Spontaneous spatiotemporal waves of gene expression from biological clocks in the leaf
Spontaneous spatiotemporal waves of gene expression from biological clocks in the leaf
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DOI：
10.1073/pnas.1118814109
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发表时间：
2012-04-24
影响因子：
11.1
通讯作者：
Millar, Andrew J.
中科院分区：
文献类型：
--
作者：
Wenden, Benedicte;Toner, David L. K.;Millar, Andrew J.
驱动动物日常节律的生物钟在一些组织的细胞之间紧密耦合。这种耦合深刻地影响细胞节律性，是当代理解昼夜生理和行为的核心。相比之下，对植物细胞生物钟的研究在很大程度上忽略了细胞间偶联，据报道，这种偶联非常弱或不存在。我们利用荧光素酶报告基因成像技术监测拟南芥叶片的昼夜节律，达到接近细胞水平的分辨率。在没有环境循环的情况下生长长达3周的叶片可重复性地显示出与细胞间偶联一致的基因表达时空波，使用多个报告基因。在单个叶片中，不同区域的相位差异可达17小时。在叶片之间观察到广泛的模式，而不是昼夜节律特性的共同空间分布。暴露于光-暗循环中的叶片总是具有完全同步的节奏，而这种节奏可以迅速地去同步。在恒定光照4 d后，一些叶片与没有任何节奏输入的叶片一样不同步。在这样的叶片上施加光暗循环，结果在2-4天内实现了完全同步。因此，所有细胞的节律与外部光暗循环的耦合远比细胞时钟之间的耦合强。恒定条件下的自发去同步是有限的，这与异质时钟之间的弱细胞间耦合一致。细胞间的弱偶联和异质性都与解释分子研究和理解植物生物钟的生理功能有关。
The circadian clocks that drive daily rhythms in animals are tightly coupled among the cells of some tissues. The coupling profoundly affects cellular rhythmicity and is central to contemporary understanding of circadian physiology and behavior. In contrast, studies of the clock in plant cells have largely ignored intercellular coupling, which is reported to be very weak or absent. We used luciferase reporter gene imaging to monitor circadian rhythms in leaves of Arabidopsis thaliana plants, achieving resolution close to the cellular level. Leaves grown without environmental cycles for up to 3 wk reproducibly showed spatiotemporal waves of gene expression consistent with intercellular coupling, using several reporter genes. Within individual leaves, different regions differed in phase by up to 17 h. A broad range of patterns was observed among leaves, rather than a common spatial distribution of circadian properties. Leaves exposed to light-dark cycles always had fully synchronized rhythms, which could desynchronize rapidly. After 4 d in constant light, some leaves were as desynchronized as leaves grown without any rhythmic input. Applying light-dark cycles to such a leaf resulted in full synchronization within 2-4 d. Thus, the rhythms of all cells were coupled to external light-dark cycles far more strongly than the cellular clocks were coupled to each other. Spontaneous desynchronization under constant conditions was limited, consistent with weak intercellular coupling among heterogeneous clocks. Both the weakness of coupling and the heterogeneity among cells are relevant to interpret molecular studies and to understand the physiological functions of the plant circadian clock.