The Circadian Clock Sets the Time of DNA Replication Licensing to Regulate Growth in Arabidopsis

First author: Jorge Fung-Uceda; Affiliations: Centre for Research in Agricultural Genomics (西班牙农业基因组学研究中心): Barcelona, Spain

Corresponding author: Paloma Mas

The circadian clock (生物钟) and cell cycle (细胞周期) as separate pathways have been well documented in plants. Elucidating whether these two oscillators are connected is critical for understanding plant growth. We found that a slow-running circadian clock decelerates (使...减速) the cell cycle and, conversely, a fast clock speeds it up. The clock component TOC1 safeguards (保护) the G1-to-S transition and controls the timing of the mitotic cycle (有丝分裂周期) at early stages of leaf development. TOC1 also regulates somatic ploidy at later stages of leaf development and in hypocotyl cells. The S-phase is shorter and delayed in TOC1 overexpressing plants, which correlates with the diurnal (白天的) repression of the DNA replication licensing gene CDC6 through binding of TOC1 to the CDC6 promoter. The slow cell-cycle pace in TOC1-ox also results in delayed tumor progression in inflorescence stalks (花梗). Thus, TOC1 sets the time of the DNA pre-replicative machinery to control plant growth in resonance with the environment.

生物钟和细胞周期是植物中两个独立的通路，各自的研究已经十分透彻。至于这两个通路是如何联系起来的，这对于我们理解植物生长是非常重要的。本文发现一个慢的生物钟会减缓细胞周期，相反，一个快的生物钟则会加速细胞周期。生物钟组件TOC1蛋白会维护细胞从G1期向S期的转变，并控制叶片发育早期有丝分裂周期的时间。TOC1蛋白同时还能调控叶片发育晚期及下胚轴细胞的体细胞倍性。在TOC1过表达的植株中，S期时间变短，这与DNA复制许可因子CDC6基因白天被抑制有关，而CDC6基因是由于TOC1蛋白直接结合到其启动子区导致的其表达水平受到抑制。TOC1过表达植物中细胞周期的减缓还延缓了花梗组织中肿瘤的形成。因此，TOC1通过调节DNA复制前的时间响应于外部环境，控制植物生长。

p.s. 细胞有丝分裂分为分裂间期和分裂期［M (Mitotic) transition phases］，其中分裂间期又分为G1 (Gap 1)、S (DNA Synthesis)和G2 (Gap 2)期。G1期：RNA和蛋白质合成旺盛时期，为DNA的合成做准备；S期：DNA的复制；G2期：有活跃的RNA和蛋白质合成，为纺锤丝形成等做准备。

通讯：Paloma Mas (https://www.cragenomica.es/staff/detail/paloma-mas)

研究方向：生物钟功能的分子机制。

doi: https://doi.org/10.1016/j.devcel.2018.02.022

Journal: Developmental Cell

Published date: 22 March, 2018

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