The A-type cyclin CYCA2;3 is a key regulator of ploidy levels in Arabidopsis endoreduplication
The A-type cyclin CYCA2;3 is a key regulator of ploidy levels in Arabidopsis endoreduplication
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DOI：
10.1105/tpc.105.037309
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发表时间：
2006-02-01
期刊：
影响因子：
11.6
通讯作者：
Aoyama, T
中科院分区：
文献类型：
--
作者：
Imai, KK;Ohashi, Y;Aoyama, T
植物细胞经常经历核内复制，在没有有丝分裂的情况下染色体DNA连续复制的过程。有人提出，核内复制在其进入时受有丝分裂周期蛋白依赖性激酶活性的调节。然而，尽管植物严格控制每种细胞类型的倍性水平，但其终止的调控机制仍不清楚。在寻找内复制调控因子的过程中，拟南芥细胞周期蛋白A基因CYCA2的启动子；3，在内复制终止期毛状体的发育和增殖组织中显示活跃。利用植物编码高度冗余的细胞周期蛋白A基因的情况，我们能够对CYCA2进行功能解剖；3使用零突变等位基因。CYCA2空突变；3半显性地促进了成熟器官的内环并增加了倍性水平，但它们对进行内复制的细胞比例没有显著影响。与此结果一致，CYCA2；3 -绿色荧光蛋白融合蛋白以剂量依赖的方式抑制内环。此外，CYCA2破坏盒中的突变；3稳定了细胞核内的融合蛋白，增强了约束。我们得出CYCA2；3负调控内环，是拟南芥内重复倍率的关键调节因子。
Plant cells frequently undergo endoreduplication, a process in which chromosomal DNA is successively duplicated in the absence of mitosis. It has been proposed that endoreduplication is regulated at its entry by mitotic cyclin-dependent kinase activity. However, the regulatory mechanisms for its termination remain unclear, although plants tightly control the ploidy level in each cell type. In the process of searching for regulatory factors of endoreduplication, the promoter of an Arabidopsis thaliana cyclin A gene, CYCA2; 3, was revealed to be active in developing trichomes during the termination period of endoreduplication as well as in proliferating tissues. Taking advantage of the situation that plants encode highly redundant cyclin A genes, we were able to perform functional dissection of CYCA2; 3 using null mutant alleles. Null mutations of CYCA2; 3 semidominantly promoted endocycles and increased the ploidy levels achieved in mature organs, but they did not significantly affect the proportion of cells that underwent endoreduplication. Consistent with this result, expression of the CYCA2; 3 - green fluorescent protein fusion protein restrained endocycles in a dose-dependent manner. Moreover, a mutation in the destruction box of CYCA2; 3 stabilized the fusion protein in the nuclei and enhanced the restraint. We conclude that CYCA2; 3 negatively regulates endocycles and acts as a key regulator of ploidy levels in Arabidopsis endoreduplication.