Genetic linkages of the circadian clock-associated genes, TOC1, CCA1 and LHY, in the photoperiodic control of flowering time in Arabidopsis thaliana
Genetic linkages of the circadian clock-associated genes, TOC1, CCA1 and LHY, in the photoperiodic control of flowering time in Arabidopsis thaliana
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DOI：
10.1093/pcp/pcm067
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发表时间：
2007-07-01
影响因子：
4.9
通讯作者：
Mizuno, Takeshi
中科院分区：
文献类型：
--
作者：
Niwa, Yusuke;Ito, Shogo;Mizuno, Takeshi
在拟南芥中，开花时间是通过生物钟来调节的，生物钟测量日长并根据外部符合模型调节光周期CO-FT输出途径。然而，与生物钟相关的主要基因TOC 1、CCA 1和LHY与经典的CO-FT开花途径之间的遗传联系尚不清楚。通过采用一组突变体，包括极早开花的toc 1 cca 1 lhy三重突变体，我们证明了CCA 1和LHY作为光周期开花途径的负调节因子具有冗余作用。部分冗余的CCA 1/ LHY功能在很大程度上但不是绝对地依赖于作为激活剂的上游TOC 1基因。参照突变体中CO和FT的表达谱的检查结果表明，该时钟电路确实与CO-FT输出途径相关，如果不是排他的话。对于这种连锁，某些开花相关基因GI、CDF 1和FKF 1的相位控制似乎是至关重要的。此外，TOC 1和CCA 1/ LHY之间的遗传连锁与负反馈和正反馈回路相容，目前认为这是生物钟的核心。本研究的结果表明，昼夜节律钟可能会在白天打开光周期输出通路的出口。在目前的时钟模型的背景下，这些结果将讨论与以前的发现，相同的时钟可能会打开一个出口的早期光形态发生的输出途径在夜间。
In Arabidopsis thaliana, the flowering time is regulated through the circadian clock that measures day- length and modulates the photoperiodic CO - FT output pathway in accordance with the external coincidence model. Nevertheless, the genetic linkages between the major clock-associated TOC1, CCA1 and LHY genes and the canonical CO - FT flowering pathway are less clear. By employing a set of mutants including an extremely early flowering toc1 cca1 lhy triple mutant, here we showed that CCA1 and LHY act redundantly as negative regulators of the photoperiodic flowering pathway. The partly redundant CCA1/ LHY functions are largely, but not absolutely, dependent on the upstream TOC1 gene that serves as an activator. The results of examination with reference to the expression profiles of CO and FT in the mutants indicated that this clock circuitry is indeed linked to the CO - FT output pathway, if not exclusively. For this linkage, the phase control of certain flowering- associated genes, GI, CDF1 and FKF1, appears to be crucial. Furthermore, the genetic linkage between TOC1 and CCA1/ LHY is compatible with the negative and positive feedback loop, which is currently believed to be a core of the circadian clock. The results of this study suggested that the circadian clock might open an exit for a photoperiodic output pathway during the daytime. In the context of the current clock model, these results will be discussed in connection with the previous finding that the same clock might open an exit for the early photomorphogenic output pathway during the night- time.