Light regulation of circadian clock-controlled gene expression in rice.
Light regulation of circadian clock-controlled gene expression in rice.
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DOI：
10.1046/j.1365-313x.2001.01063.x
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发表时间：
2001-06
期刊：
影响因子：
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通讯作者：
N. Sugiyama;T. Izawa;T. Oikawa;K. Shimamoto
中科院分区：
文献类型：
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作者：
N. Sugiyama;T. Izawa;T. Oikawa;K. Shimamoto
使用转基因水稻幼苗表达的萤火虫荧光素酶（luc）基因下的水稻CA B（叶绿素a/B结合蛋白）启动子的控制下，我们证明了光如何影响昼夜节律钟的CA B基因的转录。光/暗夹带后，在恒定的光和暗（DD）条件下观察到超过5天的节律性luc表达。在DD的不同时间点施加光脉冲后，分别观察到CAB基因表达的各种时间模式。我们首先研究了两个不同的属性相关的夹带机制的生物钟：自由运行周期（FRPs）和相位重置的光脉冲的注量率依赖。尽管FRP的缩短与注量率有关，但DD的FRP几乎等于中等注量率恒定光照下的FRP，表明这种注量率依赖性可能不能完全描述水稻生物钟的夹带。在水稻幼苗的转录水平上也观察到了光脉冲引起的生物钟的典型相位响应。因此，每日周期亮/暗转变时的相位重置可能足以解释水稻的夹带机制。我们进一步证明，除了对急性反应具有门控效应之外，光脉冲还可以以相位依赖性方式在第一个昼夜节律峰处激活昼夜节律钟控制的CAB 1 R基因表达。这表明，光激活昼夜CAB基因表达在每日光/暗周期的生物钟活动。
Using transgenic rice seedlings expressing a firefly luciferase (luc) gene under the control of a rice CAB (chlorophyll a/b binding protein) promoter, we demonstrated how light affects circadian clocks in the transcription of the CAB gene. Rhythmic luc expression was observed for more than 5 d under constant light and dark (DD) conditions after light/dark entrainment. After a light pulse was applied at different time points in DD various temporal patterns of CAB gene expression were individually observed. We first examined two distinct properties related to the entrainment mechanism of the circadian clock: fluence-rate dependence of free-running periods (FRPs) and phase resetting by a light pulse. Although fluence-rate dependent shortening of FRP was demonstrated, the FRP in DD was almost equal to that in constant light of a middle fluence-rate, indicating that this fluence-rate dependence may not fully describe the entrainment of the circadian clock in rice. Typical phase responses of the circadian clock by a single light pulse were also observed at the transcriptional level in rice seedlings. Thus, the phase resettings upon the light/dark transitions of daily cycles may be sufficient to explain the entrainment mechanisms of rice. We have further demonstrated that, in addition to having a gating effect to acute response, a light pulse can activate the circadian clock-controlled CAB1R gene expression at the first circadian peak in a phase-dependent manner. This suggests that light activates circadian clock activity in the diurnal CAB gene expression under daily light/dark cycles.