This research describes the diel phasing of the cell cycle in the dinoflagellate, Amphidinium operculatum Claparéde and Lachmann, and investigates the mechanisms that serve to link the cell cycle to the diel cycle. Unlike many dinoflagellates, A. operculatum has a naturally high division rate of approximately 1 division day(-1), which yields a nearly synchronous population, making it useful for population studies. When grown on a 16:8 h light/dark cycle, S-phase begins 10 h and mitosis 14-16 h after the onset of light, as determined by flow cytometry. Alterations in the timing of the dark/light and light/dark transitions showed that the cell cycle is entrained by the dark/light transition, with the light/dark cue being uninvolved. Cells in logarithmic phase growth also undergo diel changes in cell size (9-14 &mgr;m), reaching a maximum size late in the light phase, concurrent with mitosis. Stationary phase cells or cells blocked in G1 of the cell cycle with a cell cycle inhibitor, olomoucine, showed no size changes or reduced size changes over the diel cycle, suggesting a coupling of cell size to the cell division cycle. In Euglena, cAMP-dependent signaling appears to mediate diel phasing of the cell cycle. Therefore, the role of cAMP in cell cycle control in A. operculatum was investigated. Measurement of intracellular cAMP by radioimmunoassay (RIA) revealed that cAMP concentrations varied on a diel basis, but increases observed appeared to correlate with cell size increases, and did not correlate with light cues at the dark/light or light/dark transition. However, when cells were treated with the cAMP phosphodiesterase inhibitor, IBMX, cell cycle progression was inhibited at both the G1/S and the G2/M phase transitions. This supports a role for cAMP-dependent signaling in the dinoflagellate cell cycle and is in agreement with the documented role of cAMP in the cell cycle control of higher eukaryotes.

中文翻译：

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甲藻中的细胞周期调节，Amphidinium operculatum：识别诱导信号和环 AMP 的可能作用

本研究描述了甲藻、Amphidinium operculatum Claparéde 和 Lachmann 中细胞周期的 Diel 定相，并研究了将细胞周期与 Diel 周期联系起来的机制。与许多甲藻不同，A. operculatum 具有大约 1 个分裂日 (-1) 的自然高分裂率，产生几乎同步的种群，使其可用于种群研究。当在 16:8 小时的光/暗循环中生长时，S 期在光照开始后 10 小时开始，有丝分裂在 14-16 小时后开始，由流式细胞仪确定。暗/亮和亮/暗转换时间的改变表明，细胞周期受暗/亮转换的影响，不涉及亮/暗提示。对数生长期的细胞也经历细胞大小的变化（9-14μm），在轻度阶段后期达到最大尺寸，与有丝分裂同时发生。静止期细胞或在细胞周期 G1 中被细胞周期抑制剂 olomoucine 阻断的细胞，在细胞周期内没有显示大小变化或大小变化减少，表明细胞大小与细胞分裂周期有关。在眼虫中，cAMP 依赖性信号似乎介导细胞周期的 diel 定相。因此，研究了 cAMP 在 A. operculatum 细胞周期控制中的作用。通过放射免疫分析 (RIA) 测量细胞内 cAMP 显示 cAMP 浓度在不同的基础上变化，但观察到的增加似乎与细胞大小增加相关，而与暗/亮或亮/暗转换时的光提示无关。然而，当细胞用 cAMP 磷酸二酯酶抑制剂 IBMX 处理时，细胞周期进程在 G1/S 和 G2/M 相变均受到抑制。这支持 cAMP 依赖性信号在甲藻细胞周期中的作用，并且与 cAMP 在高等真核生物的细胞周期控制中的记录作用一致。