Kuwano Kazuyoshi, Sakurai Ryousuke, Motozu Yoshitaka, Kitade Yukihiro, Saga Naotsune
Graduate School of Science and Technology, Nagasaki University, Bunkyo-machi, Nagasaki 852-8521, JapanFaculty of Fisheries, Nagasaki University, Bunkyo-machi, Nagasaki 852-8521, JapanFaculty of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan.
J Phycol. 2008 Apr;44(2):364-73. doi: 10.1111/j.1529-8817.2008.00477.x.
The cell-cycle progression of Enteromorpha compressa (L.) Nees (=Ulva compressa L.) was diurnally regulated by gating the G1 /S transition. When the gate was open, the cells were able to divide if they had attained a sufficient size. However, the cells were not able to divide while the gate was closed, even if the cells had attained sufficient size. The diurnal rhythm of cell division immediately disappeared when the thalli were transferred to continuous light or darkness. When the thalli were transferred to a shifted photoperiod, the rhythm of cell division immediately and accurately synchronized with the shifted photoperiod. These data support a gating-system model regulated by light:dark (L:D) cycles rather than an endogenous circadian clock. A dark phase of 6 h or longer was essential for gate closing, and a light phase of 14 h was required to renew cell division after a dark phase of >6 h.
浒苔（Enteromorpha compressa (L.) Nees，即石莼Ulva compressa L.）的细胞周期进程通过控制G1/S转换受到昼夜调节。当门打开时，如果细胞达到足够大小，它们就能分裂。然而，当门关闭时，即使细胞达到足够大小，也不能分裂。当藻体转移到连续光照或黑暗条件下时，细胞分裂的昼夜节律立即消失。当藻体转移到改变的光周期条件下时，细胞分裂节律立即且准确地与改变后的光周期同步。这些数据支持了一种由光暗（L:D）周期调节的门控系统模型，而非内源性昼夜节律钟。6小时或更长时间的黑暗阶段对于门关闭至关重要，在超过6小时的黑暗阶段后，需要14小时的光照阶段来恢复细胞分裂。
