192-4.
Photoperiodic responses are observed in many organisms living in the temperate zones. The circadian clock is involved in photoperiodic time measurement; however, the underlying molecular mechanism for detection of the day length remains unknown. We previously compared the expression profiles of the Cryptochrome(Cry) genes in the zebrafish eye and reported that Cry1ab has a double peak with variable expression duration depending on the photoperiod. In this study, to understand commonalities and differences in the photoperiodic responses of ocular Cry genes, we identified Cryptochrome genes in two other teleost species, goldfish and medaka, living in temperate zones, and measured ocular Cry mRNA levels in all of the three species, under different photoperiods (long-day [14 h light: 10 h dark] and short-day [10 h light: 14 h dark] and in constant darkness. Cry1ab mRNA levels did not show dual peaks in goldfish or medaka under the examined conditions; however, the mRNA expression profiles of many Crys were altered in all three species, depending on the day length and light condition. Based on their expression profiles, Cry mRNA peaks were classified into three groups that better synchronize to sunrise (light-on), midnight/midday (middle points of the dark/light periods), or sunset (light-off). These results suggest the presence of multiple oscillators that oscillate independently or a complex oscillator in which Cry expression cycles change in a photoperiod-dependent manner in the eye.
在许多生活在温带地区的生物体中都观察到了光周期反应。生物钟参与光周期时间测量；然而，检测日长的潜在分子机制仍然未知。我们之前比较了斑马鱼眼睛中隐花色素（Cry）基因的表达谱，并报告说Cry1ab有一个双峰，其表达持续时间因光周期而异。在这项研究中，为了了解眼部Cry基因光周期反应的共性和差异，我们在另外两种生活在温带地区的硬骨鱼物种金鱼和青鳉中鉴定了隐花色素基因，并在不同光周期（长日照[14小时光照：10小时黑暗]和短日照[10小时光照：14小时黑暗]）以及持续黑暗条件下测量了这三种物种的眼部Cry mRNA水平。在检查的条件下，金鱼或青鳉中的Cry1ab mRNA水平没有显示出双峰；然而，许多Cry的mRNA表达谱在所有三种物种中都根据日长和光照条件而改变。根据它们的表达谱，Cry mRNA峰值被分为三组，它们与日出（光照开始）、午夜/中午（黑暗/光照期的中点）或日落（光照结束）的同步性更好。这些结果表明，眼睛中存在多个独立振荡的振荡器或一个复杂的振荡器，其中Cry表达周期以光周期依赖的方式变化。
